Deep Throat Clamp

Dave Richards

Member
Messages
2,927
Location
SE Minnesota
Some of you may remember the boat cradle I built before Ian was born. It is a little pram with walnut keel and transoms. The planking is 1/8" thick pine with ash ribs. When I was getting ready to plank up the hull, I needed a bunch of clamps with deep throats. All I could find in commercially made clamps with deep enough throats were much too heavy for the application. So, since mother is the invention of necessity, I designed and made my own.

I mentioned these clamps in Stu's thread about the lightweight box he's working on. I went back to look and found I had the original CAD drawing I made. I imported that into SU and came up with what you see here.

plankclamp.jpg


The jaws are made of 1/2" (12mm) BB ply laminated to 24mm thick . In the background you can see the two halves that make up the lower half of the clamp. I actually started with a long piece, plowed the groove and the rabbet and then cut the piece in half. These were glued face to face to create the hole for the carriage bolt and the groove for the hinge. I made a similar piece with the wider groove for the top jaw.

After gluing the the plywood together I cut out the jaws using a template. they were nested so as to reduce waste.

The hinge was made from a scrap of walnut--I started with a long strip, clamped a jaw set together, inserted the walnut strip and cut it to length. By flipping the walnut strip over for the next clamp, I was able to minimize waste there, too. Using the holes drilled in the jaws (located with a jig on the DP) I drilled through the hinge piece while in situ. I drove in a 1/4" dowel dry (no glue) and flush cut it with a little trim saw.

I used a 5/16" carriage bolt with a washer and wing nut. The carriage bolts shoulder wedges into the square hole in the lower jaw. The slot in the top jaw allows the jaws to open.

The whole thing went together production line style. I made a dozen clamps in about an hour and a half not counting glue curing time.

They work very nicely and can apply an amazing amount of pressure. To prevent gluing them to the work I covered the jaws with clear packing tape. there's no finish applied to them although I suppose they'd look nicer if they were finished.

Thanks for looking.

If anyone is interested in making some of these, I would be happy to provide the SKP file or make a dimensioned drawing.
 
Brilliant! :clap:

I think you just saved me a whole lot of cash!:thumb:

Did you cut them on the badsaw?

Big Blue don't like curves, I guess the Phoenix is going to have to get done sooner than later :rolleyes:

Cheers!
 
I made these pre bandsaw. I didn't actually nest them as shown. I cut them into rectangular blanks, drilled the hole for the hinge pin using a jig on the DP. The MDF template was cut out with a hand held jig saw and worked to shape. I used a piece of dowel in a hole in the jig to locate that end of the template on the blank. For the other end, I drove in a small nail so the point just stuck out a little. Then I used a bearing guided bit in the router table to cut to shape. If I were doing it now I would indeed rough them out with the bandsaw.

Not long after I made these I sent the idea to Shop Notes as a tip. they printed it (and paid me) but they butchered it and made a single one from hardwood with mortises cut for the bolt using a mortiser. I thought that ruined the whole idea of mass producing them. Who needs :rolleyes: just one clamp for cryin' out loud?

When I asked them about it they said they though the hardwood would be more durable. It might but the plywood is plenty durable in this application.

Do you want me to send you the SKP or a dimensioned drawing?

Frank, thank you. I'm sure you have many other talents though.
 
Wow Dave, for a minute there I thought you had something going with Linda Lovelace:thumb: :thumb: :D If you don't know who that is you probably are too young to care.:)
 
I agree with Stu...brilliant! I'll be putting this one in the "Ideas" file in the event I have a need for something similar in the future. :thumb:
 
Dave, this is great, I have a piece of plywood that is prefect for this, just about the right size! :thumb:

I'm going to make them a bit thicker and a bit longer too, maybe :huh:

How long are your bolts?

Now I got to find some carriage bolts, not easy, here in Japan. :huh:

Cheers!
 
Stu, I don't rightly know how long the bolts are. I imagine four or five inches, though. In the drawing the bolt is 5" long. That's enough for the jaw opening. If you can't get the bolts let me know. I can probably help you out with that part.
 
Here's an idea I had for improving the clamps. I haven't tried it but it should work. For my purposes the flat jaws were fine and showed no tendency to slip.

plankclampnewjaws.jpg
 
That is an interesting modification Dave....:thumb:

I guess it would depend on what you are clamping, but I'll go for the flat jaws first.

Cheers!

PS nice watermark, great idea!! :wave:
 
Top