View Full Version : Worn Grinder? - Video Question

12-29-2013, 09:02 AM
So I've been breaking down the grinder and slowly cleaning up the bits and pieces.

I'm running into a few surprises -- and I don't know enough about this to make
an educated decision on my own.

I've put together a short vid (8 mins), welcome back to my garage!
pull up a chair, hot coffee is on -- would love to hear what you guys think.

Bottom line, I'm finding more wear in the machine that I expected
and I'm not sure where to go next.

I'm not afraid of trying to machine/scrape the table back in (that's not to say I'd
know what I was doing!) -- but I'd rather not -- I'd rather have a running
grinder to screw around with.

So this is me trying to make heads/tails of what wear in the ways means to actual
(hobby) usage.

Should I try to make things better now that I have it all apart?
Should I just put it back together and stick to grinding only small parts? I'm not
adverse to shimming while I grind.



12-29-2013, 10:50 AM
Well if it were me I would clean everything up good,make the few odd bits and pieces like the lock pins and put it back together.Lubricate and adjust everything and then use a dial indicator to map out the actual errors in each travel.You need a game plan before you start throwing the ball around.

I would even go so far as to test grind a few pieces and measure the actual erros in them before proceeding too much farther.

12-29-2013, 01:21 PM
I also happen to agree with Weirdscience. Your measurements seem dodgy to me. It looks like you're referencing two surfaces to each other,rather than to a known reference. Finish cleaning,bung it together,and then measure. You might be suprised,or,you will have the pleasure of calling us idiots for all eternity.Works for the ex...

12-29-2013, 02:26 PM
Thanks guys:

Wierd: would you suggest grinding the chuck? or maybe somehow working directly off of the table.

Mill: All of my measurements are to the top surface of the table. Also, I'd be the happiest camper here if all
it really needed was a cleanup.

However.. on a dry refit, snugging the table gib reduces my side to side travel significantly. It's definitely
locking up toward the ends.

And.. quick check on the dovetails themselves (the male tails on the saddle) shows about 0.006" wear in
the middle. They're "hourglass" shaped looking from the top. I took this measurement with a large mic over
dowel pins.

Thanks for watching, by the way.


12-30-2013, 10:43 PM
"However.. on a dry refit, snugging the table gib reduces my side to side travel significantly. It's definitely
locking up toward the ends."
Yeah, the joys of buying some clapped out piece of machinery with the dreams of churning out stunning pieces accurate to the nearest public hair...pretty much sums up my shop:rolleyes: you did mention that you only thought you'd use the middle six-eight inches?? You definitely want to grind the chuck in at some point,that is your final reference plane.
Seriously, put it together, use an indicator on it, and video that! Make your new purchase a lesson for the unwashed masses!!

12-31-2013, 07:35 AM
Thanks Mill. I'll be honest I've gone back and forth on this alot and I think I've talked
myself into the wrong decision ;)

I'm going to try to make things better. Famous last words maybe, but I'm going to vid the whole thing
even if I crash, burn, and turn my surface grinder into a bench grinder. Only one way to learn.

I've measured, measured again, and remeasured. I'm confident I know the state-of-the-union and
I think I have a plan for getting a little more life out.

If I were to put it back together now, I don't have enough clean travel to resurface the mag chuck!
Whatever 'resurface' means in this context.

I've gone to great care to clean up all the surfaces and mount the table belly side up on my bridgeport.

I can duplicate the surface plate measurements to within ~0.002". (indicator in the quill)
That extra 2 thou at the ends is the slop in my mill.

I think I can remachine the surfaces to within 2-3 thou, erring on the safe side.

This machine isn't so big that hand scraping those 2-3 thou away would kill me.

I do not have a 55* dovetail cutter thou. That may be for the best. :D

I knew picking up this machine was a bit of a crap shoot. But the price was right even if it takes me
two months to get it back in shape.

I only plan on doing the left-right (X axis?) of the table as that is the worst offender. I'll likely
have some droop in Y, but I can map that out on the chuck and work within that (I hope!).

Here goes noth'n!


