Thread: Help With Expandable Mandrels Please

Screw a 19mm dowel into the threads at each end and use those to centre. A cone centre will destroy the thread at the tailstock end.

Can you Screw a Nut on the thread and grab the work from It?

Cheers Tony,

If I were tackling that I would turn a slightly tapering 19mm spigot so that you are dead sure of the center being true and the same for the multi head live tail stock I have. The same idea as below when I was turning the balls for my Lazy Susan, but instead of holding the ball it would hold the tubing without any damage. If you don't have a multi head jobbie then you could turn a piece to fit over a cone and do the same job.

Thanks for the advice everyone. I was hoping to be able to buy a expandable mandrel for this project as I need it to be repeatable, so I can reuse it over and over. Otherwise I would be consistently making dowel inserts or spigots (which are all great ideas and appreciated). I was also thinking of making a pin chuck mandrel with the flat in the centre so it did not impinge on the threads. I guess I was just hoping there was something on the market that someone would know about that would provide me good service over a long period of time given the application required. Sincerely thanks for everyone's suggestions.

Originally Posted by pcan68

Thanks for the advice everyone. I was hoping to be able to buy a expandable mandrel for this project as I need it to be repeatable, so I can reuse it over and over.

You can easily make an expendable mandrill. Screw 4 pieces of wood onto an scroll chuck and shape it to size, similar to the one I made for making armbands.

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The wood is screwed into a Gary Pye wide jaw set because that one has screw holes in it but you could use a small set of cole jaws that Gary Pye sells quite cheaply instead.


Peter.

Originally Posted by pcan68

Thanks for the advice everyone. I was hoping to be able to buy a expandable mandrel for this project as I need it to be repeatable, so I can reuse it over and over. Otherwise I would be consistently making dowel inserts or spigots (which are all great ideas and appreciated). I was also thinking of making a pin chuck mandrel with the flat in the centre so it did not impinge on the threads. I guess I was just hoping there was something on the market that someone would know about that would provide me good service over a long period of time given the application required. Sincerely thanks for everyone's suggestions.

You can buy a hard plastic Not sure of the material but have a feeling it may be teflon based It is white in colour but is available from bearing services and often used for low speed bearings . I have used it as fittings for turning various one off supports but you could turn it to fit into your stainless at either end with a shoulder to match yiour final turned size [a lah pen turning] and just reuse the material over and over again . it is not cheap and It is a bitch to turn but takes a fair hiding and to me it has been great. cheers ww wally the chuck side you would turn the suitable angle to suit chuck and the other end to fit over you centre cheers

Does it have to be an expanding mandrel?

At 19mm ID & 8mm of thread length doesn't seem to give you a lot of options to hold via the thread. I would be more inclined to use an internal bush at both ends akin to oversized pen bushes between centres. Use something like the Vermec ER25mm or ER32mm Collett as the basis for the system, a 10 or 12mm round bar as the mandrel bar fixed in the ER Collet chuck one end. Then custom turned delrin "pen bushes" and a multi live centre with a bush turned to suit the live centre with a 10 or 12mm centre to receive the bar. Hold it all in compression via tailstock pressure. The ER collet chuck will permit adjusting the length of the bar to ensure firm clamping between centres.

http://vermec.tripod.com/PDFs/ER32_Page.pdf
http://vermec.tripod.com/PDFs/Live_Centres.pdf

or if you are making large quantities of them have threaded receivers made to fit the ER25 or ER32 Collet chuck on the headstock and a Vermec Threaded Live Centre the other end.

with a lathe I bought there were number 2 morse tapers with lag screws ( metal thread one end and coach bolt thread the other end) they have been real handy for making custom timber mandrel s and the teknatool multi centre has a similar lag screw setup which would be handy for what your doing!