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darryl
01-30-2010, 10:16 PM
Just wanted to run this past you all. I found the steady rest I had made some years ago. I don't like it now- it's corroded and hard to adjust, besides which it doesn't line up all that well behind the cutter. That depends on the tool holder geometry, but in any event, I'm going to make a more suitable one. Here's a sketch of what I had in mind.
http://www.glacern.net/free_photo_upload/steady%20rest%20idea.JPG

Two ball bearings mount on a fork which slides in a groove. The fork is clamped in position wherever it works. The vertical plate is attached to a bridge which mounts to the carriage, and clears the crosslide. The plate can be positioned anywhere on the bridge that lines it up where it's wanted. The ball bearings can be mounted in any of about four holes each. I've shown only one extra hole for the sake of clarity. When set in suitable holes, the slide can be adjusted so both bearings come to bear on the workpiece at the same time. The groove is set at 45 degrees and is centered on the spindle axis. The fork is likewise marked and drilled to place the bearings in precise spots such that the only adjustment required is to slide the fork till both bearings touch, which they should simultaneously. Each position of the bearings would accomodate a range of workpiece diameters, with the idea being that it's not critical that they touch only at the exact side and top of the workpiece.

I think that by making the groove at precisely 45 and aimed directly centered with the spindle axis, plus careful layout of the bearing locations, I can avoid having to make individual bearing placement adjustments when the workpiece diameter changes.

Comments, ideas-

Carld
01-30-2010, 11:41 PM
That is called a follower rest. A steady rest has three fingers and wraps around the work.

The follower rest in the photo mounts on the carriage and runs behind the cutter or leading it. The two rollers need to be independent of each other so they can be adjusted for small to large diameter work.

I missed the extra holes for the rollers and that may work but the long arms may get in the way of the work. You also need more clearance under the bottom roller for bigger work.

winchman
01-31-2010, 12:19 AM
I've never seen a follower rest with both bearings mounted on one slide. There's probably a good reason for that.

Rotating bearings will cause problems when chips are caught between the outer race and the work. They will deflect the work and ruin the surface, get stuck in the finished surface, or cause loads high enough to push the follower rest out of position. Brass inserts are much more forgiving on all counts.

Google "follower rest" and look at the images for some better ideas.

I wouldn't worry too much about accomodating large work. You won't need a follower for that, unless it's very long or very flexible.

dp
01-31-2010, 12:24 AM
I wonder if an adaption of a knurler might be a reasonable tool - in particular, a scissors type tool with smooth rollers, of course.

darryl
01-31-2010, 12:34 AM
Oh, sorry- I mistyped. I meant follower rest, not steady rest. I did realize a while ago that mounting the bearings in farther would leave a finger sticking out- as I was just in the shop measuring things out, it seems they will get in the way, and if I accomodate that, it will severely limit the diameter of workpiece I could use it for.

I've just been tinkering with another layout- same plate with angled slot idea, but with the bearings on arms which pivot, and are locked to each other with gear teeth. (there's the scissor idea). Playing with some parts on the bench, it looks like I can accomodate a 6 inch diameter workpiece, and go down to less than 1/4 inch diameter, while only having to move the slide about an inch to match that range. If I don't move the slide at all (or don't have it at all) it can handle a 4 inch diameter workpiece and go down to about 1 1/2 inch. (mistyped again, edited dimension) While doing this, the contact points vary from top and side somewhat. I'm not sure that's going to work, but it would be nice if I didn't have to use a slide mechanism at all.

That idea is intriguing- I'll have to lay it out in cardboard to see how well it might work. The diameter of the bearings is very important- seems that 3/4 inch would work just about right. On the subject of bearings, yes I have felt that it's not ideal because of the chip jamming factor.

Yes, I do realize that the plate has to clear the workpiece- my drawing could have but didn't show that. I'm off to get a sandwich now and think about this some more.

darryl
01-31-2010, 03:28 AM
Well, the tuna sandwich worked! I got some other ideas. I laid it out using some gears I had that I'll use to sync the bearing arms together with. Using available materials I can build it to get a 3 1/2 inch diameter capacity, and I can use brass discs or blocks in place of the ball bearings if I want to. If there's a lot of one diameter that I would need to do for some project, I can always mount a cutter in the chuck and bore the two blocks in place for the exact diameter of the workpiece. I will be using a groove to guide the sliding bearing holder- it appears that's the only way I'm going to get a good geometry between the bearings and the workpiece, especially to include diameters down to 1/8 inch or so. If I use brass blocks instead of ball bearings, I can fully surround a 1/16 inch wire if I wanted to.

