Hi,

I would second the boring option, if you want any hope of achieving any sort of concentricity.? If I understand you, you want to take a 12mm mount ER16 collet chuck, and convert it to a 14mm mount, yes?? And to be able to use it as originally designed, or at use it and maintain the tolerances you were able to achieve??

Using a drill press for this job seems an exercise in frustration. As pointed out by others, neither the drill press nor drills are designed for this type of work.?

I'm sure there are other ways to do this, but here's a couple of suggestions, all of which involve mounting the ER16 chuck and collet and performing a boring operation

You could make bore and tap a rod and mount that onto the headstock spindle. Turn to diameter with a shoulder. If your headstock is properly aligned, you should have a concentric rod/cylinder to mount the ER16 collet/chuck to. Then bore.

Or, a la Joe Pie on youtube - make a bushing to hold a precision ground rod?

Or, you could just buy a new chuck collet with the 14mm threads...because you still have to thread it.

hope this helps

james

On Thursday, April 20, 2023 at 08:57:12 AM PDT, Bill in OKC too via groups.io <wmrmeyers@...> wrote:

Steve pointed out to me that not all of my messages are going to the group, and he thought at least this one should, so here it is!

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)

Aphorisms to live by:

Good judgement comes from experience. Experience comes from bad judgement.?

SEMPER GUMBY!

Improvise, Adapt, and Overcome.
Physics doesn't care about your schedule.
The only reason I know anything is because I've done it wrong enough times to START to know better.

Expect in one hand, expectorate in the other. See which one gets full first.

----- Forwarded Message -----

From: William R. Meyers <wmrmeyers@...>

To: Steve Johnson <steve@...>

Sent: Thursday, April 20, 2023 at 10:23:25 AM CDT

Subject: Re: [Unimat] Widening an existing hole with a drill bit: how to guarantee concentricity?

I have been known to make mistakes about what the OP was looking for, so I went back and looked at the original message. He has a chuck with a pre-drilled hole. I'm guessing that he didn't drill it, so doesn't have the drill. Besides, depending on the the drill, the setup, and how tight the chuck was tightened can all affect how big a hole a drill bit drills when it's used, so getting a accurate hole would be a crap-shoot. Sets of adjustable reamers are relatively cheap, so OP could ream the hole to size, Still be better done in his lathe, which he says is not all together right now...

Maybe we need to find someone near him who can help him out! :)?

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)

Aphorisms to live by:

Good judgement comes from experience. Experience comes from bad judgement.?

SEMPER GUMBY!

Improvise, Adapt, and Overcome.
Physics doesn't care about your schedule.
The only reason I know anything is because I've done it wrong enough times to START to know better.

Expect in one hand, expectorate in the other. See which one gets full first.

On Thursday, April 20, 2023 at 10:06:42 AM CDT, Steve Johnson <steve@...> wrote:

Good point Bill.

Still, providing the M12 hole had never been tapped, use the original bit for centering and bore with the new tap drill size.?

On Apr 20, 2023, at 9:03 AM, Bill in OKC too via <wmrmeyers@...> wrote:

Are you sure about that? The tap drill for an M12x1 tap is 11mm. That is what I used making the collet chuck and faceplate that I worked on. Both fit the Unimat SL spindle. See the Metric fine thread chart here:??I am a bit math-challenged, but that should make the minor diameter 11mm or perhaps a bit more. If it were M12x1.5 or M12x1.75 you'd be closer, but probably not enough to get good concentricity.?

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)

Aphorisms to live by:

Good judgement comes from experience. Experience comes from bad judgement.?

SEMPER GUMBY!

Improvise, Adapt, and Overcome.
Physics doesn't care about your schedule.
The only reason I know anything is because I've done it wrong enough times to START to know better.

Expect in one hand, expectorate in the other. See which one gets full first.

On Thursday, April 20, 2023 at 09:54:10 AM CDT, Elliot Nesterman <elliot@...> wrote:

Without a milling machine or a lathe, achieving perfect axial alignment
will be difficult if not impossible. You can get close, or even perfect
if you're lucky, with a drill press. Drilling by hand you will ruin the
collet chuck.
Drills are not precision instruments. They like to wander, even once
they're in the bore. Guiding a drill by hand to achieve perfect
alignment of any sort is not possible, at least not to machinists'
tolerances.

The minor diameter of M12 is 10.106mm. This is the size of pin you would
need to set the alignment with the drill's quill. A 10mm pin will still
allow 0.1mm, 0.004", of slop. And it's likely that the minor diameter of
the chuck is a bit larger, to ease threading on a spindle nose.
Also, the drill bit should be as short as possible. Drills flex. Using a
screw machine bit (stubby bit) will help.
And, of course, you'll need to find a way to fixture the collet so it is
immobile once it's aligned and on the drill press table. The usual kind
of drill press vice does not hold round objects in a vertical
orientation very well.

Still, as you can find M14x1 collet chucks on Amazon fairly
inexpensively, you won't be out much if the enlarging doesn't work out.

Best of luck.

--
Elliot Nesterman
elliot@...


"The finest jewel cannot disguise a flawed character."