Expanding mandrels.

A set of expanding mandrels would be good for something I'm doing, and looking at Arc Euro's paper catalogue #10 I thought I'd found the ideal things:

However, it seems that Arc no longer do them, and I've drawn a blank looking for the same things from the 'usual suspects'.

Anyone know of a supplier?

Robin.

Strangely [?] Ausee seems to have them in stock : **LINK**

https://www.ausee.com.au/shop/category.aspx?catid=8384

MichaelG

Tobler do them, but I suspect the price might be rather higher.
https://www.tobler-workholding.com/en/standard-expanding-mandrels/

So do RC-Machines, but only morse taper arbors, rather than the ARC Eurotrade parallel ones
https://www.rcm-machines.com/en/machine-accessories/expanding-mandrels

I have some of the ARC ones; they do seem to work quite well, if a bit rough around the edges.

Various people do 5C ones, but they seem mainly designed for one off jobs and need turning to size for each one.

You could also look up "Expanding Arbor"  on ebay for something similar; look for 8 of them standing up in a wooden block.

Bill

Edited By peak4 on 04/10/2022 23:46:57

My experience of expanding mandrels - they break quite easily ! To minimise this, gently warm them up before use as some workshops can be quite cold overnight and it really spoils your day to bust a sleeve !

Bob

Make your own as required

It's very easy to make an expanding mandrel to suit the job in hand from quite tiny to fairly substantial.

Best made from free cutting mild steel, they can be made from brass or ali but the latter do run a risk of the job spinning and galling making removal potentially difficult.

The mandrel is roughed to the shape shown to with .5mm on diameter, drilled and tapped for the expanding screw - I've done them from 8BA to 8mm - as an average 2BA/4mm is fine for most needs and deeply centred with a centre drill.

The screws are nominally cap heads that have been previously turned to have a 60 degree taper on them.

Remove from the lathe and cut the slots - 2 - 4 or 6 depending on size - with a hacksaw, return and clean out the thread and insert screw to just nip up. Turn the OD to suit the work , Using 60 degree as opposed to a standard countersink means a lot less torque required on the screw for a given grip and use.

This is one as shown above in use to reface a slightly misaligned surface

And here's an example of a tiny one - 8BA screw

They can be reused by careful setting in a four jaw but I prefer to recycle them down wards so each is fresh to the new job.

Yes I do have a set of arc euro ones (not the same as OP) but have never used them - Nicely finished and ground their range never has never fitted any job.

Not to take a sale away from Ketan but the cost of one would buy a fair amount of EN1a to provide a good range - just needs a little bit of time and of course there's only the need to make the one required at the time - not a 'set of them'

Hope that's of use

Tug

Edited By Ramon Wilson on 05/10/2022 10:53:18

Robin

Like Ramon and Martin I make my own as the need arises. The largest in the pic is 7/8" and the smallest is 1/8". The three largest are expanded by a tapered plug and the five smallest are just drilled and tapped with a taper tap and expanded with a normal set screw. ( The 1/8' one has a 1/4" one on the other end ). The slits are made with a slitting saw, four for the larger ones and two for the smaller. (On occasion If I'm in a hurry I have just used a junior hacksaw! ). In use I chuck them in the 3 jaw "Griptru" chuck ( a 4 jaw would work just as well ), clamp the part onto the mandrel by tightening the screw, then, with a DTI on the outside of the part, adjust the chuck till it runs true. For non circular parts I just adjust the mandrel itself to run true.

John

One of those tools which I will get around to making one day. I had to make one once, but it was a special shape and not much use for general holding.