PDA

View Full Version : Round column mill guide bar alignment



darryl
05-21-2011, 10:40 PM
Ok, all you fine gentlemen still here? Good- I am starting to build the guide bar setup that will allow raising and lowering the head of the mill without losing position. Basically there will be a guide bar parallel to and in the same plane as the column. Parallel is easy, basically a pair of spacers cut to the same length is used. In the same plane is a bit more difficult.

So far what I've done is extend the elevation crank shaft and surrounded it with a steel box. One side of this box will have a brace to another part of the head, and the other side will have something that will ride the guide bar. The crank handle ends up being about 8 inches further to the left than it was before, but otherwise its operation isn't affected at all.

The guide bar will be mounted to the column via a pair of arms with clamps which can be loosened so the bar will swing with the head if I want to rotate it on the column. When I need to use the guide, the clamps would be tightened, then the head can be cranked up and down without losing the alignment. Of course the guide bar has to be in the same plane as the column, otherwise there will be a smooth, but progressive loss of positioning the more you raise or drop the head.

So that's where I'm at on this last day of the world. I'm looking for a good way to firstly get the bar aligned, and secondly to keep it aligned through the countless times it would be loosened and tightened to the column again.

I suppose that if the guide bar was rigidly mounted to the arms, it would resist being twisted off-plane, and the mating slide mounted on the crank extension housing would help to keep it 'vertical'. I think this will work, but it's also possible that by some small angular error in machining the guide bar seats that the bar will acquire some small but non-fixable twist. I further suppose that if I were to machine both arms together, then turned one upside down, that the possible error might cancel and I'd end up with the right result. I think this is the way I'm going to approach it. Any other ideas?

Just to further clarify- if I was to align the guide bar to the column and tighten the clamps permanently, all I'm faced with is aligning the bar once. The head would always ride up and down in the same spot above the base. But I do want to be able to rotate the head on the column as it becomes helpful, which it has many times. This is the remaining 'snag', after which it's just cutting, machining, and assembling parts. Pictures to follow.

Toolguy
05-22-2011, 02:14 AM
That sounds like a good plan. I think if the bushings on the head are 6" or so apart vertically, that should be enough to keep the bar parallel to the column while you tighten the clamps. It will be interesting to see how it turns out.;)

darryl
05-22-2011, 04:21 AM
I've just finished getting a new handle bored to fit the extended shaft. The old handle didn't have enough meat on it to be bored that much, plus it was kinked to one side anyway and would have put the crank even further to the left than this mod put it. So now the mechanicals of the crank extension are done, mounted, and working better than before. Funny how that happens sometimes- in this case partly due to the fact that I added a bushing for the shaft at the end of the extension.

I used a 2x3 steel tube section for the extension box. The 3 inch dimension is vertical, and I plan to mount the bushings for the guide bar above and below the tube, so that will put the bushings about 5 inches apart. That should be enough to greatly help keep the bar aligned to the column. Two things happen here- one is that the extension box has some wiggle room to allow it to be aligned to the guide bar, and the other is that I can't rely on it initially to align the bar to the column. The guide has to be aligned first, then the extension box gets removed from the elevation mechanism, mating surfaces coated in my best epoxy for this (PC-7), remounted, aligned to the guide, bolts snugged up lightly, then wait. After a full day of cure, I'll tighten the bolts a bit more, then move on to securing the bushings. Before any of this, I'll have to make the connecting arms and clamps for the guide bar.

I'm happy so far- drilled and tapped everything I needed so far without breaking a tap, and I now have a better place to clamp my work light.

darryl
05-22-2011, 04:44 AM
Here's 2000 words worth- I've temporarily clamped a piece of square tubing to the extension box just to show where the guide bar will be.

http://img.photobucket.com/albums/v136/heinrich/elevationcrankextension.jpg

If you look carefully at the right end of the extension, you see two coin sized spots- these are two inch long pieces of half inch rod that have been pressed in, then drilled and tapped so the box can be mounted using bolts from the inside of the elevation mechanism cover. How else, short of welding, can you mount the end of a tubing section to some flat surface- there surely isn't enough thickness in the material to drill and tap into the end of it. The box will be epoxied to the cast cover as I mentioned earlier, and that's as much to fill gaps so I don't crack the cast from tightening the bolts as it is to help keep the parts together as one rigid unit.

http://img.photobucket.com/albums/v136/heinrich/elevationcrankextension2.jpg

tmc_31
05-22-2011, 08:04 AM
Darryl,

Cool build man, I also have a round column drill/mill and face the same problems. I have been re-aligning the head with a laser which works ok but is not that accurate. I am anxious to see how you resolve it. Keep the pictures coming. Thanks for posting this.

Tim

Evan
05-22-2011, 09:31 AM
Use two guide bars just like the ways on my mill. Bore the pairs of holes in the end pieces together. The bars will be parallel, it cannot be otherwise. The end supports will then offer perpendicular surfaces to which you may measure in relation to the vertical column. All that takes is a square.

The end plates should be screwed together for boring. Alignment on the cross slide is easy by sweeping with a DI mounted in the chuck. You can also do the same on the mill instead of the lathe.

http://ixian.ca/pics8/bore5.jpg

1-800miner
05-22-2011, 09:59 AM
Funny, every round column I see,including mine,the belt gaurd is long gone.

tdmidget
05-22-2011, 12:20 PM
Not real clear on what you are doing here. Does the whole column rotate?

Evan
05-22-2011, 01:08 PM
I have been re-aligning the head with a laser which works ok but is not that accurate

There is a real easy way to get much better accuracy with the laser. I presume you are shining from the head to the base. Fix the laser to the head and shine it on the farthest wall you can and make a mark there. That will be an order of magnitude better, at least, as long as the mill doesn't move on it's stand or bench.

doctor demo
05-22-2011, 01:10 PM
Not real clear on what you are doing here. Does the whole column rotate?
No the col. doesn't rotate the head rotates on the col. when being raised or lowered, sort of the same problem as using a drill press and moving the table up and down.
I like Evans idea of using two guide bars instead of one, but I'm not the guy doing the work:)

Steve

loose nut
05-22-2011, 01:55 PM
Why not pin the rack to the column, accurately of course.

darryl
05-22-2011, 04:06 PM
There's been a few mentions now of pinning the rack to the column. To start with, there has to be some clearance for the head to be able to slide up and down past the rack. That clearance is in a groove at the top and bottom of the head casting adjacent to the column. My column is about 4 inches diameter, so the groove is about 2 inches from the central axis. Go out to the spindle, and you have roughly a 5 to 1 increase in the side play, so if the groove has say 2 thou of play, the best you could hope for at the spindle is to be within 10 thou. Completely non-acceptable. On my mill, the grooves for the rack to slide in have about 10 to 15 thou of play, so that would put the best case scenario at the spindle to about 50 thou. You can eyeball far better than that. Pinning the rack to the column also prevents being able to swing the head on the column. If all I wanted was an accurate ride up and down, some of these potential problems would be gone. I don't think there's any case where pinning the rack and relying on it for alignment is going to work well enough to be worth the effort.