Richard King
12-31-2013, 08:59 AM
First off let me state, I am a Professional Machine Tool Rebuilder and see some obvious issues that I would repair before assembling it to take some tests. I have no clue on your scraping skill level, so reassembling it after doing some maintenance my be your only recourse. On the table those high spots or you call them shiny spots is where the table did not wear as they fall into the saddle top oil groove. I would flip the table upside down and measure the bend of the table. This would be easy by checking the Airy points by hinging the table as it sets on the plate. Just grab the right end and push in and out and observe where it swivels or pivots. Repeat this by grabbing the other end and push it in and out approx. 2" each way.
It shoud swivel when flat at approx 30% from each end. Another thing you can do is set a surface gage on the end of the plate and rest the indicator on the ends of the table and press down and let go to see the "lost motion" or bend of the table. I would assume from the gravity and peening (tighting the T-nuts and stretching the T-slots) of the T slots it will be bent at least .005" . That is typical to all knee type machines. I see this a lot in Bridgeport Mills. I ould document the table wear better. Mic it every inch along the table and mark it on your paper as it is so much easier to see on our end. The table should be the same over the whole with-in .0005" to .001". If it isn't can you scrape? Is there a local company that scrapes or grinds?

I also see the ways as if they are lapped together so the machine has a lot of friction or if they are lapped so flat together they wring together like wring gage blocks and they stick. At a minimum I would oil flake or scrape oil pockets in the ways. The narrow column ways also concerns me as if i is worn hollow in the middle it will move from side to side just by moving he table left to right. There are some easy steps you could do, by flipping the top of the knee over on the plate with bluing and scrape it flat as I would suspect the extreme front and back is not worn and the middle is hollowed out too much like the table is. I am attaching a link to a student and friends You-Tube where he is scraping a Swiss made Mill. He had never scraped prior to a year ago when he took one of my classes. If you do not scrape maybe you can find a retired scraper locally who would help you. I know it looks impossible to do if you have never done it before, but you sound like you have the patience to become a scraper. It is actually pretty easy after you learn the basics. As the others have said, you could re-assemble it and check it, but as long as you have it apart, you can see it has errors and you can be a better detective and discover where it is worn more and we can help you determine what to do. You are correct about the multiplication of the error in relationship to the shorter magnetic chuck. Scraping is much like building a house. You start from the bottom and build up. If your foundation is level and square and as you build up everything else will go together better. Take a look at Jan''s info and it should help you scrape it or determine if you can. If you do not have the skill or the tools then putting it back together maybe your only recourse. He has several posts, showing how he scraped Ole's straight edge and how he scraped his mill all starting about 4 months ago. http://www.youtube.com/results?search_query=Haugjord%2C+Jan+Sverre&sm=12
If that fails search You Tube with his name Haugjord, Jan Sverre

Good luck and you can write me direct at Richard@Handscraping.com Happy New Year! Rich

Richard King
12-31-2013, 11:39 AM
You wrote about milling the table while i was writing my first one and i did not see it until I hit send. If your going to mill the table I would put 2 vises on the mill if you have 2 and don't clamp it to the table. If you don't have 2 vises then after you measure how much the top is bent shim under it with different sized feeler gages before you clamp it down so you would bend the table and when you release it will spring up bent. If you watched Jan's video's he has a device that checks the parallelism of his column ways. I also have a gage called a King-Way that he made a copy of to measure this. You can also get a book called Machine Tool Reconditioning and it will show you several methods to check this and it also talks about scraping as does my DVD that i sell. I cn try to find a web-page where you can down-load the book and also n the site it has The Foundations of Mechanical Accuracy by Wayne Moore (Moore Jig Bore) and the Testing Machine Tools by George Schlesinger. I don't think i should put it here as it might have some copyright issues.
Email me at my above email. Rich

12-31-2013, 08:36 PM
"First off let me state,"
Way to go Tony,you woke up the bear! The bear knows his onions,so listen closely;the breath is horrible,but the advise is gold!!

