Spindle heat, HF mini mill

ferlum

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So I have 3 or 4 hours on my HF mini mill and since I got it I noticed the spindle gets rather hot after only 20 or 30 minutes of use (by "use" I mean cutting aluminum, about 2000 RPM, 1/8 and 1/4" end mills).

It gets hot enough that changing collets with a bare hand is pretty much impossible, I usually have to grab a rag. The drawbar gets pretty hot too, to the point that it's difficult/painful to turn with bare fingers.

I have the belt drive installed but I noticed the same heat buildup before I made the switch.

Is this normal?
 
I don't have a HF mini mill but do have a Grizzly--probably the same thing.

Sounds like maybe your nut on top of the large pulley is to tight (top of spindle).

When I changed mine over to belt drive I think I read this somewhere during my research for the belt drive build.

This is not normal--I run mine for hours non-stop sometimes and the spindle is never hot (the motor gets hot as heck though)
 
I don't have a HF mini mill but do have a Grizzly--probably the same thing.

Sounds like maybe your nut on top of the large pulley is to tight (top of spindle).

When I changed mine over to belt drive I think I read this somewhere during my research for the belt drive build.

This is not normal--I run mine for hours non-stop sometimes and the spindle is never hot (the motor gets hot as heck though)

I wondered about that. Wasn't sure how much to tighten that left-hand thread spindle nut. The belt drive kit instructions only say to "make sure the spindle rotates freely." I'll try loosening it up some. Thanks for the input!
 
Good luck---hope it works out for you. I only snugged mine up, no real torque on it.
 
I have a grizzly 727 mill a little bigger but mine was too loose and it would cause a vibration under a moderate to heavy cut, I snugged it up just enough where you felt a tiny amount of drag and everything was fine. Ray
 
I have a grizzly 727 mill a little bigger but mine was too loose and it would cause a vibration under a moderate to heavy cut, I snugged it up just enough where you felt a tiny amount of drag and everything was fine. Ray

Thanks for the input Ray.

I was playing with it today and took the nut and belt drive pulley completely off. There is no difference in spindle feel. It seems a little tight even with the nut removed. I guess I'm not sure how freely it's supposed to rotate but it seems a little snug. I can turn it by hand but cannot impart any rotation after I let go -- meaning I can't make it spin at all once I let go, if that makes sense.

Before I took it apart I ran it for about 10 minutes, not cutting anything, and there was heat buildup in the spindle. As I mentioned, the spindle felt the same before and after removing the nut, so I don't think it's being cause by the nut. Not sure if there's another way to loosen the bearings a little?

I've heard people mention a bearing break-in procedure for some equipment. Is there a chance that the bearings aren't worn in?
 
It may also be that you have a couple of bad spindle bearings. Just a thought.

Bill
 
It may also be that you have a couple of bad spindle bearings. Just a thought.

Bill

Do you think that's possible on a basically brand new machine? I suppose with HF equipment, anything is possible, but bad bearings right out of the box?

It runs nice and quiet, if that means anything.
 
Do you think that's possible on a basically brand new machine? I suppose with HF equipment, anything is possible, but bad bearings right out of the box?

It runs nice and quiet, if that means anything.

Believe me I think Grizzly sells a better quality controlled machine having said that I had to tear it completely apart and put it back together correctly. Including the bearings in the head I found no grease on the thrust bearings and the bearings where not pre loaded a bit. The pulley on top had the keyways cut to shallow and the pulley did not go on all the way. I went through 5 or 6 circuit boards before I found one that worked I wont bore you with the rest of the problems but believe me you would be money ahead to take it apart and take a look... Ray
 
Believe me I think Grizzly sells a better quality controlled machine having said that I had to tear it completely apart and put it back together correctly. Including the bearings in the head I found no grease on the thrust bearings and the bearings where not pre loaded a bit. The pulley on top had the keyways cut to shallow and the pulley did not go on all the way. I went through 5 or 6 circuit boards before I found one that worked I wont bore you with the rest of the problems but believe me you would be money ahead to take it apart and take a look... Ray

Wow. I guess I shouldn't assume anything with these. Looks like I'll be taking it apart, there must be something going on in there. It was getting hot before I did the belt drive conversion so I'm pretty sure it came from the factory this way.
 
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