vaccum chucking

[jeff oldham]

can anyone tell me a quick way of centering a platter on a vaccum chuck where it is running true,,,,,

[Steve Eure]

There are adapters that screw into your chuck that have mt2 shafts so you can put it into your tail stock and align it perfectly.

https://www.woodturnerscatalog.com/p/112/4287/tmi-Reverse-Chucking-Alignment-Adapter

This is the one I use. You just need to know the insert size of your chuck.

[David Gilbert]

I have the adapter that Steve mentioned. It works OK but isn't often perfect. I find it awkward to use so normally I only use if I can't do it some other way.

First, I start my bowls and platters between centers so there is a dimple from the live center in the middle of the chuck's tenon. When I turn the platter around I use the live center to center the platter. This works very well.

If I don't have the dimple then I center the platter the best I can and then pull a slight vacuum. My vacuum system will draw 25 inches of mercury so I use a valve to bleed in air to reduce it to less than 5 inches. It will hold the platter but you can nudge it a bit to get it centered. Manually turn the platter to find the edge that is off-center and then gently tap it back. Test it for being centered and repeat. It might take a number of nudges to get it centered.

Cheers,
David G

[Grant Wilkinson]

I have an adapter from Oneway that threads onto the Oneway live centre and into my chuck. I just remove the chuck from the head stock, while the bowl is still mounted on it, and thread it onto the adapter in the tailstock. The bowl never leaves the chuck. Then, I mount the vacuum chuck on the headstock, turn the vacuum on, and advance the bowl into it.

[Jeffrey J Smith]

I use a reverse adapter to hold the chucked bowl in the tailstock, but usually find that I need to adjust centering slightly. Sliding the banjo up to the bowl and adjusting the tool rest to sit just at the tenon edge, I rotate the bowl in the vac chuck and find the high spot. Turn down the vac pressure and nudge it down until it runs true. Seems that most woods move slightly when hollowed and sanded so centering is seldom perfect when vac chucked for finishing the bottom. At least thats been my experience. Seldom need to spend much time adjusting center.

[Thomas Canfield]

I centered a 33"D platter on vacuum chuck by using blue painter tape to mark the outside of the 10" flat vacuum plate and holding it to center when turning on vacuum pump. Got it close enough for 150 rpm to do some air brush work and gentle work on tenon. A little hairy but only way to grab the platter.

[Peter Blair]

I use this method as well but have a piece of steel that is pointed and allows me to make the little dimple while the piece is mounted.

I have the adapter that Steve mentioned. It works OK but isn't often perfect. I find it awkward to use so normally I only use if I can't do it some other way.

First, I start my bowls and platters between centers so there is a dimple from the live center in the middle of the chuck's tenon. When I turn the platter around I use the live center to center the platter. This works very well.

If I don't have the dimple then I center the platter the best I can and then pull a slight vacuum. My vacuum system will draw 25 inches of mercury so I use a valve to bleed in air to reduce it to less than 5 inches. It will hold the platter but you can nudge it a bit to get it centered. Manually turn the platter to find the edge that is off-center and then gently tap it back. Test it for being centered and repeat. It might take a number of nudges to get it centered.

Cheers,
David G

[John K Jordan]

can anyone tell me a quick way of centering a platter on a vaccum chuck where it is running true,,,,,

Depending on the piece I use the chuck adapter, center point, and nudging methods mention for centering the work with vacuum or jam chucking.

However, for the quickest way to get something very precisely centered I keep a dial indicator on a magnetic base. This will let me quickly find the exact location of the "high" spot and tell me just how much it needs to be moved to get that axis centered. This eliminates a lot of trial and error and usually only takes one or two tries. Then I check again and correct for misalignment another axis. A couple of iterations and the piece is as centered as it's going to get.

Dial_indicator_IMG_20141122.jpg

This is remounting an oddly shaped piece between two jam chucks. Note that I turn dry wood so dealing with wood movement is minimal, especially with small work.

JKJ