View Full Version : Reverse clamps: any really good methods?

06-26-2015, 11:37 AM
What is the best method of applying "spreading force" to a project? Bottle jacks are great as long as they remain upright, (when used horizontally air gets into the system), as are short, stout carriage bolts rigged with nuts and washers. I need to apply such force most often when I'm just finishing up getting a steamed rib into a mold, at that point just a little push with a lot of force often gets the piece perfectly to shape. Anyone have any experience with this?

Gib Etheridge
06-26-2015, 12:07 PM
You can reverse most "F" clamps.

https://www.google.ca/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1152&bih=705&q=F+clamp&oq=F+clamp&gs_l=img.12..0l6j0i7i30l2j0i30l2.2115.4948.0.8018. 47.8ScYAmTajhg

Gib Etheridge
06-26-2015, 12:13 PM
Also, if you're willing to file the threads out of the stationary end of a pipe clamp you can turn it around and pin or thru bolt it in place. You need the ones with the wing nut or pivoting type handle so that the handle won't hit the pipe.

06-26-2015, 12:44 PM
scissor-jacks are dirt cheap at any auto wrecking yard, and give a much better feel for how much pressure is being applied than you would get with a bottle jack.

06-26-2015, 12:55 PM
wood wedges and scrap cut offs.. I find that a pack of wood wedges/shims work great. and they can be used many times through out the building process.http://ts1.mm.bing.net/th?&id=JN.%2bEXrXVU6QF61SjXXNC0bmw&w=300&h=300&c=0&pid=1.9&rs=0&p=0two of these in opposition , set with a hammer

06-27-2015, 09:20 PM
I have used bottle jacks to spread truck frames ,they don't air bound if you put the side with the fill plug up instead of down,always worked for me.I just found they can be heavy.i had a small one for lite jobs good luck frank

06-27-2015, 09:26 PM
Two lengths of water pipe, a piece of threaded rod fitted snugly in between, nuts and washers. Like a back-to-front turnbuckle.


Pete E
06-28-2015, 01:42 AM
3/4" threaded rod, piece of 3/4" pipe. washer and nut. cut them to the appropriate length. I also like a board and two wedges.

Dan McCosh
06-28-2015, 11:05 AM
Old-syle bumper jack is good for big jobs.

06-28-2015, 01:04 PM
Good advice. My bottle jacks are all ancient and have never been serviced/maintained...what is the best oil to fill them with?

06-28-2015, 01:52 PM
Hydraulic jack oil is available at any auto parts place, Walmart, etc.

06-28-2015, 02:50 PM
Good advice. My bottle jacks are all ancient and have never been serviced/maintained...what is the best oil to fill them with?

Any petroleum based oil will work, hydraulic oil, spindle oil, motor oil, ATF and etc. the appropriate "weight" is sae-20

There are additional additives in many of those that are not needed for such a "dumb" hydraulic system, but they won't hurt anything either. I would use the readily available, ATF.

edit to add; a porter-power system for auto body work can be sourced cheaply from harbor freight etc. they can do a lot of pushing, fast. (Porter was the original manufacturer of these in New Hampshire. The name has evolved into Porta-power. I have an original probably purchased thirty or forty years ago, an indispensable tool sometimes.)


06-28-2015, 03:43 PM
I've used a bicycle inner tube to spread things using air pressure.

Jim Mahan
06-28-2015, 04:37 PM
The Irwin quik clamps reverse easily. It's good to have some long ones. Actually the heads are interchangeable; you could probably build your own bar, if you needed more length than the stock bar.

Also, depending on the situation, you can cut an appropriate piece of something long and stiff but springy, and bend it to put one end into contact with your object, and the other end on an immovable thing, like a ceiling or a bulkhead, the top of the workbench. You can do a similar thing with something just too long, but rigid, and just force it in the space as far as it will go, with a nudge from a deadblow hammer or mallet. Depending on how vulnerable your object is, if you get the length just right, you get a wedge with a stable angle. When you're done, just tap it the other way.

Another version. Fill the space between the object and the immovable thing with blocks, leaving enough room for a lever. Push the lever until you've got the right force to hold your object, and then secure the lever end with a suitable weight or by attaching it to something. If you're gonna balance a force on a lever, keep your digits and other important parts out of the way, in case your lever slips.

Bob Cleek
06-29-2015, 02:27 PM
In a pinch, a suitably sized "jaw and jaw" turnbuckle and a length of stout iron pipe of suitable length work well. Good sized galvanized turnbuckles are all over the place and even a cheapo 3/8"X12" new one won't run more than around $10-15. Just stick the one side of one jaw inside the end of the pipe and the other side of that jaw over the edge of the pipe and then put a block or whatever under the opposite jaw (you could even drill a suitably sized counterbore in the face of the block with a Forestner bit or whatever, if you wanted to get fancy) and open the turnbuckle. With a big turnbuckle, you can shove a stick or rod through the turnbuckle and get quite a bit of force out of it. There are a number of other good approaches noted above. There's lots of ways to skin a cat!

Jay Greer
06-29-2015, 03:35 PM
Wood jawed double screw clamps can have a jaw extensions screwed, clamped or bolted on to both of the jaws. The adjusting screws can then be used to a mechanical advantage for the jaw extensions in reverse. Disasseembly of the clamps and re-assembly in reverse can be done as well but does take a bit of fussing. Either way, they can be used to pull things apart if the jaw span allows. A clamp can also be dedicated for taking things apart by reshaping the jaw tips from a ramp to a flat shape in a band saw. This, of course, is a drastic choice.

06-29-2015, 03:58 PM
I have a porta- power with spreading jaws to 10 tons.


Hugh Conway
06-29-2015, 04:28 PM
For smaller dimensions - a turnbuckle with cauls over the eyebots

06-29-2015, 07:49 PM
I have a porta- power with spreading jaws to 10 tons.


Interesting...something like this was exactly what I had in mind. Small, easy to get into confined spaces. Is there a brand/model that you'd recommend?

Bob Cleek
06-30-2015, 02:04 PM
I have a porta- power with spreading jaws to 10 tons.


I'll meet yer porta-power and raise ya!


Something like over sixteen tons of spreading force, which is a bargain at only about $15,000! :D :D :D

06-30-2015, 03:33 PM
Lots of great ideas. But I have to wonder, why aren't such things sold. Every other tool idea under the sun is out there.

My 2 cents for big, light work, the rods they sell to put across pickup beds.