Turning #4MT drills down to #3MT...Possible?

[PaulH]

Bought an ancient Buffalo Forge drill press the other day, guy threw in a half dozen #4MT drills. Great, but drill spindle is 3MT. Anybody ever tried to turn one down? Fool's errand. They are all old USA made drills in exc condition, maybe unused. No market for them on ebay with shipping costs so darn high. Listed 'em for 25 bucks plus shipping (USPS flat rate)...no bids. Maybe rough 'em with carbide and finish turn with HSS? Suggestions?

 

[AndySomogyi]

Isn’t the taper hardened?

If it’s hardened, you’d have to either grind or use something like a CBN insert


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[mmcmdl]

I would think there would be someone on here that would want them , and they could sleeve them up to 5s if needed . I know of plenty of 15 inch lathes on here .

 

[PaulH]

Andy S, I tested one shank with a new sharp file and it will cut with down pressure...the same file slips over a HSS lathe bit, so I would guess they are not very hard. I oughtta just do it...sacrifice 1 drill if it goes south on me.

 

[benmychree]

Machinable, but hardly worth the trouble.

 

[AndySomogyi]

Machinable, but hardly worth the trouble.

I think worth the trouble is relative.

if he’s got them sitting around, won’t fit any of his tools, they’re worthless.

but if he turns them down, they’d fit his tools, and he’d have some usable drills for free. And even if he fails at turning a taper, it’s a learning experience and he now knows more than before, and I think that’s rather valuable.

 

[AndySomogyi]

Andy S, I tested one shank with a new sharp file and it will cut with down pressure...the same file slips over a HSS lathe bit, so I would guess they are not very hard. I oughtta just do it...sacrifice 1 drill if it goes south on me.

Go for it then. Do you have a collet chuck?

If not, I’d make a sleeve collet for them, and clamp in a 4-jaw. That way you get very accurate clamping.

 

[matthewsx]

Trade them.....

Probably more likely someone on here than eBay.

John

 

[cathead]

I have a few Morse taper bits that were machined cylindrically on the bottom part of the taper for being held in
a drill chuck I guess. Now I wouldn't recommend this kind of machining on MT tapers but it has been done.
The interesting part is that the drills are still usable as MT.

My thoughts are that mmcmdl and matthewsx have the best solution to the problem.
The tang on the closest drill bit was missing so I welded on a new one so I could trust it in the tail stock.
Also, I see there is a MT4 to MT3 adapter available on E-Bay.

 

[stupoty]

I've held drill bits in slit copper pipe in my three jaw when I have needed to work on the shaft end, worked well for concentricity and grip.