# Z Axis Power Feed for Precision Matthews PM-728VT Mill



## chipinator (May 29, 2021)

Hello all.  I hope everyone is staying well.  Looking around my Precision Matthews PM-728VT mill, I began wondering if there is a way to mount a power feed such as an Align power feed to the Z axis and still be able to use the hand crank/wheel for finer adjustments.  I realize I can purchase a 3rd party Z axis power feed but I thought it might be a fun challenge to fabricate one.  Before starting, I was wondering if anyone else has attempted a project like this?  Anyone have any ideas?  Any suggestions would be helpful.


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## GunsOfNavarone (May 29, 2021)

I know there are a few threads here on the subject....some toying with the idea, some completed. The ideal way is a motor connected to end of ball screw at top, short cut/easier is connecting to the spline under the crank handle. I have eyeballed my PM727m's for a while, I hate cranking that thing BUT...if it wasn't for cranking it, I'd forget to lock down the gibs and our machines have BUTTLOADS of movement in the Z axis if not locked down.


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## chipinator (May 30, 2021)

Hey GunsOfNavarone.  Thanks for your insight.  There is a 3rd party motor that connects as you descibe at the top end of the ball screw but I think that's going to be my last option.  This is my first mill and wanting to be self sufficient, and maybe to learn a thing or two, I wanted to give it a try first or at least think through the process to see if it was even worth attempting.  Would you happen to have an idea on what type of motor I could use to connect to the spline under the crank handle or how I could even do this?  I'm trying to get some ideas at the moment.


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## GunsOfNavarone (May 30, 2021)

There is a few threads here on the subject, here is that went to completion.
Z axis
I know there are simpler versions, though simpler may not be as ideal, but get you moving in the right direction.


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## GunsOfNavarone (Oct 10, 2021)

Reviving an old thread, but have you solved this yet? If not, this looks like a great/easy fix. I'm wondering if the 728vt is close enough to my 727 to work as well...
Power lift


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## addertooth (Oct 10, 2021)

According to some sources, the Priest kit has a motor which is slightly under-powered.  This resulted in the users either having to loosen their Z-Axis Gibs, or add a gas-spring to help lift the head.  Other than that limitation (which is serious) I like the way they tie into the existing mechanism to drive the existing gear train.  A beefier motor (or geared down more) would resolve the challenges the Priest modification suffers from.

I have a PM728vt, and will admit my right shoulder is not fond of cranking the head up and down.


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## GunsOfNavarone (Oct 10, 2021)

Hmmm…the gear reducing motor is probably cheap/easy to source, I wonder if that’s an easy swap?


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## fursphere (Oct 10, 2021)

Blondihacks just did a video on installing one of Priest Tools on a PM25.   Similar in nature.


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## chipinator (Oct 10, 2021)

@GunsOfNavarone & @addertooth 
I considered purchasing a Priest Z axis power feed and spoke directly with Mr. Priest concerning the undersized motor issue.  At the time I spoke with him, it's been several months ago now, he didn't seem to think there was an issue.  Maybe he's changed his mind.  I haven't spoken to him since though.  If he sourced a bigger/better motor, I would be interested in making the purchase, but until then, I won't buy it.


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## fursphere (Oct 10, 2021)

Why not just get a stepper motor, stepper driver and power supply then add a rotary manual pulse generator?

At first it probably sounds expensive, but a power feed from PM is around $300, and the Priest Z Power Feed is $300  (with a questionable motor - I had the same thought when I saw the thing)

https://www.automationtechnologiesinc.com/products-page/mpgs/rotary-maunal-pulse-generator   - $30  (this won't work without some additional equipment
Pulse generator on amazon - $15
Nema 23 is $20 - $50 depending on rating / Nema 34 is $30 - $80 depending on rating (amazon)
Stepper Driver - $40 (+/-  (amazon)
Power Supply - Meanwell is around $40 for a 48v PSU  (amazon)

$150 + some odds and ends like bolts and coupler and stock to machine a mounting plate?   I dunno, something to think about.   And you'd get a power down feed out of it too.   If you don't might waiting a month or two, you can get it all cheaper from AliExpress.


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## chipinator (Oct 10, 2021)

@fursphere 
Thanks for the posts.  I really haven't gotten that far into it yet.  Racking and stacking priorities.  I would purchase the Priest Z axis power feed but I want a beefier motor and I don't think a beefier motor is on the horizon.  I've seen several Blondihacks tube videos and I'm glad she did this one.  I had thought about using an Align power table feed but I couldn't see how I could configure a way to connect it.  The parts you list and the video is a great idea for future consideration.