I'll start by building the mounting base to fit the carriage, then work out the fastening of the upright to the base. After that, I'll put a center drill in the chuck, then run the carriage up to it to get a mark for spindle axis. With that as a guide, I'll mill the groove for the sliding part, then mark the spindle axis on the sliding part with it in place. Locating the bearing stud centers will also be done using the center drill in the chuck, and mirror image symmetry will be used to get both bearing arms drilled exactly the same.

There will likely be a small error when swinging the arms against a workpiece. One bearing will touch and the other will have a small gap, most likely. I can accommodate that by moving the mounting base fore or aft by some small amount. I could either drill for a locating pin at this point, or just use it like that.

Sound like a plan?

Carld
01-31-2010, 09:18 AM
I like the concept of the follower rest your building. Last night after shutting the 'puter off I was thinking about it and thought if there is some way to pivot the bearing holder on the sliding finger you may have a good tool. Today you posted just such an idea.

Having the bearings open and close and pivot as well may be a great idea and as said by another, you don't really need a follower rest on large work but it never hurts to be able to go to 5-6".

Post your tool as it progresses, I may like to copy it;) :D .

philbur
01-31-2010, 09:32 AM
Having the relative positions of both fingers fingers fixed will require you to make it to a much higher degree of precision than two separatdely adjustable fingers.

Phil:)

loose nut
01-31-2010, 09:56 AM
. The two rollers need to be independent of each other so they can be adjusted for small to large diameter work.


Carl is right.

With both rollers on the same mount there will always be a diam. that is to big or to small to fit this devise, maybe OK for in between sizes. The roller will also limit the smaller size diameter's that can be held against them as opposed to small bronze bearing surface's.

digr
01-31-2010, 09:59 AM
I think you have something there, how about something like this coming in straight from the back, You wouldn't use it for large dia. work anyway.

http://i961.photobucket.com/albums/ae96/digr/rest.jpg

Carld
01-31-2010, 11:56 AM
The job of the follower rest is to keep the work from rising from the force of the cut. For that reason one roller has to be on top of the shaft. Where the rear one is located can vary as long as it keeps the work from going to the rear.

The modification darryl described in an above post may be the solution as it will allow adjustment of where the rollers touch the work. Whether it proves better than the style currently used will be seen when he makes one to test.

digr
01-31-2010, 01:51 PM
The job of the follower rest is to keep the work from rising from the force of the cut. For that reason one roller has to be on top of the shaft. Where the rear one is located can vary as long as it keeps the work from going to the rear.

The modification darryl described in an above post may be the solution as it will allow adjustment of where the rollers touch the work. Whether it proves better than the style currently used will be seen when he makes one to test.
As in my drawing I don't beleave the shaft can move up down or towards the rear IMO

radkins
01-31-2010, 02:47 PM
First let me point out that I am an amateur and maybe that is why I tried what I did. I thought the brass points on my followers were kind of crude and wondered why they, and others I had seen, were not bearings instead of the brass rubbing on the surface, just cheaper to build that way I reasoned. Simple enough to remedy so I ordered some small roller bearings from Enco and made up a set of 3 "fingers" (don't know what to call them, I told you I am an amateur :( ) for my steady rest using the bearings on the tips. What I soon discovered was exactly what was mentioned a couple of posts back and that is the problem of chips getting under the bearings and causing problems. I did this on my steady rest and intended to do the same to the follower rest but decided against it, I can see where it might cause more problems there than on the steady. Just thought this might be of interest but I guess it is entirely possible I did something wrong like maybe the bearings were too big, I have since tossed them aside and replaced the brass pieces which don't seem to be a problem anyway.

darryl
01-31-2010, 06:49 PM
I'm thinking to install a wiper which would come up from the bottom and spring load against the workpiece to help the bearings out. I can see it being likely that I'll scrap the bearing idea and just use blocks. This can all be after-the-fact changes and won't affect the way the mechanism works.

