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Steve_in_Utah

Plastic
Joined
Nov 4, 2004
Location
Utah
I have a couple of easy questions for you tool and die makers and general pantograph buffs. I just blew the dust off my Deckel pantograph that I have had for years. I think I have even figured out how to use the SOE sharpener that came with it. But I am having a hard time with the actual engraving. I am cutting annealed tool steel (A10 and A2), about .004" to .006" deep, I am trying to go with a 15deg. pointed sharpen on the bits which I believe are carbide. I guess my main questions are: What rpm should I be running? Is 25deg on the back rake angle about right? and how do you touch up the tip of a pointed cutter to go this deep, be small enough to get good detail and not break off? Also any other tips and tricks would be much appreciated. Thanks, Steve
 
Steve, these are well made and versatile little machines, I have a manual I could copy and either mail or email it to you. Let me know. My machine is the GK-21, the manual also covers the GK-12.

G
 
One of George Gortons descendents runs this site:
http://gorton-machine.org:8080/

almost all the manuals, sales literature, etc is here. You can click on any of the manual covers, and they will open.

One of out members, aboard_epsilon, runs the Yahoo pantograph site. They may have users who can give specific advice since the siteis more geared to Euro machines.

I don't do much engraving on mine (Gorton P1-3), but a point is hard to make work. It needs to be stoned to a (tiny) flat with back relief. Some do work with a point made like a pyramid. (The "cutting edges" are neutral or negative rake). I think you are going to run that wide open for small line engraving. What I do for cutting a stamp or copying something 3d (hobbyist user) is figure the cutting diameter at the depth intended, and figure sfm from that. For instance for a stamp 1/16" deep with a cutter that is about 1/16" cutting circle at the top of the cut, 5000 rpm will net about 78 sfm. OTOH if the tip is .010 at depth of cut, 18,000rpm is only going to give 47 sfm.

smt
 
Steve,

I had the exact same problem in cutter breakdown while cutting steel with my GK-21. I was never able to have a single lip cutter hold up, even when using a 60 degree included angle. I finally got results using a micro-grain tungsten carbide bit in triangular pryamid form. I tried to achieve a 60 degree included angle. Since I do not have the fixture for my SO grinder to be able to grind bits while in the machine spindle, I had a little bit of run-out of the tip, which produced a satisfactory flat at the bottom of the engraving. My largest characters were about 0.060 inch high, so I got best results at around 0.002 inch depth. I was able to duplicate the appearance of the full size stamped logo in the miniature I was making. I used the I/8 inch shank of a circuit board drill for the bit, grinding with a fine diamond wheel in the SO. I wish I had an SOE!

Jim
 
The SOE manual has some good info on cutter forms/angles and speeds for various materials plus tips on how to grind the cutters. If you need a copy email me or PM me with your email address.

Mike
 
Well as luck would have it, a couple days after posting above, I had a batch of plane irons that I had stamped my name in before hardening. Unfortunately, this batch ground out flat and on size just as the stamp disappeared.:angry:

So i did what Jim Williams did, got a couple busted (carbide) circuit board drills and ground them to a pyramid. I ground 3 ends to triangular pyramid with different angles, and one to a 4 sided pyramid. Included angles between about 52 & about 60°. (I used 2 different angle magnetic angle blocks made for a different operation, to set my spin index to the tilt. Other than "availability" there was no other calculation for angle)

In the test soft steel, the 4 sided pyramid worked excellent. But when I set up to cut the hardened A2 steel blades (Rc60+), the bit kept pushing up in the holder, so the first letter would start out bold, the next a little fainter, etc.

I held a diamond lap at what looked like a good clearance angle back & sideways, and did one positive short stoke on the tip of the pyramid. Then I removed the bushing holding the 1/8" drill in the 5/16" collet, and sawed a little more relief in one side to allow it to close up better. Reassembled everything and it engraved 3 hardened blades with no further problems. I used 15,400rpm (or something close, forget exact ratio. Whatever is "next to highest speed" on P1-3.

smt
 








 
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