Sunday, 1 March 2009

Polelathe - Dead Head



The pole lathe needs two pointed metal centres to hold the wood being turned. Power lathe centres are used to turn the wood, but on pole lathes the cord turns and the centres are fixed or 'dead'.

The two poppets are referred to as 'Head' and 'Tail'. The centre in the tail is not adjustable and can be a pointed bolt, whereas the centre in the head poppet is usually an adjustable threaded bar.

I always end up calling them 'dead heads' But lets not go there!


The simplest solution for the dead head, or centre, is to grind a point onto a length of threaded bar. M12 or about 1/2inch in this case. I use an angle grinder to take off four sides then rotate it evenly on the bench grinder to get a smooth cone, the fine grinder disc gives an almost mirror finish.

In the back of mind I knew that I'd put a few bits aside from the last rebuild of landrover suspension. The springs were snapped up by my blacksmith friends but I kept the old bolts and spring hangers. So the handle on the dead head is a landrover spring hanger (circa 1960) and the tail centre is a suspension bolt and lock nut.

Once the centres are ready it's time for the holes in the poppets - probably the most exacting part of the pole lathe as errors in alignment easy are annoying. I used a 10mm bit for the holes and a 10mm wood bit to 'ream' out the holes a little until they are a tight fit.


I drilled the holes through the poppets for the centres using a bench drill press and carefully aligned the poppet to the drill bit with a spirit level to follow the planned centre line. I drilled from each side of the poppet so the worst error is in the middle, but for once the careful alignment seems ok.

And finally the two centres get to meet. Almost. Needless to say they did not align perfectly at first. But some quick work with a belt sander on one of the poppets gets them to within about 1mm. Some more fine tuning might be necessary once the lathe 'settles in'. Now to try it out!




2 comments:

Anonymous said...

The lathe is looking good, Mark. I must build one, one day soon. You've inspired me. And you've given me a good use for my old series three! Lathe and tool parts. That'll teach it to fail on the brakes.
Andy

Woodland Antics said...

Thank you for your kind comments Andy. I really am pleased with the way its working, much improved and so much better than a exercise bike!

Sorry about your series III, I have one of those to recycle or reuse as well, but the series II's will still be going for a while yet. Failing on brakes is about par for the course for me!

cheers

Mark