I just spend the afternoon so far trying to come up with a mount arrangement to hold the bridge plate above and parallel to the crosslide. The carriage has enough flat spots in somewhat suitable areas to bolt things to, but I have to clear the gib screws and the way wiper area on one side. So far that is the most complex piece of the base, and it's now pretty much done. After I mark the locations for mounting holes, I'll prop up the apron and remove the carriage to drill and tap the holes. It's work, but it's time again anyway to clean and inspect the 'guts'.

The last time I removed the carriage, I wanted to install a way oiling system, but I didn't do it then. If I can prepare for it by drilling and tapping some holes, maybe I'll get that done this time.

Once again, I've nearly lost track of the the little project that started me on this follower rest, and now there's another 'little' project mixed in with it all :)

Must be coffee time. Yep!

Carld
01-31-2010, 07:39 PM
digr, the top roller needs to be on the top of the shaft or very near it. On the small shaft you show it may work but on the larger shaft the force of the cut will push the shaft back and the top roller may tend to force the shaft back forward again and set up an oscillation or vibration in the cut. You need a roller to stop the shaft from lifting and a roller behind to keep the work a set distance from the cutter.

Black_Moons
01-31-2010, 07:39 PM
I think one of the big advantage of the standard systems is the adjustable bar is allways directly on the axis of the force its trying to stop. ie its trying to compress it not bend it.
Also if the rollers/wipers/whatever can only stop force on the axis they are in, if you have two rollers close togethor on one side (digr's picture), yea any force directly beween them is handled nicely (force of the cutter pushing into the work), but force up/down (force from the cutter cutting the work) will be translated into a force back into the cutter, deflecting the work into the cutter further as it deflects up.

Anyone who has ever faced a little too hard on the end of a long part knows that having your work roll up onto the top of the cutter IS possable, and really ruins your day (Yes, Metal will bend that much when abused, so will plastics, No, it won't return to its origional shape afterwards, leaving you with a bent hunk of metal whiping around in your lathe, hopefuly not hiting anything too important.)

darryl
01-31-2010, 11:11 PM
Interesting. I've had work come forward on me when I was using the other follower rest. One bearing was on top, and one directly back, as these things are pretty much always made. I think I was facing at the time, come to think of it.

This lends some weight to the idea of having the top bearing somewhat forward, which with this setup will place the rear bearing a bit lower. The bearings will be further apart in this case, but not so much so that the workpiece could squeeze between them. There might actually be a benefit to doing this. I've considered steepening the angle of the slide, which would put the top bearing somewhat past top center, but that would also raise the rear bearing, which I don't think is a good idea.

In a steady rest, the third arm takes care of all this. This mechanism will allow me to place the bearings where I want, as well as having both of them touch at the same time. There will be some experimenting once this is together. Pictures too.

The rest of yesterdays tuna sandwich is going in my face right now, so after that I'll get back on the mounting base project. The tricky part is done, holes drilled and tapped, parts mounted. Now I want to see how best to place the way lube holes.

With the carriage upside down, I'm going to mill four tiny flats on the vees, then drill through them with a small bit. There will be two holes each side of the crosslide, corresponding to the center of the vees basically. I can put a single hole at the rear because it rides the flat way, and I can intersect the hole from the back of the carriage, giving me a way to pump lube to the center of the contact area for the rear way. I can't do that for the front, therefore the four separate lube points.

I'd like to drill out and thread all those holes at the top so I can screw in some short plugs to keep dirt out. To do the lubing, I'd remove the plugs, then screw in a custom made oiler nozzle. That should help keep lube from squirting up and all over the place, which is what happens now with the lube points that there are. I don't like those things, but whatever. There aren't any for the ways, so this is my plan for the next hour or two- put some in. I'll take pictures before I assemble the carriage back to the lathe.

If anybody wants to stop me from doing this as I've outlined, say something quickly, cause as soon as this tuna is down, I'm back at it.

Carld
02-01-2010, 11:29 AM
The follower rest is a very poor choice for facing the end of a shaft. For that you need to use the steady rest. It's the only one that will hold the work in a predetermined spot.

Just putting the top roller of the follower rest forward of center will not stop the shaft from wobbling around while cutting.

