Making Reamers Out Of Old Drill Bits

[HollowPoint]

I generally make my reamers out of Grade 8 bolts but, since the price of everything just goes up and up, I thought I'd try something else.

I only use my home made reamers on aluminum and 12L14 steel so hardening Grade 8 bolts is plenty good for my purposes.

I was wondering, what's the easiest way to make an old drill bit more machinable?

Over the years I've accumulated enough of them that I can afford to sacrifice some of them for other uses. I just don't want to sacrifice my metal lathe tools along the way. You know; saving money on metal stock while at the same time wasting money by ruining my lathe tools.

I've never done it before on drill bits so, is it as easy as annealing them like you would any other hardened steel to make them soft and machinable?

Thanks for the help.

HollowPoint

[RwBeV]

All I do to machine old drill bits is to get them bright red hot and stick them into a bucket of old ash's. After they cool you can machine them how ever you like. There nothing more than O1 tool steel. I then take them after I have them the way I like them and if there long enough chuck them up in an old battery drill and heat the up to bright red while spinning them and then quench them in oil. I found that buy spinning them while I heat them and quench them they don't tend to warp as bad.

Bob

[HollowPoint]

Thanks RwBeV:

I kind of figured it was done something like that but, I just needed to make sure. That's good news cause now I have a ready supply of tool-steel for some upcoming projects.

Does the Oil have to be anything specific? I harden my Grade-8-bolt-reamers in dirty motor oil and it seems to do the trick. If these old drill bits can be hardened the same way it makes it alot easier.

What are the ashes for? What does that do? Can they just as easily be air cooled after they've been annealed?

Thanks for your input.

HollowPoint

[nanuk]

I think the ashes allow it to cool slowly, you need that to soften.... if they cool quicker, they harden

that is my understanding

[HollowPoint]

I think the ashes allow it to cool slowly, you need that to soften.... if they cool quicker, they harden

that is my understanding

Ah; that makes sense.

I think now that it's nearing summer time here in Arizona, slow cooling time is easy enough to achieve without the ashes.

Maybe if I just set them out in the sun and let them cool to the ambient temperature that would be slow enough.

Thanks for the explanation.

HollowPoint

[RwBeV]

Thats what the ashes are for, but instead of cooling the metal down in a matter of minuets, the ashes cool them down over a period of hours. The slower you cool the metal the softer it is. As far as the oil I have been using the same coffee can of oil that I pulled out of my 1968 Fury III, so its at least 35 years old.

Any slow cooling will soften the metal, I just like to get it as soft as possible I dont have much for carbide cutters.

Bob

[Tokarev]

Before annealing tool steel I cover it with a coat of refractory to reduce de-carbonization.
Also for lack of ashes I heat them in an improvised furnace built of 4 thermal bricks.
The bricks soak lots of heat and allow the part left inside to cool slowly.

[trevj]

Spring for a couple carbide insert cutters.

Something with a CNMG or DNMG shape, off the top of my head, would serve well. Negative rake, at least 4 cutting edges per insert. Good for rough work.

Brazed carbide tools are mostly garbage. they have their uses, but need to be ground correctly for real usefulness, which is another can of worms.

Rough cut the drills to shape, then finish with a grindstone on a tool post grinder. Even a Dremel tool on a tool holder will work, with some care. Or just use the grinder. HSS takes a lot of heat before you see any negative effects (thus the name, High Speed Steel) and will hold an edge at red heat.

It'll save you going through the whole mess of getting the drills all hot and cold again for no useful reason. HSS takes a bunch more heat to soften than that, and if you are using crappy carbon steel drills, as soon as any part of your cutting edge gets warm, it won't be a cutting edge any more. That works against the whole lot of effort that you will have put into it by the time you start cutting a chamber. If you are going to make the effort, you might as well make the effort so that you end up with something that works well.

My two bits worth, anyways.

Cheers
Trev

[HollowPoint]

This time around I'll be using up the last of my Grade-8 bolts to make my reamers. Incidentally, the reamers I've made aren't used as chamber reamer. I guess the correct terminology is, "Cherries."

I use them to cut the cavities in aluminum bullet molds and interior shapes in cold rolled metal stock.

In the height of summer, it can get up to 115 degrees outside. On a black metal surface laid out in the sun, the temps get even higher. I figured that a part that's been heated to cherry-red and then placed in the sun would take till late evening before it cooled down enough to comfortably pick up with bare hands; unless it's done on one of those Arizona days when it's still 100 degrees at midnight. Then it may take a little longer to cool off.

Thanks everyone. I've appreciated your insights.

HollowPoint

[Reverend Recoil]

Motor oil works well for small parts but I prefer automatic transmission fluid for quenching. It does not smoke and flash into a flaming inferno as quickly as motor oil.

[uscra112]

In the height of summer, it can get up to 115 degrees outside. On a black metal surface laid out in the sun, the temps get even higher. I figured that a part that's been heated to cherry-red and then placed in the sun would take till late evening before it cooled down enough to comfortably pick up with bare hands; unless it's done on one of those Arizona days when it's still 100 degrees at midnight. Then it may take a little longer to cool off.
HollowPoint

It's the slow cooling past the phase transition that makes the metal soft. That happens well above 1000 degrees, and even in the hot Arizona sun the heat loss will still be so quick as to leave the metal pretty hard. One old-timer's method was to put the metal in a good hot wood fire, keep it hot until the metal was a bright red heat, and let the fire die out until it was cold. Took hours, but that's the right rate of cooling.

[ASSASSIN]

You can also shove the red hot part into a bucket of sand for a "slow" cool down. you can also get an even slower cool down by wrapping the part in insulation and thenshoving it down in the bucket of sand....

A

[Slam'n Salmon]

It's the slow cooling past the phase transition that makes the metal soft. That happens well above 1000 degrees, and even in the hot Arizona sun the heat loss will still be so quick as to leave the metal pretty hard. One old-timer's method was to put the metal in a good hot wood fire, keep it hot until the metal was a bright red heat, and let the fire die out until it was cold. Took hours, but that's the right rate of cooling.

Phase transition is most important. Go slow here.

[AkMike]

Just a thought to consider here. A 2 flute drill will cut a 3 lobed hole and isn't round. Is this what you want for a reamer? My hole reamers are 4-5 flutes top cut 'rounder' holes.

[quasi]

Are you talking about HSS drill bits or Carbon steel drill bits?

[HollowPoint]

Are you talking about HSS drill bits or Carbon steel drill bits?

I have both types at my disposal. My junk-drawer has a bunch of chinese made drill
bits rattling around in it. I thought I'd experiment with them before I moved on to trying to soften the american made drill bits.

For use on aluminum or other soft metals I should be able to get them to work for me. (1/4" diameter or bigger)

I'll only be using those drill bits that have enough of an un-fluted tail end that will allow me to start from scratch on a round piece of softened metal.

HollowPoint