|
Hey all,
I'm having this really irritating problem with backlash coming from the Unimat PC cross-slide handwheel.
My understanding is that backlash (for the Unimat) can come from two sources
A) Play in the slide lead nut / screw itself; OR
B) Having too much of a gap between the threaded handlewheel and the cross slide itself.
?
My main issue is with B)
?
Following the Unimat instructions, I screw in the threaded handlewheel all the way, and back it out JUST a bit, before tightening up the locking nut (on the outside).
For the life of me, I can never get it "just right". If I tighten enough so everything JUST rotates smoothly, the backlash is too much (0.07mm). If I tighten anymore, the backlash is a bit better, but the handwheel starts to bind and it is difficult to turn freely.
(The binding is strange in the sense that "tightness" occurs at certains angles of rotation only, rather than a constant heavy friction).
Could this be some issue with the bushings or something? I tried putting in small thrust bearing between the handlewheel and where it is mounted, but it didn't help much.
?
Appreciate any advice thanks :)
|
It's possible your lead screw is bent, if it is, the bearing surfaces will touch at some points and not at others, that could be the cause of the tightness.
|
Hello
Jpow:
They
also sell plastic washers to put behind the hand wheel. Allows
you to reduce the clearance with less friction.
Ball
thrust bearings might be nice if you can find any. ( I might
have some from old phonographs, etc. )
Carl.
On 4/5/2023 3:11 AM, jpow wrote:
toggle quoted message
Show quoted text
Hey all,
I'm having this really irritating problem with backlash coming
from the Unimat PC cross-slide handwheel.
My understanding is that backlash (for the Unimat) can come
from two sources
A) Play in the slide lead nut / screw itself; OR
B) Having too much of a gap between the threaded handlewheel
and the cross slide itself.
?
My main issue is with B)
?
Following the Unimat instructions, I screw in the threaded
handlewheel all the way, and back it out JUST a bit, before
tightening up the locking nut (on the outside).
For the life of me, I can never get it "just right". If I
tighten enough so everything JUST rotates smoothly, the backlash
is too much (0.07mm). If I tighten anymore, the backlash is a
bit better, but the handwheel starts to bind and it is difficult
to turn freely.
(The binding is strange in the sense that "tightness" occurs at
certains angles of rotation only, rather than a constant heavy
friction).
Could this be some issue with the bushings or something? I
tried putting in small thrust bearing between the handlewheel
and where it is mounted, but it didn't help much.
?
Appreciate any advice thanks :)
|
Hello Jpow:? I have just used some thrust bearings on my unimat when I fitted stepper motors they are working very good here is the info: 4 pieces AXK0515/AS0515 Budget Needle Roller Cage with 2 AS Washers 5x15x4mm
Phill 
|
Hi Jpow,
Having come the same way as you do, I just would like to toss in here my humble 2 cents of wisdom without any claim to UNIMAT 3 lathe mastery at all, but here goes:
In this rather comprehensive (and recommended) , published by the then importer for Unimat in the Netherlands, in Utrecht (still in existence), I stumbled upon the below passage on page 58 (see scan).?
The main point here is about the "transporteurs"? - the spindles for the different movement feeders (longitudinal, cross-slide and tailstock). According to this manual, the backlash ("speling") on the spindles is on purpose and one should not try to reduce the backlash. Coming to the field of metalworking as a woodworker, I was not surprised: when dealing with cast iron woodplanes, one encounters the same backlashes when adjusting the cutting iron.?
What one should do is to 1) either keep a record when the cross slide spindle starts to engage and the slide starts to move, or 2) avail oneself of a set of adjustable handwheels that allow you to set the wheel at zero the moment the spindle engages.?
As much as I would want to take out the backlash (I have a history of maintaining motorcycles, mopeds and bicycles, where it is all about reducing friction and taking out backlash) I have come to live with it now.?
Now hoping to hear from a few others whether this makes any sense,
Herman
?
Op 05-04-2023 09:11 schreef jpow <powster@...>:
Hey all,
I'm having this really irritating problem with backlash coming from the Unimat PC cross-slide handwheel.
My understanding is that backlash (for the Unimat) can come from two sources
A) Play in the slide lead nut / screw itself; OR
B) Having too much of a gap between the threaded handlewheel and the cross slide itself.
My main issue is with B)
Following the Unimat instructions, I screw in the threaded handlewheel all the way, and back it out JUST a bit, before tightening up the locking nut (on the outside).
