Torque to move Z axis in a mini mill?

[ChazzC]

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.

 

[Alberto-sp]

Thank you!!

 

[WobblyHand]

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.

 

[homebrewed]

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.

 

[matthewsx]

Battery powered drill driver will have a built in clutch.

Also works as a drill

 

[WobblyHand]

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).

 

[ChazzC]

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).

 

[matthewsx]

Looks like it’s on the top.

BENCH TOP DRILL-MILL VM18L

<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

 

[ChazzC]

Looks like it’s on the top.

BENCH TOP DRILL-MILL VM18L

<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

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

 

[matthewsx]

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