Odd 6 2/3 TPI elevation screw for Sanford MG surface grinder?

When I was home yesterday I forgot to look at the pitch of the elevating screw on my Sanford grinder. I thought I had a set of acme thread pitch gauges but couldn't find them. Today I looked at several sets sold by McMaster and MSC. None have a gauge for 6-2/3 TPI pitch threads. I also looked for go/no go thread gauges and again couldn't find any with the 6 2/3 TPI pitch.

I'm out of town again, but when I return I'll make it a point to measure the threads. I find it difficult to believe Sanford would go to the trouble of having a special lead screw made for their machines. Almost all the other parts other than the castings are off the shelf parts.
 
RJSakowski said:
I looked at my thread spreadsheet for the Grizzly 602. I would need a 54t. gear to cut a 6-2/3 tpi thread. Someone with a Clough 42 ELS modification should be able to cut that thread with a modified thread table as described by ian999 in https://www.hobby-machinist.com/threads/electronic-lead-screw.76101/page-16#post-778321 post # 458.
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Perhaps you just need to ask someone to make a 54 tooth gear for you :) We could form a bit of a 'can you make this for me' tree :)

That said, this says you should have a 54 tooth gear: https://cdn0.grizzly.com/manuals/g0824_m.pdf
 
ErichKeane said:
Perhaps you just need to ask someone to make a 54 tooth gear for you :) We could form a bit of a 'can you make this for me' tree :)

That said, this says you should have a 54 tooth gear: https://cdn0.grizzly.com/manuals/g0824_m.pdf
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The lathe is G0602 and no 54 tooth gear. I have the ELS installed on my lathe so no gears any more. It would require an editing of the firmware which would entail pulling the Launchpad controller and reprogramming it with my office computer. Aside from that, the 602 has (barely) enough travel to cut 16" of thread plus whatever addition features are required for the end of the shaft. The lathe's lead screw having 12 tpi, it may even work out that the thread dial would work for a 6-2/3 tpi thread.

However, I have been retired for seven years and don't take on paying jobs any more. The wife strongly disapproves of it when there are honey do jobs in the que (and it's a long que). There is a growing list of individuals on this forum who have retrofitted the Clough ELS to their lathes. Additionally, the Rocketronics ELS should be able to cut this thread and several members have their ELS installed.
 
i finally got down to the shop for a few minutes yesterday afternoon. About the only things I did were to clean up a few tools laying around and measure the pitch on the elevation screw on the Sanford Grinder. In my case the screw is a 3/4-8 Acme thread. To be certain of the pitch I used an Acme thread pitch gauge like this:

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If you choose to buy one there are a few listed on eBay. The one from HHINDT is listed for less than 1/2 the price this vendor is asking.
 
projectnut said:
i finally got down to the shop for a few minutes yesterday afternoon. About the only things I did were to clean up a few tools laying around and measure the pitch on the elevation screw on the Sanford Grinder. In my case the screw is a 3/4-8 Acme thread.
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Interesting! Are your bevel gears still 3:1 or have they been changed? With 3:1 you would only be getting 0.0416"/rev, no?

Thanks for checking!

I think I'm going to be changing the bevel gears. At this point I've changed the spindle bearings, replaced motor bearings and balanced the pulleys, replaced the crossfeed screw, and replaced the rack and pinion and I'm pretty happy with the surface finish and flatness that I'm getting. It's at least as good as my old worn out surface plate haha. I need to do something, though, as the worn out elevation screw has it so that I must be very careful with adjustments, as there's backlash and stick-slip that can make for somewhaterratic downfeeding. That led to one unfortunate gouge when I was dusting the chuck, for instance, so I had to re-do that. I'm a little concerned that the stick-slip in the vertical ways may be the bigger problem than the worn out screw, though, in which case maybe I need a chunk of iron to hang off the motor moreso than a new screw (until I get a couple hundred free hours for some scraping.)

Thanks again
 
I mentioned in post #6 on this thread I thought the gear ratio had been changed from 3:1 to 4:1

Looking for Sanford MG-612 Surface Grinder owners

I didn't offer the tooth count at that time, and I'm thinking now I miscounted. That same post does mention that rather than raising or lowering .005" according to the handwheel the spindle only moves .0041. That number would coincide with a gear ratio of 3:1 and an 8 TPI lead screw.

I'm not sure now whether the gears were replaced with an identical set or they are the originals. I'm inclined to believe they are direct replacements. They seem to be in similar condition as the leadscrew and nut. All look to be in excellent shape. I would think after 66 years of use the originals would show moderate to serious signs of wear.

The leadscrew shows slightly less than .001" backlash. The same size "ultra precision" leadscrews from major industrial vendors show a spec of +/- .0006" from the factory.
 
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