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| Fox bridge clamp question http://luthiersforum.com/forum/viewtopic.php?f=10101&t=35109 |
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| Author: | WendyW [ Wed Jan 25, 2012 2:13 pm ] |
| Post subject: | Fox bridge clamp question |
I'm using the Fox classical bridge clamp and when I tighten the screws on the wing sections1, the whole bar flexes and the ends raise up. Is it supposed to be that flexible? I'm not applying that much pressure. Thanks, Wendy |
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| Author: | JoeUlman [ Wed Jan 25, 2012 3:47 pm ] |
| Post subject: | Re: Fox bridge clamp question |
I don’t use the Fox bridge clamp accessory but looking at the picture it seems that by design you would likely get some flex in the bar as the wing screws are tightened. I’d say the important thing is to have good contact and even pressure everywhere under the bridge and also have an inside caul that matches the dome of the soundboard and is stiff enough to not flex when the wing screws are tightened. Here’s my bridge clamping set up: Attachment: IMG_1646 small.jpg the inside caul has shallow holes to position the clamps Attachment: IMG_1645 small.jpg the outside cauls are molded to match the shape of the bridge Attachment: IMG_1634 copy.jpg Joe |
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| Author: | jsmith [ Wed Jan 25, 2012 6:21 pm ] |
| Post subject: | Re: Fox bridge clamp question |
Joe, those Stew Mac clamps that you use have been tempting me for some time. They look to be pretty rigid. Can you crank them down pretty well without having them flex on you? I'd sure like to retire the big, herky deep-throat clamps I've been using forever on my bridges. |
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| Author: | WaddyThomson [ Wed Jan 25, 2012 6:50 pm ] |
| Post subject: | Fox bridge clamp question |
Gluing a bridge does not take excessive pressure. You can even do a rubbed joint if using HHG. I use. Cam clamps and a homemade bridge caul with screw-eyes as pressure points for the wings. I use my solera hold-down block for an inside caul, held in position with magnets. |
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| Author: | JoeUlman [ Wed Jan 25, 2012 7:37 pm ] |
| Post subject: | Re: Fox bridge clamp question |
jsmith wrote: Joe, those Stew Mac clamps that you use have been tempting me for some time. They look to be pretty rigid. Can you crank them down pretty well without having them flex on you? I'd sure like to retire the big, herky deep-throat clamps I've been using forever on my bridges. There is very little give to the clamps under light 'thumb-screw' pressure. As Waddy mentions, very little pressure is needed if everything fits well, i.e., the bridge matches the dome. On the other hand, a bit more pressure is needed when a dome is being created (or enhanced) by shaping the underside of the bridge and pressing the soundboard against it. And the SM clamps can easily handle that. Joe |
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| Author: | WendyW [ Thu Jan 26, 2012 2:23 pm ] |
| Post subject: | Re: Fox bridge clamp question |
Thanks Joe, I just received a couple of those same clamps from Stew Mac yesterday. I decided not to use the fox clamp on this current bridge because the bridge is not as long as usual and the wing screws don't line up in the right place. I thought about drilling and tapping and decided to just go ahead with 3 or 4 clamps. I am using a radiused caul on the inside like you do and shaped cauls on the bridge as well. I just don't understand why the Fox caul was not made of a more rigid material, but I guess it doesn't matter since not much pressure is needed anyway. |
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| Author: | Eric Reid [ Sat Jan 28, 2012 5:39 pm ] |
| Post subject: | Re: Fox bridge clamp question |
Wendy, It sounds like you've got the problem solved. For future reference, with a caul like the Fox classical, it's important that the caul is more flexible than the clamps. If not, tightening the screws on the wings could leave you with no clamping pressure at all in the center. I don't use the caul, but I do like the cast aluminum deep throat bridge clamps that Fox sells. These twist and flex much less than the pressed steel clamps. I do wish they'd made them a little deeper. You have to file away the inside throat to allow them to reach the bridge wings on most classicals. For an inside caul, a 3/8 inch thick layer of styrofoam on a domed 1/4 wood backing will conform to most classical bracing patterns with no notching or fitting required. Just tape it in place, and then clamp down the bridge. |
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