I have seen a shop made steady rest that is mounted on the carriage much like the follower rest. If you have need of containing the shaft for facing you could design your follower rest to have an add on roller in the third position for facing.

It would be much easier than setting up the steady rest to face when you were turning with the follower rest.

darryl
02-01-2010, 06:08 PM
That's another good idea, Carld. Nothing stopping me from putting a third bearing on an arm that I can bolt to the side of the follower rest. If not a bearing, then just a piece of brass on a steel arm. An easy add on after the fact- a few extra mounting holes is about it.

Progress report- I finished making the bridge add-on to the lathe carriage. Now I have something to mount the follower rest onto. The rest of my time yesterday went into drilling and tapping for oil ports, then a full re-build of the carriage assembly. All that's left of that project now is to build a right angle adapter to fit the rear oiling port, and fit some new way wipers.

http://www.glacern.net/free_photo_upload/left%20side%20of%20bridge.jpg

http://www.glacern.net/free_photo_upload/right%20side%20of%20bridge.jpg

The bridge support piece on the right is what gave me the most trouble. It had to fit as closely as possible to the carriage while clearing the gib adjustment screws and the way wiper. I milled some room for those parts, plus contoured the support piece to clear the sliding table, mount at the rear also, and give me a place for a future carriage travel indicator. That's the ear sticking out to the right. This piece stays attached to the carriage- the bridge (with the follower rest attached) is removed by pulling the two chromy bolts on the left, and two socket head bolts on the right edge of the bridge.

I did a little milling on the carriage to flatten the mounting areas, so the bridge ends up being parallel to the spindle axis both ways. I have a couple other uses for the bridge, which I'll elaborate on at some other time. For now, I just need to figure out how I'm going to mount the follower. I'd like to be able to place it at any point between the left and right of the bridge.

darryl
02-05-2010, 11:20 PM
A little update- thought I'd post some pics of the jaw mechanism for the follower rest. Still some homework to do to complete the design of the vertical support plate, but I think I have that mostly figured out. I'm waiting for the epoxy to cure on my angle mount so I can true it up, then I can refine the dovetail foot detail that will be part of the vertical plate for the follower rest.

So this is just a progress report on a project within a project within a project- but things are coming together nicely.

http://www.glacern.net/free_photo_upload/follower%20jaws%201.jpg
http://www.glacern.net/free_photo_upload/follower%20jaws%202.jpg

I thought I had two gears the same size to use for this, but since I could only find one of them, I decided to nest a gear segment into an equal thickness washer. Good thing I like making jigs- I needed to precisely center each one and bore the center hole, since the washer piece closed up on me when I cut the pie segment out. Worked out better anyway, since now I have the same size hole all through the gears, the arms, and the slotted plate. I did some calculations for center distance for the pins, and drilled a test piece- turned out to be wrong by about 3 thou (loose). Then I just did a temporary assembly of the parts and measured the distance from outside of the pins, then subtracted one pin diameter from that to give the center to center distance. I drilled the hole locations on the mill, cranking it to within a quarter thou to get it just right. The end result of that- locating holes on a direct radial from the spindle axis, and two pin holes exactly spaced from that axis, and at a perfect 90 to it. One of the locating holes is visible at the end of the slot, two more are at the other end, between the jaws. That last hole to the left is what will align to the spindle axis (fitting onto a short stub which I'll turn when I'm ready for that), and then the slotted plate can be angled up the vertical plate and the guideways for it precisely positioned.

I made both pins, since the holes turned out to be .377 diameter, and using 3/8 rod was going to allow way too much slop. The pins have a wide head on one end to help keep them perfectly vertical to the plate. There will be a cover plate over both gears, and two SH screws will tighten the whole assembly together to the vertical plate once an adjustment is made for the diameter of work being turned. In the making of the pins, I had to pay careful attention to temperature of the parts so I could get the close fit I wanted.

The reddish color on the slotted plate- that's not rust, it's primer. I'm slowly getting rid of it everytime I do something and have to sand off the burrs. On the other side of the plate I haven't worn through the black paint yet.

So far I have achieved what I wanted for the arms and gears- no binding, no play, and a precision layout on the sliding plate.

Carld
02-05-2010, 11:24 PM
Lookin' good darryl, it should turn out real nice from what I have seen so far.