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Chester 626 X axis backlash

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Tom Churchman28/06/2021 17:35:01
10 forum posts

Hello all, I have a newly acquired but second hand Chester 626 and have a problem which has probably been encountered by someone before, but a search doesn't turn up anything.

I have loads of backlash on the X axis, but the feedscrew / nut fit is ok, the problem is that the nut isn't secured to the Y axis saddle, it just sits loosely in a little hole, free to rock about, unlike the Y axis nut which is bolted down.

The nut isn't tapped for a bolt and there isn't one shown in the parts diagram, so I'm wondering if I should just tap it and bolt it down? I can't understand why it's not been done?

Steviegtr28/06/2021 17:43:44
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2269 forum posts
313 photos

I do not know the machine, but couldn't you bond the nut in place.

Steve.

Martin Connelly28/06/2021 18:43:01
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1932 forum posts
207 photos

There is a possibility that locking the nut in place may cause binding at some point in the travel. If you do lock it be prepared to have to start fixing other things as well.

One place where a cheap design causes backlash is the mounting of the leadscrew to the machine bed. This can be checked with a mag base on the top of the bed with an indicator against the leadscrew end face. As you wind it left and right the ideal would be very little change in the indicator reading. A big change shows it needs a bit of fettling. There are articles on-line of people tackling this issue if you need ideas.

RF30 leadscrew fix for example, not the same as your mill but a fix for a possible source of backlash.

Martin C

Edited By Martin Connelly on 28/06/2021 19:01:02

Clive Foster28/06/2021 19:03:35
2882 forum posts
104 photos

Tom

Are you sure there isn't a side locking screw to grip the spigot on the nut as it sits in the hole.

That style of nut retainer is quite common of small lathe top slides and not unknown on cross slides. Usually the screw is quite difficult to see and harder to reach. About 30 years back it took me about 6 months of muttering about backlash and looseness before I spotted the all important screw on my "new to me" to spot the one on my SouthBend Heavy 10 top slide.

Doing things that way means the nut can take up its correct vertical alignment naturally. Bolting down to a surface needs either shimmong or close dimensional control of nut and machine to ensure things don't bind.

Clive

Dave Halford28/06/2021 19:48:01
1818 forum posts
19 photos

You could try a layer of PVC tape to take up the slack, then see if anything binds before you resort to glue.

Tom Churchman28/06/2021 19:52:41
10 forum posts

Clive, you are absolutely correct, thanks very much.

There is indeed a tapped hole in the saddle with a missing screw which should enable the spigot to be pinched. Now fitted and a shed load of backlash is gone.

yes

not done it yet28/06/2021 20:04:51
6438 forum posts
20 photos

For completeness, is that not shown in the parts diagram - or did you just miss it while looking for something else?

Tom Churchman28/06/2021 20:13:54
10 forum posts

I was being dense, it is on the low quality diagram I have, but I overlooked it as it's shown as being about an inch laterally away from the spigot!

William Chitham29/06/2021 09:54:43
125 forum posts
52 photos

Hi Tom, I have a Chester 626 and the manual is pretty dismal. Grizzly sell essentially the same machine in America and they do a much better one, there is a link to it in this thread: 626 thread

William.

Tom Churchman29/06/2021 12:32:07
10 forum posts

Thanks William

not done it yet29/06/2021 13:10:34
6438 forum posts
20 photos

Easy to miss, I expect, with so many reports on the dismal quality of some chinese translated instructions. Even the instruction manual for my 1960s English-built lathe is poor - there is more info in the previous model instruction book.

If the screw has been missing while in operation, the nut could be worn/damaged - particularly if the machine had been used for ‘climb milling’.

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