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Grinding router bits

Radarcarve

Plastic
Joined
May 21, 2009
Location
New Mexico
I have a large quantity of 1/2" straight router bits that I would like to grind the corners off in a 1/8" radius curve, essentially turning the bit into a "dish cutter" bit... flat bottom, with rounded corners. I am not a machinist, but I have a lathe and grinding wheels. How can something like this be done? The bits are carbide, so I assume that a stone or grinding surface that cuts carbide is needed, but I am unfamiliar with all of it. Thanks, Lee Davis
 
Sounds like you need ...

1. A pedestal grinder with a green silicone carbide wheel.

2. A good dressing stone or set of rowels.

3. A 1/8" radius gauge.

4. A steady hand and a good eye.
 
Well... I have a pedestal grinder. I assume the "green silicone carbide wheel" is what will cut carbide... where would I get that? Also, what is a rowel? (Actually, I love to learn new things like this). And, since you said that I need a steady hand and a good eye, I suppose that the bits would be cut freehand on the grinding wheel. I can do that, but is there a way to automate it so thinking so much is not involved?
 
Wheels ... http://www1.mscdirect.com/CGI/GSDRVSM?PACACHE=000000099788305

Dressers ... http://www1.mscdirect.com/CGI/GSDRV...KG&SISRCH=1&SILEVL=3&SILSEQ=7&SIT4NO=66110131

Radius gauges ... http://www1.mscdirect.com/CGI/GSDRVSM?PACACHE=000000099788358

Automate it?

That's gonna cost you ... you got that many to do?

You will need to buy a tool and cutter grinder ... http://www.oliverinstrument.com/Cutter_tool_grinders.htm

Or, if you have a surface grinder and a spin jig/indexer or a tool post grinder for your lathe, you could use a profile dresser to dress a radius on your wheel(s).

http://www1.mscdirect.com/CGI/GSDRV...KO&SISRCH=1&SILEVL=3&SILSEQ=8&SIT4NO=66110131

That would speed things up a little, but your still going to have to put the clearance on by hand.
 
Last edited:
OK... I guess I should ask some specific questions, for I am not a machinist or familiar with any of this... For a grinding wheel, what am I looking for? What do you call a wheel that will cut carbide router bits... I mean, what is the material that the wheel is made from? I see loads of wheels available, but I need to know specifically what one will grind carbide. Thanks...
 
To grind carbide, you will either need silicon carbide wheels (generally green), or diamond. The silicon carbide are a lot cheaper, but they are also likely to leave you with slightly chipped edges. Either one is intended only for carbide -- not for the steel backing that may or may not be on your router bits.
 
Green grit wheels used to be used a lot in the early days of carbide, before diamond wheels on ebay were available for cheap.

Green SiC wheels do not really grind carbide, they erode the binder in the matrix and chip out the carbide grains at a microscopic level. Without a rigid machine and flood coolant, it is hard to make much headway or do accurate work with one. The wheel erodes really fast for offhand work on carbide. I used to use some about 25 yrs ago both freehand ind in a cutter girnder, and would never go back. The only one I ran that was sort of cost effective was a 20" wheel in an old Fitchburg cylindrical where we spun in port tools after rebuilding them. A 20" diamond wheel would have been prohibitive, and would have been worn out prematurely grinding partially on steel.

To start experimenting, get a 220 or so grit diamond wheel off eBay and do the corners freehand as others have suggested. It is pretty fast and easy. Before using the diamond wheel , grind the steel back of the carbide out of the way on an aluminum oxide wheel. Grinding steel with diamond wears out (clogs and erodes) the diamond wheel rapidly and is not effective.

BTW, carbide dust is not good for your lungs. Seriously. Use coolant if possible, and an adequate respirator.

smt
 
BTW, carbide dust is not good for your lungs. Seriously. Use coolant if possible, and an adequate respirator.

Or at least a shop vac with a really good filter and a dust mask.
Not only does the tungsten powder give you black lung disease, the cobalt gets in your bloodstream. :eek:
It will grind much easier with coolant if possible.

You may find it a lot simpler to send to a shop setup for this, plus they will give you a more consistent part than you can do by hand. However having your own wheel is really handy when you want to touch up some one off stuff and I certainly understand the satisfaction of doing it yourself.:cheers:
Bob
 
I have ground carbide lathe turning bits with a pink wheel on a grinder. With
very good results. Then I touch up with a diamond stone. One thing you don't
want to do is to quench the carbide in water as you grind. Air cool or dip the
steel shanks in water.
 








 
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