Anyway, Evan's suggestion is along the lines of what I came up with while trying to sleep last night. The bores to hold the guide bar must be square to the arms holding the bar, and the big end of the arms must also be machined squarely so they will extend out from the column in good alignment. I'm going to machine all the bosses on the lathe, then tie the bosses together with some flat sheet material on both sides. Each boss will have the bore and one flat side machined intrinsically accurately, and the other flat side will come very close as long as my faceplate doesn't wobble, which it doesn't. With these parts accurately made, the assembly should square up perfectly.

I wanted to mention one other thing- the middle pulley stack is on the right side of the mill. It takes up about 4 or 5 inches of vertical space, so if I had designed to put my arms and guide bar on that side, I'd lose that much vertical travel. As it is, the belt cover will lose me an inch or two on the left side, and I'm probably going to cut out a section of the cover so I can get that back. Seems this mod was destined to be on the left side.

Now that I'm clear on how to proceed, I'm back in the workshop. More pics later. Thanks guys.

Robin R
05-22-2011, 04:18 PM
What about a bar that's parallel to the column in both directions, attached to the mill base in a fairly rigid way. Then mount an idicator to the head, so it can bear on the bar in a position that's easy to see. Set the indicator to zero when it bears against the bar, then move the head up or down to the new height you want. You can then rotate it around the column, till you get the same zero reading on the indicator and things should be perfectly aligned at the new height. The big advantage over a guide that holds the head rigidly in alignment, is that you can't over power the guide.

darryl
05-22-2011, 05:45 PM
Not a bad idea, Robin. A guide bar that's fixed in place which you measure against. Could be finicky with the gauge, though. You'd probably have to dedicate a caliper to it, and mount the caliper to a slider on the bar, denoting an exact spot on the head casting to measure to. I can see that working reasonably well.

I have all along been considering the effects of flexing of the guide bar. I don't know how it will translate in actual usage, but I guess I'm going to be the guinea pic here. The bushing that rides the bar doesn't have to go completely around it, so that leaves the potential to add some bracing to the back side of it. Just a strip of flat bar on edge would offer a fair amount of stiffness.

I'm going to leave myself the option to disconnect from the guide, in case there's an application where the guide would get in the way of a large workpiece. So far, I've lost 1/8 inch in throat capacity, so nothing there basically, but also I've lost about 5/8 inch off the bottom of the head travel, the room taken up by the bottom arm. I don't recall ever having to crank the head that low, so I'm probably not going to miss any capacity there anyway. At the top I'm replacing the column cap with the upper arm, so no loss there. I can't recall ever needing the full height capacity either, so nothing will change for me there.

Well, back to it for a bit, then I'm taking a coffee and pie break. Pumpkin, mmm

darryl
05-24-2011, 02:22 AM
More work done today on this- here's an overall showing the guide bar mounted.

http://img.photobucket.com/albums/v136/heinrich/guidebarasembly.jpg

Here's a close-up of the lower arm. I've used solid pvc to make the bushings to press-fit the bar into, plus make the spacer that half-surrounds the column. The gaps between the steel plates will be filled with pvc also, which will enhance the rigidity of the arms. Both arms have the gap where the rack fits, and this will help keep the rack from skewing when you rotate the head on the column.

http://img.photobucket.com/albums/v136/heinrich/lowerguidebararm.jpg

This shows the simple strap clamp that tightens the arms to the column. One refinement will be a pair of threaded handles that will take the place of the nut, which is temporary.

http://img.photobucket.com/albums/v136/heinrich/clampstrap.jpg

When tightened, the arms are held tightly enough to the column that they don't shift with any reasonable force applied out at the guide bar. I will need to rely on the bushings that ride the bar to keep the bar aligned with the column- it doesn't take much to twist it when the clamps are loosened. Filling the gaps between the sheet steel pieces will help with this, but I can tell it won't prevent some small amount of twisting. I'll be transferring that job to the bushings that ride the bar (which aren't made yet), and I'll be spacing the bushings about 9 inches apart. That's the longest I can make that without interfering with the full range of height adjustment. So, that's my next step- the bushing holder.

darryl
05-24-2011, 03:27 AM
By the way, I discovered a method of aligning the bar to the column. It's spaced equally away from the column by the arms, but in the other plane-

I took a 1 inch thick granite slab I have and held it up against both the column and the guide bar. If it rocked, the alignment was out, simple. I checked the slab on my surface plate to verify its flatness beforehand.

tmc_31
05-24-2011, 09:57 AM
There is a real easy way to get much better accuracy with the laser. I presume you are shining from the head to the base. Fix the laser to the head and shine it on the farthest wall you can and make a mark there. That will be an order of magnitude better, at least, as long as the mill doesn't move on it's stand or bench.

Evan,

I do use the laser alignment method you recommend. I have a line on the wall about 18' from the center of the column that I use as a reference point. At that distance my laser dot is about 1/16" in diameter. By my calculations, that should get me back to within about .0026+/- of center. Plenty good for most of my work, but I would still like to be able to do better. I realize that the longer distance I have from the mill column center to the reference line, the more accurate this method will be. My reference line distance is limited by the size of my shop. I would like to be able to return to center within .0005- .001. This is the only mill I have ever had the pleasure of using so I don't know what other mills (as in a knee mill which I hope to get when I grow up) are capable of.

All the best,

Tim

GerryR
05-24-2011, 10:47 AM
I guess I just missed and passed over this thread but thought I would share a picture of what I did to an Enco benchtop mill that I had. Unfortunately, I sold the mill so can't get any more pictures.

http://i590.photobucket.com/albums/ss348/GerryR_photos/DSC00003.jpg

I put the secondary column in the back and attached the bronze-bushings guide tube to the head casting. I had the coulmn supports laser-cut so that they were pretty much dead on center-to-center from column to post and from top to bottom. The guide tube on the head was adjustable so that allignment was possible in the other axis. The supports were made with pinch bolts so that by loosening the bolts, the head could still be rotated if I needed that option, and the two columns remained alligned. They were kept as close as practical to maintain as much stiffness as possible between the two columns. It's hard to see much in the picture, but perhaps it will give some late ideas.

jep24601
05-24-2011, 10:48 AM
Evan, ..... I realize that the longer distance I have from the mill column center to the reference line, the more accurate this method will be. My reference line distance is limited by the size of my shop.
Actually if you use mirrors you will effectivly have no limitation in that regard.

tmc_31
05-24-2011, 11:21 AM
Actually if you use mirrors you will effectivly have no limitation in that regard.

