Expanding Mandrel

[VicParticipant @vic]

[VicParticipant @vic]

I need to grip some wood from inside for further operations so was thinking of making some sort of expanding mandrel. I suppose a tapered hole and socket with a drawbar should do it but what sort of materials to use or avoid for easiest operation? I have aluminium alloy, steel and a small amount of brass. The mandrel itself can be any size from about 13 – 19mm to suit. Any advice much appreciated.

[Mick B1Participant @mickb1]

If you've only a few workpieces to do on it, alli's probably the easiest and cheapest. It's also relatively sticky, so generally provides good friction to drive the work. Brass is also easy to machine but is dearer and generally has a slicker surface, so it may need more tightening to give a good drive.

Steel's probably the one to use if there are a lot of wooden workpieces to do.

Whichever you use, the expansion will be local to the cone, so it will generally work best on short bores – or longer ones with reasonably close limits – or there'll be risk of yaw. If the wall is thin, there can of course be risk of cracking the piece on tightening.

[EmgeeParticipant @emgee]

Hi Vic

Have a look at this Youtube video from Joe Pieczynski, pretty informative.

**LINK**

Emgee

 

[egaParticipant @ega]

Vic:

Why not do what the traditional woodturner would do, turn a wooden mandrel and wring the work on to it?

You don't give any details of your job save that it's "some wood" so my suggestion may be inappropriate.

ARC sell some fancy (parallel) expanding mandrels.

Edited By ega on 27/10/2018 11:47:59

[egaParticipant @ega]

Emgee:

Thanks for the link to an excellent video.

[VicParticipant @vic]

Posted by Emgee on 27/10/2018 10:05:14:

Hi Vic

Have a look at this Youtube video from Joe Pieczynski, pretty informative.

**LINK**

Emgee

 

Thanks for that Emgee, very interesting. One of those may do the job. I’ve seen quite a number of Joe’s videos before but not come across that one.

[Mark RandParticipant @markrand96270]

One thing that came as a revelation in The linked youtube video was that his expanding mandrels had a length to the left of the expanding bit at the same diameter as the work. This strikes me as a brilliant idea. Might be a common thing, but none of the commercial ones I've bought have it. It should vastly improve the accuracy of the mandrel.

That's going in the ideas file!

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