twentyover
twentyover Dork
4/21/20 8:19 a.m.

Working on a torque arm for my 76 Capri, the design calls for cutting a diagonal along a 3 ft length of rectangular tubing to add additional support at the nose of the diff.

 

I'm using a death wheel, trying to track the diagonal from 1 corner of the to the tube section to the opposing corner 3 ft away. Rather than a clean straight cut,  it looks like the surface of the ocean during a hurricane. Obviously I'm doing this freehand.

 

What tools/tricks/tools/advice can one offer to get the cut straight? This is being welded to another section of rect tubing to improve beam stiffness

 

Thanks for the assist

AngryCorvair
AngryCorvair MegaDork
4/21/20 8:34 a.m.

first thing, are you wearing your PPE?

got a 3-ft long piece of flat stock with a factory edge, that is thick enough to act as a guide? 

if yes, then practice using that on a test piece so you know how much it offsets your cut, then clamp that to the tube you're cutting and win at life.

if no, then can you snap a chalk line or otherwise lay out a straight cut line to follow?  then it just comes down to having a steady hand.  personally, i like scribing a line and then cutting with the death wheel to the outside of that scribed line.  work area has to be lit well enough to see the scribed line.  i've gotten good results with cuts up to about 8" long.

also, one big error i used to make was to start cutting through the thickness of the material right away. this causes any misalignment to be difficult to correct. i learned from a forum member (either Classic Jackets or whiskey_business, don't want to slight either one by mis-attributing this valuable lesson) to make a very light pass the entire length of the cut line, just using the weight of the death wheel.  then you've created a (shallow) track for the wheel to follow on subsequent passes, and minor variations in this shallow track can be corrected in the next pass.  a 3-ft cut might take many passes.

stafford1500
stafford1500 Dork
4/21/20 8:38 a.m.

Masking tape can be used to pull a guide line over long spans. It is easier to see than a scribe line and does not burn off/discolor like sharpie will do.

The multiple light passes is the right way to attack this cut too. It will result in slower cutoff wheel wear and less heat in the part you are cutting.

AngryCorvair
AngryCorvair MegaDork
4/21/20 8:45 a.m.

In reply to stafford1500 :

masking tape is so obvious now that i've heard someone else say it.  i wish i was smart enough to have come up with that on my own instead of trying to snap a chalk line.

Toyman01 (Forum Supporter)
Toyman01 (Forum Supporter) MegaDork
4/21/20 8:49 a.m.

Mark it well. 

Clamp your material tightly so you only have to control the grinder. Trying to hold the material and cut with the grinder will have the cut wandering everywhere. 

Cut slow, rushing makes the blade wander. I usually carefully score the entire length of the cut to help guide the wheel for the rest of the cut.  

Wear a full face shield, gloves, and long sleeves. Getting hit by debris or grabbing hot metal is distracting.

For long straight cuts, I frequently use a circular saw with a abrasion blade. 

 

wheelsmithy (Joe-with-an-L)
wheelsmithy (Joe-with-an-L) UltraDork
4/21/20 9:06 a.m.

Cut it close, grind to scribed line. Nobody cuts straight with a death wheel. Ok, maybe Foose, but I'm no Foose.

This is why the pros have plasma cutters-of course, there's some grinding to finish, no matter what.

 

twentyover
twentyover Dork
4/21/20 8:45 p.m.

The tubing being cut was 2 x 1.5 , I was cutting on the 2" side. Tubing was clamped to a table top and solid. Gloves (one mechanics, one welding as the sparks burned through Mechanic's fabric) and safety glasses were employed- Can't find a face shield since HF (rightfully) sent all theirs to hospitals. I looked. I did pick up one that looks like it's for arborists, is like a 30 mesh screen rather than a transparent  plastic plate. I will try it.

Started w/ a Sharpie, but when it crossed over the closure weld, color changes made it indistinguishable. Shot it with Dychem Blue and scribed. A little better, but only just a little.

Liking the masking tape and sneaking up on the cut line. I'll try that next time.

Have to think about how I would do the circular saw w/ abrasive blade. Need to clamp a matching piece of tubing paralleling the tubing being cut to keep the saw from tipping/blade fracture/certain death or dismemberment.

Thanks for the responses, Good stuff to think about

 

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