For the life of me, I can never get it "just right". If I tighten enough so everything JUST rotates smoothly, the backlash is too much (0.07mm). If I tighten anymore, the backlash is a bit better, but the handwheel starts to bind and it is difficult to turn freely.
(The binding is strange in the sense that "tightness" occurs at certains angles of rotation only, rather than a constant heavy friction).
Could this be some issue with the bushings or something? I tried putting in small thrust bearing between the handlewheel and where it is mounted, but it didn't help much.
Appreciate any advice thanks :)
|
Hi
Gang:
As a
toolmaker we learned to always turn the cranks the same way,
usually clockwise. This has fallen to the wayside with ball
screws and digital read outs.
Carl.
On 4/5/2023 2:26 PM, Herman de Leeuw
via groups.io wrote:
toggle quoted message
Show quoted text
Hi Jpow,
Having come the same way as you do, I
just would like to toss in here my humble 2 cents of wisdom
without any claim to UNIMAT 3 lathe mastery at all, but here
goes:
In this rather comprehensive (and
recommended) , published by the then importer for Unimat in the
Netherlands, in Utrecht (still in
existence), I stumbled upon the below passage on page 58 (see
scan).?
The main point here is about the "transporteurs"?
- the spindles for the different movement feeders (longitudinal,
cross-slide and tailstock). According to this manual, the backlash
("speling") on the spindles is on purpose and one should not
try to reduce the backlash. Coming to the field of
metalworking as a woodworker, I was not surprised: when dealing
with cast iron woodplanes, one encounters the same backlashes
when adjusting the cutting iron.?
What one should do is to 1) either
keep a record when the cross slide spindle starts to engage and
the slide starts to move, or 2) avail oneself of a set of
adjustable handwheels that allow you to set the wheel at zero
the moment the spindle engages.?
As much as I would want to take out
the backlash (I have a history of maintaining motorcycles,
mopeds and bicycles, where it is all about reducing friction and
taking out backlash) I have come to live with it now.?
Now hoping to hear from a few others
whether this makes any sense,
Herman
? 
Hey all,
I'm having this really irritating problem with backlash
coming from the Unimat PC cross-slide handwheel.
My understanding is that backlash (for the Unimat) can come
from two sources
A) Play in the slide lead nut / screw itself; OR
B) Having too much of a gap between the threaded handlewheel
and the cross slide itself.
My main issue is with B)
Following the Unimat instructions, I screw in the threaded
handlewheel all the way, and back it out JUST a bit, before
tightening up the locking nut (on the outside).
For the life of me, I can never get it "just right". If I
tighten enough so everything JUST rotates smoothly, the
backlash is too much (0.07mm). If I tighten anymore, the
backlash is a bit better, but the handwheel starts to bind and
it is difficult to turn freely.
(The binding is strange in the sense that "tightness" occurs
at certains angles of rotation only, rather than a constant
heavy friction).
Could this be some issue with the bushings or something? I
tried putting in small thrust bearing between the handlewheel
and where it is mounted, but it didn't help much.
Appreciate any advice thanks :)
|
This.
Somebody wiser than I am tought me that me that you can't ever
totally eliminate backlash on a screw and nut setup. You can
lessen it so it is less obnoxious, but you can't eliminate it. So
you will have to live with it. Since you have to live with it
there it doesn't make much sense to jump through major hoops to
get rid of the last little bit.
So you do what Carl said, the last motion is always in the same
direction, and is larger than the backlash. Sometimes that means
you overshoot and come back more than the backlash. Or if you
overshoot you come back more than the backlash and go in again
more carefully.
Ideally that last motion should be in the opposite direction than
cutting forces are going to try to move the cutter. This way the
cutting forces have something to push against instead of pulling
the cutter into the backlash zone where it can float around.
On 4/5/23 15:28, Carl wrote:
toggle quoted message
Show quoted text
Hi
Gang:
As a
toolmaker we learned to always turn the cranks the same way,
usually clockwise. This has fallen to the wayside with ball
screws and digital read outs.
Carl.
On 4/5/2023 2:26 PM, Herman de Leeuw
via groups.io wrote:
Hi Jpow,
Having come the same way as you do,
I just would like to toss in here my humble 2 cents of wisdom
without any claim to UNIMAT 3 lathe mastery at all, but here
goes:
In this rather comprehensive (and
recommended) , published by the then importer for Unimat in
the Netherlands, in Utrecht (still in
existence), I stumbled upon the below passage on page 58 (see
scan).?