12-31-2013, 09:49 PM
I didn't see any mention here of using a surface plate to check for flatness on the table. I would be inclined to do that first. Does it rock, is it humped in the middle, etc. Which side has the most error- the top surface or the dovetail slides-

I probably wouldn't be the first guy here to suggest that mating sliding surfaces together properly isn't a trivial thing. In this case you have eight surfaces that should be flat, straight, and parallel- four on the bed and four on the table. My own plan of attack would be to first check the table surface against a surface plate, since that's the easiest to do. If it rocks, shim it in such a way that as well as removing the rocking motion, you are also leveling the dovetail side as best as possible. If you're going to do any scraping, etc, then you'd want to bring the bottom surfaces into parallel with the surface plate, as that will be your only flat reference surface to measure from. With the bottom surfaces flat and parallel, you can now repair the dovetails, and of course remove some material from the very bottom of the table if that is needed to provide clearance for the table to fit the bed. Keep in mind that any material removal you do will increase the clearance in the dovetails.

Once the bottom of the table has been corrected, you now have a reference with which to check the bed. Scraping or machining the bed into correctness should allow you to fit the table to the bed in a sort of 'like new' condition. Then you can see about machining the top surface of the table.

This is just my gut feeling. As I see it, you have nothing at this point to make any meaningful measurements from unless you are referencing from a surface plate. If you don't have one, get one. They are surprisingly inexpensive.

If you do decide to take on the job of re-fitting this, be prepared to spend lots of time and effort, as much in setting up and testing as anything else. You will need patience. You will also learn a lot throughout the entire process, so you might find value in that. Some special tools will help, such as precision flats, etc.

Richard King
12-31-2013, 11:38 PM
Darryl he talks about the surface plate check on the You Tube film he did. Its on the bottom of his first thread. http://youtu.be/tIiaMKNzI6k

He and I have chatted in an Email and he does scrape and has more You Tube films on there showing how he scraped a straight edge pull scraping. He shows how he checks parallel on his plate on this you tube film. His You tube name is featony. http://www.youtube.com/watch?v=LkdkouWiDFs

Tony I hope you don't mind me telling them this.

He told me he checked the table top on a plate and it is good, so he is going to clamp it to his Bridgeport and take a clean up pass. Tony is not new to scraping or rebuilding. He also shares his experience but also is smart to ask questions as no one knows it all. My Dad use to tell me "when you think you know it all your a fool" I learn something new everyday of my life thank God. Millwrong you sure have a way with words...LOL I love your sense of humor...hey do me a favor, stop sending us the below zero temps would you. Rich

01-01-2014, 08:12 AM
Thanks Richard, but you may be giving me more credit that I deserve there. :)

First/foremost hope everyone had a safe & happy new year.

I'm going to make this a project and I'll get it on 'tape' start to finish. Hopefully I get it right (or close!), if nothing
else it'll be a good lesson.

Thanks all for the input so far, I'm sure I'll have more specific questions as I run into hurdles along the way.

Darryl, yes the table is flat as far as I can tell. I don't think this grinder has had much use but, unfortunately, the little
use it has had has been without lubrification!

My plan is to use the top and front edges as my two principal reference surfaces and take it from there.

Saving grace here is a STRAIGHT gib and the fact that the table is run on a rack/pinion, I'll need to flatten out the business
faces of the gib but I can tune out anything I scrape or cut off to get the geometry back.

Richard King
01-01-2014, 08:35 AM
I always tell my students to play detective and look for original surfaces "not worn". Like the ridges where the oil grooves left a ridge in the table flat. Measure those to help you calculate how much it is worn. I always use the "South Bend ridge" as an example too. It is on the top of the V way wear the saddle never hits and leaves a ridge. You can imagine of the bed is worn say .020" the shorter saddle must be worn that bad too, and if you want to bring it back to the original center-line you will need to either adjust everything down that much or raise the worn area's up with a wear strip of some type. Many times you can use the clearance area where a gib bottom say in the top of the saddle or knee of a Bridgeport as a reference as to how much wear there is, as that area never hits and is original. Once you look for, find and measure the ridge file it off or scrape it off so it is as low as the worn way.

Other wise if you leave it there and begin to blue up that part the ridge will hit and might tilt the part or tilt the straight-edge so it hits in an unworn area and if you scrape it and the ridge the originally geometry of the part will be changed making a mess of things when you go to "match fit" it to the opposite shorter side as it wore down the original geometry for the most part. I also tell students to use the unworn areas as well as clearance area that were machined on the same set up at the original factory. This speeds up the work for a rebuilder as you can use the factory clearance or unworn areas then the factory scraper who had to check everything to get the geometry right.

