Author Topic: Fix for Gib twist on mini lathe.  (Read 6839 times)

Offline ian_in_the_midlands

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Fix for Gib twist on mini lathe.
« on: October 02, 2014, 03:24:46 PM »
My new mini lathe suffers badly from the gibs twisting.
I see from other posts, this is not uncommon.
The compound slide it the worst. As the gib twists it raises the slide and fouls the leadscrew.

I have replace the adjusters with cone points, with little effect.

I have been recommended to drill and tap the cross slide for more adjusters.  am reluctant to do this first as the holes would have to be very close to the edge of the metal, and I have a very wobbly pillar drill.
Has anyone done this? Does it fix the twist problem. Can someone supply more details of the fix: position of new holes, pictures of drilling, angle of holes etc?

My first attempt to fix the problems will be to make better fitting jibs. I have no milling machine, so they will have to be filed by hand.
I have some brass and key steel I could use.
Brass would be easier to file, and kinder on breaking in my new files, but I have read that using a softer material for gibs can cause them to pick up abrasives and turn into a lap that wears the lathe. Is this an issue?
Would people recommend I use brass or steel?

Can I also confirm my understanding of how a gib should work:
- The gib should be a good fit in the hole, unlike the gibs supplied.
- The slide should ride on face F.
- There should be full contact on face A.
- The gib can contact at B, but fit is not critical.
- There should be clearance at C and E.
- The gap at D should be as small as possible.

Thanks.

 

Offline Pete.

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Re: Fix for Gib twist on mini lathe.
« Reply #1 on: October 02, 2014, 04:01:21 PM »
Can I also confirm my understanding of how a gib should work:
- The gib should be a good fit in the hole, unlike the gibs supplied. - Yes
- The slide should ride on face F. - Yes
- There should be full contact on face A. - Yes
- The gib can contact at B, but fit is not critical. You need a small clearance.
- There should be clearance at C and E. No, the gib should ride on C, clearance at E
- The gap at D should be as small as possible. Ideally, yes

Offline John Rudd

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Re: Fix for Gib twist on mini lathe.
« Reply #2 on: October 02, 2014, 04:20:41 PM »
FWIW, I changed the gib strips on my Sieg lathe for brass ones.....Not had a problem thus far..
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Offline Brass_Machine

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Re: Fix for Gib twist on mini lathe.
« Reply #3 on: October 02, 2014, 04:31:46 PM »
Hi Ian,

Save your time and buy the brass gibs from one of the suppliers. I plan to order a set soon myself. I figure $29usd will be worth it for my time.

In the US get them HERE.

In the UK you can get them HERE at the bottom of the page.

Eric
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Offline John Swift

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Re: Fix for Gib twist on mini lathe.
« Reply #4 on: October 02, 2014, 05:13:28 PM »
Hi Ian

fitting the brass gibbs from Arc made it possible to part off without the parting tool diving under the workpeice

the originals were under size and looked like they had been hacked out of a piece of slag

these pictures are not great but should give you an idea of how close a fit the new gibbs are

   John




Offline John Rudd

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Re: Fix for Gib twist on mini lathe.
« Reply #5 on: October 02, 2014, 05:19:08 PM »
Hi Ian,

Save your time and buy the brass gibs from one of the suppliers. I plan to order a set soon myself. I figure $29usd will be worth it for my time.



In the UK you can get them HERE at the bottom of the page.

Eric


.....and that was the choice I made....
eccentric millionaire financed by 'er indoors
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Offline S. Heslop

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Re: Fix for Gib twist on mini lathe.
« Reply #6 on: October 02, 2014, 06:22:26 PM »
I noticed this problem too not so long ago. I really butchered the original gibs and screws trying to improve them, and eventually I realised that they were a wider angle than the dovetail they were supposed to fit in. I filed them to a more acute angle, but kind of over-did it so it was now too narrow, but it was still an improvement.

If I had more patience i'd probably try scraping them with some engineer's blue. But i've been planning to get a better lathe for the last... 4 years or so, and that's put me off doing any real work on improving my existing one.

Offline ian_in_the_midlands

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Re: Fix for Gib twist on mini lathe.
« Reply #7 on: October 04, 2014, 09:46:31 AM »
Thanks for all advice.
I am afraid I ignored the bit about not making them myself.
I had the brass and the weather is grim today so I thought I would have a go.

I went with brass as no horror stories about lathe wear.
Initial results feel good. Twist appears to be eliminated.
I will give that lathe some use and see how they bed in.

Thanks again for the help.

Offline John Swift

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Re: Fix for Gib twist on mini lathe.
« Reply #8 on: October 04, 2014, 10:08:46 AM »
Hi Ian

that looks great
you will find the lathe feels a lot better

  John

Offline stirling lad

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Re: Fix for Gib twist on mini lathe.
« Reply #9 on: October 21, 2014, 01:23:14 PM »
nice neat job Ian...


...m.

Offline Brass_Machine

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Re: Fix for Gib twist on mini lathe.
« Reply #10 on: October 21, 2014, 06:31:49 PM »
Just saw this. Very nice!

Eric
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We're all mad here. I'm mad. You're mad.

Offline steampunkpete

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Re: Fix for Gib twist on mini lathe.
« Reply #11 on: November 02, 2014, 02:18:34 AM »
I also went the ARC Eurotrade replacement gibs route. Very pleased with the result and its cheap. The precious time saved meant that I could spend more time on making stuff.
Looks like a near unanimous answer.

Offline nrml

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Re: Fix for Gib twist on mini lathe.
« Reply #12 on: November 03, 2014, 04:06:27 PM »
Just as a word of warning to anyone new doing some research on the ARC brass gibs; they don't fit real bull mini lathes perfectly (at least they didn't fit mine). The cross slide gib was too thin and it didn't stop the twist. The top slide gib was too big to fit in. I filed the top slide gib down to size and used it but I ended up having to make a new cross slide gib from scratch. I guess that they are either made for Seigs (and that there are some significant differences between them and the real bull version) or the machining on mini lathes as a whole is so crude that there is great individual variation.

I can't fault the build quality of the gibs for the price or ARCs customer service.