Union Tool & Cutter Grinder Restoration Shenanigans

[RobCox]

I'm pleased I got the whole assembly to mate well with minimal play, but I can't help feeling I've gone about it all the wrong way. It was so labour intensive - there must be a better method. I suspect shimming was anticipated when these were designed.

I had a look at my Union today as I gave it a workout grinding a grooving tool for the shaper. There's a shim on the side of the gib on mine, but the bolts are barely nipped up:

Some enterprising soul has cross drilled the front gib securing screw and fitted a rod through it so it can be used as a lock:

I would say what a great idea, but I'd forgotten it was there and haven't had a need for it in the 8? years I've had the machine!

 

[DiyAddict]

Very interesting Rob. I wonder if the shim is original? Also, I wonder if the gib bolts were just finger tight as a rule - I thought mine was the only one.

In addition to its use as a Y-axis lock, the cross-drilled rod could also act as a gib tightener that could be used in cases where the y-axis needed to be rigid, for example if there was uneven weight distribution of fixtures on the bed.

Paul

 

[DiyAddict]

The last bit of fitting is the plate that holds the main table onto the saddle. This was the large piece of ground flat stock that was bent like a banana. Since I'd already ordered a new one, I did have a quick go at unbending the old one. Jumping up and down on it made no difference, so I concocted this method with a B&D Workmate:

The idea was to advance 5mm at a time then measure, until the metal passed it's elastic state. The bending you see here made no effect at all on the bow.

I had to bend it this much:

to have any effect. In fact, it straightened out reasonably well, but not consistently. After chasing tenths in the fitting stage, there's no way it's going back onto the Union. It might be a good candidate for some hardened parallels in the future, if my T&C grinder proves capable of surface grinding. We'll see.

Anyway, here's how the table, saddle and retaining plate go together:

Sorry, it's pictured upside down again, where I was making measurements on the surface plate.

The retaining plate is in brown, and it bolts to the four lands on the table. When the table is slid onto the saddle (in blue), the plate locates under the lips of the straight and vee ways.

I measured the lip's thickness on the straight way with a micrometer - it varied between 6.24 and 6.30mm along the saddle's length. The discrepancies are due to the initial wear, then the amount I've subsequently taken off the ways by scraping.

For a good fit, the lip must be equal to the difference between the straight way and the land height on the main table. I measured this on a surface plate at approx 6.12mm (See diagram).

Once again, I'm not sure how important the fit is, or what the tolerances should be. I've tried mounting the saddle and table on the grinder without any retaining plate and gravity seems to hold it in place, but I can imagine this going very wrong if you had something heavy - like a motorised workhead - on one side.

In any case, I needed to machine the lips to have the same thickness all the way along the saddle. There's no way to get a scraper to them.

 

[DiyAddict]

Here's my setup, with the current thickness variations marked on the flat ways:

The saddle is resting on some perfectly-sized cast iron parallels that arrived from Ebay the day before.

It was important that the underside of the flat way is the same height as the underside of the Vee way. This was easy enough to measure, with a DTI in the mill's spindle. Fortunately the difference was virtually zero - well within a thou across the whole length. That allowed me to do the underside of both ways in the same pass.

I used a T-slot cutter for the machining - it was all a bit tight for space:

I went slowly and carefully, milling around 1 or 2 thou off at a time:

This is where I had a brain fart. I tried to get as close to my figure of optimum thickness as I could. But actually, all I needed to do was get the thickness constant (or the underside parallel with the top ways, which is the same thing). I would then be able to get the fit I wanted simply by shimming.

Anyway, my little mill surpassed itself. It managed to get everything flat to around 1/100th of a mm:

And the finish was pretty good too. Looks like it's trammed well:

So the perfect thickness according to my measurements was 6.12mm, and I managed to achieve 6.14-6.15mm. So to get a perfect fit, I'd need to shim the retaining plate by 0.03mm, or around a thou. I did try to assemble it with no shim, just in case there was enough spring to get it to fit, but no way.

I have some 2 thou shim stock, so I'll be using that for now, until I can decide how important the perfect fit is.

Making a lead screw and nut next.
Paul