pipemakersforum.com

Hi all,
I'm a new member although I've been lurking for quite a while. I'm slowly moving into pipe making as a hobby and in the process of tooling up. I want to try and reshape some spade bits to drill tobacco chambers but have found the steel to be very hard to shape with a file (my preference over the grinder). I can heat the bit to remove the hardening and shape it nicely, but I'm not sure how to best go about re-hardening. In fact, I'm not sure that is even possible. Has anyone had luck with this approach, or should I just give in and grind slowly?
The amount of information on this forum is amazing, and I did try searching with no luck. Thanks to all who generously share their knowledge here, and thanks in advance for any tips you can provide on this topic.
Mike.

If you grind carefully you can shape and profile them without losing the temper of the steel. I used my narrow belt dander and dipped the bit fairly frequently in water to make sure it didn't get too hot.

Since you've already annealed it, you might try heating it cherry red and thrusting it into a can of water. If that doesn't work, a can of oil might. Some steels are water-hardening; some are oil-hardening (and some are probably beyond the home-shop operator).

Your best choice is shaping on a grinder and keeping cool in water nearby.

But if you need to fix the hardness of the metal, you will need to know exactly what kind of steel it is and at which temperature it must be treated. The strongest edge comes when you harden and then temper and sharpen after that.

Or you can do like I do and shape the bits and don't pay any attention to temper and just sharpen when they get dull, which is just about every time.

Yeah... ordinarily I would try to shape the bits without taking the temper out.

For the totally uninitiated, there's annealed metal which has been heated and cooled, hardened metal which has been heated in the presence of carbon usually and quenched to trap the lattice, and then tempering is a much more gentle heat treatment where you are sort of setting the metal to be a combination of hard (in order to take sharpness) and brittle (in order to not just shatter when you use it).

So assuming you have some kind of facility for this, I would guess that you are looking at shaping and some sharpening while annealed, then a heat treatment/quench, and then tempering (to what, straw?) and then final sharpening.

Use the grinder, learning to use it properly will make you faster at making more in the future. Re-shaped spade bits are disposable tools, not something to be treasured and painstakingly shaped with a file.

For what it's worth, cutting steel on a belt sander causes considerably less heat build-up than a grinding wheel. The heat is carried away from the edge and dissipated by the rapidly cooling belt. Turning the steel blue from friction can still be done, but it happens MUCH more slowly. (And the longer the belt, the slower the steel heats.)

In an earlier time, before metal-cutting abrasives bonded to flexible substrates were invented, trying to cut metal just ruined the belt in seconds. Today, instead of dulling, the crystals on the belt minutely shatter along their working edges, and what's exposed is as sharp as what broke off. (Think flint knapping on a microscopic scale) They last a surprisingly long time.

In fact, the improvement is so dramatic that grinding wheels are rarely used today in a manufacturing environment where losing temper is a consideration.

This is by far the best source for abrasive belts I know of:

http://www.trugrit.com/#

caskwith wrote:Use the grinder, learning to use it properly will make you faster at making more in the future. Re-shaped spade bits are disposable tools, not something to be treasured and painstakingly shaped with a file.

Disposable tools, that's going to take some getting used to given my tool acquisition disorder! Thanks for the advice all. I'll be grinding and will look into abrasive belts.
Mike.

Drill bits are a bit like sandpaper, they are consumables for the most part. Some drill bits can be re-sharpened to varying degrees dependent mostly on your skill set but by and large they are disposable.

When it comes to spade bits you will need to grind several sizes and they will need regular re-sharpening which over times makes them smaller and so they will need replacing. Don't waste time laboriously shaping them to perfection when you could grind them quickly and spend your time making pipes instead.

Said by a completely consumed tool addict!

But even if you don't spend that much time getting them to look perfect, make sure they are sharp enough to carve with before you use them. Your tools can never be too sharp.

LatakiaLover wrote:For what it's worth, cutting steel on a belt sander causes considerably less heat build-up than a grinding wheel. The heat is carried away from the edge and dissipated by the rapidly cooling belt. Turning the steel blue from friction can still be done, but it happens MUCH more slowly. (And the longer the belt, the slower the steel heats.)

In an earlier time, before metal-cutting abrasives bonded to flexible substrates were invented, trying to cut metal just ruined the belt in seconds. Today, instead of dulling, the crystals on the belt minutely shatter along their working edges, and what's exposed is as sharp as what broke off. (Think flint knapping on a microscopic scale) They last a surprisingly long time.

In fact, the improvement is so dramatic that grinding wheels are rarely used today in a manufacturing environment where losing temper is a consideration.

This is by far the best source for abrasive belts I know of:

http://www.trugrit.com/#

This.

As someone that makes knives (among my various and sundry hobbies), if you ruin th eheat treat of a piece of steel, you had better know WTF you're doing if you want it to make it useful again. With modern alloys, it's not as simple as taking the bit to "cherry red" (which looks orange to me) and dumping it in water or oil. Many alloys require soak time at temperature in order to properly austentize and form carbides. If you can't hit that temp, or keep the temnp consistent, heat treat will fail. And if you don't know the alloy, you're just guessing - which will lead to fail.

Use a belt grinder, a good belt (ceramic oxide is best), and keep the steel cool.