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motorworks
01-03-2009, 07:00 PM
Hi
Does anyone know where I can buy an expanding mandrel
with a size from 95-102mm or 3.750-4.000"?

I tried the usually: Travers,KBC, Shars etc with no luck.

eddie

lazlo
01-03-2009, 07:29 PM
Dunham makes their "Miser Mandrels" up to 6". I have the MM1, 2, 3, which MSC carries. They're much nicer than the Chinese copy (which I also have).

The MM5 (Miser Mandrel 5) goes 3/4" to 4 3/4", and the MM6 goes 3/4" to 6 1/4"

http://www.dunhamtool.com/expanding_mandrel.html

http://www.dunhamtool.com/images/miser_mandrel.jpg

jimsehr
01-03-2009, 10:48 PM
Google Rovi collets made in Calfornia
I have used them for years and they go up to 6 inches.
Jim

lazlo
01-03-2009, 10:53 PM
Dunham has those machineable 5C expanding collets too -- are they expensive? I nabbed a couple of the Dunhams on Ebay, but they're something like $120 each retail.

oldtiffie
01-03-2009, 11:00 PM
Is there any reason why a 3-jaw chuck with soft jaws won't do the job?

jimsehr
01-03-2009, 11:06 PM
I have the collet parts and bought them years ago. So don't know what prices are in todays market, but the expanding mandrel part in a 4 inch size is
about $80 to $100 bucks. Depends on length of them. I have used them from 5/16 dia up to 6 inch size in their 5c type.
Jim

radish1us
01-04-2009, 03:58 AM
Is there any reason why a 3-jaw chuck with soft jaws won't do the job?


Nope, suppose they would be even quicker to do it, than mucking around with a mandrel.

oldtiffie
01-04-2009, 07:30 AM
Originally Posted by oldtiffie
Is there any reason why a 3-jaw chuck with soft jaws won't do the job?


Nope, suppose they would be even quicker to do it, than mucking around with a mandrel.

Thanks radish1us.

I was going to add that if a 3-jaw chuck with soft jaws was available, the cost - providing the soft-jaws were in the shop - would be about zero. A new three jaw chuck with soft jaws may well be an ultimately better and cheaper option than expanding mandrels. There must be a finite limit to which the expanding mandrel can be turned each time to achieve a set nominal size before being "down-sized" at which stage a new expanding mandrel may need to be bought.

Longer - in this case, hollow - parts whether held on an expanding mandrel or in soft jaws - will or may require to be supported by a disk or similar which in turn is supported by the tail-stock - or perhaps a fixed (or "traveling"??) "steady" or a "spider".

Still its the OP's "call" or choice.

motorworks
01-04-2009, 09:30 AM
Thanks guys
Thoses "Miser Mandrels" look easy to make
but I would have to make two as there are two
parts to the bushing job and two different bores
(95mm for the rough and 100mm finish)

I was looking for the tapered type that work over a greater range.
I may just make two solid taper mandrels (0.0005"/1")
one for the 95 and one for the 100mm.

I though about 'soft jaws' but I need to hold both by the bore
and they are 110mm long.
Thought it may work with the disc idea/ 2 discs! ( thanks oldtiffie)


eddie

J Tiers
01-04-2009, 11:26 AM
I haven't personally seen taper-expanding ones over about 2". My set goes to 1.5" IIRC.

I see the machinable ones as really for a production job. You need something of a commitment to spend $100 on a tool for one job. Or 2x that for two different tools for one job.......

wierdscience
01-04-2009, 12:40 PM
McMaster-Carr lists one,3-1/4-4"..............$1275:eek:

Here is an interesting concept-

http://www.holdid.com/IDHOLD-XPANDREL.htm

What about a rotating tailstock chuck?

lazlo
01-04-2009, 12:48 PM
Thanks guys
Thoses "Miser Mandrels" look easy to make

Yep, looks like a quick project. It's just a bored cylinder with radial slits and a tapered plug to spread it. I've heard folks use an NPT plug to spread homemade expanding mandrels.

By the way, the cool feature about the 5C collet mandrels like Jim Sehr posted is they screw into the 5C drawbar, and the drawbar pulls the taper plug.

So you put the workpiece on the mandrel, pull the drawbar lever, and the mandrels grabs and you're off to the races...

BadDog
01-04-2009, 02:43 PM
I though about 'soft jaws' but I need to hold both by the bore
and they are 110mm long.
Thought it may work with the disc idea/ 2 discs! ( thanks oldtiffie)


eddie
How about soft jaws turned to grasp the bore on one end, and a bull center to locate the other end. I've done this but with standard ID jaws and bull center for turning the OD of heavy wall DOM tube. You could even make a TS "live mount" and make a "hat" of appropriate size with small taper on the insert section, sized for the job of the day...