Cold Rolled or Hot Rolled Steel for Torque Arms?

markz

markz

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I hit up the metal store, bought four identical pieces from their scrap bin 3/8" thick 2.5" x 3.5", I asked the clerk how you can tell if the steel is Hot or Cold Rolled, he said my pieces were Hot Rolled. I googled the terms but couldnt really tell if one is better then the other for Torque Arms.
 
Cold rolled is somewhat stronger. Hot rolled is what you want if you're going to machine away the surface of the bar, because cold rolled steel contains uneven residual stresses that can cause warping.

I prefer cold rolled for most purposes, because of its better finish and tighter dimensions.
 
In real general terms, Cold rolled is harder, has more tensile strength, and better yield characteristics.

If you buy angle iron, it's usually hot rolled. the surface is kind of pitted and rough. Flat bar stock is usually cold rolled. it has a smoother texture.

1/4" Hot rolled mild steel should be strong enough for torque arms.
 
What is more relavent is what grade of steel it is. Steel can be anything from low carbon (fridge sides etc) , to ultra high strength ( armour plating, suspension bridge cables, etc)..each with a different chemical composition.
But generally , hot rolled is just a initial forming process used on all steels to make it into whatever shape is needed...ie, flat bar , angle, channel , Plate, RSJ, etc .
Cold rolling is a "conditioning" or finishing process used to impart better strength, surface finish, and grain structure into certain steels for technical applications.
 
All the stuff the OP is talking about will be AISI 1018 or else A36. Those are mechanically equivalent to each other, generic mild steel of 0.18% carbon content with minimal alloying elements.
 
The material spec for homemade torque arms: Steel 12 +/- 6mm THK, condition: "anything you can drill"

Don't over-complicate it ;)
 
markz said:
.... how you can tell if the steel is Hot or Cold Rolled, he said my pieces were Hot Rolled. I googled the terms but couldnt really tell if one is better then the other for Torque Arms.
Click to expand...
You can usually tell a cold rolled piece by the cleaner , smoother , surface finish.
If you are looking for something that is "tougher" than regular "fencing post". Steel,..the simplest way to tell is to use a file on one edge of the piece. Obviously the tougher/harder steel will be more resistant to filling .
Experienced metal workers can tell the different carbon content of steels by the colour of the sparks from a grinding wheel.
Probably the simplest "scrap bin" choice would be shoot for a piece of stainless ( brighter silvery appearance) which will be tougher than most other scrap bin off cuts....and can be polished up, no rusting, etc etc.( but harder to work with.!)
 
I will use a drill bit to get the thin slice of metal out.
View attachment 1


Is it necessary to cut a mini slot beyond where the end of the axle slot is, to flex the steel for better clamping.
How far from the end can I go without comprimising the strength?
Finally, whats a good sized bolt to clamp the slots?
7/64 drill bit seems adequate for the 3/8" thick steel.

The $100CDN 3" diameter blades, 6A corded Dremel Saw Max cut the 3/8" thick steel decently and the Dremel got hot after a 3.5" long cut, turns out my pre-cut squares are more like 3.5" x 2.5" which fits perfect on my horizontal wheel slots. Just had to grind off a slice of the stupid disc brake lock bracket. The 3rd piece that I cut into two peices that you see laying flat on the table, I will use 2 clamping bolts to hold the steel tight against the axle, then bolt it onto the frame.

I went through one full blade on about total 7" cut length. Maybe a regular angle grinder but wider diameter would hold up better.

Anyways, I measured the slot on the MXUS 3KWV2 motor, its like a 10-11mm slot, and my cuts into the metal were as straight as can be, didnt go over 10mm at all will have to do some filing, Dremel does not offer a flap grinder/sander. I might go ahead and buy a regular Dremel which I need anyway (for foot/heel calaus; my buddy does it that way says it works good). Lots of sales on now.
 
I am having a hard time drilling holes. I'd say the first hole is half way through the 3/8, but its not progressing, using different drill bits too.
Now I started using WD40.

I must epoxy it then.
I will V cut the notch then just do a bunch of slot cuts.
 
markz said:
I am having a hard time drilling holes. I'd say the first hole is half way through the 3/8, but its not progressing, using different drill bits too.
Now I started using WD40.

I must epoxy it then.
I will V cut the notch then just do a bunch of slot cuts.
Click to expand...

Get some quality drill bits and use a 3/16 pilot drill.
 
Get some "Tap Magic" and use it sparingly. 1 drop at a time and you will be amazed. Your bits are getting too hot.
 
