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| Vacuum Holding Jig Help Needed http://www.luthiersforum.com/forum/viewtopic.php?f=10102&t=15288 |
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| Author: | Brad Way [ Mon Jan 07, 2008 2:08 pm ] |
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I am currently working on using a vacuum to hold a finger board in place while radiusing. Any good vacuum workholding tips or advice? Thanks! |
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| Author: | Bob Garrish [ Mon Jan 07, 2008 3:58 pm ] |
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Get a good seal and leave as much empty space under the part as you can without leaving completely empty large spaces underneath which might allow it to buckle. That's essentially all you'll ever need to know about vacuum clamping! |
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| Author: | Kent Chasson [ Mon Jan 07, 2008 5:22 pm ] |
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I was messing with this today and have some questions too. One on the tricks seems to be having the right gasket material and installing it so that it seals but can compress enough that the work piece can be pulled totally flat against the backer. I've been using cheep hardware store 1/8" thick weather stripping. I cut a channel for it that leaves it proud by a little less than 1/16". It's works well but not perfectly (not well enough for fingerboards, which is one of my next projects too). I think I should have cut the channels a little wider than the gasket to allow them to spread. The gasket may be spreading out between the work and the backer and keeping the work from pulling in perfectly tight. I've got some of the real vacuum tape coming from Joe Woodworker but from what I've seen on their site, he's applying the tape right on the surface. It's not recessed at all and the work piece can't pull all the way against the backer. In other words, it doesn't look appropriate for precision machining. Any specifics on gaskets that will solve that problem? |
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| Author: | Bob Garrish [ Tue Jan 08, 2008 8:09 am ] |
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Chamfer your channels or make them wider. The gasket needs somewhere to crush into. These guys have the best gasket: http://www.allstaradhesives.com/ |
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| Author: | Brad Way [ Tue Jan 08, 2008 10:34 am ] |
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Thanks for the info Bob! |
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| Author: | Dean [ Tue Jan 08, 2008 11:05 am ] |
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Also check to make sure the weatherstripping is CLOSED CELL foam. Open cell foam allows air to migrate into the vacuum. Large o rings work very well for smaller items. Dean |
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| Author: | Daniel M [ Tue Jan 08, 2008 8:19 pm ] |
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Another thing that works well is "O" ring material. Charles Fox uses it on some of his vacuum clamping devices. If I remember correctly, he used 1/8" material & routed a channel just a tiny bit less than the material diameter. This method will only work on flat, smooth pieces... should be perfect for a fingerboard. I have seen kits at a few automotive suppliers which had lengths of O ring material in two or three different sizes, a tube of O ring cement, a mini mitre box & a razor blade. I am working on some new vacuum clamps too... Hope I can still find those kits! |
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