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Hello:
This new member was rummaging through files yesterday afternoon and found this:
/g/Unimat/photo/0/46015.56320.0?p=Created%2C%2C%2C20%2C2%2C420%2C0
I can recognise it as a device to adjust/improve backlash in our dear and very backlashy DB200/SL1000 and Unimat 3.
But that's all.
No text, no details.
Is there a post for it somewhere here?
Thanks in advance.
Best,
JHM
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@JHM - the photo is from in this thread:
| [email protected] | unimat 3 cnc |
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And now I have to go make one of those for myself too. :D
- Dwayne
On Monday, June 13, 2022 at 03:01:15 PM EDT, sawbona@... <sawbona@...> wrote:
Hello:
This new member was rummaging through files yesterday afternoon and found this:
/g/Unimat/photo/0/46015.56320.0?p=Created%2C%2C%2C20%2C2%2C420%2C0
I can recognise it as a device to adjust/improve backlash in our dear and very backlashy DB200/SL1000 and Unimat 3.
But that's all.
No text, no details.
Is there a post for it somewhere here?
Thanks in advance.
Best,
JHM
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Hello: > @JHM - the photo is from in this thread ... Thanks for the heads up. > ... have to go make one of those for myself too. :D
Well ...
Let me/us know when you're done.
And please consider documenting the how-to so the rest of us may have a go at it.
I could not make heads or tails of the OPs explanation.
Thanks in advance.
Best,
JHM
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On Tue, Jun 14, 2022 at 02:15 AM, @juliushenrymarx wrote:
I could not make heads or tails of the OPs explanation.
It is essentially a split nut and he is using adjusting screws to open the gap and reduce the backlash - I think. Alternatively screws could be used to reduce the gap. An alternative is a double nut with a fixed spacing and rotate one relative to the other. That is one of the easier ones to add to a machine since you can leave the existing nut alone and find a place to add the second one. I proposed some time ago (for the DB/SL) a nut split horizontally and using a screw to press the two halves together. I think that covers most options!
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There could be an alternative - have them but not tried yet. Solder one in slightly opened state, fully drill, thread, melt alloy and fit in a corresponding hole for screw passing with a lock-nut (length position variable) or other mean with controlled tightening. Best regards, Mihai 
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Or just shorten at the threaded length (maybe, for ease).
Mihai
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i am the builder of this nut. its a splited nut.
to adjust the gap i use 2 grubscrews m2. the grubscrews press on small balls from old bearings. ball diameter 1.3 or 1.5mm
the balls pressed in after i cut the m2 thread.
the balls are used to fill the hole and give a press point. to use this nut the crossslide must be milled a slot of the size of the nut for correct position and height .
slot depht about 1,3mm
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Hello:
> ... essentially a split nut and he is using adjusting screws ...
I see.
Now I get it.?
There's also the type of fix used in 3D printers consisting of a spring loaded nut.
It could done in minutes if the replacement part (ASA 050 040 - cross slide nut) were available. ????????????????????????????????????????????????????????
Best,
JHM
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Hello:
> its a splited nut.
> to adjust the gap i use 2 grubscrews ....
> ... balls are used to fill the hole and give a press point.
Thanks for the explanation.
BTW: what is the thread specification for the cross slide thread and the lead screw?
The manual I have says and? A3A 050 030 and A3A 000 050, probably part numbers.
Thanks in advance,
JHM
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Pretty sure they're single-start threads so you can determine the threads per inch (I'm in the US) by turning the handles some number of revolutions and measuring how far the axis traveled.
Jay
Hello:
> its a splited nut.
> to adjust the gap i use 2 grubscrews ....
> ... balls are used to fill the hole and give a press point.
Thanks for the explanation.
BTW: what is the thread specification for the cross slide thread and the lead screw?
The manual I have says and? A3A 050 030 and A3A 000 050, probably part numbers.
Thanks in advance,
JHM
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The thread is M8 ¡Á 1 left handed. Taps and dies are available on Ebay, and elsewhere. This is the standard lead screw thread on Unimats, DB, SL U3 and PC/Basic. I think the thread on the U3 compound slide is M6 left handed.
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Hello: Sorry to revive an old thread ... After getting my set of qctp+holders finished, I am now looking to see about fixing the backlash issues the Unimat 3 cross slide has. From what I seen, it is very tricky business to get involved in as there is very little/no room to do much about it and on top of that the slide nut itself is very small:  Not to mention the terrible hassle you are in should you lose the damn thingy: just in case, I wrote the people at Emco last June equiring about the possibility of getting a replacement part but was promptly ignored. It seems the very same part is used in the Unimat Basic, so it may be available somewhere. But I digress ... As we know, the hole in the nut is threaded 8.0x1 LH. The thing (part no. A3A 050 040) is basically a ~10mm x 10mm x 10mm cube, with the threaded cylinder to hold it in place from above with a M4x8 countersunk screw (part no. ZSR 65 0408) being ? ~6.0mm x 5.0mm high .?
