Surface Grinder Ball Retainer Replacement

[G-ManBart]

Hi all,

I did a few searches and couldn't come up with anything, so I'm starting a new topic...hopefully in the correct location.

For background, I'm just a hobbyist plugging away in the shop learning how to turn good stock into scrap while burning up all my play money, so this isn't a critical matter.

I just bought an Enco branded 6x18 surface grinder that seems to be in pretty good condition. I've done some reading and some folks suggest maybe they were made by Harig, but others have said they were a copy made in Taiwan....the manual is clearly an imported product. Regardless of all of that, I got it cheap...like really cheap. The motor powers up, the spindle is quiet, everything moves smoothly, the lube system seems to work and it cleaned up really nicely with just some Simple Green and shop towels. The data plate says 1986, so it's been around a while, but I honestly don't think it saw much work...came out of a very small shop.

The one thing I noted was that when I went to float the table for transport I saw the ball retainers had some damage and one missing section of 5 balls from both front and back ways. Other than being in sections, rather than one long retainer, this looks like the same setup as a Harig. The table seems to move smoothly and I might be able to run it this way just fine, but thought I'd explore a fix and want a sanity check on my idea.

I'm sure the original ball retainers aren't available since Enco got swallowed up by the parent company MSC and even then, it's a 34 year old import machine...not likely finding parts. A check on Harig ball retainers that look similar showed them at nearly $200 each.

I can get the correct size acetal/Delrin easily enough, so I'm wondering if I can't make replacements. If I simply drilled holes carefully, sized for new 5/8" ball bearings like the originals, I can't see why they wouldn't work, or am I missing something? There shouldn't really be any weight on, or significant contact with the ball retainer so they should just keep the balls from escaping and spaced properly....unless I'm totally confused. It would seem even a slightly loose fit between the ball and ball retainer shouldn't really hurt anything other than creating a place to trap debris and cause wear but the only contact should be the balls and the ways, right?

It would seem that keeping the line of balls straight would be the most critical factor, so I was thinking of mounting it to the Bridgeport table (retainers are only about 30" long) and drilling the holes with the mill so it's just a matter of traversing the table to the next spot.

If there's a better way to go about this, or if I'm totally off base don't hesitate to let me know...won't hurt my feelings one bit!

Here's a pic of the grinder after 30 minutes with Simple Green and shop towels, and the ball retainers as I found them:

 

[DavidR8]

Great score @G-ManBart!
Do the balls ride on the bottom of the track in the photo or are they suspended by the plastic track?

 

[Cooter Brown]

Robin Renzetti has a great video on this....

 

[G-ManBart]

Great score @G-ManBart!
Do the balls ride on the bottom of the track in the photo or are they suspended by the plastic track?

The balls make ride on the metal track top and bottom (the top track looks the same). The picture doesn't show it well, but the inboard corners of the metal tracks are angled where the balls make contact so it's like a ball riding on a V.

Now that I look at the picture again, the discoloration on the plastic gives a pretty good indication that there isn't much contact with the table and the plastic. The lubrication system puts way oil in there and that's what causes the discoloration (I think). If the table was making solid contact it should have worn that area clean...or so it would seem.

 

[G-ManBart]

Robin Renzetti has a great video on this....

Wow...thanks! That really is a great video. The retainers on mine weren't secured with screws and the profile of the holes for the balls was completely different, but I think that video confirms my idea wasn't totally crazy. I like the added cutouts he added to help lubrication, and I think I can copy that...albeit without CNC and a lot simpler.

 

[benmychree]

You should be good to go with what you have proposed.

 

[G-ManBart]

Thanks everyone....I'll report back how it goes!

 

[682bear]

When I rebuilt my old Taft-Peirce grinder, I used 1/8 inch Micarta for the ball cages. The original cages were made of some sort of fiber reinforced board similar to Micarta.

-Bear

 

[G-ManBart]

When I rebuilt my old Taft-Peirce grinder, I used 1/8 inch Micarta for the ball cages. The original cages were made of some sort of fiber reinforced board similar to Micarta.

-Bear

Thanks!

I can see Micarta working just fine since it's stable and strong.

I measured mine at around .240" thick and dead on 1" wide. I'm not sure what material they used, but it looks like a UHMW or acetal/Delrin. I can get either in .25" x 1" and Delrin is supposed to machine a bit nicer, so that's what I'm leaning towards...the cost is pretty reasonable. I can get two 48" long sections for around $35 and that will give me plenty extra to practice on before the real deal. I don't think the extra thickness will be an issue, but if I have to deck them a bit that shouldn't be a problem.

 

[G-ManBart]

***Update***

Evidently I needed to wait three years to get back to this project!

I bought some new .625" steel balls from a bearing supplier here in Michigan, and ordered some 1" wide .25" thick acetal and those sat for ages. A week or so ago I decided I really needed to get it up and running and I'm almost done.

In the interim I read similar threads on other import machines and did the rough math on how many balls, spacing, etc. I went with 24 balls for the rear way with the flat top rail, and 22 for the front way with V rails top and bottom. I secured the acetal to a board, mounted that to the milling machine and drilled the holes using a 5/8" Forstner bit. The holes were pretty snug, so I mounted a 5/8" twist drill in my drill press and ran the acetal up/down the drill with light side pressure until the balls just barely dropped through each hole.

I pulled the table off the machine, got everything reasonably clean and noticed something interesting...the lube system doesn't provide lube to the table ways. The lube pump (one-shot style) has an output line that goes to a distribution manifold, and that has three outlets. There is a line going up to the spindle and one to each of the saddle ways, which appear to be traditional scraped V on V configuration. That's it, nothing to the table ways/balls. They definitely had some sort of dried lube/oil in there, so maybe it was just dried flood coolant...not sure.

I thought about it a bit, and I decided to add wicking felt under the balls, soak that win way oil and see what happens. I found wicking felt that just barely fits the width and makes light contact with the bottom of the balls...cut it to length, stuffed it in place and soaked it with Vactra. I put the table back on and it glides beautifully. I'm sort of wondering if adding the felt/oil is a bad idea since grinding dust could get down there. Could it just be that maybe they used an oiler and squirted some oil in from the ends to coat the balls periodically, or ran them dry?

After putting the table back on I checked and there is clearance between the acetal and the table, so it's just riding on the balls. Now I just need to rewire the cable for the feed handle and come up with a diamond dresser.

I'm thinking of running it this way for a while to see what happens, but would appreciate input from folks with experience on these machines.