View Full Version : using expandable lathe mandrels
11-17-2006, 12:17 PM
Just got some expandable mandrels from Enco and they don't have a nut to adjust for size. It looks like you insert it into the part you want to turn and jam the sleeve farther on the tapered mandrel to make it fit tight. Then, I assume, you turn it between centers.
Two questions are: How hard do I force the sleeve up the tapered mandrel and what do I use to do it? Leather mallet? Between vice jaws? How much pressure do I need to use to make it stay put?
Can I face off both ends of the part (one end nearer the headstock and the other end nearer the tailstock) without taking it out of the lathe and flipping it over? Will that ruin my concenticity if I swap end for end? Thanks--Mike.
11-17-2006, 01:01 PM
is there no way to expand them by inserting an allen key or anything from the front they must expand surely.Alistair
11-17-2006, 01:23 PM
Someone else asked that on another forum.... and I posted this about the force etc.
I use them, but I have a fairly decent older set, not "HF specials". They are pretty close, but not up there with a tapered mandrel.
You need to choose what size, since sometimes the part may fit on either of two. I usually use the smaller, as I prefer it to be towards the headstock... no good reason.... just "looks".
I have held them in a 4 jaw, used a dog, etc. Tailstock end always goes in a center.
The nice thing about the 4 jaw is that you can use it to get the runout lower. I get into the tenths with mine, with care.
Force? well you need the work not to slide and slip... I use an arbor press. I get the work where I want it on the expanding part by hand, then "set" it onto the cone with the press.
Good and firm, no need to use a cheater bar. But if it slips, that wasn't enough, or else you are expecting too much.
A 1/2" mandrel isn't going to drive a 12" pulley for a hogging cut.... If you REALLY need that kind of drive, get something onto the work as a drive pin, and use the mandrel only as a "centering axle".
As far as reversing, they'll be close but not necessarily "on". So reversing may be OK and may be not, the way the part sets might be different after removal and reversing.
I am not sure how you'd reverse the whole thing, at least with the type below, since only one end has a driving flat on it.........
Yours may look like this:
and fit like this (i'm using a 4 jaw in the pic to improve centering)
11-17-2006, 01:30 PM
They're a light press fit. Remember that you will have to press them out too. If you get them too tight, you'll gall your piece or the sleeves. They need to be tight enough not to slip but not tight enough to gall the bore. They're similar to tapered mandrels when cutting--You cut toward the big end (spread end). This would normally be toward the headstock. When you mount the mandrel between centers, advance the tailstock center to tighten. Keep checking the tightness and take light cuts. Don't try to hog-out metal.
As far as facing, you can but you risk cutting into the mandrel. If the design allows, put a small relief at the bore of your piece to allow a bit to get close to the mandrel.
11-17-2006, 01:33 PM
Ops, JT beat me to it. I notice his mandrel is a little different too. (Skip the part about tightening with the tailstock.)
11-17-2006, 05:05 PM
I face with these.I leave the end of the part hang over the expanding sleeve so you face past the end of the sleeve.I always chuck the large end and indicate next to the part.To install these I slide the part on where I want it and bump the large end on a oak 4x4 with a good wang with my hand on the part pushing down as I hit.Works great.
11-17-2006, 06:51 PM
Thanks to all that replied and to Mr. Tiers for his pictures. My sleeves are a little different than the ones that are shown in the pictures. The end that is chucked into the 4 Jaw is shorter than the one shown and I don't know if I can get it centered in the chuck. Might have to use centers and a dog with a face plate. thanks--Mike.
That type of mandrel was design by K.O. Lee for grinding parts on . You can do light machining with them But they are made to be used between centers . Big end always to chuck side so tool force trys to push the part tighter on mandrel.. To use insert sleeve into part large end of hole to be near chuck insert the taperd shaft and press to getger with arbor press. use press to take apart in reverse . Hopes this info helps all.If you dont beleave me ask J.C. Hannum
11-17-2006, 11:34 PM
I've got a huge pile of mandrels and sleeves sorta like that, except my sleeves are spiral cut rather than straight, and the arbor has a less agressive taper. Some sleeves are steel, and others appear to be some sort of bronze/brass alloy. So far they work rather well for light cuts.