Proper bearings for a mill spindle rebuild?

psionik said:

I'm a polymath ..

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I had to look this up.
Why ask for help here from us little people?

While some might consider it a waste, this is exactly how I enjoy my time.

I suppose my first error was anticipating replies outside of the concept of "don't."

Charted territory? Of course! Experts I could hire? Great idea!

But I won't gain much except a lousy properly-rebuilt mill. Where's the knowledge in that? Hmm?

So in the 48 hours since I birthed this plan here's what I have swimming in my head:

1) Proper alloy selection. Grades of steel. 1018, 1045, 3130, 4130, 4140.

2) Heat treatment. Induction hardening. Flame hardening. Case hardening. Quenching. Oil. Water. Air. Internal stresses. Tolerance creep. Grinding to specification.

3) Loads and stress. Bearing selection. Grades of precision. Cost considerations.

4) Design for assembly. Sequence parts come together. It's one thing to have a blueprint but another to create a set of parts that can be assembled in the real world.

5) Tolerances and precision. Gaps. Interference. Shrink fits. Thermal expansion. Press fit.

6) Deflection. Strength of the structure supporting and maintaining geometry.

7) Energy considerations. Friction. Force. Lubrication. Temperature. Changes in shape. Wear. Power requirements.

8) Tool consideration. What do I already own? What might I need? The machine is one thing, all the accessories and tooling are another. Hardness, toughness, machinability, ductile, malleable, work hardening, normalizing, tempering, annealing?

9) Resource management. I have played with these toys for years but should I expand my shop? Is my foundation thick enough for heavy machinery? How much time do I anticipate this project taking? Where will I be taking this afterwards? Will I build that cnc machine later? Go into production? Who would be my customers, and what would I be selling?

10) Knowledge. Online forums. What books? College textbooks? Books on specific subjects? The local bookstores? Who would I turn to if I need a quick answer in the middle of an operation? What can my friends, associates and online acquaintances teach me? How can I help them in return?

11) Software. I'm teaching myself Fusion 360. I have a couple of finished designs for full machines and a half dozen smaller assemblies. I'm now interested in stresses, material economy, deflection and forces. I'm probing the areas of finite element analysis which is fascinating. I'm going to be applying this to my next telescope mirrors as I intend to hog out glass with wet diamond tooling to reduce material weight on my next scope so it will be more portable for when I haul it out to the next star party I go to.

Yeah. All leaves on a tree, connecting to small branches, connecting to larger branches, connecting to a trunk growing from a root broadly called "engineering." Joy comes as I nurture its growth.

That's how I see it.

Perfect, sounds like you have it figured out. Keep us updated so we can all learn from your journey.

EmmanuelGoldstein, when I see the younger generation approaching life with insecurity, I try to lead by example and encourage them to understand that most limits human beings have are lies fed to them externally by those without imagination. But when I see this in adults, such as my employees - I have fired them on the spot for merely expressing that kind of attitude because when some people reach a certain age they have committed themselves to their failures and no amount of encouragement can set them on a new path. I find this mindset of doubt and negativity repugnant.

Everything can be improved. Nothing is impossible. The sky is the limit. I can do it. YOU can do it. We BOTH can do it even BETTER when we cooperate, but not when you have surrendered to the idea that someone else has you in their shadow.

If someone else has done it, it's possible for me as well. If no one ever has in the history of planet Earth, I. Will. Find. The. Way.

I admit I'm not the smartest man in the world but it hasn't stopped me yet.

Hell, I even think I'll live forever. If not, I'm still going to die trying.

And I'm going to rebuild this hunk of junk, and right or wrong - I'm going to enjoy every second that I do.

psionik said:

EmmanuelGoldstein, when I see the younger generation approaching life with insecurity, I try to lead by example and encourage them to understand that most limits human beings have are lies fed to them externally by those without imagination. But when I see this in adults, such as my employees - I have fired them on the spot for merely expressing that kind of attitude because when some people reach a certain age they have committed themselves to their failures and no amount of encouragement can set them on a new path. I find this mindset of doubt and negativity repugnant.

Everything can be improved. Nothing is impossible. The sky is the limit. I can do it. YOU can do it. We BOTH can do it even BETTER when we cooperate, but not when you have surrendered to the idea that someone else has you in their shadow.

