Hi. Recently, I saw a post that suggested that mushroomed struck tool ends could be repaired by forge welding the cracks and mushrooming back into one solid piece again. I tried this out and it worked great. The tool steel stuck together really well at a reasonable temperature. But this was in a gas forge.

Recently, I tried this trick in a coal forge. I used it on a mild steel fuller which had some severe denting and mushrooming on the struck end. Again, the trick worked really well and everything stuck together just fine. I gave it a touch with the file to smooth it up, but the file skated. So, I got out a die grinder and, wow, high carbon sparks. I had heard that poor fire management in a coal fire can cause carbon uptake. I became a little uneasy and toasted the end at the mouth of the gas forge until it was well into a sub critical anneal. Then, I made a mistake and used it. Yup, I had an accident. Two shards came flying off the head. It was still hard. The place where the shards came off was hard not just at the surface.

So, if you have poor fire control, watch out about this trick in a coal forge. Gas forges: no problem.

Thanks fo the heads up.

You used it on a mild steel fuller which had some severe denting and mushrooming on the struck end.....are you saying you hardened mild steel to the point a file skated off it??

I never tried welding the mushroom back in (but I am not good at welding yet, but should try this) Forging the mushroom together and cutting the ragged end off to make a smooth end has worked great for me.

Phil

It is highly unlikely that you can gather up enough carbon in a piece of mild steel to make any difference at all.
Thomas powers i believe posted about wot it takes to get that done. Not a short time process, A wild guess is that your mild had more than the carebon content you would expect. One thing to consider, is that you can use a hard end on a struck tool if you do not stirke it with anything hard. My tool of choice is a brass hammer.

The "fun" of old tooling is that you are never sure of what you've got!

Some old tools were high carbon WI (blister steel), others were low carbon WI with high carbon ends welded on---and may have lost the ends through wear or poor welds.

Local scrap stream made a difference too---Out here the mines provided a lot of broken rock drill shafting and so you see stuff that *shouldn't* be HC; but is as that's what's handy on the scrap pile. Old farm equipment may tend toward wagon tyre reuse even when HC would have been better. (nice in that random short chunks of reused WI wagon tyre are cheaper to buy than complete Antique Wagon Tyres!! My local scrap yard increases the price for "antiques"---at least till they figured out I didn't give a squat about stuff being antique I was buying *scrap* and would happily toss overpriced stuff back on the pile giving them *nothing* rather than a premium price on scrap they didn't have to truck 100+ miles to re-sell.)

This is why it's always a good idea to do a spark test on old stuff you will be using and not just on an end! (I have a couple of 2' long bolts that sparked "old" HC unexpectedly.)

It's amazing what I learn on this forum, it never occurred to me to reforge the mushroom, I always just ground em off. Of course tools out this way are really cheap, so maybe it would not make a lot of sense, except for the forging experience of course.

I have forge welded mushroomed ends back together but I am always a bit leery of the safety of doing so. I usually grind away the worst splintery stuff and mostly reforge the rest (rather than forge welding it). I have more confidence in that kind of repair. I am not real keen on having forge welds at the edges of struck tools... any weld is a potential weakness and it only takes ONE injury to negate the gains from many hundreds of repairs!

Hi. A bunch of clarifications are in order. First, I am sure that the tool was mild steel. I bought it as drops from a gate fab shop, and it was sheared 1.125" square. They would never use tool steel for this application. Furthermore, I only did the forge welding trick on the struck end. It was hard enough to dent my striker's sledge hammer, which surprised him. I told him about the "trick" and I placed the struck end at the forge's mouth until it had turned grey (not blue) since I was a little scared. It still was hard enough to chip. If you leave stuff sitting around in a hot coal fire, the diffusion coefficient of carbon in iron is off the charts. In my own experience, I have seen pretty deep penetration of an enriched carbon zone.

The repair worked fine on my hot cut chisel. I spark tested this, and it is high carbon steel. No problem, as forged, since I did not heat treat the welded end, only let it air cool. It was not too hard, as tested with a file. Since it was the first trial of this process, I carefully tested the chisel by using it to split logs. The mushrooming was controlled and not chippy, and it filed off at is was supposed to.

Here is a photo of the chipped tool. Oops, the attach button seems to have disappeared. I will try pasting.

Oops, doesn't work. Maybe I will put it in the gallery.

I loaded in the tools gallery. Let's see if this panel can find it.

http://www.iforgeiron.com/gallery/image/36419-chipped-tool/

Modern a36 steels can have god only knows what metals in them, as they just melt down whatever they get and pour it with no regard to the content of the steel. I have many a time taken a piece of mild from the forge, quenched it and taken it to the drill press where I'd have 4 or 5 holes go through like butter, then hit a section a few inches long where I'd just smoke drill bits. Then I'd take back to the forge, normalize it, and voila, those holes that were trashing bits became soft enough to cut. I suspect that some air-hardening steel made it's way into your batch. In the future, I'd recommend using 1045 for your fullers as it has a fair hardness with no brittleness when normalized, and can take a higher hardness if desired.

Hi Jason. That's a good point. I've seen mild steel with hard parts in it, but never that hard. I will go down to good steel with a die grinder and report back how deep the carburization was.