Jep24601,

So if I put a mirror on the wall where my reference line is now and angle it slightly so that it shoots to another mirror on the wall behind and to one side of the mill which is pointed at the original reference line wall, I can triple my accuracy? That would get me in the range I would like to be in!! But won't the laser dot grow some? How would this affect accuracy? An interesting solution, I will give it a try. Thanks.

GerryR,

That is an interesting and I think workable variation on Darryl's theme. Thanks for posting that.

You know, if we can get this head re-alignment issue resolved and figure out a good way to stiffen the column, these might make pretty good little mills. Round column mill/drills have been around forever, it surprises me that a good solutions to these issues haven't been found before. (I know, I know.. square column mill).

All the best,

Tim

darryl
05-24-2011, 09:02 PM
Somebody beat me to the mirror suggestion. If you place a mirror on the wall in place of the lines, then reflect that back to the side of the mill, you double the sensitivity and the readout is right in front of your face as well. Laser spots do grow with distance, but not by such an amount that you can't still use it accurately. The beam will either have a certain size of spot or width of line that you use to gauge by. Draw your own line chart to accommodate it .

I also have been concerned about the stand moving and throwing things off. But it's easy enough to do a 'before and after' tweaking to eliminate the problem. Say you make a cut, then need to raise or lower the head. Before you loosen the head, make an adjustment to place the reflected beam right on the marks. Make the head adjustment, then tighten. During the head movement, there should be little that would cause the stand to twist or move. I can certainly see it happening during machining, what with vibration and all.

A couple more words about my project before I go off for awhile. The guide bar I am using is the straightest piece of 1 inch bar I have, but it's not perfect. After I use this for awhile, I'll probably want to make some changes, maybe try something different for the arms- then I'll buy a piece of straight shafting for the guide bar. If the setup works well enough as is, well then I'll leave it alone. So far I've used what materials I had on hand, but I'm already wishing I'd bought some 3/4 inch aluminum plate to make the arms from. Instead of press-fitting the guide bar into pvc bushings, I'd probably buy some cast flanges, then bore and face them, then shrink-fit them to the ends of the guide bar. The arms would then be bolted to those, giving about as rigid of an assembly as you could reasonably get. I don't know if I'm going to have a problem or not keeping the guide bar in perfect alignment with the column, but the potential does exist for the arms to rotate a slightly different amount around the column when loosened for positioning. I don't want to have to check this each time I make a head adjustment.

I'll be aligning this bar the best I can, then positioning the bushing assembly that rides it. The cast housing with the extension that bolts to the side of the head will have some small amount of adjustability by loosing the screws, so I'm hoping I'll get things close enough that a future upgrade won't require more than a shims worth of adjustment.

Evan
05-24-2011, 09:41 PM
Most laser pointers can be focused. If you look at the business end there is usually a brass lens holder that is threaded into the barrel. Adjust that and you can bring the beam to a pinpoint at any distance. Instead of a mirror use a 90 degree prism from an old pair of binoculars. That way you won't have a double image from the front and second surface of your average mirror.

1-800miner
05-25-2011, 08:08 AM
Before you mount a bunch of mirrors on the wall do some research on how much the walls move from thermal expansion.
You may be chasing that laser all across the room!
I had to rework an old mine in 1984. The portal went in,perfectly straight for about six hundred feet.At four hundred feet there were two cross drifts,right and left,both straight as an arrow.
In the sixties Boeing had leased the place and set up a siesmograph consisting of two inch glass tubes on lead brick foundations running the length of the main drift and both cross drifts.The tubes were under vacuum and were still holding the vacuum when I dismantled it.
They were shooting a laser through the tubes,up the drift,to the right,then back to the left, then back to the portal so the laser path was 4x as long as the actual tunnel.Any shaker would throw the laser off the target.
To get to my point:They had built three twelve inch thick insulated doors spaced ten feet apart,similar to airlocks, at the entrance in order to keep the temprature constant.

darryl
05-25-2011, 09:17 PM
I think you'd find that the best way to use the laser is by making a before and after comparison- set the laser before loosing the head, then loosen the head, crank up or down, then fine adjust the head. You wouldn't actually expect the laser to stay tracked while the machine was running, or while the temperature or humidity in the room is slowly changing, the building settling, the stand drifting about the floor a bit, or from one day to the next, or next month. The entire procedure of zeroing the laser, cranking the head, and fine rotation of the head to zero again, then checking after securing the head should take no more than 30 seconds. If the laser spot isn't in the same place tomorrow as it is today- it's inconsequential.

The main thing I don't like about the laser alignment aid or the dial indicator of some kind is that you have to manually adjust the head to zero it in. Would it not be better to not have to futz with readings or eyeballing the centering of a ray of light-

Robin R
05-25-2011, 10:37 PM
The indicator method is pretty simple, and you could just use an indicator on a mag base, that way you don't have to dedicate an indicator to this use. Once you have a bar that is parallel to the column mounted on the mill, mount the indicator on the head and turn the dial round till it reads zero. Then just move the head to the new height you want and rotate it till you see the same zero reading, I don't think it could be much easier.

darryl
05-25-2011, 11:51 PM
Only thing easier is to have a guide and not need the indicator :)

RayMJr
06-01-2011, 01:36 PM
How about using a laser alignment tool that produces a line, like the Harbor Freight Item #93242. This even has magnets in the base. I stuck mine on the breaker box that is on the opposite wall from my drill press, 16ft away.

Place it on a wall opposite the mill/drill, use a plumb bob to align the laser to vertical, then mark the head and the base to match the projected line. You might want to put a mark on each side of the projected laser line, as it gets wider with longer distance.

Then when you want to move the head you would turn on the laser to verify alignment to the marks (make sure the machine is still where it should be), then move the head and re-align to the laser (both head & base).

Ray M.

J. Randall
06-01-2011, 10:32 PM
How about using a laser alignment tool that produces a line, like the Harbor Freight Item #93242. This even has magnets in the base. I stuck mine on the breaker box that is on the opposite wall from my drill press, 16ft away.

Place it on a wall opposite the mill/drill, use a plumb bob to align the laser to vertical, then mark the head and the base to match the projected line. You might want to put a mark on each side of the projected laser line, as it gets wider with longer distance.

