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Turning down S&D drill shank

madmachinst

Stainless
Joined
Jan 15, 2007
Location
Central FL
I just bought a 53/64 S&D drill at the scrap yard. The shank is too big for my lathe chuck. I tried filing with a bastard file and the shank seems machineable. I guess I will be going low and slow on this. I thought those drills are like completely HSS? Anyone got any knowledge that can set me straight.
 
I just bought a 53/64 S&D drill at the scrap yard. The shank is too big for my lathe chuck. I tried filing with a bastard file and the shank seems machineable. I guess I will be going low and slow on this. I thought those drills are like completely HSS? Anyone got any knowledge that can set me straight.

S&D drills have 1/2" shanks. Any smaller (3/8"?) shank on a 53/64" bit seems a bit small for drilling metal. Maybe you need a 1/2" chuck.

Or you could mill three flats on the drill shank that just fit in the 3/8" chuck when it is wide open. Then the drill would not slip.

Larry
 
This thing had like a 3/4" shank. I brought it down to 1/2 . It was a National Made in Detroit. I always thought the whole drill is made of HSS. All I know is that it cut more difficultly than 4140 Pre Hardened
 
Drill shanks are treated to be softer so (1) they won't snap and (2) the chuck cn get a bit of "bite" to keep them from slipping. Try powering a tap with a chuck and see how easy it slips....Joe
 
i once chucked a 2 1/4 hss drill and turned the morse #4 down to a straight 1 inch shank...(so if could be mounted in the turret of a CNC lathe at a shop i use to work at

after ive done that, i reliezed that any knackered drill bit shank can now be chucked and trued up on the lathe...
 
I tried to turn an MT shank down and it was SUPER HARD!

i once chucked a 2 1/4 hss drill and turned the morse #4 down to a straight 1 inch shank...(so if could be mounted in the turret of a CNC lathe at a shop i use to work at

after ive done that, i reliezed that any knackered drill bit shank can now be chucked and trued up on the lathe...

I tried to turn down the shank on an extra long MT shank drill bit to make an extra long silver and deming drill bit. It hosed up the insert pretty quick, and I didn't even get an inch of cutting done. A file barely scratched the surface of it, I think the taper shank was case hardened or something. It would cut OK on the little area by the tang. Then I tried a different brand of a similar drill bit (out of the $3/lb bin @ kitts), and it cut fine. So, before you try it, give it a file test. Make SURE it's not case hardened on the shank. I dunno about straight shank drills, never tried to turn one down. They do seem to get hosed up by drill chuck jaws though, so they're probably not hardened. :cheers:
 
drill shanks

been turning down drill shanks for years, taper shanks and straight and never came across one I couldn't cut. Don,t put flats on your shanks. You'd rather have it slip then break.:confused:
 
Do you have or know anyone with a toolpost grinder or even clamp a decent air die grinder to your toolpost then taking light cuts you should be able to grind the shank if its too hard to turn.
 
Be careful about turning down shanks on drills. You can find yourself overdriving the drill. The original size ratio is there for a reason. If you chuck up a drill in a half inch drill chuck, that was meant for a three quarter inch chuck, something is going to be over stressed. The shank of the drill, jaws of the chuck and the Jacob's taper, perhaps even the driving machine. You have a decision to make. Some call me Carlos.
 
Carlos has some good advise to follow. Just turning down a 3/4 shank drill to 1/2 in order to fit an existing chuck will not allow you to use the drill to it's full potential.
A good drill chuck is costly but a good investment Once you turn the shank you will have to be satisfied with lighter feed rates as well and less rigidity. The drill will also be more likely to slip in the chuck jaws. I have milled three flats several time to keep it from slipping. In most cases my machine would stall before anything breaks.
If you do this you can turn the shank a little larger. Just measure your chuck first. The only hard part about turning a drill shank is getting it to run true in the lathe. I have used several methods and none are perfect but all require the use of the tailstock center.
Maybe this thread will yield more on how to chuck the drill in your lathe. Walter A.
 
The only ones I tried to do were x-tra long bits.

They were morse taper mount x-tra long 3 flute drill bits. They had an area where the flutes ended you could grab them with a 3 jaw chuck if they fit in the spindle bore. It was for a shop that built custom aluminum and fiberglass construction trailers. They wanted a drill bit to be able to drill through the floor and the frame using a big hand held drill. Standard silver and deming bits were too short. They'd have to drill a pilot hole all the way through with a skinny bit, then go from the top and the bottom with a silver and deming. In certain situations, this wasn't practical, possible, or easy without separating the shell and the frame again so they could get the drill in there. So, I made them an extra long silver and deming type bit from one I found in the $3/lb bin. The first bit I tried was case hardened on the morse taper part. The second one cut OK, and they still use it. It's starting to get too short, sharpened too many times when they told me how well it worked out, I bought the rest of that size and brand bit. I figured they'd call me for another, and I could make some $$$ making them their "special" drill bits. So, they've ordered another, and I get to try this again. Things kinda slowed down a bit though, not as many aluminum and fiberglass construction trailers being built any more. Oh well, still made $$$ after buying up more bits to turn down, and this next one doesn't cost as much to make. Just time and wear on the lathe. They don't put a lot of torque on them, and they don't have to run perfectly true for drilling by hand. :cheers:
 
The most accurate way I can think of to hold the drill is to drill or bore a piece of mild bar in the lathe (but don't overtighten) to the drill size then slot one side.insert the drill and clamp in chuck in same position, that way the flutes will be running true even if the shank isn't.
 
folks around here might scream, but oh well :)

take a propane torch and heat the shank slowly until it is full and dark purple
you can wrap a wet rag around the working end to protect its temper as well.

after it reachs full deep purple let it cool slowly, by sticking it in a coffee can of kitty litter/floor dry.

after it cools you can turn it in your lathe without much trouble, and if you are careful it won't warp either,, even if it does a touch you will be turning it down and back to true anyway.

done it many times, and made extended bits for manufactures by annealing and welding on extensions as well.

i suppose it depends on how finicky you are about precision and all that, but from what i gather a drilled hole is not thought to be precision anyway and needs to be reamed to the precise size if needed.

it don't sound like you are after high precision anyway.

that is what i would do if it were me, your mileage may vary

bob g
 
bob g,
That is great way to anneal a hard shaft and I've done similar many times but not on drills as I've never found one with a shank too hard for carbide.

The only thing I do different is use a propane/Oxy torch as propane alone may not give enough heat. I also use sand instead of litter but, maybe the litter will insulate better?

Walter A.
 
qt: [The shanks of all drills are soft.]
If they were hard they would just more wear to your machine tapers, cost more and be more likely to break. Very often they may not be the same expensive steel.

Drill flutes are are circle ground and so hold well in most chucks or other devices..but flutes are hard and so they might harm your holder.. a tape or copy paper wrap is OK. Some bargain straight drills are sometimes hard all the way up so are at greater risk to break, may more tend to slip and cause more wear to a drill chuck.

Our black smith had a bucket of ashes for things to cool slowly, He also had a cut-off of an old fire blanket for a cover to let welds to slower cool.
 
You can't soften high speed steel that way. It will still be pretty much full hardness even after red heat. That's what it was designed to do. If you want to soften HSS, you need to bring it up to the proper temperature and hold it there for a considerable amount of time then slowly cool it at a specific rate.

That's all academic anyway, as the vast majority of drill shanks aren't very hard.

Edit: here's the annealing ramp for M42:

Annealing: 1600F(870C), hold 2 hours, slow cool 30F(15C)/hr max. to 1000F(540C), then air or furnace cool. Hardness BHN 235/255.
 








 
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