wooden screw clamps

[partsguy]

Hello everyone,
just a question from a new guy on the forums here
im attemting to make some screw clamps for my workshop but need to know something. The threaded rod that these clamps use, does one handle have left hand thread and the other have right hand thread??? Also what is the common size of threaded rod used 3/8? 1/2?
Thankyou in advance for the replies and am looking forward to engineering tools with all
nate from canada eh

[bitingmidge]

Partsguy,
Here a couple of liks that will tell you all you need to know. Of course the ones which have half reverse threaded rods are the best, but they also cost a lot! These work almost as well, the only downside is that the jaws have to be kept close to parallel.

http://www.woodworkforums.ubeaut.com.au/showthread.php?t=8265&highlight=sturdee+screw+clamps

http://www.woodworkforums.ubeaut.com.au/showthread.php?t=8397&highlight=sturdee+screw+clamps

If want more handclamp information there are also a couple of threads :D on threading timber and wooden clamps that you can find on this BB using the search function.


Cheers,

P

[Andy Mac]

I've been meaning to make some similar clamps, and went to a nut & bolt shop to buy LH and RH threaded bar. I had to order the left hand thread as it wasn't in stock, and it cost more but now have matching threaded bar with nuts. I plan to weld sections of them together, as per Bob Wearing's design for Improved Handscrew (from a 1984 British Woodworker mag), but with a few alterations. The nuts will be located in metal tubes that fit into holes bored through the wooden jaws, allowing them to pivot.
I should stop talking about this one, as you can never have too many clamps in the workshop!
Cheers,
Andy

[partsguy]

I like!!! I like!!!
Thanks for the post, the only thing I have a question for ya, I was wondering how exactly you are going to do the nuts in the tube thing????
I looked into getting some 5/8 brass rod machined to length with some l.h and r.h threaded holes in them, but cost was tooo much.
I know what i will be doing this week!!! making some blanks to bandsaw !!! so as I can add to my sad collection of clamps.
does anyone know the usuall jaw sizes of screw clamps 8,10,12,14 and 16's????
nate

[IanW]

does anyone know the usuall jaw sizes of screw clamps 8,10,12,14 and 16's????
nate

Partsguy,
Part of the value of making your own clamps is that you can make jaws any size and shape that suits - your choice!

But if you want something to start from, I found 3 sizes work well for me, and these are:
1. About 100 - 150mm (long) by 25mm (wide) for small clamps opening to about 100mm (3/8" threaded rod for screws).
2. 200-250mm long, 35-40mm wide for clamps opening to about 200mm (3/8 threaded rod screws).
3. 300mm x 50mm jaws for clamps opening up to 350mm. (The few bigger clamps in this size all have 1" threaded wood screws).

For nuts, I tapped some 5/8" mild steel rod. To give them a bit of out-of-parallel movement, you can just work a drill back and forth in the rod hole. While the capacity to close out of parallel might sound useful, you almost never need it, and in fact, the clamp rarely hangs on if you try it! For irregular clamping jobs, I've always found it far quicker to cobble up a couple of appropriately-shaped cauls. And the result is far more satisfactory, too.

For the sort of stuff I make, the most useful size is the middle one - I have about 2 dozen pairs and occasionally use them all (too lazy to find a couple of cauls, so just whack on more clamps!)

You really don't need to go to the bother of welding L and R hand threaded rod together - the single directional thread works a bit more slowly, but it's not a big deal.

The trickiest bit is fixing the top ('pusher') screw so that it hangs on when you open the clamp. I drilled and tapped some, and put a screw through the metal bar in the jaw. My better solution was to file down the end of the screw enough to pass it through a hole in the bar, then peen a mushroom on the end to retain it. To hold the handles firmly on the screws, I started out aralditing them and pinning through the ferrule, but later models were just screwd into a slightly undersized hole and pinned, and have beed equally durable.

Remember the nuts for both screws go in the same jaw. The bit of bar in the jaw opposite the lower ('puller') screw is just for the screw to ride through. If you just pass the screw through a wooden hole, the threads of the screw bite into the wood and cause it to jam when you are trying to open or close it, which is annoying. (Another 'fix' for that is to simply file off the threads over the part that sits within the jaw.)

The set in the pic below are the small size...

[Andy Mac]

IW,
Thanks for all that, sage advice and will save time making them.
I agree about cauls, and having a box of various used ones and wedges under the bench saves recutting them.
About holding odd shapes, I have made mods to a couple of vices with moving jaws to hold odd shapes, like branches and it still is an ask to hold them.
Partsguy,
If you still want to go with the LH/RH thing, I was simply going to match the nut's side-on dimensions with inside of some pipe or tube. Basically push it in sideways tight after drilling a suitable hole through the pipe. for the rod to go through, push the pipe into bored hole in the wooden jaw and align the nut with the rod.
Cheers,
Andy