If someone else has done it, it's possible for me as well. If no one ever has in the history of planet Earth, I. Will. Find. The. Way.

I admit I'm not the smartest man in the world but it hasn't stopped me yet.

Hell, I even think I'll live forever. If not, I'm still going to die trying.

And I'm going to rebuild this hunk of junk, and right or wrong - I'm going to enjoy every second that I do.

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You can fire me any time you like.

Regards Tyrone.

LOL

yes "the weight of my incompetence"
you ever around Boulder Colorado I'll buy you a beer
have at it, good luck

possibly of use

Look at the markings on the bearing that you're takin' out. If they're P5's, replace them with P5's. If they're not any kind of precision bearing.........replace them with the bearings available.

P5 will get you down to around .0005 runout.......standard bearing will be in the roughly .001-.0015 range.

I'm just going off the top of my head for tapered roller bearings. YMMV.

If the mill is loose, it might not pay to get "good' bearings..............but considering all things are additive.........a loose bearing on top of loose ways...............I dunno.........it's your call.

And, it depends on what you're milling. What are the tolerances you need. Lot of stuff doesn't need the tolerances that tight. If the machine is loose, conventional milling can take up a lot of slop to a certain extent.

No idea how you took "Identify the current bearings as they may be a better quality than you realize, changing their spec is unlikely to result in any improvement" to us throwing down the gauntlet as to your abilities to overcome the well documented complexity of spindle design. Rebuilding a clapped out machine is a noble goal. Wasting time and money on the wrong things while doing so is a choice and it's totally up to you. If you want to have a useful discussion here, let's start with some facts.

Tell us the current bearings so we know exactly how much of our time you are wasting. Expect some derision if they turn out to be decently spec'ed angular's.

Even for those who like to investigate things, there are some parameters that make sense to consider.

First among these is: "If I do what change I think will improve this device, is the rest of the device sufficiently decent that I will even be able to detect an improvement if there is one?".

Then there is "In the big picture, is there a more direct path to what I want which results in a simpler solution than a long development process with a series of incremental changes will?". (you may say "who cares? This is what I do". But without the tools to do what you need to do, you may be stalled early, even though you have some access to good tools.)

Suppose you want to tow a biggish boat. You own a VW bug. You are oriented to the "fix it and improve it" path.

You have many paths that could be chosen. But the incremental change path is likely to end you up with some cobbled together solution in which each part is added on to solve a particular small problem in the implementation.

Looking at the big picture, it makes more sense to buy something like an F-250 pickup. It will probably be cheaper overall.

But if you never step back, you never see that. You might modify and upgrade that VW until you end up with something like a 427 V8 on a trailer, with a flexible driveshaft to the VW to drive the original rear wheels. Each solution to some problem adds complexity... running the throttle, etc, etc, but the fixation on "I have a VW" obscures that.

A silly example? Absolutely... and intended to be that.

Why put the effort in to "modify your VW", when the best solution is likely a pallet jack to move out the original machine, and move in what you need? At that point, you have something that may allow you to make parts and investigate what you originally wanted to investigate.

Or, as in this case, just replace the bearings with a compatible type that fits the budget, and see if that is better than rusted and roached bearings.... I am sure it will be.

What you will end up with is a perfectly good mill, which is also in better condition, and is a valid starting point for any further investigations that you want to make. The existing bearings are presumably bad enough that you won't know if super good ones are actually better for the purpose than fairly ordinary bearings.

The best way to put a more powerful engine in a VW is to to an Olds 455 out of a Toronado, They were front wheel drive so you use the whole engine transaxle assy.
Years ago a local guy put one in a VW buss and would take it up the steep hill on the nearby freeway, going slow, waiting for the camero guys behind him to get pissed off and pass him. Or at least try to pass, as soon as they were next to him he would punch it and that light weight bus really moved with big block power to push it.
From the outside the only way to tell that buss was different was the full size radiator on the side. Many busses of the day had an oil cooler on the side so it was not all that out of place...

reminder, this is all to not use r8 collets and holders, including having a new floor poured.
Why swallow the fly?