... crossslide must be milled a slot of the size of the nut for correct position and height.
slot depht about 1,3mm
Hoping not to impose, I was wondering if you'd be kind enough to post a photo of what you have done to the cross slide so I could get an idea of what I was getting into.? ie: the slot you milled into the cross slide and any details you think pertinent. Thanks in advance. Best, JHM
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Hi Julius,
That nut is available from Arc Euro in the UK as a spare for the Sieg C0 lathe:
I have used those in the past but now make my own from 1/2" bronze bar (squared off to 10mm).?? That needs a standard M4 tap and a M8x1LH tap of course!
Rgrds,?? Richard.
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Hello Richard:
toggle quoted message
Show quoted text
On Sun, Jan 8, 2023 at 03:17 PM, Richard wrote:
... available from Arc Euro in the UK as a spare ...
Indeed ... Thanks for the heads up, I had seen it last week while looking for a solution for the backlash in my U3, thinking that maybe a part from some other lathe could be modified/adapted. Good to know this one fits.? 8^)
... make my own from 1/2" bronze bar ...
Last year I made a nut (sans the spigot) to use along with the original nut and a coiled spring to separate them, making a device such as those used in hobby CNC machines to reduce backlash:  But it was a failure as there is very little space between the top of the feed screw and the bottom of the slide:  It is ~ 0.90mm without counting the crest of the feed screw thread, so it is probably down to ~ 0.70mm. A coiled spring expands under tension and altough I managed to file/sand one and make it work to reduce the backlash, at some point the slide would jam. The nut is a ~10mm cube and the way it moves in is 10.5mm high by 12.5mm at the bottom and 13.5mm at the top. Not much room below the nut and not much to either side. Thank you very much for your input. Best, JHM
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Hey All,
I like that approach Julius and have used something similar on the Z axis of my 3D printer.
Bridgeport mills use a 'split nut' to adjust for backlash. Crude but effective.
I drew one up for the Unimat in Fusion 360?based on the dimensions of the 10mm nut someone posted for sale. Basic operation is the same, you have to cut a gap into the nut to allow it to be compressed together and then have a mechanism that allows you to squeeze it slightly to adjust the fit of the nut onto the leadscrew.
I don't have this machine so don't know how much room there is in the area where this is used so it may not work as designed. You might be able to rotate the clamping mechanism 90* to get it to fit in the space. You would have to relocate the set screws and drill a 10+ mm hole in the bottom of the clamp to allow the leadscrew?to pass through.
I've attached some pictures and a drawing (some dimensions) and the CAD file in native Fusion format and as a STEP file.
On Sun, Jan 8, 2023 at 2:52 PM Julius Henry Marx < sawbona@...> wrote: Hello Richard:
On Sun, Jan 8, 2023 at 03:17 PM, Richard wrote:
... available from Arc Euro in the UK as a spare ...
Indeed ...
Thanks for the heads up, I had seen it last week while looking for a solution for the backlash in my U3, thinking that maybe a part from some other lathe could be modified/adapted.
Good to know this one fits.? 8^)
... make my own from 1/2" bronze bar ...
Last year I made a nut (sans the spigot) to use along with the original nut and a coiled spring to separate them, making a device such as those used in hobby CNC machines to reduce backlash:
But it was a failure as there is very little space between the top of the feed screw and the bottom of the slide:
It is ~ 0.90mm without counting the crest of the feed screw thread, so it is probably down to ~ 0.70mm.
A coiled spring expands under tension and altough I managed to file/sand one and make it work to reduce the backlash, at some point the slide would jam.
The nut is a ~10mm cube and the way it moves in is 10.5mm high by 12.5mm at the bottom and 13.5mm at the top.
Not much room below the nut and not much to either side.
Thank you very much for your input.
Best,
JHM
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That backlash spring idea might fit and work if you change the leadscrew (and the nut) to M6x1LH??? Of course wear would then be more rapid.??
Personally I just put up with the backlash and replace the nut periodically!
Rgrds,? Richard.
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Hello Jay:
First of all, thank you very much for taking the time to put this together.? 8^)?
toggle quoted message
Show quoted text
On Sun, Jan 8, 2023 at 08:44 PM, Jay Perez wrote:
... have used something similar on the Z axis of my 3D printer.
There are quite a few variants and all have the same principle: a spring.
Bridgeport mills use a 'split nut' ...
