material and heat treatment for hammer heads and dies

[adbuch]

I have seen planishing hammer dies made from 4140, 4340, S3 and S7 tool steel. Can anyone tell me which of these materials is more desirable for these dies, and what sort of heat treatment and Rockwell hardness is required for the best results (performance and longevity).

Thanks!

[Richard K]

Both 4140 and 4340 will work nicely. They machine well and are readily available. These alloys also heat treat nicely.

The "S" series of tool steels are excellent but overkill. They are suited for working mateial that is heated such as a forging hammer.

[adbuch]

I would like to know what Rockwell C hardness is necessary for the planishing hammer lower dies and head. The information I have read seems to indicate that the lower dies are rc 32-35 and the head is rc 50-57 or so. I am interested in making some additional dies for the air planishing hammer I have. I can buy some 4140 CR Heat Treated round that is rc 28-32. Would this hardness be sufficient for the lower dies? Would it be sufficient for the upper die?
Thanks,
David

[Dutch Comstock]

Hi, For low use dies on a planishing hammer or post dolly mild steel will work fine. For a lot of use you will want them hardened to over 50 rockwell to hold up for long.
Air planishing hammers hit in the range of 3,000 blows per minute. For people who are going to be using your dies a lot you should use s-5 which is a cold hammer steel.The s-7 is very close in price and you will never hurt them. This quality is for the person who is going to use his planishing hammer dies to make a living with and use them daily. For the home user any higher end steel like 4130 or 4140 will do super. A high end steel that is not made for hammering will eventually start wearing the face of the hammer where it contacts and then will have to be reshaped.All of the original yoder hammer dies that were used a lot have to be refaced a lot as the steel of that time taht was used to mke the hammer dies would not hold up to everyday continuous pounding. This is where the high use of S-7 hammer steel was first started to be used and that steel holds up fine so when Clay Cook started making C>P> air hammer dies for sale to the public he made them from S-7 so that they would also last a lifetime. C.P. original factory dies did also hold up well and I think they used S-5
A couple of ideas for the home use people are that a case hardened tool also holds up for a long time and that can be done easily with a material called Kasenite. Another metal shaper, Stan Carter made his dies out of grade 8 bolts and they worked out well. Dutch