hollow arbor

[Mike Radcliffe]

Since I read of the vacuum chuck I have wondered if I can drill a hole through the center of the arbor on my craftsman lathe. I guess one would use a drill chuck with a morse taper on the tailstock. Has anyone tried this or am I on the wrong track. Thanks for any suggestions. Mike

[Gary DeWitt]

Since the arbor on a woodturning lathe encounters considerable side loading, I wouldn't drill one out without carefully considering it's diameter and strength. Here is a link to an alternative vacuum system that doesn't require a hollow arbor and will fit any lathe:
http://sierramold.com/Wvchuck.htm

[Andy Blackwell]

Mike, I have one of the chucks from Sierra Mold that has been in use for 3 or 4 years now. It has proven very reliable and you can get repair kits for them should you need to replace the "O" rings or bearings. I like it because I have three lathes and by changing the insert can use it on any of them.

Merry Xmas and a happy New Year.

[Mike Henderson]

The strength should not be seriously affected unless you drill a large hole. In a shaft, most of the strength comes from the outside of the shaft. For vacuum you only need a 1/8" hole, or maybe 3/16".

I would think the problem will be to drill straight through the shaft. Drill bits have a tendancy to wander and the wander gets worse with small bits and the deeper you drill - I hope your arbor shaft is not too long - say not more than 5"-6". As long as the wander is not too bad it won't hurt. If the exit hole is not a lot more than 1/8" off center you'll be okay but you won't know how far its off until you finish drilling the hole. Using a Jacob's chuck in the tail stock is a good way to go. Go slow and use lots of oil on the drill. Good luck!

Mike

[Jim Becker]

The other aspect of drilling it out is that it"s not soft steel...more of a machine shop job...

[Mike Henderson]

The other aspect of drilling it out is that it"s not soft steel...more of a machine shop job...
I think it's unlikely your arbor is heat treated, and if it is, I would doubt if they left it in a really hard state. There's no advantage in making the arbor really hard. The arbor rides in bearings, but the bearing surface does not ride on the arbor itself - the bearing has an inner ring that is pressed on to the arbor and the ball or roller bearings ride on that ring.

Additionally, really hard steel is subject to fracture and the arbor is subject to shock from catches when turning and significant side loading when turning an unbalanced piece. It's unlikely to be cast iron for the same reasons.

But you can check how hard the arbor is by trying to drill it. If the drill turns off a spiral of metal, the arbor is not hard. If the drill hardly dents the metal and gets really hot, the arbor is hardened. It's easy to tell.

There are other ways to check hardness (such as scratching the metal with a known hardness material) but the drill is simple and fast.

If the arbor is hardened, give up and buy the device Gary recommended.

Mike

[Mike Radcliffe]

Thanks for the ideas. My apologies for the duplicate posts. I'll blame my browser but I probably shouldn't!