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Re: G10



Original poster: Terry Fritz <terrellfone@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

I think Gerry picked TiN cobalt alloy tools cause of "me" ;-)) I use that since I work with military grade titanium a lot for "combat things". :o))

1. "Solid tungsten carbide or diamond"... too brittle... Shatters like glass... Cobalt when driven "too hard" actually "explodes" requiring surgical removal (minor) of the shrapnel... Guess how I know this :-p But it does not "break easy"... Fairly inexpensive and can take hard abuse. For "hard work", I was very disappointed with anything but Cobalt alloys... The TiN coating really likes to hold cutting oils well and "slips" off" cuttings well.

2. So much grease... It probably helps clean the stuff from last year off :o))) In my case, a full set of mill screws and bushings runs like 20 dollars... :D

3. Don't breath it ;-)))

4. Nothings burns up tools like Mil grade titanium with its very poor thermal conductivity. Typically "power tools" run too fast and just burn up... Cobalt "hack saw" blades run about right and smoke off the oils do the heat with just "hand power"... I have cut a heck of a lot of grade 5 titanium with cobalt tipped hack saw blades... The heat does not hurt the teeth and it stays nice and sharp until the teeth just start of fall off due to fatigue.

Cobalt actually gets "stronger" when hot... Most modern machines can go down to very low RPM (like 30 RPM or less in my case) to control heating.

So when going to "war" with a "mill cutter in a hand drill".... Tungsten carbide and diamond will shatter in the first secondz (your dead!!).
HS steel is like a smooth bearing surface, almost a "lubricant" ;-)))
You want cobalt alloys that can take shock, heat, and and are very hard. These wheels have "cut up" a lot of opponents, but they show zero damage still... In fact, they have "left there mark" on every forum
they have played at :o)))

http://hot-streamer.com/temp/Ti-Wrex!!-Cutter.JPG

Almost all tool cutters here are cobalt alloy now. And the main cutter I use all the time for that last five years is still the "original" one... TiN Cobalt alloy... If you don't use it, your "missing out"... G-11 fiber glass.... just cleans the "dirt" off it... :O))) And everything here is G-11 to including the surface I ate lunch off of today... :o)))

Cheers,

   Terry


Tesla list wrote:
Original poster: "huil888" <huil888@xxxxxxxxxxxx>

Gerry -

I should have been more specific. Some of the problems you will encounter when machining fiberglass-epoxy composite material include:

1. Extreme tool wear. The only suitable cutting tools are solid tungsten carbide or diamond. My experience has been that even high quality tool steel loses its edge after very limited cutting, regardless if it has TiN or other anti-wear coatings. Of course, it all depends how much material you are removing. A TiN coated drill bit may "survive" 10 holes, but look at the cutting edge under a microscope and it will be in sad shape.

2. The "swarf" (cuttings) are extremely abrasive, and machine tool ways (when using a milling machine or lathe) must be covered and equipped with a vacuum pick-up right at the cutting tool, and everything must be meticulously cleaned after any machining of fiberglass/epoxy.

3. Any airborne particles (both fiberglass and the epoxy matrix) are very irritating to the skin, and frequently cause skin sensitization after repeat exposures.

4. If the material is overheated by the use of dull cutting tools, the epoxy decomposes and releases noxious fumes. Phenolic material will do this also, but to a lesser extent.

Etc, etc.

Regards,
Scott
----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, March 06, 2007 10:09 PM
Subject: Re: G10


Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Scott,

I didn't find it harder to machine G10. That part went just fine.
The problem is: G10 is very hard on the tools. It dulls HSS very quickly. TIN coated cobalt hold up just fine.

Gerry


Original poster: "huil888" <huil888@xxxxxxxxxxxx>

Gates -

"G-10" is not a phenolic-based material, it is a very difficult to machine fiberglass-reinforced epoxy composite. For fabricating a disk for a rotary spark gap, you want to use linen or cotton fabric reinforced phenolic composite, type "LE" or "CE".

McMaster-Carr (mcmaster-carr.com) stocks 12" X 12" slabs of linen and cotton-reinforced phenolic material (as well as fiberglass G10 material ) in a range of different thicknesses, including 1/4", 3/8" and 1/2" at reasonable prices. They can ship next-day.

M-C's brand of linen-reinforced phenolic composite is called "Garolite CE". A 12" X 12" X 3/8" slab of CE material is around $23 plus shipping.

Regards,
Scott Hanson
----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, March 03, 2007 1:42 PM
Subject: G10


Original poster: "Gates" <ryker@xxxxxxx>

Hey Gang
Does anyone out there have a spare piece of Phenolic for my RSG disk?
I would need a piece 8"x 8" 1/4" to 3/8" thick.
Thanks
Gates L