'twisted' brass sheet

Rayanth · Jun 12, 2012

The last bit of my order from OnlineMetals arrived today, two 2-foot lengths of .063x.25" brass sheet. Looking at the edges, it seems obvious they used a shear to cut them. No big deal, but if that shear was not cutting all at the same time (instead cutting from one end to the other more like scissors) that may explain the problem I am now seeing :

If I lay the 2-foot lengths down on a flat surface (forgive the mess)

there is about a 45 degree 'twist' to them over their length. If one end is flat to the surface, the other end is twisted by approx 45 degrees.

Now, I don't need the full length for the project, but it's a sufficient twist that it's visible even over the shorter lengths that I will need.

Is there any way I can easily twist these back into a more flat shape without damaging them? I don't have a torch but could probably get one if necessary.

- Ryan

arnoldb · Jun 13, 2012

Hi Ryan

Clamp one end of the sheet in your mill vise, and use another vise or something that can clamp over the other end to twist it straight - that should straighten it up fairly well and evenly.

Kind regards, Arnold

Rayanth · Jun 13, 2012

Was considering that (once I get a vice) but wasn't sure whether it would necessarily twist back properly. For a first engine though I guess I need not be too picky =)

For future reference, how would I avoid this problem? Aluminum sheet at work is usually just bandsawed and then cleaned up with a sander, but it seems there should be another way..

- Ryan

b.lindsey · Jun 13, 2012

Ryan,
If you can get by with shorter lengths (like 12") then I find that brass strip material from these folks: http://www.micromark.com/metal-strip.html as well as tubing and round rods are good to keep on hand. If you ever order from them then you will get catalogues frequently and sometimes the metal strips, rounds,tubes will be on sale. I have found them to be well packaged, straight and useful for lots of things and their site/catalogue will show all the various sizes available....usual disclaimer.

That said, I agree the problem at hand can likely be un-twisted. If a vise isn't available try using an adjustable "crescent" wrench on each end and gently twisting until its reasonably flat again. At the worst it should be much better than the 45 degrees you have now.

Bill

Maryak · Jun 13, 2012

I would try beating or squeezing it between two lumps of planed hardwood.

Best Regards
Bob

MachineTom · Jun 13, 2012

Any sheet material that is sheared will have that twist, the offcut piece, which it looks like you have, will always be worse than the base piece, unless it has been straightened after shearing. To correct that first remove the burr lip that formed when it was cut, then using a rawhide or rubber hammer and a flat wood bench, beat the strip from end to end, flip and do the other side. You need to hold the stock flat to the table with one hand while doing this, not just smash it with the hammer. After that you may need to hand twist near the end that last bit.

I have brass sheet on a roll, its always been quick to straighten with this method.