Re: It's Running.... Re: Interpolating a blind hole for tapping


"Proctologically Violated©®" <UNfitcat@xxxxxxxxxxxxxxx> wrote in message
news:4a1d6de6$0$5902$607ed4bc@xxxxxxxxx

"Proctologically Violated©®" <UNfitcat@xxxxxxxxxxxxxxx> wrote in message
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Dudes,

Not a biggie, and even I can do something like this, just curious about
opinions on strategies.

For an electrical fixture part.
5/8-27 nps thread -- try finding DAT on a drill chart!
About .5" of thread, will mill/drill hole .650 deep.

Basically the OD of the tap measures .630, and we will start with a .590
hole (.020 thread depth), and finagle from there, mating-wise, with the
test fitting.

Because of the shitty set up (only 2pcs per cycle), I want to minimize
tool changes and dispense with a pilot drill, and drill (or helix) down
with a 5/16 2-flute end mill. About 260 pcs.

I see two ways to do this:

"Drill" straight down in z close to the circumference, and do
rough/finish passes.
The Q here is: how many pecks in the rough? (no pecks in the finish, I
presume).
Or:
Helix down in rough, then a full depth finish pass.
The Q here: what Z per helix revolution?

Which will give the fastest hole? Suggested speeds/feeds?

I've already programmed in the helix method, as I have an idea this is
better for chip clearance (and ergo higher overall feed?), but I'll go
with any consensus here.

Yeah, I scrapped the helixing in, in part because one suggestion here was
.05 in Z per rev, which would have been like 13 revs, so a la KG and
others, I just went in with a 2 fl 1/2 em.

I have noticed that for good accuracy, I often have to do multiple finish
passes at the final finish dimension.
Two finish passes, in this case, and even on the last pass I can still
hear a bit of a buzz!

Also, I did two G4P500's (one after roughing, one after the last finish
pass) to blast the hole clean before tapping.

So, three tools: I chamfered first, w/ .75 drill. Then interp, at the
full .64 depth, then tap .5 deep.
The finish diam pre-tap is .590. The stuff is coming out good. Will be
tumbled.

Note, tho, that when interpolating with an em just slightly smaller than
the finish diameter, the programmed speeds have to be fairly modest, mebbe
even downright low, because they define the ipm for the tool path
centerline, NOT the actual resulting *tangential* feed, which can be
*much* greater.

Mebbe cadcam figgers this out in advance.

I actually am not running this job, I just set it up.
All my buddy's KMB1 hurcos are on the fritz (those muthafuckas just seem
to EAT $1300 circuit boards), his tapping heads gone/bustid, and he found
out my fadal has rigid tapping..... :(
And he has my truck..... <sigh>

Thanks all.

Oh, perhaps an inneresting footnote:

This hole is on one face of an alum cylinder for a lighting fixture.
The other face got two 1/8-27 nps holes, which call for an S tap drill.

You can't imagine how long it took to find an effing drill that would give
the right effing diameter!! Holy shit...
Almost wound up having to interpolate *that* hole!
Or having to use a reamer.

Not the best 115 pc drill set, but wow, what variations. Some bits drilled
on the money, others .010 over-size. .010!!

And then, when all was said and done, the tap itself seemed to be loose-ish
for the sample male thread provided.
Man, what an ordeal, that was "solved" by basically saying, Fugit, it's good
enough....

--

Mr. PV'd

Mae West (yer fav Congressman) to the Gangster (yer fav Lobbyist):
Hey, Big Boy, is that a wad (of cash) in yer pocket, or are you just
glad to see me??







.

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