Then when you want to move the head you would turn on the laser to verify alignment to the marks (make sure the machine is still where it should be), then move the head and re-align to the laser (both head & base).

Ray M.

Ray, Welcome to the forum, if you had read more than the first post you would have noticed the laser deal has been discussed in detail.
James

darryl
06-01-2011, 11:29 PM
Since the project is completed for now, here's a final picture. This shows the uhmw guides in place.

http://img.photobucket.com/albums/v136/heinrich/guidebarfinal.jpg

As hoped for, the head does not move sideways when cranked up and down, unless I choose to loosen the clamps and make that adjustment. There is no play detectable by eye or feel with this setup, but of course the proof will be in the pudding. Maybe sometime soon I'll be machining some pudding, and at that point I'll be checking for errors.

At this point though, it's nicer to be able to crank it without having it also spin on me. That's almost worth it right there.

The bushings are adjustable, and as I have them now, they grip the guide rod lightly so as to eliminate play, but also slide up and down with minimal friction.

A definite positive is that both ends of the rack are moved along evenly when you rotate the head. Anybody with a drill press will appreciate this improvement.

I want to re-build the arms one day and replace the rod with a known straight piece of material. The concept won't change, but the method of clamping the arms to the column will change, and the method of attaching the guide rod to the arms will change. I talked about some of these changes in an earlier post. That's it for now on this project. It works. I'm on to the flat bar bender project now.

MarkBall2
07-26-2011, 12:34 AM
Dang, I need to try this. I just got my mill mounted on the stand & got it running, so I'll need to tram it into position.

darryl
07-26-2011, 02:03 AM
Mark, this mod doesn't affect tramming as you can't alter the tilt of the head riding the column. You can alter the tilt of the column by shimming where the mounting bolts attach the column base to the machine base. The entire mod rides with the column and is completely immune to any adjustments that are made to the alignment.

I haven't done much machining on the mill lately, but the last job I did required me to raise and lower the head for a hole drilling operation. Sure was nice to have the head remain on-axis as I cranked it up and down.

I don't know if I mentioned it before, but it's also easier to crank now because you don't swing the head back and forth as your crank handle goes forward or backwards. I had a technique before where I would put force against the head to counteract the tendency to swing as the crank passed through the top of it's rotation, then through the bottom of it. It took a bit of coordination, and it was tiring. I don't miss that.

Good luck with tramming your mill, Mark.

calstar
11-11-2013, 12:47 AM
The indicator method is pretty simple, and you could just use an indicator on a mag base, that way you don't have to dedicate an indicator to this use. Once you have a bar that is parallel to the column mounted on the mill, mount the indicator on the head and turn the dial round till it reads zero. Then just move the head to the new height you want and rotate it till you see the same zero reading, I don't think it could be much easier.

Just got my first mill drill and found this thread while searching alignment. If someone has pics of the indicator method mentioned here please post them.

thanks, Brian

darryl
11-11-2013, 01:49 AM
Brian, if you just got your mill, then you would have some considerable work before you to get a parallel bar set up on it. As Robin R suggested, the indicator tip would bear against the bar, and you would crank the head up or down, then move it sideways until the reading returned to the zero. Mounting the indicator, especially with the magnetic base, would be easy to figure out at this point. Bear in mind that the method described is only to give a reference point for the position of the head as it is able to rotate around the column- useful only when you raise or lower the head to suit tooling, height of workpiece, etc- it has nothing to do with the actual alignment of the machine itself, called tram.

If you are understanding of this, then go back to my last pic and see the vertical bar that's been added parallel to the column. Any place you could mount an indicator such that the pointer can bear on the front edge of the bar will then do the job. In my mod, I've extended the crank out to a point past the edge of the bar. If you took away the uhmw collars that ride the bar, and the associated bracketry, you'd see that you could easily mount the magnetic base indicator to that crank extension housing. Your mill won't have that housing, so you'd have to mount the indicator base to the side of the head somewhere and adjust the position of the indicator so the point can rest on the front of the bar.

MarkBall2
11-11-2013, 08:20 AM
Forgot all about this thread. I used Daryl's method on my mill/drill. I aligned it square with the table, then mounted my vise & aligned it square. After that was done, everything was tightened down & it remains square if I crank the head up or down.

http://i10.photobucket.com/albums/a110/MarkBall/Projects/Enco%20Mill/Mill%20Alignment%20Brace/IMAG0224.jpg (http://s10.photobucket.com/user/MarkBall/media/Projects/Enco%20Mill/Mill%20Alignment%20Brace/IMAG0224.jpg.html)

http://i10.photobucket.com/albums/a110/MarkBall/Projects/Enco%20Mill/Mill%20Alignment%20Brace/IMAG0223.jpg (http://s10.photobucket.com/user/MarkBall/media/Projects/Enco%20Mill/Mill%20Alignment%20Brace/IMAG0223.jpg.html)

Dieseldoctor
12-17-2013, 06:55 AM
Since I just obtained a round column mill (see "help identifying a mill drill") this thread caught my eye. Darryl and Markball, you guys did a nice job on your modification. Everybody has their own way of doing a job so I will give you my thoughts on what I would have done with your design. Instead of the two bushings and bracket that is fastened to the crank extension box I would have obtained two ball bearings (something like blade guide rollers from a band saw). One bearing would be rigidly mounted to the back side of the crank extension box so it would run up and down the front center of the auxiliary column. Then I would mount a bracket 90 degrees to the back side of the crank extension box and about 1/2" to the inside of the auxiliary column. This bracket would extend back past the column. To the end of that bracket I would hinge a bar coming across the back of the column. I would mount another bearing to this bar so it would ride the center of the back side of the column. To the outboard end of this bar I would hook a pretty strong tension spring and hook the other end of the spring back to the crank extension box. If I do my mill, for the column I will use a 3/4" X 2" or 3" inch flat bar with one 3/4" side surfaced straight. Bearings will ride on the two 3/4" sides. If I can keep the head within .001" I will be proud.

dian
12-17-2013, 02:43 PM
so how many bearings?

sasquatch
12-17-2013, 05:03 PM
Nice work guys, some creative thinking there.

darryl
12-17-2013, 10:24 PM
Diesel, I like your idea. That gives a way to take out all play without adding friction to the up/down motion. You would want to add something to keep swarf out of it though, otherwise the bearings will want to roll over it.

I've been using the mill with this attachment on it for more than two years now and have had no problems with it. There was one time where the loss of the bottom 5/8 inch of head travel came to light- the cutter I wanted to use probably extended no more than about an inch below the bottom of the quill, and the flat workpiece was mounted directly to the table surface. It was a few moments before I realized that I could just lower the quill-

PeteM
12-22-2013, 08:38 PM
I'd suggest that putting a DRO on the mill and having an easily located datum point is most likely to get accurate results. With a decent indicator, a "chair" for corners, and maybe a centering scope it's pretty quick to get back within .001".

