View Full Version : Expanding mandrel help.....

05-24-2009, 02:19 PM
Ok... I have a couple sets of these inexpensive expanding mandrels, like what MSC and Enco sell. My question is, whats the preferred method of pressing the spring sleeve onto the shaft???? Im thinking there has to be a better way than what I have come up with...

I have looked high and low and not found any "directions" or examples of folks using these and how they press the sleeve on..

And Im really just interested in learning about these. I do have oh so many other mandrels and 5c holders that work great. But I still would like some idea for these. Thanks again!!!!! JR

These are the type Im "trying" to use

Rich Carlstedt
05-24-2009, 03:10 PM
I like to put the work on the sleeve, and then open my vice jaws and place a shop towel accross the jaws , and set a Brass or Aluminum ring/heavy washer ON the jaws (loose) and then drive the work and sleeve on further by hitting the heavy end of the expanding mandrel downward with a Leather Mallet .
A leather mallet is the only tool to use in my book.
the shop towle prevents scoring of the taper from the vise jaws.
The loose ring should be big enough to not get stuck on the taper, yet small enough to bear on the sleeve.

To remove, reverse direction, but same operation.

If you do not have a good selection of brass rings, make some Aluminum soft jaws for the vice and you have an adjustable surface to use that will not mar the mandrel. Just make sure the top surface is parrallel.
A marred mandrel becomes scrap..


John Stevenson
05-24-2009, 03:23 PM
Never given that question a thought before.

I just put the work on the mandrel, slide the sleeve down until it grips the work, then holding the work bump the large end on a piece of alloy or nylon block that's handy to open the sleeve up.

Like I say that simple I have never had to think about it.


05-24-2009, 04:25 PM
I use either Rich's or John's method depending on the mood I am in. If I had an arbor press, I would use that too, pressing the mandrel into the sleeve, backing up the sleeve per Rich's method.

They are more intended for use on grinding operations where forces are lower, heavy cuts can loosen them.

05-24-2009, 04:49 PM
I lube the mandrel and then use an arbor press and rubber tipped dead blow for "bumping". And as JC said, light (very light) cuts when used on the lathe. I've also got some one piece mandrels that are primarily for grinding, but work well enough when facing off or turning toward the big side.

05-24-2009, 05:21 PM
I use a tuna can full of lead for a bump pad. Insert the sleeve in the part, slide the sleeve on the arbor hand pressed then rap the big end on the lead pad a couple of times. Let inertia do it's work. I mount the big end toward the headstock and cut toward the headstock. Never had one come loose even with fairly heavy cuts. To remove the part, rap the small end on the lead pad.

When I'm finished, I swish the arbor and sleeve in some solvent to clean then oil and put away. A still have a wooden box on my project list so they just go back in the plastic bags and paper boxes. :o

05-24-2009, 09:32 PM
Don't lube the mandrel parts or the part you mount on it. Put the sleeve in the part, insert the mandrel and rap the end with a dead blow hammer and then put it in an arbor press and bump it once or twice.

I have had them come off if there was oil on the parts. Be carefull of the part getting hot as it will get loose on the mandrel.

05-24-2009, 09:58 PM
I wondered about the lube part, I was told both ways from various people. More lube to get it to slide further, expand further, and put more force on part ID; but maybe make also it easier to slide back and loosen. I figured as long as you are putting cutting forces toward the big end, the better bet was to use the light lube, which also helps prevent galling. But it always worried me, hence the "very light" cutting forces. Is this wrong?

05-25-2009, 01:50 AM
Ok... I guess Im not gonna be able to use the arbor like I wanted. What you guys have described is what I saw mostly. The mandrel needs to be out of the head stock for seating, either a arbor press or if in the head a dead blow "hammer". I like the can and lead deal.

But I have many parts that I would have liked to use this mandrel for, kinda like a factory. No time to remove the mandrel each time I need to seat a new part. And its not so much the seating of the part, plenty of room on that side. Un-seating the spring sleeve after every part is an issue. No room between the head and the sleeve really to unseat it for the next part.

I made a plastic U shaped deal to un-seat the sleeve, a hammer tap or two releases it. While its still chucked up. I was just thinking this cant be the way they were designed to work??? Gotta make a tool to release the tool? Never used them before.

And really, they werent made for production work, not that Im doing that, maybe 20 parts, but even then its a pain to have to remove the center shaft and go to the arbor press for each one..

Nuther thing,, They are meant for center to center with a dog to drive them. Did you see that? Yeah, the taper goes all the way up to the flat. The flat is for a dog to drive on. So you have to set it up for a center to center hold with a dog driving the mandrel. Am I wrong?? I wanted to chuck the mandrel up, in the lathe jaws. But I didnt see a parallel line. So I checked it with the mic. Yup, tapered all the way to the flat spot, then it is parallel.. So you cant drive these in the chuck. You need to have points at both ends.

Makes sense really. They are prolly ground point to point, so for any accuracy you need to run off the original pilot points...

