View Full Version : M-head step pulley bearing nut

12-30-2011, 07:20 PM
Quite a while back, I got a new old stock replacement spindle for my
B-port M-head which is mounted to my small Clausing knee mill.

I decided it was time to change it out due to the ever present
chatter caused by the worn out splines in the existing spindle
and mating splines in the pulley assembly.

A search around the forums did not produce anything specific
to the M-head, so I decided to just have at it.

After removing the drawbar, and loosening a bolt on the side of the
aluminum casting for the step pulley housing, the whole upper
assembly just lifts right off, exposing the under side of the
spindle pulley bearing assembly.
I could see that someone had been in here before me as shown by
the damage to the slots in the sides of the nut which needed to be

It appeared that a special tool is required (which I do not have) so,
I made this tool to remove the old damaged nut and to install
the new one.
The tool is made from black iron pipe turned in the lathe to a
diameter equal to the disance across the slots in the nut.
3/16" steel keystock fit the slots nicely so I cut four lengths
at 1" and clamped them into the slots in the nut, placed the nut
on the end of the turned pipe and welded them to the pipe.

Then remounted the tool in the lathe and turned the "fingers"
at an angle to clear the tabbed washer beneath the nut.

12-30-2011, 07:30 PM
I had some difficulty trying to hold the tool in place with one hand
while turning a wrench on the hex head on the opposite end of the
assembly as the new tool kept leaning to the side.

So I turned this plastic bushing to keep the nut removal tool
centered and it worked beautifully.

12-30-2011, 07:49 PM
Nice job,beats the pin punch/hammer method by a mile.

12-30-2011, 07:59 PM
With the special nut removed I next tapped out the steel core from
the pulley bearing assembly.
Then separated the bearing housing from the pulley, which allowed the pulley
to be taken out of the large aluminum casting.
And now I have a good pile of separated parts that I will start to
clean all the gunk out of using some kerosene.

Also you can see the new spindle in the last pic (its the one on the right)
and the old spindle on the left with one bearing still mounted.

I really want to reuse that same bearing on the new spindle but have
not as yet tried to remove it from the old one.
If I try to pull it off by pulling on the outer race will it damage
the bearing????
I have NO money to replace the bearings.
Is there a simple method one can use to remove that bearing
without causing any damage?????

Thanks for any input in advance.

12-30-2011, 08:17 PM
Great job on building the tool. Don't let it get away I have a M head & may need to rent it from you sometime. Thanks for showing the pics! Eric

12-30-2011, 09:22 PM
Assuming those are the correct precision bearings (ABEC-7), yeah, I'd want to reuse them too. New ones are probably pretty expensive.

I would certainly avoid pulling on the outer race. Make up some kind of rig so you can pull (or push) on the inner race. Heating/cooling may help, if you can contrive to heat the inner bearing race while cooling the spindle. Steel expands/contracts 6 millionths of an inch per inch per degree F, so if you can get a sizable temperature differential between the two the bearing may just fall off.

12-30-2011, 09:28 PM
Mgreen, great tool you made up and thanks for posting the great pics and info.

That "6" step "V" pulley on the motor shaft, is that from this mill?

12-30-2011, 10:08 PM
I have a liquid line on my propane tank, so I would run some on the shaft and see if I could shrink it enough to remove the bearing. Our Wal Mart now sells dry ice that could be used similarly. If it moves a little a puller could be used on the inner race.

12-30-2011, 10:35 PM
They may just bump off by dropping the spindle upside down on a block of hardwood.

01-04-2012, 08:49 PM
Hey wierdscience'
I tried to bump off by dropping on a hardwood block, to no avail.

I thought if I turned up a steel ring that I could heat up
with a torch to a nice red, and stood the spindle upright and
sat the heated ring on the inner race for a while, maybe that would
expand the race and then try to bump off dropping on hardwood.

Anyone think that will do the trick???

I made up a second special nut removal tool, this one fits the
bearing nut on the upper end of the quill and is smaller than the
first one.
Also turned up a bushing for this one that fits inside and keeps the tool central.

01-04-2012, 09:14 PM
I did have some sucsess using Wierd's suggestion to "bump off by
dropping on hardwood" method in regards to getting a top bearing
out of the upper end of the quill, although it did not come out
far enough.

So I bent up 2 pieces of 3/16" thick steel flat bar
at an angle a little past 90 degrees so the ends would only
touch the outer race, wiggled them in one at time,
and stuck a wood wedge in between them to keep them spread
apart and then C-clamped it together.

Using a small wooden dowel inserted from the bottom,
I tapped the bearing the rest of the way out.
The spindle bearings are 3205 as seen in the pic above.

I spent a while squirting and sloshing with kerosene to clean them
and everything else out, there was a fair amount of gunk
and chips and such that came out.