Ahh, Brigdeport milling machines. Serious stuff.
Crude but effective.
Many intelligent solutions are. But it doesn't look crude to me.? 8^)
... cut a gap into the nut to allow it to be compressed ...
There would be no problem with that. Just maybe, given the size of the nut, finding a thin enough saw blade.
... a mechanism that allows you to squeeze it slightly ...
That's the exact moment at which the elephant enters the room. Like I mentioned previously, the OEM nut is a 10mm cube and the way it moves in is 10.5mm high. So there's only ~ 0.50mm vertical space available. As the saddle is made from die cast aluminium, the way is shaped like a flat bottomed inverted cone to facilitate the separation from the die during manufacture. It measures 13.5mm at the top and 12.5mm at the bottom. So the nut moves along the centre of the way with barely any wiggle room. ie: ~ 0.50mm at the bottom, ~1.50mm to each side at the top and ~1.00mm at the bottom. I'm afraid I don't see room for a clamp + set screws there. 8^/ Idea: I have been wondering if the M4x0.7 screw than holds the nut in place could push a very small brass/teflon/? bearing against the 8.0x1 thread and help reduce the backlash. Or maybe the screw could be made from very hard brass and have an acute/pointed end. ie: by design (in theory), the feed screw axis and the M4 screw axis intersect at 90¡ã and as a consequence of that, the screw's point would run inside the thread and (hopefully) reduce or eliminate the existing backlash. Make sense? Obviously (if it works) such a screw would have to be replaced when the point gets worn and start to slip. But anything is better than this incredible design flaw from Emco's engineers. Once again, thanks for your input. Best, JHM
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Keith,
I agree that a double nut could be used effectively to adjust and control backlash. That in my experience, is preferable to a ¡°split¡± nut that has to be squeezed or forced together by some means to effect the adjustment. A double nut simply uses two nuts that are in line with one another, but opposed. The space between the two nuts is adjusted to control backlash. Thanks for mentioning this method as offers precise adjustments.
Dick
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Based on Julius' and other comments I modeled some of the other options discussed.
I'm not familiar with the machine and not sure I'm correctly visualizing the clearances?around the nut from the verbal descriptions.
Two of the designs seem pretty plausible if you have the taps and equipment to fabricate your own nut.
I think you could probably get away with cutting the slot with a hacksaw blade or a jeweler's?saw.
Jay
True Split Nut Design. Slot in line with the threads.
??  Modified version of my earlier design.
Set screw on the bottom pushing a plastic plug into the thread.
On Sun, Jan 8, 2023 at 7:47 PM Julius Henry Marx < sawbona@...> wrote: Hello Jay:
First of all, thank you very much for taking the time to put this together.? 8^)?
On Sun, Jan 8, 2023 at 08:44 PM, Jay Perez wrote:
... have used something similar on the Z axis of my 3D printer.
There are quite a few variants and all have the same principle: a spring.
Bridgeport mills use a 'split nut' ...
Ahh, Brigdeport milling machines.
Serious stuff.
Crude but effective.
Many intelligent solutions are.
But it doesn't look crude to me.? 8^)
... cut a gap into the nut to allow it to be compressed ...
There would be no problem with that.
Just maybe, given the size of the nut, finding a thin enough saw blade.
... a mechanism that allows you to squeeze it slightly ...
That's the exact moment at which the elephant enters the room.
Like I mentioned previously, the OEM nut is a 10mm cube and the way it moves in is 10.5mm high.
So there's only ~ 0.50mm vertical space available.
As the saddle is made from die cast aluminium, the way is shaped like a flat bottomed inverted cone
to facilitate the separation from the die during manufacture.
It measures 13.5mm at the top and 12.5mm at the bottom.
So the nut moves along the centre of the way with barely any wiggle room.
ie: ~ 0.50mm at the bottom, ~1.50mm to each side at the top and ~1.00mm at the bottom.
I'm afraid I don't see room for a clamp + set screws there. 8^/
Idea:
I have been wondering if the M4x0.7 screw than holds the nut in place could push a very small brass/teflon/? bearing against the 8.0x1 thread and help reduce the backlash.
Or maybe the screw could be made from very hard brass and have an acute/pointed end.
ie: by design (in theory), the feed screw axis and the M4 screw axis intersect at 90¡ã and as a consequence of that, the screw's point would run inside the thread and (hopefully) reduce or eliminate the existing backlash.
Make sense?
Obviously (if it works) such a screw would have to be replaced when the point gets worn and start to slip.
But anything is better than this incredible design flaw from Emco's engineers.
Once again, thanks for your input.
Best,
JHM
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NapierDeltic
OldToolmaker