Not made for any production work huh? Ok, just was trying to use them for a quick change arbor, not gonna happen. Back to the 5c arbor.. Thanks guys!!!!! JR

05-25-2009, 05:59 AM

You may want to consider making a contraption along the lines of a glaze breaker or cylinder hone,a screw-type expansion shoe unit with the adjustment/release mechanism toward the head stock. I suppose it would depend on how many units you need to produce if it were worth the bother.
Of course if you were to make one, many here would hold you in high esteem. (and ask for the drawings after you work out the bugs)

05-25-2009, 08:58 AM
My set of mandrels have a straight section where the flat is and I chuck them up there. If total accuracy is needed I use the 4 jaw and my 3 jaw has at worst .002" runout so if that is ok I use the 3 jaw. I also use them between centers when needed.

I do use the mandrels for production because many times that's the only way to turn something. It's also faster than the solid tapered mandrels. I don't see where removing the mandrel from centers, popping the mandrel out and moving the sleeve to a new part and popping the mandrel back in is a problem. It should all be included in the bid to do the job. Even if you have to remove the part and flip it around to do the other side it should be included in the bid time. By the way, did I say don't try to machine towards the tailstock (small end of the mandrel) because you will get a real nasty surprise when the part comes off.

05-25-2009, 09:47 AM
Not knowing all the details, but turning on centers is not at all complex. Removing an expanding mandrel from an on centers setup, removing the finished part and reinstalling the next part to machine should take no more than 30 seconds.

KO Lee mandrels do have a straight section for chucking. Imports and some others the taper is full length.

05-25-2009, 01:46 PM
Yeah, you guys are right. Its not all that slow to remove the mandrel and tap the parts on and off then re-install. Actually quicker to remove from centers cause I dont have to open the chuck. The live center stays put in the head. But... The drive dog either has to come off every time or a tool to tap the spring sleeve has to be made.

And yes, mine are the cheap ones, tapered all the way to the flat. How do you (Carld) chuck up to that area, the flat messes everything up for jaw placement.

Basically I was just being lazy. I didnt want to have to remove my chuck, but I did. I am using a 5C expanding collet to turn the parts. I was just hoping for a quick way to seat and remove the part on the mandrel without removing it from the lathe. So it would just be a simple tail stock sliding issue.

Thanks for all the great ideas... JR

Rich Carlstedt
05-25-2009, 10:34 PM
I don't take off my chuck when I use a taper mandrel.
I have KO Lees, which you can chuck on, but for dead nuts concentricity, I chuck a small piece of round stock-laying around- and then turn a 60 degree +/- center point. its faster than removing a chuck, and installing a #3 MT dead center, and more accurate in my opinion. Then the driver is driven by a chuck jaw.

05-25-2009, 11:54 PM
My "cheap" imports aren't tapered the full length. The taper stops at the flat so they can be chucked if desired. I wouldn't exactly call them cheap though. I had to buy a few at a time over several months to get the set. Or maybe it's just me that's cheap. :o

I do what Rich does when I don't chuck them. The less chance of dropping a chuck the better and pulling a chuck increases the chances.

05-26-2009, 01:31 AM
My "cheap" imports aren't tapered the full length. The taper stops at the flat so they can be chucked if desired. I wouldn't exactly call them cheap though.

Yeah, I know Ken, they werent cheap, just not out of the world costs. And really, they are dead nutts on for roundness. I dont like the idea of sliding a hardened sleeve that has sharp edges over a ground hardened mandrel. I see the sleeve scoring the mandrel already.

But anyway.. I really tried to chuck the end of the mandrel up, with the flat how do you do it??? I tried with the three jaw, no luck, tried the four jaw, no go. And maybe with the larger mandrel you can grab the end, but for the .750" mandrel I just dont see it. The flat spot is RIGHT in the area for the jaws to grip. Id love to see a pic???? JR

05-26-2009, 09:00 AM
JRouche, you may have to machine or grind a straight area when the flat is to chuck on. I have four K.O. Lee mandrels and have thought about getting the two next sizes up. If I have to buy the imports I will turn the area by the flat down so I can chuck it up. I will try to find some K.O. Lee's first.

J Tiers
05-26-2009, 09:10 AM
Agree on use of arbor press for install/removal. It is the easiest. but the other methods are generally fine also.

You can take a pretty good cut on a piece mounted on that style. It depends on the ratio of ID to OD.... a huge piece with a small ID will not be easy.

I have a set of those, Champion brand, I think, and they are great. I understand that they are not as concentric as a one-piece, but they do quite well, and I don't have so much material tied up in special mandrels.

Mine have a dogging area just like the reduced section on a regular tapered mandrel, I would assume all ro, or how would you use a dog? But it is not ground concentric suitable for chucking. If you do chuck, I'd suggest a 4-jaw.

Yes, always cut towards the fat end... that tightens the part by the natural cutting force.