The main point here is about the "transporteurs"?
- the spindles for the different movement feeders
(longitudinal, cross-slide and tailstock). According to this
manual, the backlash ("speling") on the spindles is on
purpose and one should not try to reduce the backlash. Coming
to the field of metalworking as a woodworker, I was not
surprised: when dealing with cast iron woodplanes, one
encounters the same backlashes when adjusting the cutting
iron.?
What one should do is to 1) either
keep a record when the cross slide spindle starts to engage
and the slide starts to move, or 2) avail oneself of a set of
adjustable handwheels that allow you to set the wheel at zero
the moment the spindle engages.?
As much as I would want to take out
the backlash (I have a history of maintaining motorcycles,
mopeds and bicycles, where it is all about reducing friction
and taking out backlash) I have come to live with it now.?
Now hoping to hear from a few others
whether this makes any sense,
Herman
? 
Hey all,
I'm having this really irritating problem with backlash
coming from the Unimat PC cross-slide handwheel.
My understanding is that backlash (for the Unimat) can come
from two sources
A) Play in the slide lead nut / screw itself; OR
B) Having too much of a gap between the threaded
handlewheel and the cross slide itself.
My main issue is with B)
Following the Unimat instructions, I screw in the threaded
handlewheel all the way, and back it out JUST a bit, before
tightening up the locking nut (on the outside).
For the life of me, I can never get it "just right". If I
tighten enough so everything JUST rotates smoothly, the
backlash is too much (0.07mm). If I tighten anymore, the
backlash is a bit better, but the handwheel starts to bind
and it is difficult to turn freely.
(The binding is strange in the sense that "tightness"
occurs at certains angles of rotation only, rather than a
constant heavy friction).
Could this be some issue with the bushings or something? I
tried putting in small thrust bearing between the
handlewheel and where it is mounted, but it didn't help
much.
Appreciate any advice thanks :)
|
Hello,Carl
Aggreed!
Backlash compensation was the first thing we learned in trade school when learning to operate the lathe. The same principle applies to most any machine tool,
although theses days many machine tools are outfitted with ball screws which pretty much eliminate all backlash. Most of us hobby machinists though, are using plain lead screws equipped machines.
Dick
|
I have the same backlash on the cross slide of my U3.? I placed a thin,? small diameter brass washer between the knob and the lathe.? This reduced the diameter of the contact circle between the knob and the lathe and so reduced the change in backlash caused by the back of the knob not being exactly perpendicular to the lead screw axis.? There was still a bit of backlash, but still a definite improvement.
|
When I rebuilt my SL, reducing the backlash as much as possible was a goal. However, there was a point of diminishing return as the hand wheel rubs against a rough uneven casting. With any flex in the screw train that gives a ¡°tight spot¡° as the hand wheel is rotated, exacerbating the problem. I tightened the hand wheel until it touched the casting, put on the nut and then tighten them together by hand, felt it then after a few tries gently tightened the nut. I had hit the ¡°sweet spot¡° that seems to work best. So short of machining that piece of casting behind the hand wheel to make it smoother, one needs to revert to the old primitive machining days of always moving your cutting tool into the work piece. Which is to say, you always back off a couple of turns on the handle and then go forward to remove the backlash and make your cut. ?I think that the casting is a poor enough bearing surface, so even placing thrust washers behind it would not illuminate the ¡°problem¡±. ?
That is to see if you consider it a problem, which I really do not. Anything that uses a lead screw into a tapped casting is going to have backlash. It is actually engineered that way.?
I have equipped my Unimat with dial indicators on both axis ?to enable me to see the backlash with every cut made.?
|
On Thu, Apr 6, 2023 at 02:37 PM, Quinn Golden wrote:
you always back off a couple of turns on the handle and then go forward to remove the backlash and make your cut.
