The clutch material I used is 1/4" thick leather from S.R.Sikes in Mpls Mn. This thickness left about 3/8" of the clutch cone showing outside of the clutch pulley when reassembled and with the clutch fully engaged; a good thing.
The material comes in 1/64" increments. It worked out fine that way for me, but you might try 2 or 3 64ths thinner stuff.
Dimensions: 2 1/2" by 10" per facing. You'll need two per hammer.
This leather comes pre-buffed specially for this application. The smooth side is the clutch facing side. I bought 4 feet of it for $15 including shipping. The original facings were attached with 10 3/16" diameter copper rivets about 1/2" long, (then trimmed to length). I couldn't find the right diameter so I used 3/16" X 1/2" aluminum pop rivets. They worked wonderfully well. You'll need 5 rivets for each clutch "shoe".
Here's how I did it (after a lengthy tutoring from Ollie Juaire!).
Note: Having one or two helpers would be a lot safer than doing it alone as I did!!!
Remove the drive shaft from the hammer. It weighs about 200#, so be careful.
I clamped an 8 foot elm 2X4 to the hammer frame (as a Gin Pole). The upper end extended 3 feet or so above the top of the hammer. I attached a come-along to that upper end and used a strap between the come along and the shaft. (Be sure to fasten the clutch pulley to the shaft if it's a center pulley model,so it doesn't fall off as you lower the shaft!)
Then I carefully lowered the shaft to a flat work surface where I could safely handle it. Next I slid the clutch pulley off the shaft so the shaft assembly would be easier to work on.
After removing the old facings and cleaning up, I cut the leather to fit.
Note that the shoes are cone shaped so some edge trimming is in order.
Next, I located and punched the five 3/16" holes in each facing. (Remember, smooth side out!).
I Soaked the leather in tepid water for at least 3 hours (more is better).
The soaking softens the leather so the rivet heads can be pulled down below the level of the leather during installation and be out of contact with the clutch cone even after considerable wear.
(Note that the rivet holes in the cast clutch shoes are countersunk.)
When the wet leather becomes pliable, I fit the facings to the clutch.
- I Poked all 5 pop rivets through the leather and into a clutch shoe hole to assure alignment.
Now I begin pop riveting:
-Draw each rivet up slowly so the leather stretches down into the countersink.
-After each rivet has drawn down well, make one final pass to "pop" the rivets off.
In my case the steel shanks broke off about 1/4" down into the rivet, so there was no way
that the steel shank could ever scratch the clutch cone.
-Now slip the clutch pulley tightly over the clutch shoes to help form the leather facings
to exactly fit the cone of the clutch.
-Let the leather dry completely. (2 or 3 days?)
-Remove clutch pulley.
-Grind down ends of leather so if they were to curl up later on they could not rub on the clutch pulley cone.
If this curling were allowed to occur, it could cause the hammer to run-on.
-Now liberally rub Neatsfoot oil or Mink Oil into the clutch facings.
The facings must not run dry.
-Finally, reassemble and adjust the hammer.
-Add more Neatsfoot oil or Mink Oil lubricant if facings appear shiny.
Update: I wrote this article in about 1987 and now, in March of 2009, that hammer's clutch is still working fine.