Taking up backlash on J&S surface grinder

Saxguy,

Check this thread out on another site, it's a total rebuild of one just like yours including the X axis lead screw and nut on page 2.
I added the link but for some reason it didn't take the first time.

Joe
 
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Hello, Saxguy :)

I just dealt with the same issue on my DoAll DH-612 manual surface grinder, mine had roughly .075" worth of backlash (1.9mm) which is right at 3/4 of a turn of the handwheel. Mine is 10TPI or .100" per revolution (2.54mm per revolution), when I took it apart I noticed that the thread thickness on the lead screw was only about .025" thick on the screw and in the nut (roughly .6mm).
I made the mistake of putting my finger inside the nut and I cut my finger slightly because the threads were so sharp, you would think I would have known better than to do that!! Lol

Anyway, there are no replacement parts for mine since DoAll quit making them and there are no aftermarket parts that I'm aware of so I had to make a new lead screw out of 4140.
Instead of making a threaded bushing for the nut, I decided to make the lead screw about .135" larger, there was plenty of bronze left on the nut for a larger diameter lead screw and nothing else restricted me from doing that.
I had to take mine apart to rework the ways and the oiling system anyway, fortunately, mine is much less complex than yours!
Nice looking grinder BTW!!!

With your J&S, I would think that a minimal amount of backlash is a MUST since it has auto feed.
Mine is manual feed in all directions but 3/4 of a turn backlash was just too much! In fact, the X axis would completely quick working soon if I had left it alone.
I would think that a ball screw would be hard to keep from getting crunchy if even a slight amount of grinding swarf gets onto those balls (just a thought, I have very little experience with retrofitting surface grinders).
Grinding swarf is what caused all the damage on mine so my main goal now is to mitigate the grinding swarf by either adding a good vacuum system close to the wheel or maybe a better coolant recovery setup? Whatever it takes to keep that nasty swarf from eating up parts that are in contact with each other is the goal.

I don't plan to install a DRO as someone suggested, I use a test indicator on a mag base for sidewall grinding and that works pretty well for me.
Mine does have a gib lock on the X axis and that helps for sidewall grinding.

BTW, trying to take up backlash on worn lead screw threads doesn't usually work because the threads will bind when the lead screw moves into an area where the wear is less. If the only wear is in the nut, then it would work.

Questions:

1 - Do you have any repair manual drawings or a web link to a replacement lead screw and nut for your grinder?
2 - Is this the lead screw and nut that you need? https://www.andmar.co.uk/spares-82-saddle-cross-screw-and-nut
3 - Roughly how long is the lead screw is on yours?

4 - When you retract the lead screw to a portion where there is less wear, how much backlash do you observe?
The reason I ask is this: if there is very little backlash where there are less worn lead screw threads, that would mean that the nut has fairly good threads, if the backlash is only slightly less, then the threads in the nut are worn somewhat equally .
I've seen cases where the lead screw is softer than the bronze nut (Not hardened maybe or just soft steel?).
I plan to send y new one out to be hardened and tempered by a pro, if I do the hardening, it would probably wind up NOT straight anymore!! :-D

This hobby/business always has it's challenges and expenses!

Sorry for the long response, just trying to help if I can.
Hi Joe, thank you for the great reply, and expansive help. Bit busy with Christmas day fests here right now (wife is glaring at me for finding more interest in machine hobby forum than helping her cook etc).... Just one quick observation mind you, is that my lead screw is no where near as worn. By eye it is hard to see any noticeable wear, maybe just a slight thinning of the middle section. All the wear is in the nut pretty much. Might just make a new bronze push-fit and machine out the old threads on the nut. The cost of a replacement nut/screw is just far too much for me.
I'll come back to you soon, but must appease the missus right now.... or else!
 
No worries, I wasn't expecting a response so near to Christmas.
Got to keep the missus happy and full of Christmas Cheer :)
We'll chat later.

