Getting Rid of Mushrooms

On 2/5/14 I wrote about hitting hard on hard and touched on the issue of tool mushrooming but didn’t go on to address proper tool dressing.

Unless we made the struck tool we probably don’t know about the alloy or how the heat treatment was done.  We trust the working end of the tool has been tempered properly for wear resistance and that the struck end has been left softer to prevent chipping.  Some mushrooming of the struck end can be expected with this strategy.  Still, dressing the struck end to prevent excessive mushrooming is a good safety plan.

I found one explanation of the tool maker’s intent at

http://www.flatlandforge.com/Warranty.htm  operated by Jim & Kathleen Poor.

“Thank you for your interest in our tools. We strive to bring you the best and safest tools on the market today.

We will warranty our tools against manufacturing defects by gladly replacing tools that fall under the guidelines outlined on this page.

Our tools are made of S-7, shock resistant air hardened tool steel. Each tool is hardened ONLY on the working end's, while the striking surface has been tempered back (or made slightly softer). This unique feature is primarily for safety.

With normal use, our tools are designed to mushroom slightly at the striking end of the tool (or top of the tool), and should be dressed back with a file or grinder depending on amount of use. We soften, (or temper) the tops of the tools to reduce the chances of chips flying off the tool when struck by an off (or wild) blow from a hardened hammer face. It takes a little more time and expertise, but we feel, the safer the tool, the better.

The working ends of our tools are hardened for maximum wear. This does not mean that they will last forever! But, with regular care and maintenance, these tools should last you a long time. So keep the working end of the tool COOL as you drive it into hot steel. Don't let the tools get extremely dull, keep them sharp by using a file. Don't drive them into the anvil. Hit them solid and square. Off blows from the hammer are usually the reason forging tools get wrecked.

We hope you enjoy your new tool. Be sure to look for articles on care and maintenance of the tools in the industry trade magazines.”

Some other References:

http://www.ccohs.ca/oshanswers/safety_haz/hand_tools/struck.html

http://joneakes.com/jons-fixit-database/1703-Dressing-your-tools-for-safety

http://www.toolboxtopics.com/Construction/Generic/Cold%20Chisels.htm

http://www.listoftools.com/grinding_operations/chisel_head_grinding.html

Mushrooming which I've accepted.

Excessive mushrooming.

Very Sharp or Very Dull

This phrase occurs to me from time to time. I heard it used by a demonstrator at a conference. Unfortunately I can’t recall that person who said blacksmithing tools generally fall into two categories, the very sharp and the very dull. I also recall a blacksmith who emphasized the importance of keeping punches sharp. These phrases usually come back to me when I’m dressing a tool face or making a new tool or perhaps relieving the edges on a die.

It is pretty obvious that cutting becomes fullering at some ambiguously fine line. Hammers, too, are essentially fullers until the face radius is zero in which case they become flatters.

Neither dull cutting edges or sharp fullering edges are very useful. What ever the working surface radius it seems to work best when highly polished. That is where the progressive smoothing from coarse wheel grinding to belt sanding to silicon carbide wheel preliminary polishing to hard felt wheel and buffing compound finish polishing is important. The highly polished surface seems desirable no matter whether it’s a face tool or and edge tool.

The forging atmosphere is a corrosive one. I can easily see that the rust forms on steel surfaces fastest in the forge room. Every spring die which was once polished is today rusty because it has been affected by the humidity and the chemicals in the coal smoke. It’s just not practical to keep all the tool faces mirror bright so it’s always a matter of thinking through the work process and deciding what is “good enough.”

http://www.persimmonforge.com/

Nol's Mushroom

A few years ago I purchased a 3.2 pound Swedish pattern forging hammer from a conference vendor. At home I tried using it and was disappointed and soon quit using it altogether. Then a year or so later in August, 2004, I was at the Rocky Mountain Smiths conference and watched Nol Putnam use a similar hammer very effectively. At a break I looked closely at his hammer and noticed that the cross peen was somewhat mushroomed which softened the sharp radius a lot. I asked him about it and found he had intentionally made the modification and liked it.

At the time I couldn't quite remember what I found dissatisfying about the hammer but decided to check it out. Back home I tried the hammer again and the face seemed to work fine but the cross peen was so sharp it was too severe to use in the manner I usually needed. So, I decided to modify it and try again.

I heated the cross peen with the torch a few times and struck the anvil until I felt it looked about like Nol's. I'm just guessing, but I think, the radius changed from .25" to 1.5".

That seemed to make all the difference in the world in the usefulness of the cross peen and today it is my most used forging hammer. Subsequently, I purchased two of the 2.2 pounders and modified them in the same manner.

I'm a believer in keeping the hammer and anvil faces smoothly dressed and have a linear bench workstation set up for touching up the hammers and other tools - bench grinder; belt sander; Scotch-Brite silicon carbide deburring wheel; hard felt wheel with polishing compound. A 120-grit flap wheel on an angle grinder works well on the anvil face.

I have made hammers and have helped students make their hammers, but now it seems to be nice exercise in craftsmanship but not a cost efficient practice for me and I might never make another. On the one hand, my hammer assortment is considerable and, on the other hand, those who specialize in tool making can make a nice hammer for $35-$40 and I can't, if my time is worth anything. Business is business, time is money and all that.

At this address http://www.anvilmag.com/smith/blcasabs.htm you can find "Blacksmithing as a Business" by Nol Putnam. It was published in ANVIL Magazine, January, 1996.

http://www.persimmonforge.com/