# Rockwell 21-100 Milling Machine Spindle / Pulley Splines



## swarfrat (Dec 16, 2019)

Hi All.   I am at the rebuilding part of putting a Rockwell 21-100 milling machine back into working condition.   I just picked this machine up about a month ago,  it seems like it has had a good life, and has not been abused too badly.   It is fully disassembled, and came apart with no real difficulty.  I think it had the original bearings in it.  the paint is mostly off of this machine, now, and paint prep underway.  The ways look to be serviceable, but I have not checked to see how precise they are, yet.  

The focus right now is on the spindle / quill, and drive pulley. I have been scouring the net for information on spindle bearings, preload, and such, and think I have a decent grasp of the bearings. I have a matched duplex set of lower spindle bearings here, with a light built in preload, and there is a similar set of pulley bearings on the way. The journals for the bearings are in good shape. The residual caked up grease in the quill and adjacent to the races looked like New Year's glitter, the bearings were shot. All the bearings in the machine were shot. Everything cleaned up well, and I have been studying all of this before re-assembly. Some of the best bearing information I have found, has been on forums talking about Bridgeport spindle bearings. 

I notice that the spindle spline fit into the drive pulley hub splines is not as close as I think it might should be. There is rotational wear in the splines, and radial wear, as well. It looks like it would run as is, maybe it is enough wear to begin causing some noise? It also looks like this fit is the 'weakest link' in the accuracy of the head, as the spindle bearings / pulley bearings are handled, and the wear in the quill / head does not seem too bad. 

How much wear is acceptable in the spindle / pulley hub splines? How should these pieces fit, ideally.

At what point is it worth fabricating a new splined pulley hub that is matched to the worn spindle splines? ( the wear in this fit seems to be fairly even between the two pieces, maybe a little more in the hub than in the spindle) 


I would like to bring this machine back to life as much as reasonably possible. If the quill / head is revived to a good state of being, I see some way maintenance, measuring, and scraping in this machine's future. 

This machine looks like lubrication was not thought out all the way, so I am planning some minor changes in that department.


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## benmychree (Dec 16, 2019)

I should think that involute splines would be self centering under load; why worry about fixing it if it is not yet known if the situation effects operation?
It would not be an easy matter to make a sleeve with new splines for the pulley, looking for a new pulley for the machine would be a better approach.


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## swarfrat (Dec 16, 2019)

You have an MSC catalog number for that pulley hub?   I do not see one.  Looking for a used part, where this machine is in relatively good shape, among the species, and any machine that is parting out is almost certainly to be in worse shape, seems like my lifetime odds for that are not very good.   

Machining a new part is a much better option, IMO. It is a 'doable' task. 

My question was, how much wear is too much?


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## benmychree (Dec 16, 2019)

Looking for a part is looking online for sources of parts, including e bay, a lot of stuff goes "over the falls" there, a favorite search, where you are notified as items of interest come along.  Too much wear is when it effects the work being done, figure where that condition lies, and act accordingly.
An accurate spline being machined into a sleeve is no easy simply task; yes, I have done it, but with the proper tools and machinery.


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## swarfrat (Dec 16, 2019)

What's ebay?

BTW... you have owned and rebuilt one of these 21-100 milling machines, right? If I were guessing, I would guess that you have not. But, since you are posting on this thread, you must know firsthand, right? Nearly 4,000 posts is a lot of knowledge.

My 'spidey senses' tell me that used parts in good shape for this machine are not widely available. Looking on the internet is a good idea. Not sure why I did not think of that.


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## benmychree (Dec 16, 2019)

It constantly amazes me how many posts are answered by so many folks who give specific answers with directions to find things that the original poster had not a clue as how to find things.  So far as to my qualifications as to how to go about things, experience wise, I am 75 years old, and have apprenticed to the trade at age 19 and worked at the trade all the time since then, had my own business doing repair and manufacturing of parts and products; I have repaired lots of machines, rescraped  several; even if I have not specifically worked on some little C.S. mill, I am quite aware of general machine construction and how things work --- and don't work.


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## swarfrat (Dec 16, 2019)

It constantly amazes me how many people just post on forums, (just to hear themselves talk????), without actually having anything really pertinent or directly accurate to say concerning the o.p's inquiry.   



Respectfully, benmychree, can you please not post on this thread anymore.


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## john.oliver35 (Dec 16, 2019)

Hi Swarfrat - I have a 21-100 that I had torn down a couple of years ago.  The original bearings were OK, but  I did need to tweak the preload a bit with shims to improve runout.

The splines are a little loose on mine as well.  The spindle will pound a bit under heavy loads, but not enough to an immediate concern.  Making new shaft and pulley insert are on my list of things I will probably never get around to.  You might want to give it a try once you get your bearings installed.  If it makes too much noise you can always pull it apart again.  In my experience, it was more work to get the table tuned up and ways consistently tight on the 21-100, and the spindle splines can be left for another day if you want to make some chips in the meantime.


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## swarfrat (Dec 16, 2019)

Thank you, John.

There are no plans currently to initiate the fabrication of a new hub. The first step, besides finishing the cleaning, painting, and some general maintenance of the thing, is to get the quill and the head in place and running, just to see what I actually have, here. I am hopeful that the results will be good. This mill was purchased from someone whom I have seen some posts on forums, about this mill. I was told that it ran, and that it worked decent. That may have been the case, but the spindle was noisy and the bearings were absolutely shot. Conceptually, I understand the preload, and the new bearings I got feel like the right stuff. The nomenclature is correct for what I have seen for BP bearings, only in different sizes. We will see if the spindle spins true.

I do not fully understand how a worn fit in the spindle splines will affect things in the long term, still studying things and trying to learn it. It is not a huge amount of wear. It looks like the spindle mics around 0.005" less on the diameter in the splines, than the spindle where the splined hub does not contact. The wear inside the hub is more significant, but does not look catastrophic or galled. The splines are still clean and smooth.

Fortunately, I have a good mentor, an 85 y/o retired master machinist with the coolest shop I have ever seen, operated by a single person. He says 'run it'. I wanted to hear from other 21-100 owners. He had several way back when, as second-op machines, but they were not worn out. He is willing to fabricate a new hub. If the rest of the machine comes together nicely, and it is indeed, a true weak link, I will have some time before deciding to have a new hub made. I am not really a 'Spring chicken', but when these old masters leave the room, the world will be losing some real wisdom.

This is my first milling machine, and I am very much looking forward to putting it to work in doing prototype work for my business.


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