Merry Christmas to ALL :)

Joe
 
Don’t forget bellows to cover the leadscrew. Mine were deteriorated which lead to my problems. I replaced with bellows for mountain bike front forks. They were a exact size. I’ve seen people use bicycle tubes which seemed to work well also.
 
Saxguy,

I am really curious, is the lead screw for the Y axis on your surface grinder 2.5mm pitch or 2.5mm for each turn of the handle?
Whenever you get time to respond is fine :)
Thanks!!

Joe
 
Saxguy,

I am really curious, is the lead screw for the Y axis on your surface grinder 2.5mm pitch or 2.5mm for each turn of the handle?
Whenever you get time to respond is fine :)
Thanks!!

Joe
Hi Joe, its a 10mm lead, 5mm (double start) pitch.
 
Hi Joe, its a 10mm lead, 5mm (double start) pitch.
Thanks Saxguy,

So, if I understand it correctly, in Imperial terms it's a 5-TPI thread form with the threads cut at a rate of 2.5-TPI (cut twice at 180° apart?)
That would make the cross slide travel .400" for one turn of the handle? Is that right? (actually .393" or 10mm metric equivalent).
Forgive me, I'm not too familiar with the metric version of ACME screws so the above would be the closest Imperial conversion, If I understand it correctly.
I understand the double start threads and the advantage of twice the travel with the same number of turns, but converting from threads per inch for 29° ACME to metric pitch 30° Trapezoidal takes me a minute to wrap my mind around!! Whew!! :)

I saw where the replacement nut and lead screw for that machine are nearly $1,000 USD
I would try to make my own as well!!

Best of luck to you!!

Thanks Saxguy!

Joe
 
Thanks Saxguy,

So, if I understand it correctly, in Imperial terms it's a 5-TPI thread form with the threads cut at a rate of 2.5-TPI (cut twice at 180° apart?)
That would make the cross slide travel .400" for one turn of the handle? Is that right? (actually .393" or 10mm metric equivalent).
Forgive me, I'm not too familiar with the metric version of ACME screws so the above would be the closest Imperial conversion, If I understand it correctly.
I understand the double start threads and the advantage of twice the travel with the same number of turns, but converting from threads per inch for 29° ACME to metric pitch 30° Trapezoidal takes me a minute to wrap my mind around!! Whew!! :)

I saw where the replacement nut and lead screw for that machine are nearly $1,000 USD
I would try to make my own as well!!

Best of luck to you!!

Thanks Saxguy!

Joe
Correct. I'm a bit phased myself.... but I'll give it a good go.:)
 
I found this for you...http://www.lathes.co.uk/jonesandshipman/page4.html and a bigger one, but usually all th designs are about the same. http://lathes.co.uk/jones-shipman-surface-grinders/ Do you have a parts manual?

Also you may be able to find one of these new one that you can machine to fit and a new acme screw you can splice into the old handle end. http://www.greenbaymfgco.com/ACME-nuts.php
Hey Richard, thank you for that link (no mortgages in there I noticed ;-))
I have seen the website before, and have actually purchased from them. I must have missed this particular page though.... very nice.
Parts manual, yes, I was given a full manual from another gentleman on this forum (but through email), which I was most grateful of.
I think I'll have a bash at making a bronze insert first, but failing that, I might look at buying one. The second link you put from Greenbay is fantastic. Looks like they may even have on on the shelf? I will get in touch just to price one up first.
I used to purchase a fair bit from the US, but recently it has become very expensive and sometimes impossible. For some reason many companies have stopped dealing with overseas enquiries. Either that else the freight just kills it. I used to have a friend in the US who posted me the odd item, but he passed away nearly five years since.
New Zealand has its up sides, but also we really struggle for many things here. Population of less than 5 million, and in the middle of nowhere. The stuff we do get here is usually crazy money too. I have stopped looking at ebay as I just get sick with jealousy! LOL
Thank you again Richard.
 
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