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Cam Clamp Construction Question
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Author:  John Cavanaugh [ Mon Mar 20, 2006 4:24 am ]
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OK, I'm about to reveal the depth of my ignorance and the shallowness of my woodworking skills.

I made up a pattern for some 9" cam clamps yesterday, mostly working from Sloane's book on classical guitar construction. I cut the jaws from some 4/4 beech and mortised the slots for the bar (1/4 by 1 inch aluminum). The mistake I made is that the slot in the lower jaw isn't parallel with the center line of the jaw, so the business ends of the clamp don't align correctly when the the jaws are assembled to the bar.

Can anyone give me any tips for getting this alignment correct? Or is it just a matter of doing it right?

I'm feeling a tinge of regret for not buying some of Paul Woolson's clamps. I decided to make my own because I figured the practice would be good for me.
Author:  Pwoolson [ Mon Mar 20, 2006 4:31 am ]
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You're right is thinking that the practice is indeed good for you. I use that line of thought often.
What did you cut the mortise on? I use a dado blade on my table saw. Stand them up on end using a tennon jig and run them through the 1/4" dado blade. Then I make a little filler piece to, well, fill the void after the bar is inserted. I've never had much luck with mortising bits on a drill press. If that is your method, I'd suggest lots of fences, stops and clamps to hold the bugger solid.
Unless you are WAY off there's a pretty easy fix for this. Wait until you get it totally done and then clamp the jaws tight and parallel with each other. Then you can just scrape, file, sand or run it through the thickness sander to get them to line up right.
Hope that helps. Paul
Author:  John Cavanaugh [ Mon Mar 20, 2006 4:43 am ]
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[QUOTE=Pwoolson] ... What did you cut the mortise on? I use a dado blade on my table saw. Stand them up on end using a tennon jig and run them through the 1/4" dado blade. Then I make a little filler piece to, well, fill the void after the bar is inserted. I've never had much luck with mortising bits on a drill press. If that is your method, I'd suggest lots of fences, stops and clamps to hold the bugger solid.[/QUOTE]
I drilled several holes with my drill press and then cleaned out the slot with wood chisels and a file. I don't have a table saw, but I can see that would be a lot more accurate.

[QUOTE=Pwoolson] Unless you are WAY off there's a pretty easy fix for this. Wait until you get it totally done and then clamp the jaws tight and parallel with each other. Then you can just scrape, file, sand or run it through the thickness sander to get them to line up right.[/QUOTE]
I think this one may be far enough off that it can't be saved. But it's not much of a loss; less than a buck for the wood and I figure that practice is always good.

Thanks for your help.
Author:  csullivan [ Mon Mar 20, 2006 4:52 am ]
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I really like Paul's way of making the mortise because it just about
eliminates the possibility of mis-alignment. But, if you made them as the
book suggests (drill and chisel), you could epoxy some pieces of veneer
to the 2 cheeks of the mortise and refit the aluminum bar.

Paul, not to change the thread, and I'm sure you've been asked a million
times, but did you make your little animation of the guitar player? Or did
you hijack it from somewhere? I never tire of seeing it.
Craig
Author:  Pwoolson [ Mon Mar 20, 2006 5:58 am ]
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John, Craig has a pretty good fix. If you don't want to shim it, you could just cut a piece to fit the slot, fill it and re-mortise it. One thing that might be helpful is to draw a center line the length of the slot. You can then sort of push the non-spinning drill bit into it. Then when you go at it with a spinning bit, it will sort of drift into the little cavity you made.
Craig, it's stolen from somewhere but I have no idea where. Some freeware site that had fonts and clipart and the like.
Author:  crowduck [ Mon Mar 20, 2006 8:37 am ]
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I've 'been thinking about' one of those Mortising Machines from Harbor Freight for this task. They are $99 at HF, but I wonder if they're any good. Anyone know?

CrowDuck
Author:  Michael Dale Payne [ Mon Mar 20, 2006 9:50 am ]
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Save 5 times that amount and get a desent table saw and dado set up and you will be 10 times happier
Author:  Pwoolson [ Mon Mar 20, 2006 11:02 am ]
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[QUOTE=crowduck] They are $99 at HF, but I wonder if they're any good. Anyone know?[/QUOTE]
I feel pretty confident in saying NO they aren't good. This is because nothing, and I mean nothing, from HF is good. I don't want to sound like a tool snob here but there is nothing in that store of good quality. There are things that are of adiquate quality to use but nothing is good.
Don't get me wrong, I've got several things from HF (clamps are the best things purchased there) but I've been very disapointed with every machine I've purchased from them. And in a field where accuaracy is quite important...you won't get it from any machine at HF.
Also, unless you are making a LOT of clamps or are a cabinate maker, you won't use that mortising machine much at all. In my opinion, it's $100 bucks don't the tubes.
Author:  csullivan [ Tue Mar 21, 2006 12:28 am ]
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Amen Paul,
I've never used a mortising machine that produced a decent mortise. They
never seem to make nice even cheeks. And if the tip of the drill wanders
slightly because of grain, the mortise is no longer straight. Better to
spend the $100 on something that'll get used all the time.
Craig
Author:  Dave Rector [ Tue Mar 21, 2006 2:57 am ]
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I own a Delta mortising machine and due to lack of uses for it, it is going in my next garage sale. I find that unless I am making cabinet doors or something I just don't use it.
Author:  Daniel M [ Tue Mar 21, 2006 3:34 am ]
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When I first approached my luthiery guru & asked him to teach me, he suggested I make a dozen cam clamps as a first project.
I rushed out & bought some Maple & aluminum & finished the clamps in jig time. Only after that, would he show me the ropes & help me through my first couple of instruments.
I do the same today, with anyone who asks if I can help them build a guitar.
Not only does it provide practice with some fairly precise woodworking, (poorly made cam clamps are a real frustration) but it quickly sorts out the dreamers from the folks who are really interested in putting in the necessary time & effort.
Even if your clamps don't end up as pretty or as effective as some store bought ones, They will become valued old friends for their usefulness as well as the lessons they taught.
Sorry to get philisophical on you... But I just love my old cam clamps!
That being said, If I wasn't spending all my spare change on pretty wood, I'd rush to Paul's site & order a bunch of (Really Good) clamps!
Good luck with the fix on your clamps... and go out & get a decent tablesaw as soon as you can. I started with an old Craftsman 9" that cost me 25 bucks at a yard sale. after a little work on the fence, it served me well for years.
Author:  mikev [ Wed Mar 22, 2006 1:54 pm ]
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Paul, are there clamps still available, I thought they were all spoken for.
Mike
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