The Opposite of a Clamp - an Expander?

[Andy Kev.]

I've just started work on fitting out the interior of my tool chest (surely the longest running project in woodworking history but I regard it as my apprentice piece) and I've come to a bit where I'd like to have the pressure of a clamp but in a place where no clamp would fit (it would need an 18" throat, if throat is the right word). So it occurs to me that an ideal solution would be a sort of anti-clamp: something which could be expanded as opposed to contracted in order to exert pressure. I'll probably end up jamming a couple of battens in place but this got me wondering if such a thing has ever been developed. Does anybody know?

 

[Eric The Viking]

Use cramp heads (incorrectly "clamp heads). They are reversible and you make your own bar, as long or as short as you like: http://www.axminster.co.uk/axminster-tr ... set-505546. But this sort of thing is also easily reversed: http://www.axminster.co.uk/axminster-tr ... r-ax945572.

Honestly, for a one-off, a length of wood, square-ended, with an identical pair of wedges, should do it fine. Make one wide wedge and rip it in two...

 

[AndyT]

A pair of cast iron clamp heads, used on a length of wood, can be assembled inside out to work as a spreader. Any of the systems based on steel pipe such as the Pony brand can do the same.

Not sure I can visualise what you need, but an offcut of something fairly stout plus a pair of folding wedges would probably do it.

Eric types faster than I do, but it's nice to agree!

 

[memzey]

At the opposite end of the cost spectrum; Bessey K bodies can be reversed to work as spreaders and they do so with the same force as they cramp; that is to say a lot! Given the cost of these though I wouldn't suggest buying Besseys just for this job, rather if you have one or two it's worth noting that they can work this way. A lath and some wedges can do the job but depending on how much pressure you need I might go with thinner stock, slightly over long and bent between the parts being spread, like a big spring. Hope that makes sense.

 

[Hot stuff]

The cheap Lidl quick action clamps can be reversed to work like this. The biggest I think are 300mm but you could easily pack them out to 18". The only problem will be finding them in stock somewhere.

 

[skipdiver]

I have these in various sizes that can be reversed, as shown in the picture.

http://www.healystool.co.uk/Quick-Grip- ... 25338.aspx

 

[profchris]

A turnbuckle between two blocks is a possible solution.

 

[knockknock]

Be aware, reversible quick clamps usually spread farther than they clamp.

My 300mm (12" clamping) quick clamps spread to around 20" (170-515mm) . Mine are from Lee Valley.

 

[Andy Kev.]

Thanks for all the replies and tips. I do like the look of the cramp heads. The distance to be bridged is just under 2' and I have a pair of cramps where I can reverse one head as shown in some of the links. Should they not be long enough, the local tool shop has similar ones in stock.

Thanks again.