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markdamachinist

question about punches

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Hi I'm new to blacksmithing and of course been doing a lot of reading on the Internet, I have a pretty good idea of how most of the tools, and basic processes but one leaves me wondering my question is,
I understand you use a cold chisel for cutting COLD and from what I can gather is
Any tool you use to punch hot work is
UNHARDENED which means I can take a pcs of soft tool steel and punch a redhot pc of steel , I can understand the reasoning that it'll ruin the temper on a hard tool
But will any type of rod be able to be used as a punch? Maybe some of you could enlighten me kinda limited on resources for now and don't wanna waste or wreck anything if I don't have to thanks.

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As long as it is thick enough that it won't bend, you can use any old metal scrap out there for hot punching. I like my punches about 1/2" to 3/4"

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The better punches are made of steel that stays pretty strong even when heated... like H series steels.  You'll find that medium carbon steels of any kind will make pretty good punches.  Yes you can use mild steel to punch with... but you'll get limited service from it.  Better IMO to stick with medium carbon for such tools and then go to the better alloys for tools that will be used for high production purposes.

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I use H13 or S7 on my punches that see lots of use. The mid carbon punches work ok, but you need to use them more skillfully, you need to keep from over heating them, by removing them from the stock you are punching sooner so that they do not over heat. The tempering temps for the mid carbon might be around 500f, on H13 it will be around 1000f.

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Balcones Forge has had Mark Aspery down for the last two year for our workshops and big demos.  He likes to use sucker rod to make a lot of his tooling.  I picked up 2000 lbs of it at the salvage yard a couple of years ago and used it for the fence around our yard.  It was 25 cents a pound at the salvage yard.  Save the ends if you do this, they make great hardie tools.

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Let me take a swing at this:

 

Beginner: automotive coil springs make decent punches in a normalized state, keep them cool by dipping in water regularly during use.

 

Intermediate/advanced:  High alloy punches like H13, S7 retain substantial hardness even when buried in glowing steel; do not dip in water but let air cool

 

Advanced:  Hofi uses tungsten carbide tank penetrators picked up from the desert to use as tooling that doesn't really notice the heat that much

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"There's a reason we do this, but at some point sharing our reasons appears a waste of time."

 

Now that was a nice response to a reasonable question.

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Sometimes I tell my students that everything I tell them is true at this stage in their learning; but will change as they learn more.

 

Sort of like that answer to the question "Can I do XYZ?" where the answer is "I can do XYZ; but if you have to ask you probably can't, or shouldn't".

 

Why I broke down my answer on punches into "starting out" "experienced"  and "weird outlier"  (and oh do I love my H13 slitting chisel!)

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So true in every field.  Beginners are commonly told not to mix oil and water paints... but pros often do it!  Good reasons in both cases too.  Where trouble happens is when addressing a mixed group or thinking that you are advising a beginner who turns out to be an extreme expert pushing the envelope all out of shape!  The advice for one level can be quite different than that for another level of understanding!  Experts will usually sort the differences but beginners can get in lotsa trouble by hearing stuff not meant for their ears!  Why "a little knowledge is a dangerous thing"!

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Hi, another similar question.

I have some stone chisels, how suitable would they be for cutting hot metal? I dont know if they've been hardened or not.

Sorry for the lack of usefull info.

Thanks

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They would be good; but keep them cool by dipping in water unless they are a recent high alloy chisel.

 

If they cut stone they would have been hardened and often harder than metal cutting chisels.

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hahahaha, I read that as chisels MADE of stone and not knowing if they were hardened or not and I was about to call troll on it :)

 

I will add my support for the sucker rod tooling crowd, all of my kit has been forged Aspery style (guess why...) from sucker rod, and it has held up well with the business end being hardened and tempered back to roughly straw (give or take).  I have had to fix some of the smaller cross section ones as I used(abused?) them, but that's more my fault than the tool.  tools from mild will be temporary, tools from medium carbon/alloy will last longer but may still require some maintenance, tools from high alloy (as I understand it, I don't own any) are more expensive and more difficult to forge, but if used properly will probably outlast you.

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I was once give a dozen pharmaceutical punches made from S1.  (Never knew they existed).  Being a new alloy to me I went to the books, (ASM handbooks that is) and read up on how it liked to be treated.  Now in general we are always telling folks to normalize before hardening as that is common knife alloy procedure.  Turns out that you are not supposed to normalize S1.  I've been using one as a short bodied hot chisel for years now.  I've sourced enough of the high alloy stuff at conferences that I use it for any tooling that will get buried in hot metal---particularly as I have a large screwpress that really loves to excessively shove cutters and punches down in big chunks of orange hot steel.

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Just to clarify for myself as we'll... the struck end is NOT supposed to be hardened unless whatever you are hitting it with isn't, right?

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the advice I give my students is simple while you are learning use coil spring. it will hold up ok. after you feel comfortable making your punches. it is worth buying a length of h-13 and s-7. you can pick it up for about $5.00 for 6 inch for 3/4" dia. the tools you will make from these steels will hold up for many years. Some times it is more expensive to use scrap metal with the time you spend gathering, and straightening it you could have bought prime stock and made the tool.

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