01-04-2012, 09:35 PM
Earlier, the threaded cap at the bottom of the quill was hard coming off.
There is a set screw in the back of the quill at the bottom which I had
first removed, and this screw seats in a small recess in the threads of the cap, and it had deformed the threads which made it hard to unscrew.

Also there was lots of gunk and swarf in there which is now all
washed out with kerosene.

I used a thread file and some needle files to dress up and remove the deformed areas in the cap threads.
In the pic above, there are 2 counter bored holes in the bottom
face of the cap, these are through holes.

What is the purpose of them being thru holes?
Is it that oil is supposed to run out those holes as oil is gravity
fed from above?
A total oil loss system?

01-13-2012, 08:02 PM
Tried using the hot ring to heat the bearing and drop the quill on
hardwood a few times but alas, it did not work.

I was trying to save the old spindle (and give to anyone that
could have used it) but, with the bearing not coming off, I
made up my mind to cut off the spindle nose using my horizontal
bandsaw followed by setting up the spindle in the lathe and
facing off the remnant of the nose.

Then used my arbor press to press off the spindle bearing.

I soaked the 4 spindle bearings in purple zep cleaner overnight.
Followed by multiple brushings and rinses with kerosene, and
a little compressed air & a little more kero.

I applied some 30W non detergent motor oil to all the race ways
and balls, and reinstalled all the bearings and spacers.

Upon reading some postings either on this forum or elsewhere
(cant remember which) I was able to determine that the counter bored
holes in the underside of the cap at the bottom of the quill
are for a spanner and also probably to allow oil to drip out as
the oil dribbles thru the spindle bearings.

I did not have a spanner for this purpose so, I made one
using a piece of aluminum from my junk collection.
A little work at the lathe, followed by drilling, using the drill press
rather than the mill obviously because the mill is all apart, then pressed
in the turned steel pins and a cross handle and I now have a good
workable spanner for the job at hand.

Using the new spanner the quill cap was installed and the hole for the rear set screw was lined up and the screw put in.

The bearing nut special wrench worked like a charm using it and
the steel core with the internal splines from the driven pulley
the restrain the spindle shaft from rotating, thus allowing the
nut to be tightened.

01-13-2012, 08:44 PM
Here is a couple pics showing the difference between the old
spindle and steel pulley core with the worn out splines,
and the new set of both installed.

This should be a major improvement with the new parts and
a thourough cleaning and re-installation of the old bearings.

I was getting ready to mount the motor but,............
I decided that while I had the motor and pulley removed,
having the motor on the bench, I plugged in the motor and
turned the switch on and could see the step pulley wobbling.

So I removed the pulley, set up 2 indicators.
The lower indicator is positioned just to the side of the
set screw flat on the shaft and zeroed, when the shaft is
rotated 180 the indicator drops back 3 or 4 thou.

The upper indicator drops back 8 thou.
So, the motor shaft extension is off center and leaning.
I may just put the pulley back on and mount the motor
on the machine and see how things seem, and if I
dont like what I think will be some vibration, then
I might take it off again, and perhaps turn a new extension.

Maybe the best way would be to remove the old extension,
disassemble the motor, mic the original motor shaft, partly turn
a new extension, fasten it to the motor shaft, then mount
the motor shaft/rotor/extention as one in the lathe and
turn the extension O.D. in situ. .............

01-13-2012, 08:46 PM
Nice work! Can I send you my M head mill for an O-Haul?

01-13-2012, 09:34 PM
As someone else has been inside the machine, check that the extension coupling has not been re-seated in a different position than original, with the potential cause of the observed tilt, being a prior burr on the motor shaft itself.

Chuck up the extension in your lathe and check if the coupling runs true.


01-13-2012, 10:06 PM
http://i72.photobucket.com/albums/i169/kooldoozer/Machines%20and%20Stuff/IMG_0110.jpg (http://i72.photobucket.com/albums/i169/kooldoozer/Machines%20and%20Stuff/IMG_0110.jpg)
http://i72.photobucket.com/albums/i169/kooldoozer/Machines%20and%20Stuff/SDC10585_2.jpg (http://i72.photobucket.com/albums/i169/kooldoozer/Machines%20and%20Stuff/SDC10585_2.jpg)
http://i72.photobucket.com/albums/i169/kooldoozer/IMG_0254.jpg (http://i72.photobucket.com/albums/i169/kooldoozer/IMG_0254.jpg)
http://i72.photobucket.com/albums/i169/kooldoozer/IMG_0011.jpg (http://i72.photobucket.com/albums/i169/kooldoozer/IMG_0011.jpg)

Welcome to the 8520 club.


01-14-2012, 04:23 AM
Hey Doozer - great minds think alike! I have made a collet holder exactly like yours hanging off the DRO bracket :)

MGREEN: Really nice work on your milling head - you obviously take a great deal of care over your tools.