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Sandford MG Acme Thread

Mar-Gun

Plastic
Joined
Jan 15, 2021
I just picked up a Sandford MG Surface Grinder looks like is was made in 1959 the same year as me. I got it home and washed off some 64 years of grime and the Ways look to be in pretty good shape. not sure which has had more wear and tear it or me. The Cross Slide Acme Thread Screw is not in very good shape its pretty loose in the Middle. So Monday I'm going to order a 3/4-6 Acme Rod and a Bronze Nut and make a replacement. My question concerns the Acme thread on the backside which controls the Height. Its obviously a finer thread than the other one or is it? Somebody has already been in there and it appears that a new Bronce Nut has been made for it. Somebody has stamped the Nut with a Centerpunch a couple of times in what looks to be a way to tighten up the clearances a bit. Since I will be making a new cross slide shaft maybe I should be doing both. The Interweb has it that this was a one-off Thread size just buying some Rod Stock is not going to happen. Since some of You must have one of these machines and its probably the first part to wear out somebody here must of delt with it before. Since its wide open on the back its easy to look at.
If somebody is scrapping one out I could use the Cover that goes over the wheel that sez Sandford.
 
Contact Green Bay Mfg. As they make Acme screws and nuts in stock. I'm a professional Rebuilder and I buy from them. Their website has all the sizes of left and right hand threads. Check it out and let us know what you find out.
 
I called and ordered the 952 Bronce Nut and some 4140 Threaded Rod in the 3/4 - 6 LH from Green Bay Mfg so it will be headed my way soon. The Lady who answered was very professional and knew what she was selling its sounded like a small town company with customer service. So all is set for the Cross Slide Screw. The Vertical is still a puzzler I'm counting 54 Threads in 8 Inch's or a 6.75 Threads per inch. I see my Lathe can cut a 6.5 Thread and ElseWare on the Web I have seen other people measure it at 6.5. So, I could make a replacement I haven't cut threads on a Lathe since my Highschool days, but it would be a good refresher. Green Bay also had a 8 Threads per Inch available and I could use that. I would think that a finer adjustment would be better than a course one. This would throw off the Marks on the adjustment wheel, but I could just machine them off and re mark them. Or could I ? It would have to come out to a certain number around the wheel somebody better at math would have to figure that out. I could just leave it blank and rely on a Dial Indicator or a DRO which is probably better way anyway. I would think that the Mitutoyo Style that were made for the Bridgeport Quill would work quite well.
 
Check the dial calibrations for that axis. That should get you the pitch, when combined with any gearing that may exist between the dial and the screw.
 
Just an update. I got the Acme Rod from Green Bay and after an hour or two I had machined the Threads off the one end and made it match the original. Well kind of, turned out the Original was close to 7/16 but it wasn't. And the Threaded end and the Nuts that hold the hand Wheel on were all an odd size and thread count. I ended up boring the Hand Wheel out and making a Bushing. The new Threads didn't match the original Acme Thread at all. The original looked as though it was made from a 7/8 Rod and then turned down to 3/4 as the Threads were thicker than the Green Bay Threads. Sure, glad I ordered a new Nut to go with it.
Had to re wire everything. When it was removed the movers must have cut everything. For some crazy reason the wire going from the Magnetic Vise was Orange Extension Cord on one end and Black OEM coming out of the Vise itself. I assumed that it was not going to work but it does.
Another issue was getting a new Serpentine Belt for the Motor. My local Autoparts store ordered a few but no go. Talking with Gates produced no results. However, in 3 minutes on Amazon I had an exact match, and we are good to go.
I have one question. How strong should a Mag Chuck be? A one-inch washer is difficult to pry off by hand with no tools, but it can be done. Not sure how much of a test that is. And if that's not enough is there anything that can be done? At 65 years old it's not the only thing that's not holding as much as it used to.
 








 
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