Taft Peirce ball way grinding

JPD · Mar 9, 2021

Greetings all,

Recently acquired an early Taft Peirce No. 1 surface grinder, with fine feeds. Y and Z axes seem smooth, X axis was missing 2/3 of the balls. I transported the machine with wooden dowels in place of the balls, but that may have been unnecessary. Ordered new g25 bearings to install after cleaning up the hardened ways, but even with new bearings the table travel is rough and rumble. I would post a picture of the ways but with camera and lighting issues, all you’ll see is what looks like a perfectly good surface. In the right light I can see dents, bruises, etc on the well worn ball track.

Question is, can I remove the ways for grinding without any risk of alignment issues? A local rebuilding shop says they recently worked on the same machine, but I thought I would put it out here and see if any of you fellow Taft Peirce owners had any thoughts. I would assume the manufacturer would have ground the ways off the machine, and installed. I just want to be aware of any pitfalls before taking anything off.

Thanks in advance

JP

SIP6A · Mar 9, 2021

JPD said:
Question is, can I remove the ways for grinding without any risk of alignment issues? I just want to be aware of any pitfalls before taking anything off.

That’s exactly what you want to do. When you take them off there will be a scraped surface that they mount to. The only issue you need to be aware of is that they need to be ground so that the table sets parallel to the Z axis when you regrind the chuck you don’t want to be grinding more of of say the front edge than the back edge of the chuck.
which means that the same amount needs to be ground off of each one.

JPD · Mar 9, 2021

Thanks

We can work out the numbers, but am I right that there will be a difference in removing from the pair of v ways, and the v and flat? I will likely upsize the balls depending on amount of material removed. They said it was a recent rebuild and will follow up with the previous customer to check how it all went together.

JP

Milland · Mar 9, 2021

You may want to confirm with your grinding company that their machine is in good shape on its own ways, such that anything they grind will be straight and true. If their machine is off by a thou or two, why bother?

If you get properly ground ways, you might want to find a company that stocks Grade 10 balls, they'll run better and wear the ways more evenly. And stay with the original size, or even smaller if possible - you want as many points of contact as possible.

rklopp · Mar 9, 2021

Milland said:
...you want as many points of contact as possible.

Not sure. There will be a tradeoff between more contact points and higher contact stresses with smaller-radius balls. Calculations needed...

Milland · Mar 9, 2021

rklopp said:
Not sure. There will be a tradeoff between more contact points and higher contact stresses with smaller-radius balls. Calculations needed...

In this case, I'm sure the effect of contact stress from the smaller diameter will be minimal, as he can't fit significantly smaller bearings onto the ways without the height changing too much. At most, 10% smaller is possible? And perhaps one more ball, so actual changes will be small either way.

Of greater effect (I'm pretty sure) will be using more accurate balls, which insures you don't have one or two high ones taking more load and inducing more stress.

JPD · Mar 9, 2021

Replying to both, not sure how going to a smaller ball is possible. The phenolic ball cage would have to be milled thinner. Not sure how lowering the table would interfere with the x axis drive gear, if that can be lowered. I’m going to stick to 1/2 or as close as possible, maybe 13mm. G10 balls yes, I just bought the g25 for evaluating whether to grind.

Thanks for all the info
JP

Brandenberger · Mar 9, 2021

JPD said:
Replying to both, not sure how going to a smaller ball is possible. The phenolic ball cage would have to be milled thinner. Not sure how lowering the table would interfere with the x axis drive gear, if that can be lowered. I’m going to stick to 1/2 or as close as possible, maybe 13mm. G10 balls yes, I just bought the g25 for evaluating whether to grind.

Thanks for all the info
JP

It would be good to hear from the grind shop how much they would intend to grind off
between the V's and flats.

Assuming you want to try to retain near perfect parallelism of the current table top
to the spindle axis (which would therefore best preserve the alignment of the drive gear too),
they would need to calculate the acceptable material removal ratios from 3 V's and 1 flat right?

-Phil

682bear · Mar 15, 2021

I did this on a T-P #1 a couple of years ago... I removed the ways and had them ground at work... I also replaced all of the ball bearings, and made new ball cages out of phenolic.

I don't remember how much material was removed, but it worked out great. The old T-P grinds like a new machine.

-Bear

CarbideBob · Mar 15, 2021

An option not for the fainthearted is to lap the ways.
This done with a very long piece of drill rod and free abrasive.
It is actually fairly easy to do if done baby steps
Bob

JPD · Mar 18, 2021

CarbideBob said:
An option not for the fainthearted is to lap the ways.
This done with a very long piece of drill rod and free abrasive.
It is actually fairly easy to do if done baby steps
Bob

At first I shrugged this off, but I’m thinking that at $800 the grinding isn’t going to happen any time soon. So I’d like to hear thoughts on Lapping.

First, stone the ways to remove any possible burrs. I’m picturing doing one way at a time, with the other way set with all balls and cage to maintain table alignment. 36” long precision ground 1/2” aluminum rod from McMaster, with free abrasive, chucked in a drill and slowly spun while stroking in and out. Do I need flex joint in the drill, or a better alignment to ensure straightest travel possible? Do I need to cut relief into the lap? Brandenberger suggested about every inch or so cut a relief, I think that makes sense but is that sensible? Any thoughts? Do I lock the table or let it travel as the lap travels? I’d be inclined to lock it.

