Measuring spindle runout

While that tells you how close to a circle your spindle tracks at the point of contact, it in no way indicates whether the bearings are true, or not. They'll be, probably, at least as close as the reading you achieved, but there's no guarantee that the surface you're testing is concentric with the bearings, or round. Even checking the R8 taper can be deceiving in that collets wear the spindle unevenly, particularly when they're keyed and always locate in the same place.

Having said that, if you find your spindle to be less than a half thou, that's a pretty good sign the bearings are not trashed. I'd suggest that for an old machine, it's quite good. How noisy is the machine when you run it fast? Expect some noise, for BP's are known for their noisy spindles.

Harold

Thanks. When I run it very fast (100 Hz at highest speed), it is noisy, hard to quantify, but nothing alarming/.

Was the tip of the indicator inside the spindle taper for this test? If you want to try measuring accumulated runout of the spindle and holder, try chucking up a dowel pin and measure the runout with the indicator tip against the OD of the pin. With a long pin you might also try measuring runout on the pin at different distances from the spindle nose.

It's not a good idea to run such tests under spindle power - just rotate the spindle by hand.

Mike

outside

That, though, would introduce a few more sources of inaccuracy.

I agree, though in my defese I must say that the spindle rotated extremely slowly, maybe at 30 RPM.

The noise in the BP's is usually from bad or worn plastic shims in the J2 head. They are part of the adjustable speed control in the head. The other source of noise is the timing belt in the lower part of the head that gets worn. If you ever decide to replace them, there are two different sizes of bushings and shims depending on the motor HP.

John

My own conclusion about this mill is that, due to very intermittent use (it belonged to a printing company), it is in basically like new functional condition. The flaking, runout, etc all point to that. I think that the noise is just normal.

You could have placed the tip onto your nose for exactly the same useless results.

Nick

Don't start! Now he'll want to know whereabouts on his nose...

Mike, it makes sense, thanks. I did the same on the inside of the spindle, with approximately similar result (very little indicator movement, under 0.0004").

That's not bad numbers for a used machine. One thing to look for is a pattern. If it's round, you'll get a consistent, smooth reading. What you may have is wear where the collet has seated, assuming the spindle has the collet key still intact. If so, you may detect three distinct changes per revolution as the indicator goes over the relief area of the collet, where there would little or no wear (inside the spindle, on the tapered area) as opposed to the area where the collet bears as it's tightened. If that's the case, what you'd be interested in is how consistent the three areas are where the collet bears. If they're uniform, even less than the .0004" you discovered, you're in pretty decent shape.

Harold

I don't think that sort of test will be as useful as measuring the runount on the taper inside the spindle nose.

True, but it will give you an idea of the combined runount on both the spindle and collet or EM holder, which is useful to know.

Well, it's your indicator .

Mike

Harold, thanks, accuracy of my indicator is not enough to really discern what was going on. If I was to make an estimate of the travel of the indicator needle, based on what I observed with my eye, my best estimate would be 0.00025" total travel per revolution. Since accuracy of this indicator is likely no better, or worse, than this number, I do not have a good base for making any conclusions beyond saying that it is likely to be below 0.0005".

The practical implication of these numbers, I think, is that I can use this mill with carbide endmills. I tried milling steel with carbide endmills and everything seemed to work. One of the first useful millings was shortening the Y travel set screw handle by about 1/8" using a carbide end mill. (it was too long and was hitting the table). I milled a little flat top on the handle. It Worked fine.

Some more developments are that I set it on blocks, removed the front bar with casters, and the rear casters, though attached, are suspended in the air.

I also bolted it down to the welded base.

My Z axis handle was not in a great shape and slipped from the "star" that it engaged. I drilled/tapped a hole along the axis of rotation of this handle, and the 1/4 screw with a special washer that pushes the handle forward and prevents slipping. I hope that I was clear.

I worked in precision grinding for several years. You come to terms with the lack of precision of mechanical indicators. Some are better than others, certainly, but none of them come close to the precision of electronic indicators.

You're more likely to have runout in collets or end mill holders beyond that which you've discovered, so if that's your concern, you're fine. Runout doesn't preclude the use of carbide, it just makes it more difficult to achieve a fine finish. The slight variation if depth of cut isn't much of an issue, but the feed rate as it relates to the high point is---that will determine how fast you can feed. You're not likely to notice anything that runs out under a thou. That's not to say it's not important, but the problems are manageable.

I trust you're discussing the knee, not the spindle? If that be the case, yes, I'm clear on what you did. Anything that will keep the dogs in contact should work fine----especially considering that axis isn't powered. You want to be cautious if you power any handle that won't disconnect.

It sounds like you got a decent machine, and I think you made a great decision in buying one. The time will come when you'll wonder how you got by without it. I got totally burned out on my machines back in '83, and have not used them much since. I quit commercial machining entirely------and I still don't derive much pleasure from running them-----but there's no way in hell I'd consider selling them, either. Once you've had them, you can't get by without them.

Harold

Next time..measure the INSIDE of the taper.

Gunner

"Try thinking of the Libertarian Party as a rolled-up newspaper, useful in making the Republican puppy (I've given up on the Democratic bitch) go where he's supposed to -- not on that beautiful antique carpet we call the Constitution." -- L. Neil Smith, Bill Clinton's Reichstag Fire

On Sun, 10 Jun 2007 22:48:55 -0500, with neither quill nor qualm, Ignoramus2277 quickly quoth:

If you really want the spindle runout numbers, remove the belt and try the test again, moving the spindle with your hands back and forth in line with the DI. That'll give you the slop numbers to work with, Ig.

Yes... I did that after all, the measured runout is below the resolution of the 0.001" Federal indicator.

Yes, the knee.

Sure. Right now they are not powered.

They are a hobby for me, I make my money mostly by computer programming, at work as well as on a few websites that I have. But I hope that the mill will bring me some practical benefits, will let me fix some equipment one day etc.

Thanks Harold.

Congratulations on the nice looking mill, Ig. I bet you're going to like it. A lot.

Pete Keillor

Pete, thanks. I hope that I will enjoy it, in fact, I already do.

igor