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Harbor Freight Mini Mill Motor Swap

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Mr.Ven

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#1
Well, I’m new to this forum and to machining, so please try to be understanding when I ask stupid questions... here’s the first one. I just bought an HF mini mill (model 44991) and just happen to have a Shop Fox mortising machine that I no loner use/need. It has a 3/4 hp, 8 amp, 3450 rpm motor that I’d like to put on the mini mill. Whattaya think? Am I crazy, or can this work?
 

RandyM

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#2
Welcome to the family.

The first thing about this site is no one has ever asked a stupid question since day one.

Second thing, you are among kindred spirits, modifying our machines is what we do.

All we ask is that you share your projects with us. Fair enough?
 

GoceKU

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#3
Welcome, Mr.Ven i've often found myself wanting and doing just that, putting bigger motor in hobby machines, and my experience is, if you can find direct replacement or very little modification and cheap do it, but is not worth it spending more than few hours in modifications, you'll better off buying a decent sized industrial machine and restoring it.
 

markba633csi

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#4
The only concern would be the speed- is it faster than the original? It might tear up your endmills faster if you do a lot of steel parts
Mark
ps also I believe you need a dc motor if the mill has a speed control
 
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Mr.Ven

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#5
Welcome to the family.

The first thing about this site is no one has ever asked a stupid question since day one.

Second thing, you are among kindred spirits, modifying our machines is what we do.

All we ask is that you share your projects with us. Fair enough?
Thanks, Randy... and I’ll be happy to share!
 

chips&more

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#6
Hi and welcome. Is the HF mill working as it is? Anything is possible, but why? Maybe like putting a 427 in a VW Beetle. If it isn’t broken don’t fix it. Could be a good lesson in “why” for the next time. Or, it could be screaming little HF mill! That motor on the HF mill is intergraded into the mill and made to work with the vari speed control and is 4/5hp. Does not look like an easy swap. What is wrong with it the way it is?...Dave
 
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FarmDad

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#8
I think over the years I have seen a few threads where guys converted them to belt drive and put bigger motors on them . I have no idea how well it worked out though . Mine at least has plenty of motor for the gear train it has so if i were going to try and increase power that's the route i would likely try . I really suspect though that they are not rigid enough to cut much more than they will handle in stock form .
 

silence dogood

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#9
Whoo. The motor on your hf is rated at 2500rpm. The other motor is a 1000 rpm faster. you may end up eating alot of end mills. I suppose that you could use the mill for wood, but then I don't know how the gears hold up. I don't know if any one has done this with a mini mill, but maybe you could try a tread mill motor. That way you could get variable speed.
 

RandyM

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#10
Hi and welcome. Is the HF mill working as it is? Anything is possible, but why? Maybe like putting a 427 in a VW Beetle. If it isn’t broken don’t fix it. Could be a good lesson in “why” for the next time. Or, it could be screaming little HF mill! That motor on the HF mill is intergraded into the mill and made to work with the vari speed control and is 4/5hp. Does not look like an easy swap. What is wrong with it the way it is?...Dave

Dave, sometimes it is just about the project.
 

Downunder Bob

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#11
Well, I’m new to this forum and to machining, so please try to be understanding when I ask stupid questions... here’s the first one. I just bought an HF mini mill (model 44991) and just happen to have a Shop Fox mortising machine that I no loner use/need. It has a 3/4 hp, 8 amp, 3450 rpm motor that I’d like to put on the mini mill. Whattaya think? Am I crazy, or can this work?

G'day Mr Ven. This is the forum for asking questions, no dumb questions here, the only dumb or stupid questions are the ones you never asked, we are all here to help and learn, even the most highly trained of us can still learn. I don't know much about the machine in question, other than it is a mini mill. The first question I'd be asking before fitting a more powerful and faster motor, what will you be overloading. The makers of most machines tend to put motors on them that will not overload the drive train. nor damage the structure of the machine.

Apart from the modifications that will no doubt void your warranty, will it really be worth it. What do you hope to achieve, apart from the satisfaction of doing the conversion.
 

chips&more

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#12
Dave, sometimes it is just about the project.
Randy, not sure about your project list? But mine is about 10 lifetimes long. And I only have 1 lifetime to do it in. That means I’m about 9 lifetimes over booked with projects LOL...Dave
 

RandyM

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Randy, not sure about your project list? But mine is about 10 lifetimes long. And I only have 1 lifetime to do it in. That means I’m about 9 lifetimes over booked with projects LOL...Dave
My point is, that unlike you and I, there are some people that don't have those lists. ;) Sounds like he is just looking for something to do.
 

chips&more

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#14
My point is, that unlike you and I, there are some people that don't have those lists. ;) Sounds like he is just looking for something to do.
Something to do you say? What if the folks on HM with no project list volunteered their shop time to the HM folks with too long a list. Could be a new thread on HM?
 

RandyM

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Something to do you say? What if the folks on HM with no project list volunteered their shop time to the HM folks with too long a list. Could be a new thread on HM?
Good luck with that. :encourage:

NOW!

Back to topic.
 

royesses

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#16
Well, I’m new to this forum and to machining, so please try to be understanding when I ask stupid questions... here’s the first one. I just bought an HF mini mill (model 44991) and just happen to have a Shop Fox mortising machine that I no loner use/need. It has a 3/4 hp, 8 amp, 3450 rpm motor that I’d like to put on the mini mill. Whattaya think? Am I crazy, or can this work?

Welcome to the forum Mr. Ven.
The HF mini mill has plastic gears in the spindle box. They would not put up with the new motor very long. LMS does sell all metal gears for the mini mill. You would also have a plastic drive gear on the spindle and one on the motor that would be a problem. You would need to adapt the motor mount and drive gears to fit. The motor controller would not work on an a/c motor. The mini mill has a dc motor. You could wire the new motor to 120 volt directly without a controller but would lose the variable speed. Some guys have used treadmill motors and controllers but it is a lot of work . LMS sells a belt drive kit. It just does not seem to be a worthwhile project. Also it could be a problem if the new motor is heavier than the original as the spindle box may not want to stay up with that extra weight. I put in the belt drive kit and air spring on mine and got rid of the two speed gears completely. I'm very happy with it. I don't know if you are familiar with Little Machine Shop but they have just about everything there is for the mini mill in parts and accessories. Great people who are very helpful.
Little Machine Shop -LMS

Roy
 
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silence dogood

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#17
Welcome to the forum Mr. Ven.
The HF mini mill has plastic gears in the spindle box. They would not put up with the new motor very long. LMS does sell all metal gears for the mini mill. You would also have a plastic drive gear on the spindle and one on the motor that would be a problem. You would need to adapt the motor mount and drive gears to fit. The motor controller would not work on an a/c motor. The mini mill has a dc motor. You could wire the new motor to 120 volt directly without a controller but would lose the variable speed. Some guys have used treadmill motors and controllers but it is a lot of work . LMS sells a belt drive kit. It just does not seem to be a worthwhile project. Also it could be a problem if the new motor is heavier than the original as the spindle box may not want to stay up with that extra weight. I put in the belt drive kit and air spring on mine and got rid of the two speed gears completely. I'm very happy with it. I don't know if you are familiar with Little Machine Shop but they have just about everything there is for the mini mill in parts and accessories. Great people who are very helpful.
Little Machine Shop -LMS

Roy
Roy , you stated the problems with motor conversion much better than I did.
 

silence dogood

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#19
Roy, you are very kind. Now I wish to address this to Mr. Ven. Please don't think that Roy and I are giving you criticism. What we are giving you is knowledge. With knowledge, you can make better decisions. That is why there are no dumb questions on this site.
 
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