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PolskiFran
03-30-2004, 03:17 PM
I ordered 2 new (import) lathe mandrels, 1 1/8 & 1 1/4. I took notice the center holes were on the small side. I didn't realize how small until I put a 14" dia. flywheel on the mandrel, put it in the lathe and bent the end of the soft center from the weight of the wheel. The center holes measured about .135" (at the largest part of the hole). I measured the center holes on some of my other mandrels; 1/4" man.- .187 to 1"man. - .312. I've contacted MSC, McMaster-Carr and KBC, all of their products have the same small center hole. I was also told there is no spec on the center drill size for mandrels so there shouln't be a problem. Does anyone know of any brand of mandrels that a being produced with apropriate size center holes?

DR
03-30-2004, 03:53 PM
The mandrels I have are from KO Lee (the grinder people), I believe the centers are fairly large. I'm not near them now, but could check later if you're interested.

A 14" flywheel seems a little on the large side for a 1-1/4 mandrel doesn't it?

Maker
03-30-2004, 04:05 PM
I just checked a couple of my larger mandrels and they range from .340 to .250 (on a 1.2375 mandrel). Maybe you need hardened centers?


Alex

wierdscience
03-30-2004, 10:21 PM
There is a difference between grinding and machining mandrels you know and small centers are it.

J Tiers
03-31-2004, 12:21 AM
Weird, I was told the taper is different too.

True?

False?

wierdscience
03-31-2004, 12:42 AM
I have some K.O. lee's in the box yet and they list as .0005" per inch,dunno what the machining ones are,never paid much attention.

PolskiFran
03-31-2004, 02:24 AM
DR,
The flywheel is from a 1913 Sandow engine I'm restoring. It has a 1 1/8" bore. I'm only going to take some truing cuts to make it look good. I would appreciate any comparison of other mandrels.

Maker,
I don't have a drive plate or headstock center for my big lathe, I've usually chucked a piece of 2" dia. steel in the 4 jaw and turned the 60deg taper on the end and driven the lathe dog against the chuck jaws. It does save on the back not having to remove the 14" 4 jaw from the lathe.

Wierd,
I never knew there were special grinding mandrels. But then I'm always the apprentice.

Most of my other mandrels are cleveland (the drill co.) and a few older imports, but they all have substantial center drilled ends. These are the first ones I've seen with such puny centers. A good cut, or an accidental bump of the tool against the part could snap the tip off even a hardened center.

Thanks,
Frank