Sensitive spindle build

Has anyone any references to aid in the construction of a sensitive grinding spindle suitable for bench lathe applications?

I would like to produce something with about 2 inch stroke.
A device that would fit up to the KDK QC tool post, even if just clamped in the usual tool position, and be powered by.....? an overhead/back bench jocky belt system.

I am considering plain bearing construction for compactness and quietness. Preferably a C.I yoke and a length of 7/16 or 1/2 inch drill rod for the quill. The work end to be threaded 3/8- fine to suit jacobs rubber flex collet chucks. The "handle may indeed be fitted with a ball bearing as a suitable finger hold ;-) The drive could be centered between bearings or less desirable I think, on the handled extremity.
Comments on the use of oilite or other self lubricating bearings? I am not opposed to having spares on hand and renewing them frequently. Or would C.I. rod turned up as "replaceable bearings" be a better choice? I could not help but put a drop of "turbine oil" at the correct location before any use ;-)
A lapped close running fit is what is desired. I could appreciate a clamp up housing to extend the service life of any bearings.

This link shows commercial offerings, but without the feature of "stroke", I may as well stick with the tool post grinder.
www.anglo-swiss-tools.co.uk/grindingspindles.html

Thus far, I have not run across any vintage equipment nor have I seen raw castings suited to this task.

A Levin unit is "too much". in many ways.


All comments welcome!

CalG

I am not sure how well the plain bearings you describe will work. Especially if they are straight cylindrical bores. Tool post grinder (TPG) is going to have fairly high thrust and radial loads on it. A plain cylindrical bearing may work (briefly) for one of those directions. I have no idea what Schaublin used but I imagine it was a conical plain bearing so the runout could be adjusted as the bearing wore.

It sounds like what you want to build is a "spindle cartridge."
Here are some links to some articles on building your own:
http://metalworking.com/dropbox/spindle1.pdf
http://metalworking.com/dropbox/spindle2.pdf
http://metalworking.com/dropbox/spindle3.pdf

The rest of mounting and motoring and whatnot is up to you. I would copy what others do (that works.)

One can pick up a used Dumore with a bunch of accessories all in a fitted case for $500 (or less.) Depending how you value your time it may not be worth it to make your own.

-DU-

DU

Thank you for your comments.
I wish I had the ability to extract a photo from some old literature to show the nature of the device in mind. The cover of "Modern Toolmaking methods" by F. Jones, reprint Lindsey publications. has just such a device pictured.

But.. a sensitive grinding spindle has no thrust component as the lateral motion is determind by the pressure of the operators finger tips!

Presently, a fully stocked Themac J45 answers all the larger TP grinding work I require.

I also have a nice roller element spindle assembly if only a smaller unit is wanted, But alas, the linear motion is then still left to the carriage or compound. Not what is wanted!

A Sensitive spindle would be for much more delicate applications.

Kind regards

CalG

You really need a preloaded precision bearing pac for a grinder spindle which are normally assembled in a clean room. Then the spindles get tested for several hours with precision load, heat and current draw measurements. Even a couple ten thousandths of run out or end play will cause a rough finish. You might be able to use an aircylinder for the movement once you get a working spindle.

CalG,

Interesting... never seen a "sensitive spindle" as you described it, not for the grinding wheel anyhow. Sounds like a challenge. Perhaps as MisterT describes and mount it in an air-bearing (for the "stroke".)

-DU-

I have failed in my description of tool and application

With no disrespect to either DU and MisterT:, A large hammer is not needed to kill a mosquito ;-)

The spindle in mind is not "ultra precise", rather "ultra simple" and thus flexible.

I'll try to get a picture somehow.

Comments appreciated still!

CalG said:

I'll try to get a picture somehow.

Click to expand...

Got CAD (or even MS-paint or whatever)? Draw us a picture.

-DU-

It sound like what you want is a watchmakers pivot polisher only bigger. The Schaublin unit illustrated at the bottom of the page you posted in your link is what your describing. The Schaublin unit pictured has a stroke of 2 9/16 inches. It has a maximum rated speed of 18000 rpm Hardinge also made similar attachments.

I have seen very small spindles made where there was only one half of a bearing that was made like a "V" block. It used belt tension to hold the spindle in place. These spindles were hardened steel running on agat

SIP
I have seen those "half bearing" units as well. .
The V-block/mandril techique is common for optical work, centering lenses and the like.
Close...., but no. Jewel bearings sound fun however.
Agat, garnet, ruby? I must have something kicking around ;-)

I do not see the stroke mentioned available on the pictured Schaublin unit. I will pursue additional information.

Thanx
\
Cal

Cal:

I got that piece of information from a Schaublin catalog. Not much more information than that. The end where the grinding wheel mounts has a 2 degree taperd hole in the end, has a 30mm pully groved for 6 mm belt. Thare are also arbors listed to go in the hole in the end of the spindle.

Todd

Like the rest, I have a problem visualizing exactly what you want, but how about an air spindle similar to an end mill grinding spindle, but much smaller, that has a long quill running in a air bearing that allows it to spin, much faster than the end mill spindle is turned, of course, and can smoothly slide axially? Air bearings are not hard to make and you have the advantage that movement is exactly parallel to the spindle. You would need to mount a ball bearing knob on the end to control axial movement.

Bill

There are a variety of ER collet extensions with parallel shanks available, I used an ER11 one from Bison with a 1/2" shank 160mm long to make a grinding/light milling spindle. A couple of light duty bearings in a cylindrical housing with a belleville washer preload, driven by an overhead gear. Works well and gets a lot of use. A variation on what I made should do what you want, the spindle is the most tricky item and they are not expensive. Then again, if what you want is so uncritical, maybe something could be done with a Dremel....

- Mike -

The Schaublin unit at the bottom of the link page is dead simple. The spindle as Sip said has a 2 degree taper for mounting little split collets or arbors. It's hard as hell. I can't remember what the bearings are (have to dig mine out), but the smaller versions from Levin etc. used hardened steel bearings. The advice I was given was to run it dry and at full tilt boogie, apparently at almost 20k they make their own kind of air bearing.

I've only used mine once, to grind a hole through a piece of ruby. I couldn't resist putting just a little oil on the spindle. Seemed to be ok. I'll dig mine out and take a few pics if you want.

HelEx

Thank you for the suggestion.

Having looked to the ER extensions, 16 cm may be long enough to offer a reasonable stroke, but that would limit the bearing spread.

What mounting arbor do you use to fit up say a 55 mm diameter abrasive wheel?

Thanks, I'm thinking.....

CalG

Screwmachine

Your comments are very interesting. DRY?
I would not have imagined, but Hard on Hard, lightly loaded is an interesting condition.

Photos would be truely appreciated!

Could a pair drill bushings and length of W-1 drill rod serve? That would be too easy. The drill rod may not be hard enough in the as delivered condition to run dry.
One bushing in some sort of compliant material (lead, plaster of paris, delrin etc). to ease alignment issues. I suppose that depends on the stability of the bearing holding yoke.

Ideas are forming.

Cal

http://cgi.ebay.com/Tool-Post-Grind...emQQptZLH_DefaultDomain_0?hash=item5ad5762b11

This add pictures a Very light duty sensitive tool post grinder.

I'm thinking of something a bit more substantial.

CalG