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Concentricity, Tapers and Bearing query.

David Nolan

Plastic
Joined
Apr 14, 2021
Hi, I'm planning on building my own mill at some point in the future. I'm not buying one because I figure it will be much cheaper to build one with my specificications, I already have a mini mill. I am however a little apprehensive, I've had issues with spindles being slightly out concentricity wise in the past and it caused me a lot of grief. So I want to get a better picture of how to assemble a (practically)perfectly concentric spindle.

I'm unsure of a few things. So my tools are mostly MT3 tapers, what I'm wondering is do most mills have an internally cut taper to mate with a given taper type, presuming they use a Morse tapers that is. Or is the 'socket' just a regular hole that is sized proportionally to the given taper size. Obviously it would be great if a regular hole would do the trick cause it' a lot easier then cutting an internal taper which I would most likely have to outsource.

(I can't use the actual motor spindle as the spindle like on a router because, I need to step down the rpms before it gets to the tool, cheap chinese spindles don't do so good at low speeds and I want low speed for steel)

Second question is about bearings... How on earth do I get the right fit on a bearing so that the concentricity is of a perfect tolerance, I'm most likely going to buy the spindle body and the bearing seperately so how do I ensure a good fit. I feel like I have the wrong idea here, maybe I'm being way to ambitious. Do I buy a tapered spindle or tapered roller bearings or do I need to manually cut the spindle body to the exact right dimension so it perfectly press fits with into the bearing. How would a lay person like myself go about this? Can I buy these together, ready to assemble and where? I live in Ireland... I mean I have nightmares about concentricity. Please give me some advice, cheers.
 
Spindles are most often ground for fit on the bearing races and
ID ground to fit the tapers. Maybe you are thinking it is a lathe job ?
Yes rough out on a lathe, heat treat/harden the spindle, then ID and
OD grind. Many times the ID taper is ground in it's own bearings.

--Doozer
 
A little gentle advice - don't do this. Just save up and buy a working machine, you will be far, far ahead in time and money with a functioning machine you can actually use.

And if you want to get OCD over concentricity, keep in mind that any collet, any toolholder, and any cutting tool you use will have their own errors. Try not to let the worry dominate your life.

Best of luck!
 
Hi, I'm planning on building my own mill at some point in the future. I'm not buying one because I figure it will be much cheaper to build one with my specificications, I already have a mini mill. I am however a little apprehensive, I've had issues with spindles being slightly out concentricity wise in the past and it caused me a lot of grief. So I want to get a better picture of how to assemble a (practically)perfectly concentric spindle.

I'm unsure of a few things. So my tools are mostly MT3 tapers, what I'm wondering is do most mills have an internally cut taper to mate with a given taper type, presuming they use a Morse tapers that is. Or is the 'socket' just a regular hole that is sized proportionally to the given taper size. Obviously it would be great if a regular hole would do the trick cause it' a lot easier then cutting an internal taper which I would most likely have to outsource.

(I can't use the actual motor spindle as the spindle like on a router because, I need to step down the rpms before it gets to the tool, cheap chinese spindles don't do so good at low speeds and I want low speed for steel)

Second question is about bearings... How on earth do I get the right fit on a bearing so that the concentricity is of a perfect tolerance, I'm most likely going to buy the spindle body and the bearing seperately so how do I ensure a good fit. I feel like I have the wrong idea here, maybe I'm being way to ambitious. Do I buy a tapered spindle or tapered roller bearings or do I need to manually cut the spindle body to the exact right dimension so it perfectly press fits with into the bearing. How would a lay person like myself go about this? Can I buy these together, ready to assemble and where? I live in Ireland... I mean I have nightmares about concentricity. Please give me some advice, cheers.

It's books or the time to go read freebies that you need to buy first. You Tube vids. PM threads on restorations. Actual specification of ACTUAL mills.

The real-world USEFUL work folk accomplish with even a bady worn mill of great age.... if only it is a REAL one, not a Chinesium wanker-seed-corn-malted-mash.