There are probably few import mills, round or square column, whose columns and spindles will repeat to .001" at any point on the x-y table when cranked from low position to high position right out of the box. The columns (typically, say, 4" diameter equivalent) themselves deflect under load -- and one can expect greater deflection when a much smaller bar is attached as a reference line. Getting both the column and that bar perfectly perpendicular to the table (which itself may sag .003 or so over its travel) is another challenge. Do all that -- and get that extra indicating bar tightly constrained -- and the cranking effort also goes up (leading to deflection if everything isn't perfectly aligned).

Point being that the laser method is probably good to blacksmith's tolerances of .01 or so and actually indicating the part might be best to do .001 or better. If one can adjust a head to an indicator, why not just adjust the table to re-find a parts' reference point in about the same time.

Dieseldoctor
12-29-2013, 10:32 PM
Been working on my mill, cleaning, adjusting, mounting motor, making broken parts etc.. Also been thinking about the round column. Darryl, why do the bushings that follow your secondary column need to be so tight. My thought is, if the head is rotated clockwise so that the side of the crank extension is hitting the secondary column when you start moving the head, and is rotated clockwise till it hits the secondary column when you stop moving it, isn't that all it needs? Does it really matter if it wanders off a little during the trip as long as it winds up in the same plane when it stops? I'm thinking that when I get far enough along to do something along these lines that I will drill and tap the base right below the column and put a clamp there to secure the bottom of the rack. Then take the head to the top and dial it into the same plane and make a clamp to secure the top of the rack. Thereafter, any time I park the head will just make sure the head is pulled clockwise against the rack. Accuracy should be as good as the rack is straight. I do hobby work and one or two thousands is good for me.
I got a new 2 HP motor mounted but my step pulley is probably not the right steps. I did a little milling on mild steel with a 3/8' roughing mill at about 800 RPM making a slot (full width) taking a .100 DOC. Is that about right or was I pushing it too hard? It sounded good and took very little torque to feed the "Y". Could I go with a deeper DOC?
Also when I got the mill it had a end mill holder in the spindle. It was hard to drive out all the way. I used penetrating oil sprayed up in the spindle and tried a wire brush up in the bore thinking maybe it was rusty. Still I have to use the drawbar to pull the collets all the way in and drive it all the way back out. Looking at the collet I can tell it is the top part that is tight. I took a 6 inch piece of 3/8" steel cable, taped it tight about 2 inches from one end, frayed it out bigger than the bore on the top end, chucked it in a drill and ran it up the bore for a long time. Didn't help. Is the bore supposed to be tight like that? The collets slide right in my mini-mill until the taper starts hitting. Is it too loose? Thanks in advance!

MarkBall2
12-29-2013, 11:35 PM
There are many different ways to keep the head aligned with the table, this was the easiest & least expensive for me to do.

I originally built the aluminum brackets then bored the holes for the alignment bar. The bronze bushings were to allow the crank extension to slide easier...... a bit of grease, wind it up/down a few times & it slides quite easily now. The reason the flat bar extends back to the alignment bar was to provide a bit of room for an overhanging item to be milled. I wanted the alignment bar out of the way, rigid enough so it wouldn't lose it's place yet easy enough to move the head up/down. For me it works best this way.

I think your DOC is fine & 800-900 rpm should be ok. Your collets should slide in most of the way with little resistance (I'm assuming an R-8 spindle) & tighten with the drawbar. I haven't had any endmills come loose & they spin accurately. Maybe try a brake wheel cylinder hone in the bore? Just make sure to clean it very well after you do this. You might use some layout dye on the collet to see where it's tight also. That might be better to help identify where the problem is.

Canuck75
01-08-2014, 04:37 PM
Since the project is completed for now, here's a final picture. This shows the uhmw guides in place.

http://img.photobucket.com/albums/v136/heinrich/guidebarfinal.jpg

As hoped for, the head does not move sideways when cranked up and down, unless I choose to loosen the clamps and make that adjustment. There is no play detectable by eye or feel with this setup, but of course the proof will be in the pudding. Maybe sometime soon I'll be machining some pudding, and at that point I'll be checking for errors.

At this point though, it's nicer to be able to crank it without having it also spin on me. That's almost worth it right there.

The bushings are adjustable, and as I have them now, they grip the guide rod lightly so as to eliminate play, but also slide up and down with minimal friction.

A definite positive is that both ends of the rack are moved along evenly when you rotate the head. Anybody with a drill press will appreciate this improvement.

I want to re-build the arms one day and replace the rod with a known straight piece of material. The concept won't change, but the method of clamping the arms to the column will change, and the method of attaching the guide rod to the arms will change. I talked about some of these changes in an earlier post. That's it for now on this project. It works. I'm on to the flat bar bender project now.



Darryl.

I wish I had been a member and seen this article before I went my own way.

In any case, I used the "pinning the rack to the column with guide blocks bolted to the head" solution. It works for me. With the head at the bottom and locked I edge found a 1-2-3 block and set all axis on my DRO to zero and moved the table a bit out of the way. After raising and locking the head 5.5", lowering and locking the quill 5.5", I brought the table back to see what the readings would be - .001" on both X and Y. Moved the table away again, returned the quill, lowered the head, locked everything and brought the table back and realized .001" readings on X and Y again. I can retain my X and coincidentally it proved that the column is accurately trammed. This wouldn't work if the column was not accurately trammed.

Did you do a before and after raising the head check and what accuracy results did you get?

I also found all the other contributors ideas and comments very interesting. My system works for me. I will try and post some pictures if anyone is interested.

Canuck75
01-08-2014, 05:36 PM
What about a bar that's parallel to the column in both directions, attached to the mill base in a fairly rigid way. Then mount an idicator to the head, so it can bare on the bar in a position that's easy to see. Set the indicator to zero when it bears against the bar, then move the head up or down to the new height you want. You can then rotate it around the column, till you get the same zero reading on the indicator and things should be perfectly aligned at the new height. The big advantage over a guide that holds the head rigidly in alignment, is that you can't over power the guide.

The big problem is getting the indicator to read zero as you re-clamp the head again. You have to fiddle. I've tried this idea. Sorry

darryl
01-08-2014, 06:48 PM
The extent of my testing has been to raise or lower the head to suit the tooling, then check to see whether they are in the same axis. My most usual operation is drilling a pilot hole, then enlarging that to eventually be able to bore. The head would often have to drop for the boring operation, as the length of the drill bits, the chuck, and the arbor would normally be longer than the boring bar holder. At any rate, the test is to see how offset the boring cutter is when it enters the hole. I'm sure it stays within a thou, but then I'm not usually moving the head more than a few inches.

