Sharp as a ... bit.

[Guest jackdm3]

What's your experience with drill bit sharpeners? Which brands are worth the money? How does one sharpener apply edges to the different angled bits, like pointed or blunt tips? Or do I need to buy a bench grinder for the odd ones, too?

[MacGyver]

I think as a general rule, your experience with a drill bit sharpener will be more dependent on how the bits were treated beforehand.

I've got a friend who has a sharpener that he paid a good bit for, and was unhappy with it because it wasn't doing a good job on his bits. Problem was that he had been running most of his bits way to fast and essentially annealing them by getting them too hot. If you remove the temper, the bits are trashed. No sharpener is going to work.

I know a lot of people like the drill doctor brand.

[Guest jackdm3]

Yeah, if it's blued, it's dead.

[MacGyver]

Pretty much. I used to wach my grandfather sharpen bits on a whetstone. He did chisels and plane blades this way, too. It took a little bit of technique, but I'd think it wouldn't be too hard to learn - so long as you aren't sharpening a lot of bits.

[Guest jackdm3]

Which brings me to the 60 or 70 1/8" to 1/2" I want to do.

[MacGyver]

Yeah, that would put a cramp in your hand for sure.

The one that I've used that I have been most impressed with is the Darex v390. It's ridiculously expensive unless you're sharpening a ton of bits - regularly. The drill doctor systems seem to work well on your standard 135 degree bits, and they say they'll do split points as well.

Somebody should make a jig for a bench grinder that doesn't require you to make space for another machine in your shop. All most machines seem to be is small diamond wheels with a free spinning chuck to let the bit rotate as it comes in contact with the wheel.

[Guest Lester Weevils]

Is it feasible to heat a burned bit and plunge it into water to re-temper it? If so, would something cheap like a common propane torch get it hot enough?

As you can tell, I know less than nothing about the topic.

Was surprised a few months ago how hard ordinary old high-speed-steel bits are. Needed to cut an old bit into a short stub, to get it in a cramped space.

The bit stem would cut easy, but that wasn't short enough. Tried to cut halfway up the spirals-- The dang old drill bit just took all the teeth off a portable metal bandsaw blade in about 5 seconds. Amazing.

=====

On the sharpener angle, long ago had a water-cooled bit sharpener that worked pretty good, when I was drilling lots of electronic chassis. Can't recall the name of the gadget. The bad thing was after a couple of years, the water rusted out all the innards of the gadget. Maybe that was a design flaw, not making a water wheel waterproof? <g>

[Guest jackdm3]

I suppose so. I worked in a spring shop for 5 years. The springs had to get yellow-orange, get formed and shocked with water and straight to a vat of high-flashpoint oil, pulled out to drain and then heated to cherry and cooled. I definately believe you may be able to re-temper as we did when a piece turned out weak.

[MacGyver]

Is it feasible to heat a burned bit and plunge it into water to re-temper it? If so, would something cheap like a common propane torch get it hot enough?

As you can tell, I know less than nothing about the topic.

So... tempering metal is a process that is actually the reverse of what most people think.

When you heat a piece of metal up to a certain temperature and then let it cool slowly, you are annealing the metal, or making it pretty soft.

When you temper a piece of metal, you actually want to get it to it's hardest point, and then bring it back down to the degree of softness you require. So, to your example, if you were to heat your bit up with a torch and then plunge cool it, it would be hard and brittle. As an interesting experiment (wearing eye protection) heat an old bit up with a torch to a mild cherry red, and then plunge it in a bucket of water. Take it out and drop it on the floor, and it will shatter like a piece of glass.

The way I was taught to temper metal when learning old school blacksmithing was to polish it at this point and then appropriately start to heat it back up. You would see a color spectrum start to appear (like appears on your drill bit when you really heat it up) and stop when you get the working part of the tool to where you want it.

That is a very rustic explanation, and modern heat treating makes old school tempering pretty much unnecessary. It's a neat skill to know at least a little bit about, though.

Edited June 11, 2010 by MacGyver
Jack beat me to the explanation

[Guest jackdm3]

It could very opposite as well, as you point out. The way we processed the springs was using "spring steel" and performing the hot-cool process in order to maintain flexibility in the leaf springs you have in your truck. They've obviously gotta be flexible and should return normal position for years to come.

[MacGyver]

Absolutely.

The starting point of the metal defines the starting point of the process, I guess.

In Lester's drill bit case, it seems that your bit has been annealed by heating it up in whatever media you are drilling and then letting it air cool. You would need to get the hardness back up by heating it and then plunging it, and then heating it back up until it's where you want to work with it.

I'll give it a try over the weekend. I just inherited a bunch of old tools, included in which were hundreds of drill bits that had been run too fast and trashed. I don't have a sharpener, so I'll have to try my hand at it on the bench grinder when I'm done to re-dress the cutting edge.

[enfield]

I own a Drill Doctor and have used it successfully on HSS, cobalt and carbide bits up to 7/16".

[peejman]

We have a drill doctor here at work and the machinists tell me it works pretty well. We drill holes in things like titanium, inconel, and hastelloy so sharp bits are a must.

MacGyver's statements above regarding temper/anneal are correct. When you overheat a drill, you anneal (soften) it and it won't hold an edge. You could try the blacksmith heat-treat methods, but honestly... (steel) bits are cheap.

[MacGyver]

You could try the blacksmith heat-treat methods, but honestly... (steel) bits are cheap.

Agreed.

I'd call it more of an academic exercise to see if it could be done. I think you would have a tough time getting the whole working surface of a drill bit to the correct hardness with a torch.

With a name like MacGyver, though....well, you know.

[Guest Lester Weevils]

So... tempering metal is a process that is actually the reverse of what most people think.

When you heat a piece of metal up to a certain temperature and then let it cool slowly, you are annealing the metal, or making it pretty soft.

When you temper a piece of metal, you actually want to get it to it's hardest point, and then bring it back down to the degree of softness you require. So, to your example, if you were to heat your bit up with a torch and then plunge cool it, it would be hard and brittle. As an interesting experiment (wearing eye protection) heat an old bit up with a torch to a mild cherry red, and then plunge it in a bucket of water. Take it out and drop it on the floor, and it will shatter like a piece of glass.

The way I was taught to temper metal when learning old school blacksmithing was to polish it at this point and then appropriately start to heat it back up. You would see a color spectrum start to appear (like appears on your drill bit when you really heat it up) and stop when you get the working part of the tool to where you want it.

That is a very rustic explanation, and modern heat treating makes old school tempering pretty much unnecessary. It's a neat skill to know at least a little bit about, though.

Thanks for the education, MacGyver

It sounds like this would require some level of skill, which counts me out <g>. As you said in another message, "bits are cheap" <g>

[DaveTN]

Drill Doctor works well.

If you learn how to do it, it’s faster to sharpen them by hand.

But it would have to be a very big drill for us to justify the cost of a machinist taking the time to do it.

At home all you need is a bench grinder.