The journey you think to start can easily leave you having spent 20,000 Euro to build a mill not half as good as one you can purchase, used, for less than 2,000 Euro.

Major companies have gone broke trying to build mills. And some had over a hundred YEARS of success at it, already.

Worse?

A(ny) of those "MMSO" (Milling Machine Shaped Ojects") are good only for teaching progressively higher levels of increasing dangerous ignorance.

If concentricity you barely understand is your nightmare ALREADY?

Even LESS sane that at present as well as impoverished.

Air Power Spindle - YouTube

There is a WHOLE UNIVERSE in that gap - just above.

Which part of it do you wish to chase?

And would you be closer to a realistic goal-set to learn to operate the advanced machines as a reliable employee - where the machinery was being furnished?

Otherwise?

Case in point:

"There was this poor, misguided sod somewhere in Eire who could not even spell "specifications", let alone understand them ...."

Get thee to reading more and assuming less.

Or you shall become he.

TANSTAAFL
 
Try building something like a simple dividing head you can use on your existing mill, and see how much effort that is, then imagine that 100 (or few hundred) times more time consuming and 50x more difficult, and decide if you want to build a whole milling machine. Not to mention you will need a much larger milling machine than the one you want to build, to machine the parts for it. And a really nice lathe. And a bunch of other stuff.
 
Try building something like a simple dividing head you can use on your existing mill, and see how much effort that is, then imagine that 100 (or few hundred) times more time consuming and 50x more difficult, and decide if you want to build a whole milling machine. Not to mention you will need a much larger milling machine than the one you want to build, to machine the parts for it. And a really nice lathe. And a bunch of other stuff.

Meahh. Find an ancient horizontal. Rescrape it.
- learn to be a mill hand.


Find a vertical's head. Rebuild that, too.
- forget half of what you just learnt

By then, common sense might have entered?

:)

THEN one can... pick a BETTER mill to.... rebuild..

:)

I don't hear a bank account shouting several tens of thousands of US$ or Euro, either one to buy NEW off no "presume Morse Taper".

"Packaged" spindles looking for tables, ways, and traverse are everywhere.

"Packaged" tables, ways, and positioning looking for spindles, not so much

DIY of either costs more than purchased. Not less.

"Practical Manufacturing" thing when building more than just the one.

See what it costs to build ONE motorcar .. from scratch.. that you can get road-legal-licensed in the EU.

Might start with the airbag system? Or "système de freinage anti-blocage" (ABS) braking sensors, computer et al?

That'll keep yah outta pubs and brothels for easily a hundred years off the back of the cost of the tests, alone!

Used Jaguar XJ8-L, OTOH, was but $10,600. One mill was $400. The other was $500.

Build my own DINNER was still possible off the savings.

My age, cooking is better than Old Iron or sex, either one.

Cook a meal several times a day, and no one calls you a pervert.

And you don't even have to starve to death from non-stop scraping of rust nor shagging.

What's not to like?

:D
 
Nah. Build a BASIC mill from kit, at least yah LEARN sumthin' "realistic" off it.

There was no "Kit" with the gingery books, you were to collect beer cans, dig a hole
in the back yard, add a blower and some charcoal, ram up some dirt, and pour everything.....:ack2:
 
This may sound negative, it's not meant that way, I'm being factual.But it sure as hell won't be cheaper to build one instead of buying. That contradicts the cost savings of mass production and why the concept was invented in the first place. And if you have to ask basic questions like you have, it already shows you don't understand or know nearly enough. Yes it could be done by a very few on a learn as you go process, that's how we got to where we are now.But I strongly doubt .001% would or could see it to completion. As a start buy a copy of the book Machine Tool Reconditioning. Everything in it will relate to what your wanting to do and it's exactly what you need to know and a hell of a lot more before even starting. I'd estimate the metrology equipment required will be close to or exceed the cost of buying a half decent mill. Then double at the minimum those costs for materials or castings. Just rebuilding a machine tool back to as new accuracy's and condition is a black hole for both time and money never mind building one from scratch. Buy a worn out Bridgeport for cheap and start learning everything you can about machine tool rebuilding. Then rebuild it, and by the time your done you'll then understand what's involved.
 