Two things would be vital- the guide bar needs to be parallel to the column, and the guide bushings need to maintain a rigid position with respect to the head. In my picture you can see the bracing I used to help with this. It was not trivial to achieve the alignment of the bar to the column, but once that was done, the rest of the mechanicals were aligned to the bar.

The upper and lower guide bar mounts were machined as a pair, so that ensures the bar is parallel in spacing from the column. More problematic was getting the bar in the same plane. I actually used a piece of granite to help with this. I checked it on the surface plate to see if it was flat, then held it against the column and clamped it there. The guide bar was then clamped to it as well, and then the bar mounts secured to the column. I figured that once the bar was secured in alignment, then the guide bushing assembly aligned to it, I could loosen the guide bar mounts on the column if I needed to rotate the head. So far it seems to have worked out. You see that my guide bushings are fairly far apart, which helps keep the bar aligned if I loosen things up to rotate the head.

I do have problems with the idea of mounting the guide bar to the base of the mill. If that's done, any flexing in the base or column, or tramming adjustments would affect the parallelism of the bar and column. Personally I would not do it that way- the column is what the guide needs to be parallel to, and when you tram, the guide bar should move exactly with the column. It should be mounted to the column, as I've done.

As far as overpowering the guide bar- yes that's certainly possible, but I don't think it's an issue. By the time you have the head raised or lowered, and you go to re-clamp it to the column, I think any flexing you might have done to the guide bar has relaxed. I used a 1 inch solid bar, which I selected from a longer piece to be straight- tested by rolling it across a surface plate. Nothing stops you from using a larger diameter bar if you feel the need to, and it probably would be best to purchase it by spec- round and straight. In fact I would suggest that you select it for those properties. It will cost more, but not much considering it's relatively short. I plan to replace my bar at some point with a closer tolerance one.

Canuck75
01-09-2014, 12:32 PM
Darryl

First of all I think you have done a great job on this mod. I understand how it works but not sure how you achieved the necessary accuracy on the Y plane to align the guide bar with the column axis. Additionally, when released to rotate the head for whatever reason, what kind of accuracy do you get when the head is repositioned and guide arms re-clamped?

I went through a lot of "what ifs" before I started my project and established a couple of parameters. First: On such a small mill it is unlikely that one would be doing work that needed one to rotate the head either out of the way or to reach far corners of a work piece; second, if you do rotate the head you relatively loose some of your Y travel range not having a "ram" to compensate - sort of a self defeating move. Even in a commercial machine shop I seldom had to rotate the head and always needed to use the "ram" to offset the change in Y reach. Having accepted this, it made the bolting the "rack to the column with associated guides" as an acceptable solution.

Dieseldoctor
01-11-2014, 08:23 PM
Canuck, I would be interested in seeing pictures of how you clamped your rack and the guide blocks you use. I still don't see why guide blocks are really needed. If a certain point on the head is touching the rack or aux guide bar when you start to move the head and is touching when you stop moving the head what difference does it make if it wanders a few or even several thousands on the way up or down. If the rack or aux guide bar is in an accurate plane then everything should be good. So far I haven't had a problem but if it becomes one, I will start with clamping the rack in an accurate plane and just make sure that before I lock the head in the new position that I take the "slack" out in a clockwise rotation.

mike4
01-11-2014, 08:38 PM
Having read this thread with some interest as I would like to modify one of my drills to where it is possible to move the table up or down without it moving sideways , as I often have to drill a pilot hole , drill to size, countersink or cut out for bolt head , several times on a piece.
I was thinking of two collars , one at the top and the other at the bottom of the column , with a rack between them , the rack being fairly heavy (twice normal thickness) , so that the table can be positioned for the job and locked anywhere around the column ,so that it can only move up or down .
Michael

darryl
01-12-2014, 05:20 AM
Mike, it sounds like you want to do the same thing with your drill press that we have done with these mills. I'm assuming that your idea for the twice normal thickness rack is as a guide and a means of raising and lowering the table- I know some drill presses don't have a rack, and you just loosen the clamp and manually slide the table up and down. Maybe I'm wrong here- maybe you do have a rack to raise and lower the table, but it's a sloppy fit and is too flexible anyway to use as a guide bar.

Need more info-

Somewhere up in this thread, or maybe a different one, someone suggested using a solidly mounted ball bearing running against the guide, with a spring-loaded ball bearing opposite that to force the play out of it. I do like that idea, and I think it could result in a fairly compact mechanism which could be well-suited to a drill press. The guide could remain fairly close to the column, as long as it's outside of the tables hub, the part that rides up and down the column.

I'm just thinking now- I bet there's a way to make the guide fixed to the column such that it is never free to revolve around it. From the guide to the tables hub would be a piece that surrounds the column and has the hub within it. It might be slotted top and bottom, where bolts would pass through into holes that you drill and tap into the tables hub. Loosen those bolts and the table can swing left and right. With the bolts tight, the table can only move up and down.

Hmm- there's going to be some interaction with the clamp that secures the table to the column, but I bet that can be overcome. I'm going to think on this- I could use it on my drill press as well.

darryl
01-12-2014, 07:11 PM
I went down and had a look at my dp today. Because I never angle the table, I have the option to mount a 'control bar' that would surround the column, extend rearwards to ride a guide bar, and extend forwards as well to surround the bushing where the table stem inserts. Think of this piece as being a connecting rod, but with two small ends. The big end fits around the column.

Arranged like this, the forward small end controls the position of the table in rotation around the column, while the rear end is guided by a bar. Little is needed to fasten this piece to the tables mount that rides the column.

This piece, plus the two that would hold the guide bar (one upper, one lower) could be machined together, so they would operate smoothly once assembled. The upper and lower pieces would be the collars, and would accommodate the rack. This would be good for the rack as well, since it no longer would have to skid around in a retaining collar such as it does normally. You would use the same fastening method for the collars as you would for the control piece, so nothing there throws anything off. On my dp, there is lots of room for thickness on the collar pieces, so in theory they could control the alignment of the guide bar quite well anytime you loosen things up to rotate the table about the column. The guide bar need only be far enough from the column that it clears the clamping area on the tables mount, which would act to further restrain the guide bar from becoming out-of-parallel with the column. On a dp, I think the alignment obtainable like this would be plenty good enough. It looks like a quite straightforward project to enhance the workings of the dp. I think I'm going to do it-

Canuck75
01-17-2014, 12:45 PM
Canuck, I would be interested in seeing pictures of how you clamped your rack and the guide blocks you use. I still don't see why guide blocks are really needed. If a certain point on the head is touching the rack or aux guide bar when you start to move the head and is touching when you stop moving the head what difference does it make if it wanders a few or even several thousands on the way up or down. If the rack or aux guide bar is in an accurate plane then everything should be good. So far I haven't had a problem but if it becomes one, I will start with clamping the rack in an accurate plane and just make sure that before I lock the head in the new position that I take the "slack" out in a clockwise rotation.


