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iansrobinson

Flat Bit Or Forstner Bit For Drilling Ball Joint

4 posts in this topic

I've got these two 4" beechwood wooden balls for ball joints:

 

wooden-balls.jpg

 

What should I use to drill out the 1" and 1.5" diameter holes: a flat spade bit or a forstner bit?

 

Thanks for any help you can offer.

 

ian

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Hi Ian,

 

I drilled a pair of Birch wooden balls for my build using flat bits. I advanced them pretty slowly and they cut ok. I bolted the balls between two pieces of wood with circular holes in - just like the way they are held in the Dalek itself, then clamped the whole thing to the pillar drill table.

 

When I did mine I drilled each one halfway, then turned it upside down and drilled it through until the holes met in the middle. They lined up well, but I did have the luxury of a pre-drilled 6mm pilot hole to keep them on track. If you can find a drill long enough to make one I'd start with that.

 

Best of luck with this!

 

Jonathan

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Hi Ian. Personally I would go with the forstner bit. The flat/spade bits are very hard to control and not very accurate either. You also seem to get a lot of break out as well.

 

The forstner bit gives a more accurate and cleaner cut. As Jonathan says above, try to pilot drill the holes first then widen with the forstner. Nice balls by the way!

 

Simon

 

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To report back here:

 

With one vote for each, I let the friend whose pillar drill I was using have the deciding say – and he suggested forstner. So I bought a couple of Planet Long Series forstner bits, and drilled out those holes. Drilling all the way through, I splintered the exit holes a little, and a couple of the screws holding the supporting frame together grazed the balls – but nothing a little filler can't fix.

 

Things I'd do differently next time:

 

- Use a pillar drill with sufficient vertical movement to drill a ball in one go. The bits were plenty long enough, but there wasn't enough vertical movement in the drill to descend 4 inches. So halfway through drilling each ball, we had to stop the drill and wind up the base plate. The bit head helped keep everything nearly aligned around a vertical axis, but there was a little lateral movement, resulting in a slight kink in the tunnel. I had to do a lot of hard sanding afterwards inside each hole to allow easy passage for the tubes.

 

- Lots of good bracing. I used an old resin ball joint bracket from my disassembled dalek, with screws in each corner onto a wooden base plate, to hold each ball in position. But there was a lot of vibration, which may have contributed to a not-quite-perfect cut.

 

- I'd consider drilling 9/10ths the way through from one side, and then turning the ball over and cutting in from the other side to avoid any splintering of the exit hole.

 

IMG_5449.thumb.jpg.42efe017457b012742311e344e6b6515.jpg

 

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