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There was no "Kit" with the gingery books, you were to collect beer cans, dig a hole
in the back yard, add a blower and some charcoal, ram up some dirt, and pour everything.....:ack2:

Still cheating. You'd have the dam' BOOK! Not much help to the OP.
Reading challenged. Or maybe just butt LAZY?

"Ask on PM!!! FREE MAGIC falls out of the SKY!"

See: "One Hoe for Kalabo".

There's one of the most stark eye-openers ever filmed.

One Hoe for Kalabo - YouTube

US Steel's release, back when it was new-news, 16 mm AV film for schools, had a sound track. The iron-workers were singing a memory saga as they worked.
Plus explanatory voice-over in English.

Ore is VERY low-grade.
They need the mud from a termite mound to build the furnace as won't fall apart.
The rod-pumped bellows that provide a hot enough fire are animal leather.

Their "book"? Passed-on for thousands of years by oral tradition.

Humans. We JF do whaever we need to do when we need it badly enough.
 
Odd! We had to watch One Hoe for Kalabo way back at the beginning of of the machinist program I took, but it was different than that Youtube version. Same title, but the one I saw contrasted the local blacksmith with modern manufacturing. The point being that our relative standard of living was made possible by high speed machine processes. By the 1950's when I was an observer there, I suspect that the smelting illustrated had been pretty well replaced by re-purposing of more readily available steel - oil drums, kerosene tins, anything that could be reshaped into something else.

The OP proposition of building a mill reminds me of another episode of no- effing-idea-of-what's-involved. At the foreign car repair shop where I worked we got a call to ask if we could set the timing on a Triumph Herald. No problem, the counter man said. We should have had a clue when the car came in towed, rather than driven. The longer story was that the engine had been disassembled by a kid before he went off to college. His father reassembled it, and when it wouldn't start, the only thing he could think of was that the timing was off. When our mechanic looked at it, that wasn't the beginning of its problems. He saw, for instance, that the fan had been spaced out with nuts behind it so it would clear. That was because it had been installed backwards. And that was just one of the most obvious problems. The mechanic couldn't assume that ANYTHING had been installed correctly. Just a timing adjust? OP's enthusiasm has just about the same level of knowledge.
 
The OP is obviously either a troll or a total moron.

He wants to know if just drilling a straight hole in his homemade spindle, to accept his Morse taper tooling, will work.

Why does anyone take the time to reply to an idiot such as he, other than, to quote W. C. Fields “Go away kid, you bother me.”? Or maybe something a bit stronger, such as FOAD?
 
Because on occasion, just like a deity we take care of fools and drunkards?
Except that attempting to explain special relativity to a fool or a drunkard is itself a fool’s task. “Go away kid, you bother me” is the kinder response, as you will only confuse him further.

Sort of like the Proxxon mill thread. Hard to believe that so many people took so much time providing serious answers. (Sorry - that one is on Home Shop Machinist)

Not criticizing anyone’s answers, just expressing my surprise at the waste of time.
 
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Odd! We had to watch One Hoe for Kalabo way back at the beginning of of the machinist program I took, but it was different than that Youtube version.

Yazz.. the US Steel version alternated Mesabi range mining, open-hearth furnaces, hot rolling mills, segued to high speed machinery producing modern hoes on big presses at Ma-deuce machine-gun cyclic speed, just LOUDER!

:)

As to half-assed assembly?

"Guy I bought it from said I'd have to start by pulling the head.."

Yahreally. Inline motor.

Guy pulled the head, shone a light.

Gravel was looking back at him.
Not in the bores.

Under the motorcar!

Fuggabuncha useless "overhead"!
No pistons, rods, crank, or oil pan!

:D

A GOOD mechanic always has a few parts left over some dam' fool in Engineering got badly wrong.

A BAD mechanic has enough to open a store!
 








 
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