Dieseldoctor

Not being very computer literate I had too much difficulty posting pictures on this forum. I checked out "The Hobby-Machinist" in which I found it easy to post pictures (no disrespect intended here) and have posted threads with pictures there.

The rack was roll pinned and bolted to the column to .000" accuracy along its length. With respect to the need for guide blocks, there is a wide gap in the head casting for the geared rack and therefore useless to keep the X when moving the head. The guide blocks are fitted to the rack and therefore are able to do this.

Sorry about the tardy reply.

Motorman1946
03-17-2015, 02:56 PM
I went down and had a look at my dp today. Because I never angle the table, I have the option to mount a 'control bar' that would surround the column, extend rearwards to ride a guide bar, and extend forwards as well to surround the bushing where the table stem inserts. Think of this piece as being a connecting rod, but with two small ends. The big end fits around the column.

Arranged like this, the forward small end controls the position of the table in rotation around the column, while the rear end is guided by a bar. Little is needed to fasten this piece to the tables mount that rides the column.

This piece, plus the two that would hold the guide bar (one upper, one lower) could be machined together, so they would operate smoothly once assembled. The upper and lower pieces would be the collars, and would accommodate the rack. This would be good for the rack as well, since it no longer would have to skid around in a retaining collar such as it does normally. You would use the same fastening method for the collars as you would for the control piece, so nothing there throws anything off. On my dp, there is lots of room for thickness on the collar pieces, so in theory they could control the alignment of the guide bar quite well anytime you loosen things up to rotate the table about the column. The guide bar need only be far enough from the column that it clears the clamping area on the tables mount, which would act to further restrain the guide bar from becoming out-of-parallel with the column. On a dp, I think the alignment obtainable like this would be plenty good enough. It looks like a quite straightforward project to enhance the workings of the dp. I think I'm going to do it-

Hi All - this is my first post on here, hope I'm doing it right, couldn't find a button to just post a reply, it had to be "reply with quote"?

Anyway, I have a round column mill/drill and was thinking exactly along these lines of maintaining alignment. But, I was thinking of just locating the guide bar at the bottom and have two guide bearings fixed onto the head, and was wondering about possible sideways movement of the guide bar when racking the head up and down. Now I think I might just have a guide bar support on the top as well, reading all this. However, I did want to ask a question, was thinking of a ¾inch diameter guide bar of precision ground MS - does the team think that diameter is big enough?

Chris

MarkBall2
03-17-2015, 03:15 PM
3/4" O-1 drill rod is what I used. I would think 3/4" would work.

Paul Alciatore
03-17-2015, 03:59 PM
I see this thread has floated up again.

I have used round column mills and fought their inherent problems. I often wondered just how effective these alignment bars are. Has anybody ever measured the repeatability of the spindle position when using them? I mean actual numbers like +/- 0.003". I can't imagine it would be much better than that.

If I were doing this, I think I would use a laser and a mirror to bring the beam back to a target on the mill. Simpler, easier and probably cheaper and more accurate.

jcurrell
03-17-2015, 05:03 PM
I see this thread has floated up again.

I have used round column mills and fought their inherent problems. I often wondered just how effective these alignment bars are. Has anybody ever measured the repeatability of the spindle position when using them? I mean actual numbers like +/- 0.003". I can't imagine it would be much better than that.

If I were doing this, I think I would use a laser and a mirror to bring the beam back to a target on the mill. Simpler, easier and probably cheaper and more accurate.

I got around the problem by taking the coulomb off, set it up on another big mill so it is parallel with the travel and with the two mounting holes vertically in line putting the top where the rack would normally be, then machined a 1/8 " deep slot so it was bite on a 3/4" crs key. bolted in with 1/4 flat head screws. The crank block was replace with a block fitting around the key with brass strips on both sides set screws from the out side go in one side to two pins with 45 degree angle on the to be a gibb. Then a Prinsess Auto implement jack with 90 degree head is mounted to the block down to a bracket to raise and lower the head.

PStechPaul
03-17-2015, 08:02 PM
I think I posted in a similar thread that I plan to drill holes through the bottom support for the column, and the head, so that I can install some large set screws, probably with conical or bull-nose points, and make mating holes in the column at maybe 1" intervals. Then I should be able to get fairly consistent position at most heights and it should help with rigidity. As it is now I have to use an extension bar on the clamp handles to make it tight enough not to turn when milling.

It would also be good to rig up a counterweight to make it easier to raise the head. Or maybe a large sprocket and chain drive on the crank to motorize it. Then again, the exercise is good for me! :rolleyes:

darryl
03-18-2015, 01:51 AM
A 3/4 inch bar should be ok, though you could do some math and see that a 1 inch bar is very much more rigid. One of the keys to maintaining alignment is to have the guide bushings that ride the bar far enough apart and rigidly fixed in position with regard to the mill head.

Maintainable accuracy is pretty good with my setup. I'd be choked if I couldn't stay within 3 thou of axis when moving the head up and down. I'm pretty sure I'm keeping within about 1 thou- remember also that I don't usually need to move the head up or down more than about 3 inches or so to accommodate a tooling change.

There are two control arms holding the guide bar, and while they do contribute to keeping the guide bar in the same plane as the column, the uhmw bushings do this to a much greater extent. What's important here is that these bushings can't flex from their positions relative to the head. The axis through the bushings stays parallel to the column and planar with it because of the rigid mounting and bracing- and this is what keeps the guide bar aligned. You can loosen the top and bottom guide bar clamps where they tighten around the column, then reposition the head, then re-tighten the clamps- and you don't lose the positioning integrity of the guide bar. It's almost completely a function of the bushings and their positional accuracy with regards to the axis of the head.

The spindle axis parallelism accuracy is another thing, but there's no way to change things if that doesn't match the head axis accuracy. Luckily enough- or by reasonably careful manufacturing accuracy- these two axis match well enough that the machine is useable. If this weren't the case, the machine would be almost totally useless.

All of this has nothing to do with tram, and the tram adjustment process doesn't affect the accuracy of the guide bar relative to the column, nor the potential for the spindle axis to go off when the head is raised or lowered.