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## RodSME (Oct 11, 2021)

I have a PM 940V.  I made an adapter that replaces the hand crank.  The adapter has a hex on the end.  I use a drill and socket to drive the Z drive shaft.  The position of the Z axis handle of the 940 is different from your 728.  I do also have a Grizzly G0619.  The Z axis handle was quite a pain to use.  I fixed that by using an electric drill.  I posted that solution on hobby-machinist.  Maybe this will give you an idea for at least a stop gap approach: https://www.hobby-machinist.com/thr...z-axis-of-a-grizzly-g-0619.84157/#post-744037


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## Cletus (Oct 11, 2021)

The Align power feeds sold by PM are very good quality, the Z is $330.00 and 45 minutes assembly time including bolt-on, drill a hole and done!


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## chipinator (Oct 11, 2021)

@RodSME 
The electric drill is a good idea.  Never thought about it.

@Cletus 
The Align power feeds sold by PM is what I was actually looking at.  However, I didn't think it would fit on my PM-728VT.  I don't want to spend the money just to find I can't get it to fit or work for that matter.  Have you installed one with this version of mill?  If you have, I would be interested in seeing a couple of photos if you would be willing to share.


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## Cletus (Oct 11, 2021)

No experience with the PM-727VT at all.  Give PM tech support a call and have a chat with them on that application, they will surely know.


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## chipinator (Oct 11, 2021)

@Cletus
I actually gave PM a call about using an Align power feed after I initially posted my question and at least in their estimation, there is no way to use an Align power feed for the Z axis on my mill.  If there is, I would like to know how.


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## rwm (Oct 11, 2021)

I have been toying with this. I like the idea of using a stepper motor a lot. If you ever go to CNC you have one axis done already.  I have been considering alternative ways to attach a motor to the end of the Z lead screw. I decided on a coupler (lovejoy or some other) with the hub threaded to M12. I would then machine a slot in the hub and put a clamping screw on the side to lock it like a shaft clamp. I think that is better than the wave washer design and will not damage the threads. Heck, you could do that and a wave washer.
Like this:





Robert

Like this actually:




One end could be threaded m12.
R


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## Cletus (Oct 11, 2021)

Ahhh, then, I stand corrected. A stepper motor may be a very logical and viable solution.


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## fursphere (Oct 11, 2021)

rwm said:


> I have been toying with this. I like the idea of using a stepper motor a lot. If you ever go to CNC you have one axis done already.



I think this is partially true.  CNC conversations usually swap out the acme screw for a high quality ball screw (reduce / eliminate backlash).  This may not even be needed on the Z axis, but all the kits come with a Z ball screw. 

For a simple up / down power lift, the acme screw should be fine.    And you'll have the stepper for a CNC conversion later, if desired.


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## rwm (Oct 11, 2021)

fursphere said:


> I think this is partially true.  CNC conversations usually swap out the acme screw for a high quality ball screw (reduce / eliminate backlash).  This may not even be needed on the Z axis, but all the kits come with a Z ball screw.
> 
> For a simple up / down power lift, the acme screw should be fine.    And you'll have the stepper for a CNC conversion later, if desired.


This is a great point. You could still use the stepper but you would be making a new adaptor to connect to the new ball screw shaft.
Robert


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## GunsOfNavarone (Oct 12, 2021)

@rwm  I was actually looking for your thread on this topic to post the priest conversion. You seem pretty set on the steeper route, can't say I blame you. I have been talking about doing something about my 727m's Z axis for a long while now. Might have to sit down and plan it out. Some good info came of this thread, I'll have to do some advanced head scratching now.


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## Damn Yankee (Dec 25, 2022)

Hi All, and happy Holidays!

Having a Weis VM25-D, I lurk about this forum often as the two mills are (except for a few details) virtually identical particularly for this discussion. I too, wish to add a Z-Axis motor, but I would also like to add *plunge milling* to eliminate Quill deflection. So, I am writing to this sub-forum for thoughts and ideas. In fact, I hope it might be a Project with members' input.

With all gearmotors, the problem becomes the hand wheel is useless as you are fighting the gear reduction whose added effort to spin the hand wheel is proportional to the ratio of motor shaft RPM/gearset output RPM. Not entirely impossible to use the handwheel (unless the gear reduction is worm and wheel), but sure is way too much effort, especially fighting head weight when moving up. 

