I have to manually tidy these up with a scalpel, then burnish with a fine ballpoint.
Is it my cutting speed, or depth (about 1thou) or is it just a common issue for everyone?
Starting to irk me...
Comm truing problem
Started by
swodem
, Jan 09 2017 06:58 AM
6 replies to this topic
#1
swodem
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Posted 09 January 2017 - 06:58 AM
I am able to get a good finish on my comms, but always seem to have at least one comm trailing edge, sometimes two, that are full of rough swarf still connected to the comm.
I have to manually tidy these up with a scalpel, then burnish with a fine ballpoint.
Is it my cutting speed, or depth (about 1thou) or is it just a common issue for everyone?
Starting to irk me...
I have to manually tidy these up with a scalpel, then burnish with a fine ballpoint.
Is it my cutting speed, or depth (about 1thou) or is it just a common issue for everyone?
Starting to irk me...
Steve Meadows
#2
Samiam
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Posted 09 January 2017 - 07:45 AM
I got the same result when truing up cheap Chinese crap (CCC).
Sam Levitch
"If you have integrity, nothing else matters, and if you do not have integrity, nothing else matters."
Robert Mueller, special counsel (2013)
"... because people have got to know whether or not their president is a crook."
Richard M .Nixon, Nov 17, 1973
"Fool me once, same on... shame on you. Fool me... you can't get fooled again."
George W. Bush
"If you have integrity, nothing else matters, and if you do not have integrity, nothing else matters."
Robert Mueller, special counsel (2013)
"... because people have got to know whether or not their president is a crook."
Richard M .Nixon, Nov 17, 1973
"Fool me once, same on... shame on you. Fool me... you can't get fooled again."
George W. Bush
#3
havlicek
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Posted 09 January 2017 - 07:46 AM
Hi Steve,
The finish does look fine, and the issue you have is really not an issue at all.
The comm metal's (copper) hardness can and does vary, which will affect the way it cuts/machines. The width of the slots can also vary which can have an effect on all this... as well as your tooling.
When you're done making your cut, just drag (don't push) the back (not the cutting edge) of a #11 X-Acto blade down each slot starting at the bottom (near the tabs) and finishing at the top. The blade's thickness is generally a good fit for the comm slots and will do a nice job cleaning out whatever gets in there.
-john
- Rob Voska likes this
John Havlicek
#4
glueside
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Posted 09 January 2017 - 07:52 AM
When I used to cut arms I would use a US government ball point pen and smooth out all three comm breaks. It was something about the size of the ball in the pen that was perfect.
Jeff Strause
Owner, Strause's Performance Racing (SPR)
USSCA 2016 4" NASCAR Champion & 4 1/2" NASCAR Champion & Retro Can-Am Champion
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#5
MSwiss
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Posted 09 January 2017 - 09:25 AM
It's pretty random, depending on the sharpness of your bit, and while I've cut very few Chinese comms, the material probably matters.
I've cut 1000's, and sometimes, they will cut, leaving zero debris in the slot.
John's technique of cleaning out the slots is the typical production method. You're sort of shoveling out the debris, not cutting or picking it out. No reason to put anything sharp in there, unless some epoxy has wandered in during production.
On my own arms, I typically used a piece of .014" thick mylar, cut from wing car diaplane material. I never did any ball point burnishing, production or for personal use.
That burr should arc away, quickly, in break-in.
I've cut 1000's, and sometimes, they will cut, leaving zero debris in the slot.
John's technique of cleaning out the slots is the typical production method. You're sort of shoveling out the debris, not cutting or picking it out. No reason to put anything sharp in there, unless some epoxy has wandered in during production.
On my own arms, I typically used a piece of .014" thick mylar, cut from wing car diaplane material. I never did any ball point burnishing, production or for personal use.
That burr should arc away, quickly, in break-in.
Mike Swiss
Inventor of the Low CG guide flag 4/20/18
IRRA® Components Committee Chairman
Five-time USRA National Champion (two G7, one G27, two G7 Senior)
Two-time G7 World Champion (1988, 1990), eight G7 main appearances
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17B West Ogden Ave., Westmont, IL 60559, (708) 203-8003, mikeswiss86@hotmail.com (also my PayPal address)
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#6
Phil Hackett
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Posted 09 January 2017 - 10:30 AM
Copper is a gummy material that rarely cuts burr-free edges. It's part of the process.
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#7
gotboostedvr6
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Posted 09 January 2017 - 12:02 PM
That cut looks good to me.
Clean it out with 8.5 x 11 printer paper cut in a strip.
Never use anything hard to clean the slot. Ball point pen tips are hard and remove the sharp comm slot line which is counter productive to preserving the life of the comm.
Clean it out with 8.5 x 11 printer paper cut in a strip.
Never use anything hard to clean the slot. Ball point pen tips are hard and remove the sharp comm slot line which is counter productive to preserving the life of the comm.
David Parrotta