I also say it is easy to learn how to scrape, but knowing wear to scrape and how much to take of is a "trade" and you need to learn from someone. One of my students Glen down in Kansas said he read and re-read the Connelly book "Machine Tool Reconditioning" but never "got it" until someone showed him how. That is why I ask my students and others who know how to scrape to show others how. I would guess over the past 10 years since the internet has bloomed more people outside factories have learned to scrape then ever before. So Daryle, Tony, Millwrong and you others please show someone what you know to pass on your skills. Happy New Year!! Rich

01-01-2014, 01:43 PM
well I took the plunge.

I must admit pucker factor here was pretty darn high. You see, I have a pretty worn out mill.

Despite being worn, I've gotten used to its quirks and can, to some degree, predict what it will
or won't do.

Just as a reminder, wear in grinder table was ~0.010-0.011". Given what I know of my mill, and
what I'm willing to scrape, my target was to get that variation to about 0.003" over the whole
area (8" x 24").


I suppose these photos don't really mean anything, but I was able to get a finish milled surface over
both rails and along the whole length to within 0.0028"-0.0032" -- thats much more reasonable to scrape!

Even that range is misleading. My mill has some strange wear in it. Those are local high spots and I think after
even the first rough scraping that total surface variation will be within 2 thou.


Also, -- and not sure if this was a waste of time or not -- I left a small section of original surface. Average depth is
about 1/2 a thou in a 1" range.. 0.001" max.. and tapers off pretty fast. I wanted to be sure I wasn't chasing my
tail and end up machining all the features clean off! :)


I'm getting it all on video but will be a while before I have enough together to tell a story.


01-01-2014, 02:42 PM
Tony,it's only money! I'm sure like me,you have pissed it away on really stupid ideas! I'm looking forward to seeing the first bluing! That is where I get excited. It's the launching of an iterative process towards perfection;real or perceived. Although one of the better purchases I've made is a Biax power scraper. Speeds the process immensely!
Rich, most people tell me that the only skill I have is producing methane...

J Tiers
01-01-2014, 11:40 PM
I probably would have stuck it on a reference flat, and tried under it with feeler gauges to see if the mic measuerments were OK... Basically a sanity check. For both the dovetails and the table top. That assumes you have a big enough flat, or a long enough straightedge.

And there is a difference between the way the table is used, and the way it is being measured..... it is USED supported in the middle, sagging at the ends.... that measurement is done with the ends supported, and the MIDDLE sagging (if it is worn hollow on the surface that is down). Depending on the accuracy wanted, that could be significant.... the table is reasonably thin vs its length.... most likely not an issue for you with your desired 1 thou window.
end EDIT

Because that is a bit different to a regular SG, being that it has a knee and column like a mill, as opposed to a rise and fall head, it won't act like a regular SG for wear.... since it is worn hollow in the middle, the table will just follow that hollow path and everything on it will be ground to the equivalent radius. I think you are doing right to fix it.

But you have now opened the can of worms.....

You will at least have to do the saddle to match the new as-scraped dovetails..... and I share Rich's concern about the column ways and knee as the table weight plus mag chuck and work shuttle back and forth. Maybe locking the knee would fix it, but then it might also shift things unpredictably.

Once you start on this there really isn't any stopping until you do the whole thing.

the column and table you can do "independently". The table has a known goal.... straight dovetails, flat and even, and table parallel to them. And the column ways have a reference in the wheel spindle. So you can get them both right without too much extra 'stuff". The mag chuck removes the need to sweat the t-slots too much.

But once you start in the saddle and knee, you will need some more stuff, like good 90 deg references.... And I don't see going to the trouble to do the table, and then letting the column, knee and saddle be whatever they are with whatever slop they have.

I think you've got a project there.....

As you probably already know, doing the check per the last photo assumes that the surface that is "down" against the flat is , well, *flat* and doesn't have it's own issues. That wouldn't change the relative measurements (at least not if it is sitting in a stable and repeatable position), but it could change how much you need to take off at each end.

01-01-2014, 11:48 PM
Well, chances are that we will stand to learn something through this re-build- I will anyway. Good luck with it, Tony- takes some grit to step into a project like that.