DIY Cam Clamp pivot question

[B3nder]

I'm making some cam clamps from one of Robert Wearings books.

They are formed using 3 pieces to make the top and bottom jaws to allow for a snug fit on the bar.

The (possibly stupid) question I have related to the position of the cam and pivot.

The drawings seem to not have any info nor does the text shed any light on where the cam pivot shops go.

On the moveable jaw I put a hole in the centre of the jaw in the vertical. Then offer up the cam lever and drill a hole through.

So I've done this on two clamps. One works well the other not at all.

I'll try and sort out some pics to clarify.

Anyone got any suggestions or a good plan to follow.

Thanks.

 

[scooby]

I've made a few of these and, like you, had varying success. I think the most important aspect is the shape of the cam in regards to the position of the hole. There needs to a gradual and progressive increase in pressure as you rotate the lever. Too big a jump in pressure and the cramp would have a tendency to just let go.

This video might help if you've not seen it before. Skip to around 12 minutes.


He mentions that the distance from the edge of the lever to the hole is roughly double on the wider side.

 

[B3nder]

Thanks I've seen the video before but missed the note about the distance.

Glad it wasn't just me who had issues making them.

I'll draw up the design and post back here with the details.

 

[B3nder]

To follow up I found the following resulted in working clamps:

1.Get the cam lever as flat as possible with respect to the bottom of the moving jaw. Closer to 20 degrees or less ratuer than closer to 45.

2.Hold the clamp jaw shut when drilling the holes.