In my humble view and with no ill will to Priest Tools, their Power Lift kit seems cheesy. The control plate looks like something I made as a kid, PWM would have been a nice addition, but I get it - it is a "Power Lift" only device, no need for speed control. The gear motor appears to be a run-of-the-mill unit available anywhere:  https://rex-engineering.com/wp-content/uploads/2018/05/EX-BLDC.pdf. In fact, if you want to roll your own, my guess any surplus outlet like surpluscenter.com will have a comparable replacement. In any event from several reviews, the Priest gearmotor seems to be running on fumes just for its sole purpose: quick Up/Down. If my first link is correct as to the motor, it has 240 in/lbs (or lbs/in for the scientifically minded). Perhaps Priest can correct or confirm that torque spec? In any event it seems from reviews and videos of their product, it is running on the hairy edge. More motor or higher motor speed and more gear reduction is needed just to go up and down.

I would like to add this feature. But I also want to plunge mill into mild steel. Since this is homebrew and limited by experience and funds, motor/gearhead will not be the limiting case here, rather the rigidity and integrity of the mill. Will the column flex, leadscrew break, etc... I think that will be empirically found - you know when you are driving your mill too hard. So, now it gets down to the motor/gearbox...

As stated previously, I personally would like to use the hand wheel as well as the power feed. Now we are talking either a BIG motor and small ratio gearbox ($$$), still with a difficult hand wheel turn.
A moderate, higher speed motor with more gearing. Perhaps the hand wheel will need two men and a boy to turn.
A high torque motor with a worm/wheel combination. In this event, there is no turning the hand wheel.
Of all the options, I like #3 with a clutch for engagement and disengagement. Gives me the force which I need to penetrate my work and allows me to use my handwheel. Of course, the clutch is the hard part .  I think dog clutches are entirely too complicated and I invite those who have made such clutches to toss in their thoughts for maybe I am completely wrong.

To me, a homebrew, cam-actuated is perhaps the easiest. But you need to dead-nuts on the lobe of the cam (for disengagement and release) and the Neutral detent has to be in command of Neutral, but not so stiff that it takes much effort to move the lever. Tolerances are important here. It could be a catastrophe for the lever to engage accidentally or in a panic, the operator cannot find neutral. Has anyone experience with lever-operated eccentrics/cams with detents?

I was thinking a bevel gear on the leadscrew and one on the shaft of the gearmotor. The gearmotor could either be pivoted or laterally slid for disengagement, though I expect lateral is best from perspective of positive engagement. The movement of the gear, if by cam could be engaged by spring action and disengaged by cam (not fail-safe) or engaged by solenoid and disengaged by spring (safer but bulkier).

Thoughts from this forum are very much welcome.

John


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## slow-poke (Dec 29, 2022)

I added power lift for $13 on my Round column mill using a wiper motor from a Saturn Vue, might work for you.

Action video...... https://www.dropbox.com/s/26wb19hzack3i44/VerticalLift Movie-short.wmv?dl=0


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## Damn Yankee (Dec 29, 2022)

I


slow-poke said:


> I added power lift for $13 on my Round column mill using a wiper motor from a Saturn Vue, might work for you.
> 
> Action video...... https://www.dropbox.com/s/26wb19hzack3i44/VerticalLift Movie-short.wmv?dl=0


I like how quiet that is - you did a nice job. If it has enough torque you could add PWM and plunge or touch off...

I don't want to give up my handwheel and a gearmotor would require a clutch to take it in and out.

I have a NEMA 34 stepper motor, driver, and controller I hadn't used so I tossed them on the electronics bench to check them out. I think I dialed the frequency in right, but it is no load and might need some tweaking once doing work. Today I purchased a 14mm keyed LoveJoy coupler for the motor, a 1/2 to get drilled and tapped to M16 x 1.5 for the Z-Axis leadscrew, and a heavy-duty spider. I have a chunk of 1 1/2" x 6" x 6" aluminum for the spacer/adapter between the motor and the top of the column. It will drive the leadscrew directly.

Once I machine-out the aluminum, it is strictly a bolt-on affair. The only resistance to using the hand wheel will be the pole magnets of the stepper, which won't be hard to overcome but might give it a clunky feel as you rotate it. A variable reluctance stepper would prevent the pole magnet problem but would provide less torque than the PM version. In any event, it was the highest torque I had at 12 Nm. It will certainly power raise and lower. I am curious what it might do in a plunge situation.

In any event, I still have to mill the spacer/adapter plate; hopefully I can get to it this weekend. I need to put a 1 1/2" hole in its center. Either I use a hole saw then a boring bar or I pop for an annular cutter. Once I have it together, I toss some photos and thoughts.

Thanks,
John


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## rwm (Jan 3, 2023)

This^ is exactly what I want to do. Please keep us updated on your progress with pics! I hope the NEMA 34 is big enough. I had the same idea to thread one side of the coupler and use a screw to clamp it to the shaft. Not bearing on the shaft, but closing down the threaded collar. I would like to see your driver setup.


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