This is what I was taught to do and have done on all my larger lathes, but on the small SL it was a problem that needed more looking at if I was to use power on the screws, my first thought was I could not get the backlash down to an acceptable level because the cast was a little rough and the aluminium hand wheel was dragging and wearing off creating more backlash, I could have turned some hard plastic washers but having used very small bearings in other work I opted to use the small thrust bearings and I found I could get a really good feel turning by hand and under power it works so well for me. With a wipe of grease on assembly these fit well, feel well and one less thing to worry about when machining.  ?? Phill
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Are there some of these thrust bearings that we can install on our manual lathes?? No boring big holes, etc., if I want to go back to original.
|
Yes John, you don't have to change anything just slide them on the shafts, I don't know where you can get them your side of the pond but this is the place in the UK:
4 pieces AXK0515/AS0515 Budget Needle Roller Cage with 2 AS Washers 5x15x4mm
Phill
|
Yeah that completely makes sense, I have a Taig CNC machine that uses the same technology as a Unimat, and I program the backlash compensation into it.? When it reads the code it compensates for backlash due to its design. ? ?
What were the part numbers of the thrust washers that you settled on ??
I wound up settling on about .0035 backlash on the Y(cross slide) and .0025 on the X.?
However in my case I am convinced that the backlash on the cross slide is in the Cross slide itself and not the handle. ? ?
I¡¯m not sure buying another used one would make it any better, I might buy another ¡°new old stock¡± if I can find it. ?
On Thu, Apr 6, 2023 at 02:37 PM, Quinn Golden wrote:
you always back off a couple of turns on the handle and then go forward to remove the backlash and make your cut.
This is what I was taught to do and have done on all my larger lathes, but on the small SL it was a problem that needed more looking at if I was to use power on the screws, my first thought was I could not get the backlash down to an acceptable level because the cast was a little rough and the aluminium hand wheel was dragging and wearing off creating more backlash, I could have turned some hard plastic washers but having used very small bearings in other work I opted to use the small thrust bearings and I found I could get a really good feel turning by hand and under power it works so well for me.
With a wipe of grease on assembly these fit well, feel well and one less thing to worry about when machining.
 ??
Phill
-- Quinn Golden
603-491-1451
|
Thank you everyone for the advice / knowledge sharing! I've realised that for my case, backlash is from both handle assembly (maybe 30% of the backlash) AND cross slide nut (majority of the backlash)? While I accept some backlash will?always be there, I can't help but think of other possible?ways to minimize it. Might this idea be feasible: The cross slide nut is approx 10mm x10mm x 10mm cube.? Is there enough material to modify?the nut into an anti-backlash design, i.e. a) Cut a slit through the nut b) Tap a tiny thread for a screw to finely adjust the size of the slit gap (so as to apply pressure on the threads, minimizing play)
Alternatively, replace the entire nut with some anti-backlash design. The only thing is that its going to be a pain to adjust it, as my UNIMAT PC doesn't leave much room to access that nut with the slide assembled fully.
@Quinn
- One option might be to just replace the cross slide nut, and / or the entire leadscrew, ASSUMING the backlash is due to heavy wear on the threads. - Arceurotrade has a that looks like it could fit with some minor modification.
Yeah that completely makes sense, I have a Taig CNC machine that uses the same technology as a Unimat, and I program the backlash compensation into it.? When it reads the code it compensates for backlash due to its design. ? ?
What were the part numbers of the thrust washers that you settled on ??
I wound up settling on about .0035 backlash on the Y(cross slide) and .0025 on the X.?
However in my case I am convinced that the backlash on the cross slide is in the Cross slide itself and not the handle. ? ?
I¡¯m not sure buying another used one would make it any better, I might buy another ¡°new old stock¡± if I can find it. ?
On Thu, Apr 6, 2023 at 02:37 PM, Quinn Golden wrote:
you always back off a couple of turns on the handle and then go forward to remove the backlash and make your cut.
This is what I was taught to do and have done on all my larger lathes, but on the small SL it was a problem that needed more looking at if I was to use power on the screws, my first thought was I could not get the backlash down to an acceptable level because the cast was a little rough and the aluminium hand wheel was dragging and wearing off creating more backlash, I could have turned some hard plastic washers but having used very small bearings in other work I opted to use the small thrust bearings and I found I could get a really good feel turning by hand and under power it works so well for me.
With a wipe of grease on assembly these fit well, feel well and one less thing to worry about when machining.
 ??
Phill
Quinn Golden
603-491-1451
|
So on the SL the cross slide does not have a ¡°nut¡° in it. The Cross light itself is threaded to match the lead screw. So adjusting for wear is hopeless unless one can find a good as new cross slide.?
As for your idea to modify the nut, it is valid. The attached photo shows the method to take up the slack in the tag system. ?
