# Torque to move Z axis in a mini mill?



## Alberto-sp (Sep 30, 2022)

Hello.

I have a weiss WM18L. Is not very known. Is slightly smaller than SIEG 2.X. I want to put a motor to drive the Z axis. Not CNC, but just to move it because the hand wheel is a PITA. The problem is I have no idea about the torque necesary to move it. Any clue?

Thank you

Best regards


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## jwmelvin (Sep 30, 2022)

Affix a stick to the wheel and hang weights until it moves?

Or a small torque wrench.


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## Alberto-sp (Sep 30, 2022)

Thanks for your answer. The hand wheel is horizontal and I dont have a torque wrench


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## jwmelvin (Sep 30, 2022)

Alberto-sp said:


> Thanks for your answer. The hand wheel is horizontal and I dont have a torque wrench


Piece of string and a spring scale of some sort (even one home made)?


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## markba633csi (Sep 30, 2022)

Some people have used a cordless hand drill to serve as a poor-man's power feed, if that gives you some idea.  A small lightweight motor + gearbox.
I believe I saw one that used an automotive windscreen wiper motor


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## WobblyHand (Sep 30, 2022)

Alberto-sp said:


> Thanks for your answer. The hand wheel is horizontal and I dont have a torque wrench


Do you have a fish scale?  It is a spring with a hook.  You put your caught fish on the hook, and the weight of the fish stretches the spring.  There is a pointer on the scale to read out how many kg the fish is.  

You could attach a bar to the hand wheel that is 10, 20, or 30cm long.  Hook the fish scale on the bar.  Keeping the bar perpendicular to the fish scale, pull the fish scale horizontally and read how many grams or kg it requires to start moving.  The length of the bar times the "weight of the scale" is the torque required.  

For example, let the bar be 20 cm long.  If the scale reads 1 kg, then the force is m * g = 1kg * 9.81 m/sec^2 = 9.81 N.  Therefore the torque is 9.81 N * 20cm or 1.96 Nm.  For the most accurate reading, fix the bar to the center, and to the rim.


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## Alberto-sp (Sep 30, 2022)

Thanks for your answers. But don't you have a clue about the torque aprox? To avoid measuring it


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## WobblyHand (Sep 30, 2022)

Alberto-sp said:


> Thanks for your answers. But don't you have a clue about the torque aprox? To avoid measuring it


Have no idea what the required torque is.  A fish scale can't be too expensive.


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## matthewsx (Sep 30, 2022)

The tip for a cordless drill is a good one. You could engineer a solution by calculating required torque, etc. Or just cut to the chase and put a nut you can drive with a drill.

Cheers,

John


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## tghsmith (Sep 30, 2022)

most of the small mills have a stupid small "knob" on the Z.. I made an adapter and mounted a real hand-wheel,, moves easy, finer adjustments..


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## ChazzC (Oct 1, 2022)

Alberto-sp said:


> Thanks for your answers. But don't you have a clue about the torque aprox? To avoid measuring it


I checked my Little Machine Shop 3990 High Torque Mini Mill (a SIEG SX2 variant) using a small digital tension scale (yes, my wife has already told me I have too much stuff) on the knob of the replacement hand wheel I installed last year:











Near the top of the travel it took ~2.5 kg to start the hand wheel in motion, acting on a moment arm of ~22mm. Using Wobbly's calculation, 2.5 x 9.81 x 0.022 = 0.54 Nm. As the motion of the hand wheel is transmitted to the Z-Axis rack through a (very) inefficient drive system, I would plan on a conservation torque of at least 1 Nm, and would include some type of slip clutch in your design.


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## Alberto-sp (Oct 2, 2022)

Thank you!!


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## WobblyHand (Oct 2, 2022)

Alberto-sp said:


> Thank you!!


This gets you in the rough region of required torque.  However, there could be as much as 0.1x torque to 10x torque.  Your mill is different!

You really should measure it yourself.  The motor and driver are a lot more expensive than a simple fish scale.  It is worth buying a fish scale to avoid buying the wrong motor and driver.  That way you will spend the least amount of money for your needs.


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## homebrewed (Oct 2, 2022)

There are other reasons to get yourself a spring scale (A.K.A. fish scale).  I use one to set the downforce on my 4x6 bandsaw.  That's one of the weak points of the design, there is literally NO indication of how much downforce you've got.


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## matthewsx (Oct 2, 2022)

Battery powered drill driver will have a built in clutch. 

Also works as a drill


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## WobblyHand (Oct 2, 2022)

matthewsx said:


> Battery powered drill driver will have a built in clutch.
> 
> Also works as a drill


I suspect the hand wheel is not easy to get to, or the positioning is awkward.  Having a drill driver would not help in that case.  Just because it worked out fine for your mill, does not mean @Alberto-sp 's mill is the same.  Or your shop layout is the same.  