I have the machine partially disassembled for the usual cleaning, replacing meter units, etc. I have a feeling the bearings in the x axis feed could be replaced. And any thoughts on thinning out the phenolic ball cages? They are rubbing on the ways, is that a design feature or a breakdown due to wear?

michiganbuck · Mar 18, 2021

Here find an old thread on a TP rebuild.
https://www.practicalmachinist.com/...ictures-255453/?highlight=Taft+Peirce+rebuild

We used to rebuild Cincinnati #2 TC grinder ball-way racks by grinding them and then put a shim under the rack to restore original casting clearance. The V and the flat did get a different amount of take.

Cincinnati company told us to stay below .04 take because of heat treat. Adding a different size ball could put the ball at a different pace, so another thing to consider.

I have run brand new ball way grinders and think that an oil scraped way runs smoother and so gives a better surface finish... Agree they are harder to pull.

I had a fellow who once told me that a lower-class grinder must have had the ball racks ground in place last because the rack set was just milled in so grinding the racks out of the casting was a turkey shoot. The error might have been him and not the machine, who knows.

JPD · Mar 28, 2021

Giving this another shot...

Anyone with ideas about lapping the v ways? Am I asking for trouble? Worst case they go to the grinder...

SIP6A · Mar 28, 2021

Grinding the ways is the best way, and the fastest way to get the machine back in service.

After reading your post about using a piece of drill rod to lap a radius in the "V" way for a ball to ride in, all I've got to say is, that's a really bad idea. A piece of drill rod in an electric drill is just going to flex like a wet noodle and just make thing worse.

The only suggestion I could make over doing lapping rather than grinding would be to start out with a piece of Dura-Bar about five times as tall as it is wide and longer than the length that your lapping. On one edge mill the male "V" then scrape it or have it ground straight. Scraping would be the better choice as it would have space to hold the compound.

Giving the number of hours to do this you might be farther ahead to get a part time job for a few months and earn the $800.00 to have them ground.

If you don't have the money or time to fix this properly you should just clean it up and put it back together and use it as is.

Orbital77 · Mar 28, 2021

SIP6A said:
Grinding the ways is the best way, and the fastest way to get the machine back in service.

The only suggestion I could make over doing lapping rather than grinding would be to start out with a piece of Dura-Bar about five times as tall as it is wide and longer than the length that your lapping. (So it will not deflect) On one edge mill the male "V" then scrape it or have it ground straight. Scraping would be the better choice as it would have space to hold the compound.

Giving the number of hours to do this you might be ahead to get a part time job for a few months and earn the $800.00 to have them ground.

The lap must be SHORTER than the lapped.

SIP6A · Mar 28, 2021

Orbital77 said:
The lap must be SHORTER than the lapped.

OK, how do you keep from lapping low spots?

Any lapping I've done or seen being done was done with a lap many times bigger than the part being lapped.

CarbideBob · Mar 28, 2021

SIP6A said:
Grinding the ways is the best way, and the fastest way to get the machine back in service

Fully agree this the best and maybe the most expensive way to get back into service.
For sure if a unlimited cash account this the way to go.
I will ask as to your have done in person such a hack and it is certainly a hack along with ways to go wrong.
Ante up your real world experience in trying such and the good or bad. Benn there and done that? Tell us about the wrong in results.
I have done it with drill rod and for sure everything screams so wrong and just garage shop type crap. Yet worked...
Sure I'd like to go to grind but most of the shops can not do micron or below.'

You here in my backyard .. name the shops alive capable of such grind.
Bob

Orbital77 · Mar 28, 2021

SIP6A said:
OK, how do you keep from lapping low spots?

Any lapping I've done or seen being done was done with a lap many times bigger than the part being lapped.

I'm not talking about "any lapping", I'm talking about a specific case. When the lap must be SHORTER than the lapped.
The simple explanation here is that you never saw lapping done for this specific case and the right way.

SIP6A · Mar 28, 2021

CarbideBob said:
Fully agree this the best and maybe the most expensive way to get back into service.
For sure if a unlimited cash account this the way to go.
I will ask as to your have done in person such a hack and it is certainly a hack along with ways to go wrong.
Ante up your real world experience in trying such and the good or bad. Benn there and done that? Tell us about the wrong in results.
I have done it with drill rod and for sure everything screams so wrong and just garage shop type crap. Yet worked...
Sure I'd like to go to grind but most of the shops can not do micron or below.'

You here in my backyard .. name the shops left capable or such grind.
Bob

I was always taught that when working on machine tools you fixed them the correct way, so no I've never done a hack repair on a machine tool. I have never understood why people are so damn cheap when it comes to there shop. I was also taught that you can only do the best work with the best tools. I looked at probably a 100 T - P grinders before I bought the one I have for this very reason, I didn't want to go through a bunch of work before I could start grinding parts.

As for a shop that could do that class of work there is Ort Tool & Die in Erie Michigan. But seeing it's more than two blocks from your shop I'm sure it's too far away.

SIP6A · Mar 28, 2021

Orbital77 said:
I'm not talking about "any lapping", I'm talking about a specific case. When the lap must be SHORTER than the lapped.
The simple explanation here is that you never saw lapping done for this specific case and the right way.

That's fine how do you lap with a short lap and not lap hollow? There is a lot more to lapping than just smearing some compound on a piece of cast iron and going to town.

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