Ok, I've driven back to the shop to get some numbers for you. I've gone through all the parts I've disassembled and the ball bearings I spoke of aren't located on the spindle but on some peripheral attachments.

The head bearings seem to be: RM9110NPP and the ball bearing I spoke of earlier was RM9308NPP

But don't quote me on this as they are rusty and difficult to read and I may have some of the characters incorrect.

Those both show up as bridgeport bearings, so I think your numbers are good.

I'm curious to why the answers didn't come somewhat more like this:


“Ball bearings do not have high load capacities relative to other designs, and are usually used on smaller or lower quality machines

Tapered roller bearings are often used on bearing spindles at RPM ranges of around 3000 and lower. They are great at supporting radial and axial loads, however one must design a means of establishing “preload” for proper use.

Angular contact bearings are available for higher RPMs such as fast CNC spindles, and can be found manufactured to very high degrees of precision, although they can be costly. They are often used in pairs to accommodate thrust loads in both directions. They also require preload considerations.

Roller bearings can be combined with any of the above types to supplement their load capabilities.

Combining several bearings near the same end of a shaft can improve accuracy and precision due to the averaging effect of all the rotating and contacting surfaces, but not so much as a single bearing manufactured to tighter tolerances. Disadvantages of this approach is increased cost and more heat generated from rolling friction."


Rather than (to paraphrase) -


“You’re in over your head.

Replace with original parts and be done with it.

You can’t improve on the past.

Other people are certain to arrive at better solutions than you will.

You have no business fooling with someone else’s design.

Your lack of experience will doom your efforts to failure.

We have experience / do this for a living / you don't.

It's not worth the effort.

You are wasting your time."


I can only explain this psychologically.

I've pulled maybe close to a dozen different bearings out of this machine so far, and after some more research, I've concluded that bearing identifications were invented by Satan.

I was expecting some kind of industry standards of nomenclature, and where some seem to exist others seem to defy convention and some seem to be missing altogether.

I don't know what the P rating on any of the bearings are. They do have "PP" carved into some of them. Some are stamped. Some have no markings that I can identify.

psionik said:

Rather than (to paraphrase) -

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You're going to strawman people trying to help you? Very cool.

CarbideBob said:

I had to look this up.
Why ask for help here from us little people?

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Because I thought I could find info here.

How should I see these statements, if not discouraging?

No strawman, direct quotes:

"
I'd advise you to replace the bearings that are there with the same exact type that the machine was designed for.

expensive precision is wasted on a normal machine

Spindle design is no joke

Give it up. You're kidding yourself.

This is premature optimization, another famous trap to the new player.

you are in over your head

designing and making a spindle is often above most people's talents.

many of us do this exact thing 5+ days a week. We know exactly how to address this for the best outcome given a particular set of performance requirements, no research or guesswork needed

Why ask for help here from us little people

Expect some derision

just replace the bearings with a compatible type that fits the budget
"

I've stated that I might alter the design because of the possibility of moving to CNC and a higher speed spindle. What I'm interested in are bearing considerations. The above statements add nothing to my understanding.

Not to discount those who have been helpful and encouraging. I appreciate you. I just wonder where all the nasty attitude is coming from. Perhaps I go about life differently than other people, but I am the last to be discouraged. Challenges are my bread and butter, and that is the ancillary point I've been trying to make so that we can get back to business.

To reiterate, my goal here is twofold: 1) To learn about bearings and 2) To experiment with their use.

What is not my goal is 3) To get this machine up and running with minimal hassle. Why? Because I have decades to kill and money to burn.

psionik said:

Because I thought I could find info here.

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Info that is publicly documented everywhere? Seems to me seeing how this thread has progressed you came seeking attention more than anything.

psionik said:

And Bakafish... who has helped me so far? I still haven't received a straight answer about pros/cons of different bearing types beyond what I already know.

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I look through the responses and see helpful, well reasoned advice from experienced people. You seem to see something different. At this point you have made your dramatic entrance, and given us a good taste of your character.

psionik said:

All the advice I've received so far is that I'm going about this all wrong if I don't simply replace bearings with stock equivalent.

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Did it ever occur to you that, just possibly, this might be the right take? Or are you the kind of person that thinks being a contrarian at every step makes you smarter than us plebs?