On Thursday, April 16, 2015 at 9:37:37 AM UTC-7, Jim Wilkins wrote:
"jon_banquer" wrote in message
...
On Thursday, April 16, 2015 at 4:39:56 AM UTC-7, Jim Wilkins wrote:
wrote in message
...
On Wed, 15 Apr 2015 17:15:10 -0400, "Jim Wilkins"
wrote:

"whit3rd" wrote in message
...
On Wednesday, April 15, 2015 at 6:26:25 AM UTC-7, Joe Gwinn
wrote:
In article ,
Ignoramus18077 wrote:

On 2015-04-13, Don Foreman
wrote:
On Sun, 05 Apr 2015 07:47:14 -0500, Ignoramus10114
wrote:

I have an aluminum heatsink that I need to tap , I wanted
to
know if I
should use 6-32 or some less coarse thread like 8-32 would
be
better?

I go the other way with aluminum -- I use forming taps, not
cutting
taps, and lubricate with soft wax made for the purpose.

But, a heatsink might require a very flat top surface; a
forming
tap
will raise
the surface slightly as it deforms the material, so it might
not
be
suitable
for this particular application (unless a second operation
follows,
to
flatten the mating surface you've just disturbed).

http://www.katonet.com/article/mindrilltapping.html
"Good machining practice dictates that a countersink be provided
at
the top of the tapped hole. Countersinking is recommended before
tapping to create a good starting thread."

Easier said than done, though.

-jsw

easier said than done? How? Hit the top of the hole with a
countersink, or a drill a few sizes bigger than the hole if you
can't
afford (or can't find ) a countersink. Best done in the drill
press,
but for crying out loud it's "just" aluminum - you can do it with
the
drill bit in your bare hand if you have to.

My Clausing 8525 mill lacks a DRO to easily repeat a pattern so
countersinking after drilling is a tool change at each location
that
loses precise depth on blind holes, since the chuck jaws move down
as
they tighten. I don't have countersinks with shanks as long as
drills,
to cut before hitting the depth stop, and there isn't enough quill
travel to allow hand countersinking or clearance to swap chucks and
arbors.

Maybe I should buy a set of intermediate length center drills to
use
as countersinks and spotting bits. I have only the long ones. Burrs
on
steel deflected larger drill bits.

I do swap the drill, countersink and tap on through holes.
Hand-tightening the chuck is enough to start a tap straight by
pulling
on the drive belt.

-jsw


Use extensions with collets:

http://www.mscdirect.com/product/det...gle-PLA+-+Test


My first model Clausing 8525 is limited by its low spindle to table
height and B&S7 collets. It's very nice for milling small parts in a
home shop but the working envelope is smaller than a mill-drill's.

I could do that on a Bridgeport if I could fit one in my basement.

-jsw



I'll take your word for it, Jim. I don't really have any experience with the home shop type machine you mentioned. I've always used what commercial machining job shops have available.

When I setup production jobs on a Bridgeport Series I I used collet extensions to solve the issues you described.