On 5/3/2011 3:52 PM, John Doe wrote:
Lots of questions about tapping this.

2017 aluminum collar/rod
64 mm length (about 1" will be used)
22 mm outer diameter
8 mm inner diameter

The rod will be pushed into the hub of the skate wheel and the
assembly will screw onto the arbor of the cordless drill. That
looks like a more simple and efficient way to mount the wheel.

http://www.flickr.com/photos/27532210@N04/
http://www.flickr.com/photos/27532210 N04/ (sign removed)

I need to thread the 2017 aluminum collar described above.

For what it's worth, I have this little tap and die set.
http://www.lowes.com/pd_232550-1083-...ductId=1065037

Is the collar's 8mm inner diameter appropriate for 3/8 inch 24
thread?

Not really.

This tap & drill chart online-
http://www.newmantools.com/tapdrill.htm
says that the standard drill size for 3/8-24 is a #Q drill bit

which this drill chart online-
http://bobmay.astronomy.net/misc/drillchart.htm
says is .332" inch.
Note that it also indicates that a #Q drill is 8.4328 mm diameter, so an
8mm hole is -probably- too small to attempt with a cheap tap.


Otherwise, what size drill bit?

Can the inner diameter be accurately enlarged simply by drilling
into the 8mm collar hole? There was a recent thread about that, I
think, but the discussion was not perfectly clear to me.

Sure, in a lathe.
Possibly close enough, in a milling machine with a coax indicator.
Not freehand.


Searched Amazon for "3/8 24 thread tap".
(Other online merchant reference links are invited.)

For regular-length taps, I like the Hertel spiral-point taps at Enco. A
3/8"-24 is about $7.50. They have a better cutting edge than the usual
China generic straight flute taps, but 8mm is still quite a bit
undersized of a hole.


Union Butterfield okay?

The thread length will be 1", or greater if doing the whole 64 mm
collar at one time (I guess not).

If you can find a thin-shank tap you could tap most of the 64mm length.
A regular 3/8" tap won't go that deep though. You cannot tap in from
both ends, because the threads won't match up in the middle.

You can try to search eBay for 3/8-24 pulley taps, there's some for $10.
You can grind the shank diameters down on a bench grinder. Also note
that many pulley taps are usually plug or bottoming taps, and you may
need to start the threads with a regular-taper tap.

If the threads must be straight, you'll need a machine-guide to do
that,,, a tapping press, a drill press, a mill or a lathe.


The tap finish, like black oxide, makes no difference for tapping
into 2017 aluminum?

tap finish doesn't matter much really, at least for hand tapping


A tapered tap is unnecessary since it is a long hole? The main
concern is that the collar/wheel assembly is secure and centered
on the drill arbor, so that the wheel spins without bouncing. A
very close collar& arbor fit would be nice.

Im not sure of the question, but it sounds like you want a lathe here.


Is "H4" better than "H2" for this?

In taps, the "H" number is the measure of looseness, or oversize of the
tapped threads. Increasing numbers mean increasing looseness. I would
suggest H1 if you can find one, but H2 & H3 are the more common fit
sizes (common zinc-plated hardware store bolts are probably H3-H4 fit).


Thanks.