Everyone makes the same mistake when first drilling something as hard as mild steel, which is to run the drill too fast and apply too little force (feed). This is encouraged by mains-powered hand drills, which often lack torque and run fast. I prefer a battery drill instead, but a drill press is the best option. You can't run a drill too slowly, it'll just take longer to cut. And that's what it does: cuts. It's not an abrasive tool, it needs to continuously slice into the material just like carving wood with a sharp blade. If it's a largish drill (3/8 or 10mm) and you're using a hand-held drill, don't be afraid to put a significant portion of the bodyweight behind it. If it squeals or stops cutting, stop. The only thing persisting will do is to overheat the bit and ruin it.
 
I ended up snagging a drill doctor sharpener years back. drilling larger holes in thicker material without a press makes it rough on the bits (and wrist when doing a bunch of 3/4 and 1" holes in 3/8" with a high torque handheld drill).
The bigger bits get pretty expensive, so it's nice to be able to sharpen them easily. Maybe that metal shop can do 4 u?

Punx is right, also on stepping the the bits from pilot to final hole size, much easier on the equipment and user. Other than that, 3+ bits for that size hole, and a decent variable speed drill with some torque.
 
With 3/8 thick steel each side, any will do.
You will never find a hub that can spin in them, even if they are made out of any rusted scrap steel you can find.

I use 1/4 each side through axle torque plates, and couldn't inflict any damage no matter how hard and powerful I ride.
 
I did use a small drill bit, it cut great, stepped it up a few sizes and cut great again. I started breaking bit with too much downward force which for steel like you said is a big no-no. I have two drills one is a Dewalt Cordless and a big corded drill with handle. I will buy some new bits, lots on sale, and use some drilling fluid.

These are the bits I used are Mastercraft, Titanium Coated says Metal on the case.Similar product.

Lots of sales on today, I will buy

http://www.canadiantire.ca/en/pdp/mastercraft-titanium-drill-bits-100-pc-0540659p.html
The ultimate score: http://www.canadiantire.ca/en/pdp/mastercraft-metal-and-masonry-drill-and-drive-set-170-pc-0543256p.html
http://www.canadiantire.ca/en/pdp/mastercraft-29-piece-titanium-drill-bit-set-0543661p.html#.Vm8nc78YHuY
 
Markz, don't buy any drill bits that are not HSS (high speed steel).
Ignor the shiny coating, it does nothing for you at home, and most of them are fake coatings anyway !
Any quality drill bit will cost a few $$$'s each !....even for a 1/4" bit.
 
Ah I was just at the store, bought the Titanium's, I will return them and get some HSS bits, I read too that Cobalt is good as well need the split point though so it doesnt wonder.

Just found a drill bit case that states HS on them, they worked great!

http://www.garagejournal.com/forum/showthread.php?t=137492
Old 02-09-2012, 07:45 PM #3
Gtamazing
Banned

Join Date: Oct 2010
Location: Fort Erie On.
Posts: 609

Default Re: Cobalt vs Titanium
Those titanium drills from Canadian Tire are junk(I have the full index).
Click to expand...
 
M42 cobalt steel is harder, more wear resistant, and more hear resistant than M2 high speed steel. But it's also more brittle. Both of them derive much of their hardness and high heat capabilities from cobalt.

I can reiterate the observation made earlier that pulling a chip constantly is key to getting decent performance and lifespan out of a cutting tool. The worst thing you can do from the standpoint of the cutting edge is to wipe it on the workpiece under lots of pressure, but without pulling a chip.
 
Thanks, yes I saw that on youtube, keep an eye on the shavings, steady pressure not too much, not too little. I felt the HS bits bite, the shavings were more courser which is good then the tiny pin points I had with the Titanium. Maybe next time I will go with 1/4" hot rolled. No good deals on the Cobalt bits anyway, I will snag some HSS High Speed Steel bits tomorrow when I return my digital measurement caliper (the digital part goes random, CT is good for returns, I returned some rusted used truck rotors in the new box with about a 10 minute head scratcher talk with the manager, someone got a steal of a deal and it sure wasnt me.) and the Titanium bits.

I couldn't believe how not-busy the store was today. I will look for more gifts as well, still need my brothers and his gf, plus my bro's ex wife. I dont know when Indigo/Chapters order will show, nor the Call Blocker purchase.
 
I have no clue what the difference between these 2 items. The ones I've been using (on the right) states on the package they should last 6x longer.
drill bits.jpg
I will try the package on the left and see.
 
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