On Thu, 02 Mar 2006 19:51:41 -0700, Trevor Jones
wrote:

Norm Dresner wrote:

| Does the chuck have a number stamped on it?
|
| Tom

There's an upper case "C" and "K" separated by a stylized drawing of an
elephant head, ears & trunk and underneath is the size "13 m/m"

Norm

On the strength of that information, I will up my bet to TWO American
nickels.

I seem to recall a similar brand mark that apeared on some India made
chucks. 13 mm is soooooo close to 1/2"

Cheers
Trevor Jones

I agree at this point..with Trevor

The simple way to find out..is to stick any MT2 taper gizmo in it and
see if it fits properly.

Gunner, machine tool mechanic.




"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3

According to Norm Dresner :

[ ... ]

Don

I had to drill a hole yesterday and was using a #75 drill. Using my
7-diopter OptiVisor I could see no wiggling of the end of the drill which
should be an indication that the runout is pretty small. I've finally
gotten a dial indicator and magnetic base and I intend to measure the runout
as soon as I can get to it. Since the chuck does in fact close to (pretty
close to) zero and if the runout is as small as I think it is, I'd probably
be a fool to replace anything even though I'd love some more modern
conveniences.

That I find amazing. What brand of 1/2" drill chuck is it which
closes down to grip a #75 drill bit?.

Can you check whether it will grip a #80?

If it does not, you can go for the sensitive adaptor (either the
one in the eBay auction to which I pointed, or another similar one)
which will also give you more control and feel in feeding the drill bit.

I've done down to #70 in the tailstock of my small lathe -- an
Emco-Maier Compact-5/CNC, with a 0-1/8th Albrecht chuck on a #1 MT
arbor. And that worked well enough in 12L14 steel -- but I kept
worrying about the lack of feel that the leadscrew gave me with that
tiny a drill bit, so I was *very* careful.

Good Luck,
DoN.

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--- Black Holes are where God is dividing by zero ---

According to Trevor Jones :
Norm Dresner wrote:

I had to drill a hole yesterday and was using a #75 drill. Using my
7-diopter OptiVisor I could see no wiggling of the end of the drill which
should be an indication that the runout is pretty small. I've finally
gotten a dial indicator and magnetic base and I intend to measure the runout
as soon as I can get to it. Since the chuck does in fact close to (pretty
close to) zero and if the runout is as small as I think it is, I'd probably
be a fool to replace anything even though I'd love some more modern
conveniences.

[ ... ]

One alternative solution to drilling with very small bits is to make an
auxilary table that will raise the work to the drill bit. The last one I
saw was about 2 inches in diameter and used a rack and pinion to lift
the table. it only had about a half inch of travel but would allow at
least some feel, rather than guessing at the feed.

That is actually quite similar to many of the sensitive drill
presses to be found on eBay currently.

I agree that feel is an important consideration with such tiny
drill bits.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

According to Norm Dresner :

[ ... ]

I'm planning on removing the chuck this weekend and measuring the taper.
BTW, while nobody's ever found any reference to a half-size JT, there is
something called a 2-short between #2 & #3.

O.K. That could be what they used -- though Lord only knows why
they would mark that on the machine, when there is a Morse taper socket
in the spindle to allow you to change arbors for whatever size your
favorite drill chuck happens to take.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

replying to Norm Dresner, drillpress wrote:
I also have a JT 2 1/2 Chuck on a Columbia 515 drill press made in Taiwan. I
compared the taper dimensions with the published Jacobs taper dimensions and
found that it was likely consistant with a current Jacobs 6 taper. I
purchased a new Jacobs 6 chuck and it fit perfectly. I have no idea how that
conversion can be explained.

--
for full context, visit https://www.polytechforum.com/metalw...nt-478760-.htm

replying to drillpress, Chitty wrote:
Looking for info on a JT 2 1/2 taper drill chuck also.
Mine is a similar Taiwan marketed in North America.
The Jacobs 2 1/2 taper is its very own taper but used widely in the era on
Japanese configuration but appears to be no longer available these days. The
JT 6 is close but a different bird.
Anyone have any luck?
The spindle on my machine is a one piece unit with the lower end being a male
JT 2 1/2 that is intended to mount the appropriate chuck directly to the
spindle without the typical double ended arbor between the spindle and chuck.
Only option I’ve found is to pull the spindle and hope a machinist can
convert the spindle without error to a modern available taper.
Share your info please!

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for full context, visit https://www.polytechforum.com/metalw...nt-478760-.htm