Hand grinding tool bits

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p pfeiffer
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Joined: Fri Apr 29, 2011 12:58 pm

Re: Hand grinding tool bits

Post by p pfeiffer »

This is an endless argument: Here's my bit. My first instruction on this was right after dropping out of college. I was aiming at an apprenticeship. Took machining course at the Vo-Tech. The first thing we did was learn to grind our own single point tool. Water quenching as we went. No mention of "micro-fractures! (First way learned that works has a STRONG INFLUENCE on what we think is correct!)

Challenge for all you micro- fracture enthusiasts. Try to find me any reasonable evidence that your "micro-fractures" have had ANY DETRIMENTAL EFFECT on your work. I have ground and quenched (water) for decades. When the tool is dull, I resharpen it. I almost never HONE a tool edge. Honing can help get a better finish, but I can't prove the tool lasts any better! And while someone else is honing his tool, I am cutting again.
SteveM
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Re: Hand grinding tool bits

Post by SteveM »

pete wrote: Mon Aug 13, 2018 6:34 pmI have read about leaving the tool alone after grinding for even a couple of weeks before a final hone will give a sharper and longer lasting edge.
If your tool is sitting for weeks, it's not cutting during that time, so even if it DID make it last longer, waiting two weeks so that your tool can last a few hours longer seems like a net loss of time.

Steve
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tornitore45
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Location: USA Texas, Austin

Re: Hand grinding tool bits

Post by tornitore45 »

I found that honing or finishing HSS, with a fine diamond stick, on the top where the chip slides reduces BOE particularly cutting aluminum.

The quenching argument is moot, if the bit is not burning you hand you can quench it, if it burns you are hurting yourself needlessly, chill out.
Mauro Gaetano
in Austin TX
SteveM
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Location: Wisconsin

Re: Hand grinding tool bits

Post by SteveM »

tornitore45 wrote: Tue Sep 18, 2018 12:50 pmThe quenching argument is moot, if the bit is not burning you hand you can quench it, if it burns you are hurting yourself needlessly, chill out.
Well said.

Steve
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Harold_V
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Re: Hand grinding tool bits

Post by Harold_V »

p pfeiffer wrote: Tue Sep 18, 2018 12:15 pm I almost never HONE a tool edge. Honing can help get a better finish, but I can't prove the tool lasts any better! And while someone else is honing his tool, I am cutting again.
That one is a "no brainer". A tool that is honed WILL yield better service life, but unless you use a tool for producing multiple items, you'd have no way of determining the difference. By making identical parts, you can judge by the number of parts produced before sharpening is required.

Here's what's wrong with your logic.

When you grind a tool, the wheel introduces ridges to the grind. Yeah, they're miniscule, and you'd like to think that they make no difference, but the harsh reality is they fail at the peaks, the beginning of tip failure. Remove the peaks and they offer a more resilient surface, one that doesn't fail as easily.

Don't want to believe that?

No problem. Many of us go through life rejecting things that we choose not to believe. That's what people do--made quite obvious if you consider that the world is divided on the issue of global warming. Some insist it's nonsense, while others accept the findings of those who support the concept.

That said, if you'd like to see tip failure in a way that is pronounced, try threading with a sharp tip tool. Observe where failure begins. Unless you've done something really stupid, it will be at the very sharp tip of the tool. It rounds off, and does so quickly. As the top fails, the (failed) material is dragged through the cut, rounding the edge all the more. Now think how that affects a tool that isn't honed.

Honing does more than improving chip flow.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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