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Mcgyver
05-02-2006, 04:21 PM
I've a benchtop T&C and am thinking of getting a diamond wheel to sharpen carbide and was hoping to get some of your input and wisdom. I've been trying to find info, but it seems specialized enough that its not that easy to come across

1) generally, can i run it the same speed as a conventional wheel - ie can i use ot on a conventinal grinding machine ?

2) I have no coolant system on this machine - will it work dry?? or am i asking for trouble.

3) use will be mostly for endmills, so thinking a fine, cup style wheel - any recommendations and/or ideas you can share on what wheel to get?

4) I've read the dust from sharpening carbide is a hazard, unsure whether its the dust from the wheel that's the problem, or if its the carbide itself, or both - how much of worry is this - any thoughts guys?

5) how do you, or is it necessary to, true up/dress the wheel?

sorry for so many questions - any and all help greatly appreciated

Evan
05-02-2006, 04:32 PM
Dry is not good. Diamond breaks down at a rate directly proportional to temperature and starts at about 600C. At the grinding interface the temperature is much higher than that.



Product Name: Solid Carbide End Mills, Drills, Countersinks, and other tooling
MATERIAL SAFETY DATA SHEET
...
Routes of exposure:
Grinding or heating cemented tungsten carbide product will produce dust or fumes of potentially hazardous ingredients which can be inhaled, swallowed or come in contact with the skin or eyes.
Acute (short term) effects of overexposure:
Inhalation: Dust or fumes from grinding or heating this product can cause irritation of the nose, mouth and throat when inhaled. High levels of cobalt may cause irritation of the lungs resulting in fluid
build-up (pulmonary edema). This reaction may be delayed for up to two days and may be fatal.
Symptoms of overexposure include productive cough, wheezing, shortness of breath , and chest
tightness.
http://www.endmill.com/software/MSDS_C.pdf



5) how do you, or is it necessary to, true up/dress the wheel?


You don't "dress" diamond wheels. You can clean them by touching a piece of broken AO grinding wheel to them.

Mcgyver
05-02-2006, 06:09 PM
Evan, thanks for the informative response - appreciated. too bad i couldn't have been better news though ;)

I knew you can't use a diamond wheel on steel, but didn't realize it was that susceptible to heat. doesn't sound like i have too many options, maybe a mist system for coolant? I'm loathe use coolant on the little machine, although maybe i'm worrying too much, if its just mist it's not going anywhere that the grit wouldn't go anyway. that and some kind of dust collector

Michael Az
05-02-2006, 09:39 PM
When you mount your diamond wheel, just snug up the nut and put an indicator on the wheel. You should be able to true it some, then tighten the nut.
Michael

wierdscience
05-02-2006, 10:20 PM
I would not use coolmist unless you have a vaccum to suck it up instantly,it can be just as bad as the carbide dust.

The're is nothing wrong with water-sol coolant in a drip feed,it's what the Baldor grinders use after all.No dust and the mess stays cool.

Scishopguy
05-03-2006, 04:42 PM
For a dry coolant you can use a vortex tube. They are pretty good for milling and turning operations. You still need to vacuum up any dust, as with all grinding operations, so as to not get silicosis. Carbide dust is carcenogenic, I think. Anyway, bottom line is to not breathe any of it.

Jim (KB4IVH)

japcas
05-03-2006, 05:17 PM
I use diamond wheels at work to custom grind carbide blanks into endmills and sharpen used carbide endmills. I grind on a Cincinatti Monoset tool grinder. It has no provisions for coolant nor do you need it. If the tool is getting hot we do use a vortex tube to cool it but very rarely do I need it. Most of the time the heat comes from the diamond becoming loaded. The machine does have a vacuum chute around the wheel and below the workpiece so almost all of the dust is captured. I usually wear a dust mask when grinding carbide also just for a little extra protection. If you just want to touch up your carbide endmills then your tools won't even be getting hot. Just use the vacuum to keep the dust down to a minimum.

Evan
05-03-2006, 06:30 PM
You might want to consider increasing the respiratory protection you use. The cobalt binder is extremely toxic and hexavalent chromium very carcinogenic.



Respiratory protection: Use an appropriate NIOSH approved respirator if airborne dust concentrations exceed
the appropriate PEL or TLV. All appropriate requirements as set forth in 29 CFR 1910.134 should be met.
Protection factors for respirators recommended below are based upon those as listed in 29 DFR 1910.1001 (g),
Table 1. The following type respirators should be used at a minimum:
Up to 0.5 mg/m 3
(Co) a half mask air purifying respirator with a dust/mist/fume or high efficiency filter.
Up to 2.5 mg/m 3 (Co) a full face piece air purifying respirator with a high efficiency filter.
Up to 5 mg/m 3
(Co) a full face piece powdered air purifying respirator with high efficiency filter.
Up to 20 mg/m 3 (Co) supplied air respirator with full face piece operated in positive pressure mode.
Above 20 mg/m 3 (Co) a self-contained breathing apparatus operated in positive pressure mode or a supplied
or unknown air respirator with full face piece operated in positive pressure mode with auxiliary
self-contained air supply.

Note that even the lowest level requires an air purifying respirator. .5 mg per cubic meter is only .2 parts per million concentration. That isn't very much.

japcas
05-03-2006, 07:56 PM
Evan, are most of the diamond wheels on the market using the same type of bonding agents? I guess I need to check on this.

Evan
05-03-2006, 08:06 PM
It isn't the wheel, it's the carbide tooling that uses a cobalt binder.

japcas
05-03-2006, 08:15 PM
O.k. I misunderstood you. I knew the carbide was bad for you but didn't think it was quite that bad. I thought the dust mask was enough.