If I did anything over again with this project, it would be to use solid material for the quide bar control arms instead of building them up from multiple pieces. I've had no problem with it as is, but general wisdom would suggest that solid is better.

Keep in mind that if you duplicate something like this, the bottom control arm thickness does subtract from the degree of head travel possible. Even though in this case the arm is only about 3/4 inch thick, this limitation has bitten me once or twice-

Motorman1946
03-19-2015, 07:33 PM
Thanks for the replies. I reckon a ¾" bar would do OK too, was testing the mill today and there was very little effort required to turn the head whilst racking it up or down.

Tried a laser on the mill option today. Having spent best part of an hour resoldering wires to the laser bit out of an old level and changing batteries and cleaning it all up ended up binning it and immediately found I had another laser that actually worked. It gave out a laser line instead of a laser dot, but I laid it horizontally on top of the quill pulley wheels which gave a vertical line, copied the line with a vertical pencil line on the wall opposite, then tried racking the mill head up and down. Had a load of faffing about to get the head to give the laser line exactly back on the pencil line, it wanted to keep shooting past the mark, but disappointed with the result. Not only did it seem too much messing about - the guide bar arrangement I can see will be a largely "fit and forget" device - but it did not give me an accurate re-alignment, was about 3 thou out in both the X and Y axis. Was that due to the method or due to inaccuracies in the column/tram set-up. No time to sort it today, and now very little time for the next month also as other commitments are pending, so that's something else to think about. One thing though, I put a digital angle gauge on the top of the column and it did not budge when racking the head up and down, even though it did show an error of 0.3 degrees compared to the table. Why is nothing ever easy or straightforward?

Chris

darryl
03-20-2015, 12:59 AM
'fit and forget'- that's pretty much what the guide bar is. I played with the laser thing a bit, but didn't persue it much because I knew that it still meant fiddling with the head to get an alignment.

By the way, I'm still going to recommend a 1 inch bar over a 3/4 inch one for the guide bar because it is going to be able to control the head better, resisting the twisting effect from cranking the head up and down to a better degree. You also have to resist the effect of clamping the head tight, which will tend to rotate the head a bit as you tighten it to the column.

tbsmith
05-02-2016, 03:08 PM
Resurrecting an older thread, here's my approach to the head alignment problem. I used a guide bar similar to what others have used, but I only attached it to the column near the base. That's because I had some 1" thick aluminum and I didn't want to cut the belt guard to accommodate an upper bracket. Prior to that I used a laser, and bounced it off a first-surface mirror back to the mill. Here are some pics:
http://i483.photobucket.com/albums/rr193/lapsmith/IMG_3752_zpszvvgykgl.jpg

http://i483.photobucket.com/albums/rr193/lapsmith/IMG_3753_zpsht59pw1y.jpg

http://i483.photobucket.com/albums/rr193/lapsmith/IMG_3755_zpscqbbij88.jpg

http://i483.photobucket.com/albums/rr193/lapsmith/IMG_3760_zpsbjomemgi.jpg

I also installed a motor to drive the head up and down, as shown in the pictures (with chain guard removed).

As someone else mentioned, keeping the alignment bar parallel to the column is critical. At first I thought the 1" aluminum plate would be good enough to hold it, since I machined both holes in the same setup, so I know they were parallel. But there was about .017" of misalignment from top to bottom depending on how I torqued the collar bolts. So I added the auxiliary support that is attached to the mill base and allows me to tweak the alignment using the two mounting bolts.

The arm that is mounted to the head has a bronze bushing mounted in a sub plate (to allow for adjustment). The vertical guide bar is 1" diameter TGP (turned ground polished)

For an alignment check, I used a short .625" bar in a collet and indicated it from the table. Then I raised the head and inserted a long bar, and indicated that. They were within .0015" so I am happy. When indicating the rods, I rotated them and took the average reading to account for any bends in the material. I'm not sure if this is the best way to measure this, so if there is a better way , let me know.

The laser setup can be seen in one of the photos and I used it to help confirm the alignment. The mirror is mounted about 15 feet from the mill. You can see the laser dot on the white scale attached to the belt guard, I estimated each line to be about .001"

mars-red
05-02-2016, 03:19 PM
Well it seems I'm not allowed to add pictures.

You have to host them off-site somewhere, and hot-link to them. I use google photos, lots of folks here use photobucket. There are others out there too. One of the "sticky" threads here is how to post photos, that's worth checking out.

MrSleepy
05-02-2016, 04:41 PM
And its not too difficult to host them here if you know the process.

Paul Alciatore
05-02-2016, 04:45 PM
I assure you that you are allowed to post photos. But they must be on a hosting site on the web, not just on your own hard drive.

Read the sticky thread on posting photos. Read all the way to the bottom as more up to date and simpler instructions have been added since that thread was first posted. It is easy.

http://bbs.homeshopmachinist.net/threads/62262-Posting-Photos

Mike Amick
05-02-2016, 08:20 PM
Welcome to the site tbsmith.

I'm betting there are a lot of guys with mill/drills that would really like to see your
approach.

So don't fret about how to post the pics ... just figure it out and get them posted.

KenShmid
05-03-2016, 02:00 AM
Some good photos and information can also be found in this thread:

Rong Fu Mill/Drill Column Stabilization. (http://www.hobby-machinist.com/threads/tips-for-owners-of-rong-fu-rf-20-rf-25-rf-30-rf-31-mill-drills.38796/#post-376579)

old mart
05-03-2016, 10:20 AM
I have tried the laser method, but it has its limitations. My laser is a cheap gunsight, the focus is not great, with white card for the target, the spot is fuzzy, I found the spot was better on black card due to reduced halation.

Another possibility might be replacing the lifting rack by a larger ground bar screwed at intervals to the column and having the lifting screw at the back of the mill.

mayfieldtm
05-03-2016, 03:06 PM
The guide bar method is far superior to any Laser setup.
Setting up and maintaining for any reasonable accuracy is just too messy.
A building grows and shrinks considerably over a course of a day. (that Thermal problem someone mentioned)
Great idea that works poorly.

I sold my mill so I can't take photos.
I used a Guide bar that was mounted on the bottom end only and supported by 8 oversized screws that made it adjustable.
I used a permanently mounted Indicator that could be moved into position against the bar to reset the position after moving the head.
The indicator offers a very low load against the bar, thus, the whole setup was light weight and did not need to be heavy duty.
I used the setup for years without having to realign the guide bar.

Tom M.

tbsmith
05-03-2016, 03:55 PM
Thanks for all the tips on how to upload pictures. They are now there in my original post.

Tom S