Bob Bergman at Dan Cruzan's shop April 2, 2002
Report on Bob Bergmans Demonstrations At The
Furnacetown Blacksmith Guild / NJBA Meet and the NJBA April 2nd Meet At Dan Cruzans
Bob Bergman demonstrated his power hammer the Kickass 75. He demonstrated tooling and techniques that he has developed for this hammer. Bob can be contacted for more information at;
Postville Power Hammers
N 8126 Postville Road
Blanchardville, Wi 53516
1 888 535 6320
Fax 1 608 527 2494
This report has been provided by Anton Holdstrom;
Bob Bergman's KA 75 Air Striking Hammer
Designed for low air consumption, Low weight, and low cost
Flat dye style forging
Designed to duplicate man with sledgehammer.
If a lot of long tapers are needed, this is not the machine.
Designed like old time steam hammer. Cylinder moves and ram is stationary. Most cylinders are stationary and the ram moves. One cylinder the air comes in above the ram to move case up, the other the air enters from below and the cylinder moves down.
For cold work, drop pressure down.
ATF fluid lubricate every 4-5 hours / wash WD-40
Cylinders are 2.5" id x 2 = 5 @ 100 psi = 500 LB? Mass times velocity squared
Longer the tools, less speed of head so less power.
Punching hammer has tendency to roll so keep tools short.
1) When hammer is up, it is on
2) Don't lean against hammer.
Seven (7) Basic Processes
1) Tapering - drawing
Any taper - establish the point first, so you can control the length.
A bird's mouth will always happen is start tapering too close to end.
Start back 1/2 the thickness of material. If going to perform and blunt taper, taker a few Hits back to pop the center out, than start taper. Don't go round and round when tapering, only work square, octagonal or edges.
Power hammer - tapering in steps then use flatter to remove steps.
Solid sound indicates bottom so move in or out.
Taper - towards you - back edge of dye
-- away from you - front edge of dye.
2) Upsetting - making thicker
Don't use too heavy of a hammer
1:3 Rule - Diameter : maximum distance that may be upset without problems (1/2" : 1 1/2")
3:1 Max force from top to bottom to meet in center, 4:1 starts to fold
Upsetting - 3:1 width to length ratio, if greater the object will bow or fold
The fold or shut never goes away. If keep hitting, the shut will go deeper.
Corollary to 3:1 rule; if working longer stock must control heated area to prevent bow.
1) H 13 - cutter
1750 - 1800 air harden, heavier material use fan
High chrome - hot working
2) 4140 - dyes Not very high in carbon but is tough.
3) 5160 - snapper, cutter,
Also truck springs
No heat treat, air cool enough
4) A 36 & super quench
5) 8260 track pin
6) S-7 some jack hammer bits
Jackhammer bit - 20 degree taper with 80-degree bevel on very end.
Hit and wiggle, can use graphite grease or coal dust for deeper holes. 20 degree taper prevents sticking. Final drift can be made from mild steel and Gunther quench. Faster than drilling and nice swelling around hole.
Slitting - circumference = 3.14 and 1/2 = 1.57" and slit 75%.
4) Fullering or Grooving
The groove sets off the twist. Rounding corners, grooving and twisting looks like rope.
Chamfer corners cold, example railing.
Go past stopping point and come back.
Marks cold and cuts hot.
Cut on alternate sides for a full cut, if rotate 90 degrees only cutting half material.
Does not use flux, very little scale is generated if welding heat is reached fast.
Too long and clinker sticks to metal and scale is generated to prevents weld.
1) Volume - Area - Resistance - Force
2) Cut stock 120" / handles 16" / spring handles 30" and make 10 or 15 at a time.
3) Offset tenon - very easy to do Blacksmithing. Hard if machined.
4) 30 degree taper Max - or shoots out.
5) Walter - blue plastic backing for grinding wheels
6) Handles - 1/4" x 1" nice
7) Ball peen hammer - point the peen and use for punch
8) There seems to be a size like when I was doing the springs that the thickness about 1/8"
Seems to be the thinnest. Maybe due to cooling effect
Cutting - back bevel the cutter 2 degrees to keep cutting straight. No bevel - cutter will tend to roll.
Hard stop to prevent edges from touching.
Turn dyes over to omit the chilling effect.
Dye must be chamfered to allow metal to flow out.
Snub End Scroll
If too tight a bend - crack can start from shut. Roll away clockwise.
1/4" x 1" flat and cut end on 45 degree
heat and than center the point.
Veining chisels very steep angles and can do cold.
Hard surfacing rod and dye grinder. Go back over again but stop before all flat is gone.
Take flat stock and bend in the shape of "S". Fuller with cold cutter. Straighten flat stock.
Fish from Horseshoe:
1) Use ball to start mouth, round hot cutter to open mouth.
2) Eye - ball peen punch
3) Gills - same round hot cutter.
4) Heels - flair out and use flatter
Make a ball and flatten
Hold in jaws and drive down to offset with hammer
Punch hole for mounting
Preparing the scarf for welding
Bend about 1/2" back onto itself. Work to taper and than point.
This makes a large upside down thumb profile.
If bring to welding heat very fast, than don't need flux because very little scale is generated.
Tongs - Quick & Regular
1) 90 degree with 1/2 face blows to start jaws.
Turn towards the hand, which is going to hold it.
2) 45 degree with 1/2 face blows to start eye
3) 90 degree to set eye size and start reins
Bob made a block with recess to prevent eye from getting too thin.
Quick tongs are made using 5/16" or 3/8" rod to set eye area.
Heat and twist for jaws. The twist does stress the area