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How do you re-center a piece if you have to remove it from the chuck? I have an Excell-1 vacuum I use for laminating. I'm sure it'll work for chucking. I just don't understand how to keep the project centered if I need to use the vac fore something else. Could someone post pics of the chuck itself and how the hose connects to the lathe? Thanks.
Grab the piece with minimal pressure - maybe 5 - and center it by eye.
Bring the toolrest over near the rim and hand spin.
As you observe the distance vary between the rim and the rest, lightly tap the piece in the needed direction to mitigate the variance.
Rinse, lather, and repeat until the distance is the same throughout a full rotation.
Bill I just finished my set up yesterday. I had a gast vacuum pump that I'd picked up for vacuum pressing, I ordered from Packard the 3" and 6" Holdfast chucks and their vacuum adapter kit. Went to the big blue BORG and set up a bleed off valve, my two hoses where different sizes so I had to work that out. Not a big deal an extra $10 in parts.
Bill if you watch Mike Mahoney's "Hollow Form" video he shows his trick for centering the form. Basically he get the form close by eye, then brings up his tool rest, spinning the form by hand, he puts pressure on the outside of the rim with his thumb to feel the high spots. You can't move your form at full pressure so a bleed off valve helps. He just kept spinning by hand until he got rid of the high spots...at that point you are very well centered. Works very well, used it on a 15" flame maple platter, and a 12" mesquite bowl.
Sorry I'm in the middle of working on a damaged front porch today and probably tommarrow. Old, fat, handicap guys move a little slow. I will get pictures posted with in the next few days. If you would like to come try my set up give me a call at B&L RV & Mini Storage in Benson.....Hope this helps...Bruce
Saw your new seg. pic's at Woodworker Source the other day, looks great.
Make all future turnings a perfect sphere. Then you don't have to worry about centering. :D Actually the toolrest method mentioned above works, it is just a little frustrating learning to bump with just the right pressure and direction. You get the hang of it after awhile.
Depending on your live center I have a PM 3520 lathe and it came with a live center like the oneway has and you can buy an adapter to fit on the live center to reverce the bowl while still on the chuck to the live center.
http://www.packardwoodworks.com/Merc...acc-rtc-owadap
or you can get one like this to fit in your tailstock.
http://www.packardwoodworks.com/Merc...s-acc-tlstkadp
works great and it will be right everytime with no guessing!!!!!!
Or you can make a dimple on the bottom of your blank to mark the center before you chuck it up. When you set up the vacuum chuck, all you have to do is line up that center point with your tail stock center.