Backlash on SX2p mill

This topic has 14 replies, 6 voices, and was last updated 3 May 2019 at 18:35 by Alan Vos.

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28 April 2019 at 17:51 #26582
BOB BLACKSHAW 1
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@bobblackshaw1
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28 April 2019 at 17:51 #406927
BOB BLACKSHAW 1
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@bobblackshaw1
My SX2p mill has .2mm backlash on X and Y, is this normal or is the screw on the way out.

My lathe which has had good use over four years has .05mm backlash,

Is any adjustments that can be made for the mill, or any other type of screw that will give minimal backlash.

If I don't climb mill it can be a bit light on the handle and can jump the .2mm backlash, so Im always aware of the problem.

Thanks Bob.
28 April 2019 at 17:58 #406929
JasonB
Moderator
@jasonb
Have you tried adjusting the two grub screws in each of the nuts, they will take some backlash out.

Nuts that hold the handles on can also affect endfloat of the screws may want nipping up a fraction
28 April 2019 at 18:07 #406931
HOWARDT
Participant
@howardt
As Jason said adjust the leedscrew nuts. If you wind the axis out to its maximum the adjusting screws can be seen. Adjustment stretches the split nut to apply some tightening on pitch. You have to do it at the end of travel then see what happens at the mid position, which is were most slack probably is. Mine is only three years old and reasonably worked but still adjusts ok.
28 April 2019 at 20:38 #406957
BOB BLACKSHAW 1
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@bobblackshaw1
Thanks for the replies. I didn't realise that grub screws are on the nut, Ill have ago in the morning.

Thanks Bob.
28 April 2019 at 22:10 #406974
Neil Wyatt
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@neilwyatt
+1 for adjusting the leadscrew nuts.

Neil
29 April 2019 at 18:36 #407083
Alan Vos
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@alanvos39612
I found that even wth the leadscrew nuts adjusted, there was still more backlash than I liked (I don't recall the numbers). This was traced to float at the hand wheels. Adjust out the float, too tight to turn. Easy to turn, too much float. Much improved by boring out the bearing blocks to add needle roller bearings. Smoother as well. There is plenty of metal. If you mess up, the blocks are cheap enough to replace. I could probably come up with a photo or two if interested. SX2P Bearing Block
29 April 2019 at 19:47 #407094
Russell Eberhardt
Participant
@russelleberhardt48058
Like Alan, I added thrust bearings to the support blocks. Here is a DXF file of my working drawing for the modification along with a slight mod to the leadscrew:

**LINK**

Russell
1 May 2019 at 18:23 #407373
Alan Vos
Participant
@alanvos39612
Posted by Alan Vos on 29/04/2019 18:36:38:

needle roller bearings.

Correction, thrust ball bearings. The thrust needle roller bearing is helping clamp the tool post.
2 May 2019 at 08:47 #407447
BOB BLACKSHAW 1
Participant
@bobblackshaw1
Can you tell me what bearings I need, and where to get them.

I got the backlash down to .05mm, had no idea that those small screws were there.

Thanks, Bob.
2 May 2019 at 18:26 #407514
Alan Vos
Participant
@alanvos39612
Posted by BOB BLACKSHAW on 02/05/2019 08:47:27:

Can you tell me what bearings I need, and where to get them.

I used F8-16M (2 per axis) from ARC. (Do ARC keep order history for ever?) Russell's drawing showed the same size and the same general arrangement. Though I did not modify my leadscrew. Diagram 4, part 23 of the SX2.7 looks much the same.

IF I recall correctly, the fiddly bit is getting the outside bearing slightly proud so that the handwheel neither binds, nor shows a large gap.
3 May 2019 at 10:13 #407577
BOB BLACKSHAW 1
Participant
@bobblackshaw1
Hello all, any idea how I can open the link on Russell's thread, its Drop Box file. I cant open it on my computer, haven't a clue what Drop Box is.

Thanks Bob.
3 May 2019 at 10:18 #407579
JasonB
Moderator
@jasonb
her you go as you will need something to open the DXF file that is on dropbox anyway.
3 May 2019 at 10:30 #407581
Russell Eberhardt
Participant
@russelleberhardt48058
Hi Bob, I'm not sure if you will need to modify the end of the leadscrew. I was fitting a stepping motor for CNC so possibly needed a bit more length at the end.

Yes, the thrust ball bearings came from ARC.

FYI a DXF file is one that can be opened by almost any CAD software or just a DXF viewer.

Russell
3 May 2019 at 18:35 #407627
Alan Vos
Participant
@alanvos39612
One additional note. To avoid binding, you need to align the centre of the bearing block with the centre of the leadscrew nut. When you re-assemble, leave the bearings and two bolts attaching the bearing block slightly loose. Crank the handwheel so that the bearing block is as close to the leadscrew nut as it goes. Tighten the two bolts. Now you can set the bearing pre-load.
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