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Jet-16 Mill/Drill spidnle/bearings getting hot

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SuPeRBaD

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#1
I got recently got a new to me Jet-16 mill/drill and the spindle and bearings get extremely hot after about 5min. Not sure if these machines came stock with a zerk fitting on the spindle head from what I can tell on the manuals I found hiding around online they did not have one. There is a zerk fitting on mine so I tried pumping some grease into to it and it seemed to take a lot of grease I got about 5oz pumped into the fitting. This did not help with the spindle heating up.

How much grease should be pumped into the fitting to properly lube the bearings? Do these machines usually run hot on the spindles? Is there anything I can try to prevent the spindle from heating up so hot?

Thanks for any and all help.

Mike
 

JimDawson

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#2
Over greasing can cause the bearings to run hot. Is it getting hot at moderate speeds? I'm not sure what the proper lub is for those spindles. When I had my spindle rebuilt by the C & M in Tualatin, they told me that they lubed it with some special grease, and never needs to be lubed again. I guess I might check the pre-load on the bearings.
 

SuPeRBaD

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#3
Jim

It was getting hot running at 1000RPM & 380RMP it does not seem to matter what speed it is at. The upper bearing does not have nearly as much heat coming off it, would guess it to be only 5deg hotter than when off but the lower bearing gets hot enough to fry some eggs.
 

JimDawson

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#4
This is not a good sign. I would disconnect the belt and see if the spindle turns freely. A little resistance is OK, but it should turn pretty free.

The next step would be to pull the spindle out and loosen the bearings up and re-set the pre-load. Maybe clean out the bearings and use whatever the recommended lube is. Maybe it needs new bearings.
 

sdunt

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#5
I'm attaching a photo walk through of how to teardown and rebuild the spindle on these machines.. Its not hard. If you don't have a press to get the spindle out, a couple of ALL thread rods, like 2 - 1/2 inch by 36 inches long and some plate iron can be fashioned to press the spindle out.

As for grease, when I did this on my OLD RF - 30 I used black lithium grease on all of. I'm not a production shop and the lube on my machines is needed more to prevent corrosion for as long as they sit idle..
 

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SuPeRBaD

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#6
Jim-
Thanks for the help and the name of the speindle repair shop. I might try and replace the bearings on my own I would hope its not as hard as replacing some axles bearings on a truck, the hardest part was getting the pressed bearings out.


sdunt-
Thanks for the info on how to tear it down that will come in handy for when I try replacing the bearings.


I will let you guys know how it went after I'm done will be a few weeks until I get the time to start tearing into it, got a lot of projects going on at once, I'm sure you all know how that goes
 

SuPeRBaD

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#7
One more question about the spindle bearings, what kind do you guys recommend replacing the old ones with. should I stick with the original ones 30206 for the top & 30207 for the top or should I go a different route, also does any one know where I can find a new lower dust cover/oil seal.
 

JimDawson

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#8
I would probably go have a chat with McGuire Bearing. They can recommend a good lube also. They should also have the seal. The dust cover is another issue, maybe from Jet? Maybe McGuire can help with that too.
 

Vegemitesandwich

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#9
You have probably found out by now that grease zerk goes to nowhere an empty void. Your bearings are shot or most likely your spindle nut has gotten too tight. there are 2 left handed nuts behind the boiler plate jammed together. they will default to tighten if the jam gets loose. New bearings are common off the shelf at most industrial bearing supply outlets. Good luck and remember Left hand threads.
 
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