Making a sensitive drill for lathe advice request

[Christianstark]

Hi all,

So after numerous broken drills, I have decided to make a Joe P style sensitive drill for my lathe. The chuck I am using is a tiny 0 to .25 Llambrich , and I ordered a 0JT to 1/2” straight shank arbor. My thinking was to machine a 3MT adaptor to insert directly into my tail stock, and ream to .501 for a no slop slip fit. Alternatively, I could fit 5/8” into my keyless chuck, and ream that to .501.

First, what do you suggest here?

Second - If I were to machine the 3MT insert, would you recommend:

Drill to pre ream size, ream. Then machine the MT in same set up with fat side towards tail stock,, test fit on my pass through headstock dead center adaptor, and part off? This would include machining a “tang” on one side just smaller than the small diameter of a 3MT, and then flip it and put in an ER40 collet for drilling, reaming, and machining the taper. Once the hole is reamed I could chamfer and use a live center for support while machining the taper for the tail stock, but would need to remove it to test fit.

Or

Machine the 3MT first, and then flip the part and mount it in my head stock 3MT adaptor after fitting, seat with brass mallet, and then drill, and ream from tail stock? This could risk breaking the taper and galling, but I doubt forces would be that high.

Or

Something completely different.

Thoughts?

 

[mmcmdl]

I made 2 with 1/2" straight shanks . They are both on the lower right hand side of the picture next to the small Albrecht . I just cut , drilled , bored and reamed an old busted up MT3 drill that I had lying around . Works fine for me .

 

[Christianstark]

I made 2 with 1/2" straight shanks . They are both on the lower right hand side of the picture next to the small Albrecht . I just cut , drilled , bored and reamed an old busted up MT3 drill that I had lying around . Works fine for me .

 

[Christianstark]

Nice! I don’t have a tail stock drill I could repurpose for that. If my machining fails miserably, I may try that. I assumed an old drill would be hard to machine though. Is it softer in the middle?

 

[Bi11Hudson]

I use a sensitive drill on a regular basis. Mine was bought as a complete kit. The chuck is rated as 4mm, but will handle up to 3/16 inch. The shank is 8mm, 5/16", straight. That allows me to use it numerous places, lathe, several drill presses, milling machine, and hand drills. In my case, it works well for me, your use may be completely different. The straight shank allows it to be used in a common drill chuck any where.

.

 

[mmcmdl]

Tapers are soft . ( machineable ) I have a straight shank to a MT3 internal taper that was very handy in doing these type of G jobs . Perhaps you could put out a word on here that you need a broken MT3 shank drill . I'm sure someone has a few that the drill itself is trash .

 

[MrWhoopee]

I made mine from the 1/4" Jacobs chuck off an old B&D drill. It's threaded 3/8-24, so I made a 3/8 straight shank. Then made a 1/2" OD x .375 ID sleeve for it to slide in. Chuck the sleeve and feed the chuck by hand. Just the thing for those tiny drills.

 

[Christianstark]

 

[Christianstark]

 

[Bi11Hudson]

That looks more like a 1/8 or 6mm drill. Large to my thinking. I was in mind of a drill smaller than Nr 60 or 1mm. For big stuff I have a drill chuck that is mounted on bearings. Essentially the same as a live center but with a chuck. Ready to use it, I grab the outside of the chuck. If it feels like it's struggling, I let go. Brass is bad for digging in. When I release the chuck, it spins with the work and can be drawn out under power. A freewheeling chuck is usually thought of as a waste. But I have several uses for it. Not the least is friction welding small stock. . .

.