Carbide cutters

[monty]

Does anyone here make their own or sharpen/shape carbide cutters? I ask because I came across some carbide blanks that I would like to have made into cutters and, if possible, attached to to a pen mill.
I have 2 pieces 3/4 X 3/4 X 3/16 with SQT; 243P3; T-04 stamped on them, another the same size with SPC; 633; HA, one with SNG; 633; T04 and one I can't read. I would like to get these sharpened and a hole drilled in the center so I can screw them to a tool to use as a scraper on my pens.
I also have 4, 1/2 X 1/2 X 1/8 with similar markings that I was hoping could be shaped and "welded" to a barrel trimmer and sharpened.
Is this cost efficient to do or should I just buy them already sharpened?

[TDHofstetter]

I grind some of mine - I sometimes buy brazed-carbide toolholders for my metal lathes, and they never arrive with either the rakes or the edges right. I've got a special grinder for that purpose, with silicon-carbide grinding wheels.

The hole drilling is a BIG BIG BIG challenge. That takes a diamond drill, expensive and fragile. Typically carbides with no center hole are used in a toolholder with a clamp to hold 'em in place.

Carbide is easy to braze or silver-solder. Ordinary plumbing or electronic solder won't work well enough, but silver solder works just fine. The trimmer would need to be VERY FLAT so the the liquified brazing or silver solder can flow into the joint, but it won't fill any significant gaps.

Lots of carbide grades can't be brought to the brilliant sharpness you'd want for these purposes. Some grades can be... but HSS is nearly always perfectly sufficient for woodturning. If you're turning lots of extremely abrasive wood (teak springs to mind), the carbide may prove to be your best bet. For nearly any other wood, HSS is my choice.

[Leo Voisine]

Sounds like you have some square metal cutting turning inserts. They are typically held in a tool holder with a clamp. 1/2 x 1/2 is a common size.

Carbide can be ground but with a special grinding wheel. Diamond is the most common, but you can get a carbide wheel for a pedestal (bench) grinder.

Carbide is made via a powdered metal process. In it's raw state, it is a powdered metal. It is actually tungston carbide. It is mixed with a binder, usually cobalt and pressed into a form to very near net shape under extreme high pressure. The pressures are to the tune of over 100 tons per square inch. Once pressed into a very near net shape it is sintered in an atmosphere controlled furnace at a temperature where the binder is almost molted and all the tiny particles weld together.

After the carbide is cooled, it is then ground to form a sharp edge. Oh yes carbide can be sharpened to a very sharp edge. Most end mills nowadayz are made from a micrograin carbide. That means the powder particle size is about half the size as a "normal" powder particle size. Therefore when you buy carbide cutters you always want to look for "micrograin".

In process - carbide is very hard and can run very hot. Carbide can easily withstand temperatures where the steel being cut is near molten, but the carbide itself will remain as hard as if it were cool.

Carbide is hard. Carbide is also very brittle.

Glass is hard, and glass is brittle.

There are only two things on the earth that are harder than glass - one is carbide - the other is diamond.

[TDHofstetter]

Um... diamond, and silicon carbide, and tungsten carbide, and zircon, and aluminum oxide are all harder than glass. Picking nits, I know.

Ferric carbide is borderline.

[Leo Voisine]

carbide is carbide, and carbide is harder than glass.

Tungsten is what carbide is made of. Silicon is not harder.

I already said diamond.

And NO Aluminum oxide is NOT harder than glass.

And your nits are not harder than glass either ;D ;D Though, they may be brittle. Comes with age.

[Beamer]

Since my nits are younger, I thought I'd google some ...

www.reade.com/Particle_Briefings/mohs_hardness_abrasive_grit.html

This says Aluminum oxide is AS hard as Tungsten carbide, which is harder than Lead Free Glass. Interesting.

I dunno how valid it is, but have a couple nits

[TDHofstetter]

Apr 11, 2010 17:45:30 GMT -6 Leo Voisine said:

carbide is carbide, and carbide is harder than glass.

Tungsten is what carbide is made of. Silicon is not harder.

I already said diamond.

And NO Aluminum oxide is NOT harder than glass.

And your nits are not harder than glass either ;D ;D Though, they may be brittle. Comes with age.

Na, wait.

There are lots & lots of different molecules that're all carbide - the "carbide" is just the raw carbon content of the molecule. The other element decides which carbide it is - tungsten carbide is the one commonly used for tooling, and silicon carbide is the one used for abrasives (silicon carbide is harder than tungsten carbide, which is why you can use a silicon-carbide grinding wheel to shape & sharpen tungsten-carbide tools), and ferric carbide is what makes carbon steel hard. There are lots of other, softer, carbides, too.

You doubt that aluminum oxide is harder than glass? Pick up yon AlOx sandpaper (I've done this, I know) and wipe it across your windowpane. If it's harder than glass, it'll scratch the glass. If not, it won't. It does.

[monty]

OK, I know know that these can be sharpned, but is there an "easy" way to drill a hole in the middle of them?

[TDHofstetter]

Nope. No easy way at ALL. Best you can do is a diamond burr in a Dremel tool... and that'd be crazy tedious at best.

[Leo Voisine]

Apr 12, 2010 7:35:29 GMT -6 monty said:

OK, I know know that these can be sharpned, but is there an "easy" way to drill a hole in the middle of them?

NO