On Thu, Apr 6, 2023 at 12:17 PM jpow < powster@...> wrote: Thank you everyone for the advice / knowledge sharing! I've realised that for my case, backlash is from both handle assembly (maybe 30% of the backlash) AND cross slide nut (majority of the backlash)? While I accept some backlash will?always be there, I can't help but think of other possible?ways to minimize it. Might this idea be feasible: The cross slide nut is approx 10mm x10mm x 10mm cube.? Is there enough material to modify?the nut into an anti-backlash design, i.e. a) Cut a slit through the nut b) Tap a tiny thread for a screw to finely adjust the size of the slit gap (so as to apply pressure on the threads, minimizing play)
Alternatively, replace the entire nut with some anti-backlash design. The only thing is that its going to be a pain to adjust it, as my UNIMAT PC doesn't leave much room to access that nut with the slide assembled fully.
@Quinn
- One option might be to just replace the cross slide nut, and / or the entire leadscrew, ASSUMING the backlash is due to heavy wear on the threads. - Arceurotrade has a that looks like it could fit with some minor modification.
Yeah that completely makes sense, I have a Taig CNC machine that uses the same technology as a Unimat, and I program the backlash compensation into it.? When it reads the code it compensates for backlash due to its design. ? ?
What were the part numbers of the thrust washers that you settled on ??
I wound up settling on about .0035 backlash on the Y(cross slide) and .0025 on the X.?
However in my case I am convinced that the backlash on the cross slide is in the Cross slide itself and not the handle. ? ?
I¡¯m not sure buying another used one would make it any better, I might buy another ¡°new old stock¡± if I can find it. ?
On Thu, Apr 6, 2023 at 02:37 PM, Quinn Golden wrote:
you always back off a couple of turns on the handle and then go forward to remove the backlash and make your cut.
This is what I was taught to do and have done on all my larger lathes, but on the small SL it was a problem that needed more looking at if I was to use power on the screws, my first thought was I could not get the backlash down to an acceptable level because the cast was a little rough and the aluminium hand wheel was dragging and wearing off creating more backlash, I could have turned some hard plastic washers but having used very small bearings in other work I opted to use the small thrust bearings and I found I could get a really good feel turning by hand and under power it works so well for me.
With a wipe of grease on assembly these fit well, feel well and one less thing to worry about when machining.
 ??
Phill
Quinn Golden
603-491-1451
-- Quinn Golden
603-491-1451
|
Incidentally I have installed a new lead screw when I rebuilt the lathe. ?So my backlash is in the cross slide. ?
|
Perhaps using a curved, or wave, disk spring washer under the handle would give enough pre-load to minimize the backlash. Something similar to one of these:
https://www.mcmaster.com/9714k323/
Richard B.
|
Just to confirm, what is this cross slide nut material?
|
Hi Gang:
To improve the casting is just half of the job, you need to improve the runout on the knob. Both can be corrected with a file. Use some Persian Blue, coat the back of the know and run it up to the carriage. Look for where it rubs off the know and onto the carriage. File both spots down un till the Blue rubs off the whole knob and onto the whole casting. A bent lead screw will mess this up some, but it should help.
Carl.
On 04/06/2023 9:37 AM Quinn Golden <quinngolden@...> wrote:
When I rebuilt my SL, reducing the backlash as much as possible was a goal. However, there was a point of diminishing return as the hand wheel rubs against a rough uneven casting. With any flex in the screw train that gives a ¡°tight spot¡° as the hand wheel is rotated, exacerbating the problem. I tightened the hand wheel until it touched the casting, put on the nut and then tighten them together by hand, felt it then after a few tries gently tightened the nut. I had hit the ¡°sweet spot¡° that seems to work best. So short of machining that piece of casting behind the hand wheel to make it smoother, one needs to revert to the old primitive machining days of always moving your cutting tool into the work piece. Which is to say, you always back off a couple of turns on the handle and then go forward to remove the backlash and make your cut. ?I think that the casting is a poor enough bearing surface, so even placing thrust washers behind it would not illuminate the ¡°problem¡±. ?
That is to see if you consider it a problem, which I really do not. Anything that uses a lead screw into a tapped casting is going to have backlash. It is actually engineered that way.?
I have equipped my Unimat with dial indicators on both axis ?to enable me to see the backlash with every cut made.?
|
Unimat Matt
Carl
Herman de Leeuw
OldToolmaker