Machining Hardened Drill Blanks

[Scottike]

I need to make some small shafts (7/16") for the quick change gear box on my 10x36 lathe.
My first thought was to use some jobbers length HSS drill blanks, but I'm concerned that their hardness may make it impossible or at least very difficult to drill the oil holes they need.
Has anyone had any experence machining this stuff?
Or can they be annealed somewhat in the wife's oven to make them more easily machined but still retain some of their hardness and diminsional trueness?
I had planned on using Cobalt drills, but I'm not sure that they're up to the task.
I have no real means of even flame hardening hardenening a stock like W-1 or A-1, or finish grinding them afterwards, and I'm leary about a getting a piece that's the proper size only to find that the surface is full of nicks and scratches from setting on shelf with a thousand other pieces. I suppose I could machine the pieces to diminsion without the gearbox or power feed, but using the drill blanks seemed like a better alternative at first glance, if I can get the oil holes drilled.

[becksmachine]

A little more info please. Why would you pick drill blanks? It seems to me that some TGP 4140 would work well.

Dave

[SGW]

Unless you have a programmable temperature heat-treating oven, annealing HSS is pretty much impossible. It takes a rather specific heating/cooling cycle to do it.

I think I'd get a piece of ground stock of the correct diameter, probably drill rod, and use that. I wouldn't worry about hardening. I doubt the original shafts are hardened. If the shafts wear out in 20 years, make new ones.

[Scottike]

I was thinking of the drill blanks because they are already finish ground to size (+.000 -.001) and they would save me having to turn a piece of stock to diminsion using hand feed only and might let me get the gearbox back together a little quicker.
I'm still looking at facing three gears to width and making several bronze bushings, a bit of a PITA without powerfeed, but it is what it is.
Just thought I could save myself a little pita by using the drill blanks, but that may an even bigger pita than turning new shafts from stock, considering their hardness.
I hadn't thought of the 4140, that may be more suitable as it should be tough enough to give long life, but still machinable.
I really only want to do this once, rather than once every few years.

edit: Thanks for the input guys, which material would give longest life in this application, considering no heat treatment? O-1, A-1, W-1, 4140, stainless, something else?
It sounds like the drill blank idea isn't really viable.

[CCWKen]

W-1 for common shafts. It's harder than O-1 in mill state and 4140 "pre-hard", fairly easy to machine and it's cheaper. W-1 can be hardened easier and it's forgiving if you don't have an oven. It will shrink very slightly so make/ream the bushings after the shaft. With an oil supply, I wouldn't even heat treat it.

[lane]

I think you have your terminology all wrong. Drill blanks are harden tool steel about 6 inches long . The only way to machine then is with a grinder. as far as drilling holes in them you don`t. Drill rod on the other hand comes in lengths up to 36 inches long and is ground and polished to size. you order the diameter yon need . Such as 5/8 OD and it will come in .625. This material is in a soft state so you can machine drill and tap are do what ever you need to. You can get W1 water harden , O1 oil harden. are A2 air harden . the water .oil are air is the way you heat treat it if it needs to be harden. Which for your needs does not . So any of the 3 types will work. So order a piece and machine it to your needs .

[firbikrhd1]

W-1 for common shafts. It's harder than O-1 in mill state and 4140 "pre-hard", fairly easy to machine and it's cheaper. W-1 can be hardened easier and it's forgiving if you don't have an oven. It will shrink very slightly so make/ream the bushings after the shaft. With an oil supply, I wouldn't even heat treat it.

I did exactly this when I made new shafts and bushings for my Logan QC Gearbox (W-1). It worked very well and the only difficulty I had was cutting a full length keyway in one shaft on my shaper. It was my inexperience that gave the the trouble and if it had to be done again today would pose no issue.

[Scottike]

Yea, I guess w-1 it is then, I'll get some on the way. I was hoping there someone knew a little trick to working with those drill blanks, short of a laser drill, but reality and physics strike again.

[Toolguy]

Drill Blank

You can drill a drill blank with a solid carbide drill. I would recommend the kind with 2 straight flutes. I don't know how deep you need to go, that drill may not be long enough, but then it might be. If you do that, be sure to drill it dry with moderate rpm, probably in the 300 to 600 range.