Carbide tool relief cut

[larry senen]

Can someone tell me why you would need a relief cut on a tool that you make yourself? Seems like a lot of trouble just because that's the way the commercial ones are done.
I mean the cut on top of the steel that gets the carbide insert flush with the top.
Of course you would grind away below the cutter for clearance, on the end of the steel holder.

[robert baccus]

Only so other woodturners will say wow.

[larry senen]

Right??.......

[John K Jordan]

I can imagine a geometry issue when rotating the tool if the cutter is further away from the point of contact with the tool rest. This wouldn't matter if it was only used as a scraper, flat on the rest but it might if rotated significantly for shear scraping.

All the carbide tools I use are recessed and my favorites have the cutters in angled recesses. These are primarily for cutting, not scraping with razor-sharp edges. (Hunter tools)

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BTW, they do work ok as scrapers. Mike Hunter said some beginners and kids like the tools made from flat bars since it is takes no skill to keep them flat on the rest. The two at the top (Hercules) are made from square bars and are easy enough to control in rotation when using as a gouge. It is amazing how smooth these will cut and how controllable they are. (No, I don't work for Hunter, just like the tools.)

The one on the bottom (Clewes Mate #1) is made from a wider rectangular bar. I just got it and have not yet formed an opinion.

For making tools a small milling machine would be a great toy, er, tool.

JKJ

[Doug Rasmussen]

Can someone tell me why you would need a relief cut on a tool that you make yourself? Seems like a lot of trouble just because that's the way the commercial ones are done.
I mean the cut on top of the steel that gets the carbide insert flush with the top.
Of course you would grind away below the cutter for clearance, on the end of the steel holder.

I think what you're referring to is commonly known as the insert "pocket".

A pocket is usually needed if the insert is non-round to prevent is from turning or rotating under cutting forces. With a round insert the problem doesn't exist.

In metal cutting operations where insert technology came from a screw by itself without the support of a pocket wouldn't be strong enough under metal cutting forces.

Until I saw JKJ's posting of the Hunter tools I didn't know anyone made positive rake cutting tools with carbide inserts. I wonder why Hunter doesn't also offere diamond shaped inserts that would allow use for beading and getting into square corners?

The attachment show a popular 35 degree diamond which is useful for tight areas.

[Brice Rogers]

I've made a handful of carbide tipped tools and have (up to this point) always made a close-fitting pocket to capture the insert. But, I note that Eddie Castelin (Capt. Eddie) may not do that. Instead, he uses superglue to keep the insert from rotating. He applies heat when he wants to move it. So, maybe that would work.

Geometry-wise, if you put in a relief of, say 0.1", that means that you are cutting closer to the support point (the bottom of the tool and the top of the tool rest). The further this distance is, the greater the potential rotational force. This would apply primarily for a rounded tool holder, but not so much on square bottom holders.

[David C. Roseman]

[snip]
Mike Hunter said some beginners and kids like the tools made from flat bars since it is takes no skill to keep them flat on the rest.
[snip]


Not just beginners and kids. ;)

[John K Jordan]

...Until I saw JKJ's posting of the Hunter tools I didn't know anyone made positive rake cutting tools with carbide inserts. I wonder why Hunter doesn't also offere diamond shaped inserts that would allow use for beading and getting into square corners?...

I've used a variety of carbide tools and however Mike does it, there is no comparison. They cut like a razor sharp gouge, but different. Boxes, hollow forms, spindles, bowls, platters, end grain, side grain, cutting, scraping... Turning some colored acrylic rods recently I got coves and flats that looked polished, much cleaner then even my spindle gouges.

I don't know about the status of his diamond shaped cutters.

JKJ

[Len Mullin]

First off, who ever told you, that you needed to? You don't need to, you can make one however you want. I have made them both styles, one with just the top flat surface, and one with the shoulder cut out by almost a 1/8". The one with the material removed was a much nicer tool to use, the insert stayed where it was put. The one without any material being removed, was a bit of a pain. The insert would twist around a bit so that it wasn't touching the wood square on, and I broke a couple of the inserts on that type. Why they broke I'm uncertain, but, I wouldn't be surprised if it was from not being inset for more support. I disliked it that bad, that I soon changed it to match the other one.
Len