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Hey guys,

so I’m just starting working on leaf spring and I wanted to make a hot cut tool to use to cut pieces off/ to shape. I had a piece of I-beam that I spent most of the day grinding a single bevel grind into (subtle hollow grind) then proceeded to try and hammer the hot Leaf spring on top of it. It barely scratched it... happy to include pics if that might help. Any thoughts as to why this might not have worked? I didn’t make the edge razor sharp for fear of losing the edge but it’s relatively sharp. My Anvil is also a 4 foot piece of heavy I beam so it’s kinda the theme...

I didn’t do any kind of heat treatment to the I beam, not really sure what type of steel it is. Anyway thank you all in advance 

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 Structural shapes: I beam, wide flange, channel iron, angle iron, etc. are mild steal designed to NOT get hard and completely inappropriate for a hot chisel.

If you have another leaf spring grind a CONVEX edge on one side a little longer than the other spring is wide. You can hold it in one hand and hit it with a HEAVY hammer to cut steel under it. This tool is called a HACK. Maybe more properly a "Top Hack."

Do NOT grind a concave edge "hollow ground" it's good for slicing meat and shaving and is as wrong for a hot cut as a bic razor. Convex edges are better supported against impacts and the geometry spreads the steel being cut so it's in contact with the blade over the minimal distance for less friction and heat transfer into the cutter. 

You could start hitting yard/garage/etc. sales and pick up old chisel sets or try a tool rental for worn jack hammer bits. Spade bits are ready made hot cuts they just need shortening, a square shank for the hardy hole or a handle and sharpening. Worn jack hammer bits are excellent for the stock pile and cheap.

Frosty The Lucky.

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Thank you frosty. I wasn’t sure what the usefulness of the I beam would be. That being said after hitting the hot leaf spring on it several times it didn’t deform at all. is the issue simply that I needs to be even harder? Because it’s not like it marred or damaged the edge I put on the I beam in any way. 

as for the color, it was a bright orange. 

Thanks,

Gabe

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Yellow, just like forging. As Jerry is trying to point out a shape and edge profile like an axe is appropriate to both hot and cold chisels, hacks, and cut off hardies. Thinner blades for hot and thicker blades for cold, much like thicker axe  blades for green pine and other soft woods and thinner for green hardwoods (thin blades stick in soft woods and chip when the uncounted a knot, thus the old practice of sharpening a double bit axe to two different profiles. 

The curved or cambered shape excerpts force in a smaller area wile the convex profile lends strength to the thinner edge profile. Even a big box store cold chisel can benefit from being reheat treated and regrinding, they tend to be to soft (for liability reasons) and two acutely sharpened. I have cut 3/16 mild plate and many a rivet this way 

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Also if you were using a hardy type chisel it must be mounted securely so there is no give. If you are using a top tool hot cut the steel being cut must be backed with a heavy nonmoving plate so all the force goes into cutting steel and not moving the workpiece and backer around.  If you are using a commercial anvil it is suggested that when using a hot cut you put a cutting plate over the face so as to not damage it when you cut through.

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Make sure that the length of the cut is not that long.  That is the reason for having a slightly convex edge on the hot cut.  Remember, focus the force into a small point.  If you are trying to cut a 1" line in that leaf spring, you probably won't be able to hit it hard enough to make much headway.  Once you establish a groove, progress will get better.

 

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Welcome to IFI, where in the midst of a seemly endless supply of non sequiturs and bad puns, there abides of community of genuinely knowledgeable and helpful people!

Where are you in the Bronx?

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  • 1 month later...

I see that your improvised anvil is a 4' long piece of I beam. While the geometry of your chisel should be corrected, as others have mentioned, the fact that your chisel didn't deform your leaf spring at all, even when it's bright orange, seems to indicate there is more than just your tool at play here. With most improvised anvils (and anvils in general for that matter) the goal is to have sufficient mass under your working surface to support the strike from your hammer and to reflect or rebound that force back up into your material. By doing this you are effectively hitting both sides at once. The hardness of that working surface also plays a role, but let's put that aside for the moment.

The problem with I beam is that there is very little mass to support that force you're trying to impart on the hot piece of steel, especially if you're not hitting directly over the web. This means that rather than the force traveling down, through your material, into the anvil and back up again, it's spreading out radially in the form of vibrations. Like dropping a pebble into water. 

When selecting an improvised anvil, it's all about the mass underneath wherever your hammer will be striking and not about the total mass of the object. My first "anvil" was a piece of steel I found at the scrapyard by me, it was ~2.5" in diameter and maybe a foot long weighing 20lbs or so. I set it up as a post anvil and I was off to the races. If instead of that piece, I grabbed a 20 pound piece of 1/4" plate the results would have been different.

I think you should consider not only changing the material/geometry of the chisel, but also what you're chiseling on. Even a mild steel chisel with a super thin grind should be deforming bright orange steel. You might roll that edge over constantly, but it will cut. Unless all that energy is being redirected away from where you're pointing it.

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