Re: [CAD_CAM_EDM_DRO] CNC Threading question for Jon...

http://www.micro100.com/

Go down the page to the orange box, select threading tools.

Scroll down the left hand list and under threading tools select Mills.


Those cutters apparently have min and max thread pitches. (Makes
sense...) The miminum pitch on the TM250 is 0.025 (40 TPI) The maximum
thread pitch on the TM250 is 40 thou, 25 TPI. Apparently it wouldn't do
a 5/16-18 TPI, for example. It would do 5/16-24 though, but it would be
reaching... It would just fit in the hole for 5/16, which is about
17/64". The TM-250 would do 3/8"-24, but not 3/8-16.

I wonder how picky the cutter is about the max pitch ? These cutters
look nice, but the combination of their diameter and the limitation of
the thread depth doesn't make them useful for many thread size/pitch
combinations. Am I missing something ????

I'm working on a canned helical threading routing for TCNC. (I did one,
ie G76 for external threading on the lathe and I did a helical milling
routine as well... this is "just" a combination of the two.)

I'm wondering if one could attain a deeper (ie coarser) thread with the
standard TM-250 mill if one did multiple passes, offset in the Z axis if
necessary, the way that one offsets the lathe threading bit when doing a
G76 routine ?

For example, could one do a first cut, go back to the start position
offset a bit up (ie cut "depth" tan 29 degrees) take a second cut, go
back to the start position, offset a bit down, take another cut, etc ???

I'm wondering (aloud) if the TM250 depth/thread pitch rating is based on
cutting all the thread in one pass ?

BTW: there looks to be a free(?) program for generating helical thread
patterns for machines that don't have a built in canned cycle for doing
such.

I'd love to be able to automate some/most of our threading with a single
$45 tool and some custom GCode routines... I don't care if it is a bit
slow because it needs multiple passes. I'm just tired of having people
turning taps by hand.

For one off prototype work, I wonder what is a better way to automate
thread cutting: tapping head, "rigid" tapping or thread milling with one
of these single row thread mills ? *IF* one can get coarser pitches
with multiple passes, a single thread mill would cut all threads, metric
and imperial 5/16" and above (within reason) with only one tool
change/setup.

Kim

On Wed, 2003-10-22 at 11:31, Jon Elson wrote:
> Kim Lux wrote:
>
> >No offense taken, Jon ...
> >
> >Now to be a total hypocrite: in our CNC threading conversation, you
> >mentioned an ROW thread mill that was good for all threads above 1/4".
> >Could you expand on that ?
> >
> >
> I have to make a picture of this thing. It is a "single row" thread mill.
> Made by "micro 100", who make a wide variety of solid carbide small
> cutting tools. Their part # is TM-250. I got mine from somebody,
> but I can't figure out whose catalog number is on it. But, MSC has it
> as their catalog # 81262164 for $44.
>
> I needed to thread material for an oddball thread, something like
> 3/8-28, and got this thing, and ran a test, which came out quite well.
> I later found a tap that size on sale for a very reasonable amount.
> So, the mill did not get used for that job, but it proved the technique
> would work quite well, and I have a program that will generate the
> G code for it.
>
> If you look up that part # at MSC, they have a picture of the thing on
> the detail listing. It has 4 teeth in a single row, like a tiny
> double-angle
> cutter.
>
> >If you are busy, just give me a brand name, maybe a supplier...
> >
> >
> See, when people ask me something, I do the research for them!
> (Don't ask me WHY I do this!)
>
> Jon
>
>
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