For my mill, having a drill driver also would not be of a great benefit.  Reaching the crank is doable, but slightly awkward.  Maybe it would take a few seconds less, but the position would be just as awkward as before.  Installing a motor eliminates having to physically access that area for adjustment (post installation).


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## ChazzC (Oct 2, 2022)

WobblyHand said:


> I suspect the hand wheel is not easy to get to, or the positioning is awkward.  Having a drill driver would not help in that case.  Just because it worked out fine for your mill, does not mean @Alberto-sp 's mill is the same.  Or your shop layout is the same.
> 
> For my mill, having a drill driver also would not be of a great benefit.  Reaching the crank is doable, but slightly awkward.  Maybe it would take a few seconds less, but the position would be just as awkward as before.  Installing a motor eliminates having to physically access that area for adjustment (post installation).


I agree; I replaced the original hand wheel (hw) because it didn’t have a crank and I wanted to be able to move the head a little faster when the hw is engaged (dog clutch on the rack pinion). The OD of the new hw is about the same as the original since there’s not a lot of space and I wanted to be able to make fine adjustments when milling top surfaces.

For what I do I don’t see much value in power Z-Axis feed on this style of mini mill: on one of the larger bench mills where the head moves separately from the quill, yes, power feed on the head would be almost essential.

On the other hand, a power cross slide on my 7 x 16 mini lathe is something I’m interested in (small right angle gear head motor, clutch and variable speed), but that’s a separate thread (and a potential article in HSM/MW).


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## matthewsx (Oct 2, 2022)

Looks like it’s on the top. 









						VM18L DRILLING AND MILLING MACHINE
					

<h3><span style="color: #0862aa;">DESCRIPTION DU PRODUIT</span></h3>Petite perceuse-fraiseuse VM18L de précision au gabarit et poids contenus permettant son utilisation en laboratoire, salle blanche ou appartement pour des activités de micromécanique, modélisme, horlogerie, bijouterie...




					weiss-machines.com
				




Stepper motor with a belt drive maybe?



			https://www.amazon.com/Stepper-Motor-425oz-Length-Router/dp/B081VD4C28/ref=asc_df_B081VD4C28?tag=bngsmtphsnus-20&linkCode=df0&hvadid=80814222102121&hvnetw=s&hvqmt=e&hvbmt=be&hvdev=m&hvlocint=&hvlocphy=&hvtargid=pla-4584413749650975&psc=1
		


I’ve used this size motor on my CNC mill drill project. 

https://www.hobby-machinist.com/threads/homemade-vertical-mill-drill.77611/post-947144

John


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## ChazzC (Oct 3, 2022)

matthewsx said:


> Looks like it’s on the top.
> 
> 
> 
> ...


60 (ish) RPM Gearmotor may be a better alternative unless OP is looking for CNC - less electronics involved, just motor & variable power supply.


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## matthewsx (Oct 3, 2022)

Gearmotors are relatively expensive, I've used this type of PWM controller to run steppers without needing a full CNC setup.



			https://www.amazon.com/15-160V-Adjustable-Controller-Generator-Regulator/dp/B07HNSVMVH/ref=sr_1_15_sspa?crid=1WEQTR5CB475Z&keywords=stepper+motor+driver&qid=1664824040&qu=eyJxc2MiOiI1Ljk2IiwicXNhIjoiNS40MiIsInFzcCI6IjUuMjIifQ%3D%3D&sprefix=stepper+motor%2Caps%2C149&sr=8-15-spons&psc=1&smid=A1XXTNZI53GFRR&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExQUUyOVJHSkg5S1pMJmVuY3J5cHRlZElkPUEwNTY4MDM0M0FZR1VXU0dGSzVNOSZlbmNyeXB0ZWRBZElkPUExMDIwNDYwMlpOWEVUSEgzV0RTOCZ3aWRnZXROYW1lPXNwX210ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=
		


John


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## Alberto-sp (Oct 3, 2022)

Thanks for your answers and help

Yes you are right, I´ll buy the fish scale


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## pontiac428 (Oct 3, 2022)

No desire to calculate the torque/load/impulse?  It would be easy to do.  Work is mass times distance, and impulse can be back calculated from time, mass, and translation.  Divide the force (or force function with respect to time) by your lead screw pitch and your delta t, and you end up with peak torque needed to move a mass a given distance with a measured acceleration.  It should get you close, right?  Or you can use a fish scale.  I suppose with a fish scale, a man could measure tension for a lifetime.


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## dml66 (Jan 5, 2023)

Older thread but, I just went through this. My 7x10 HF mini-lathe needs about 7 in-lbs of torque to turn the engaged leadscrew and move the carriage.

EDIT:
Oops: just noticed it's a mill, sorry, please ignore.


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