Vacuum Chuck Question (a bit long)

[Mike Henderson]

I'm making progress on setting up my vacuum chuck but have a question.

But first, let me show you what I've done so far. I have a very small shop so I built a shelf close to the ceiling and put my vacuum system up there to get it out of the way. Then I made a manifold so that I can use the vacuum pump for veneering or chucking. Finally, I include a picture of my spinner on the lathe. This was a challenge because the handwheel does not have a hole in it but I was able to drill a hole through it and attached the plastic wheel to the original handwheel. BTW, this is a "Joe Woodworker" spinner system.

But now my question.

I'm now ready to make the "chuck" portion of the vacuum chucking system. I can easily make a flat chuck but centering the bowl on a flat chuck is a problem and you can't do that with natural edge bowls. I've seen pictures of chucks that fit inside the bowl and these seem like a very good idea - they work for nautural edge bowls and they can provide some centering action if the chuck fits against the sides of the bowl towards the bottom of the bowl.

But this is where my question comes in. When I turn a bowl, I don't make it a standard size - I make it to fit the blank I have. If the bowl has vertical sides (not tapered), it seems that only one size chuck would fit it, something like a jam chuck. But I don't want to have a dozen or more vacuum chucks sitting on a shelf.

What do you do about this? Do you use the next smaller vacuum chuck that you have and center it on the bottom of the bowl? Or do you have some way of fitting an existing vacuum chuck to a bowl, like putting more rubber tape around it? Or is there some other solution?

Mike

[Mike Vickery]

But this is where my question comes in. When I turn a bowl, I don't make it a standard size - I make it to fit the blank I have. If the bowl has vertical sides (not tapered), it seems that only one size chuck would fit it, something like a jam chuck. But I don't want to have a dozen or more vacuum chucks sitting on a shelf.

Mike

Mike,

I have two vacuum chucks one a standards drum chuck like you describe that fits inside curved pieces. I use this one over 90% of the time.

the other fits against the rim similiar to this
http://www.woodturns.com/articles/tools/vacuum_chuck.htm the only difference is mine I have a taper on so it is thicker near the spindle and thinner on the outside part of the disk. Not sure if it really makes a diference though.
This will of course not work withnatural edge pieces or other broken rim pieces.

[Dan Forman]

Mike, can't offer any help, but I'll be keeping my eye on this thread, as I have a surplus Gast pump on the way. Thanks for the idea of mounting near the ceiling, think I'll do that too.

Dan

[Jim Becker]

Mike, one size does not fit all. I currently have two sizes of drums for my system and if/when I start to turn larger, I'll need a bigger one.

Straight-sided bowls are a bit more difficult to deal with in a vacuum chuck situation as you need something long enough to get to the bottom. Although I don't turn these, I'd probably finish the bottom between centers and just trim the little nub manually as I learned to do in David Ellsworth's course.

[Harvey M. Taylor]

The old adage still holds, even among turners. Ask 10 turners how to-- and you will probably get 11 answers.I have the 3520b and I use a hex nut with 1 and a quarter 8 tpi threads #7. do not get a #8. That is used in the oilfields and will tighten before you get it all the way on. I have 4 chucks made with this nut and the different size pvc couplings. A sheet of adhesive-backed foam board cut oversized to place on the open end of the chuck. If I werent so computer challenged I would post a picture or two of my chucks. Cost about 2 bucks apiece. If you click on my name you can get my email address and I will send you a couple pictures. Max

[Mike Henderson]

I think I understand the things all of you who responded said. I think what you're saying is that many bowls are not staright sided but are more like a "dish" with angled sides. On a bowl with angled sides, I would just pick the chuck that would cause chuck to ride on the sides, but close to the bottom.

On a bowl with straight sides, the chuck has to be sized fairly accurately to the bowl so that the chuck contacts the sides just as they're curving into the bottom.

Harvey, thank you for your offer to send me pictures but I know how to make the chucks, including ones which use PVC as a standoff to make the chuck longer. What I was trying to understand was how people sized their chucks to their bowls. And I think the answer is that most bowls made by the responders have angled sides and not straight sides.

Thank you all for your comments and suggestions.

Mike

[Jim Becker]

Mike, "close to the bottom" is rare for me when using a vacuum chuck. Usually no more than half-way down for the forms I turn. BTW, straight-sided bowls are about the hardest to turn well, largely because of the abrupt transition to the bowl bottom which is typically flat. It's a hard curve to finish and you're almost forced to use a scraper as you would for a box. So if you are turning them and turning them well...that's some good skill!

[Gary DeWitt]

Another option is to have a 3/4" MDF or plywood disk mounted (and caulked) to a face plate in which you have cut several grooves in the face of varying diameters, to match pieces of PVC pipe. You mount the diameter of pipe to fit your bowl. This way you only use one faceplate, and the pieces of PVC nest as they sit on your shelf, taking up less room.

[Mike Henderson]

Mike, "close to the bottom" is rare for me when using a vacuum chuck. Usually no more than half-way down for the forms I turn. BTW, straight-sided bowls are about the hardest to turn well, largely because of the abrupt transition to the bowl bottom which is typically flat. It's a hard curve to finish and you're almost forced to use a scraper as you would for a box. So if you are turning them and turning them well...that's some good skill!
No, I usually use a scraper to finish the curve of a straight sided bowl side into the bottom. I've tried to do it with the bowl gouge but it's a lot easier with the scraper - and less chance of a catch.

But I'm really not much of a turner. I mostly only do turnings for furniture but I do turn bowls and a few others things as gifts because they're quicker and easier than building some flatwork thing. Also, in my shop, turning is messy - wood shavings everywhere.

I am interested in learning more about turning and how to do it better, but it's secondary to my flatwork -at least at this time.

Mike

[al basham]

Please look at the Oneway lathe web page they have several chucks and some good vacuum chucking information.
Good Luck .... Al Basham

[Jim Becker]

Mike, I think that you'll enjoy turning, both complimentary to your flat work as well as for an activity by itself. Practice is both essential and fun. And if you can attend local turning club/AAW chapter meetings, you'll get a lot of knowledge from others. Seeing things done in front of you really is a great learning experience. Same goes for videos. Well worth the time to watch them.

BTW, I use the OneWay drums that Al mentions (Welcome to SMC, Al) and they are great. But certainly more expensive than making your own...by a large margin. For small to mid size stuff, home-grown is great. For really big pieces, I think there is good justification for the heavier aluminum drums. IMHO, of course.