Drill depth vs. cut tap depth in blind hole

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Awl --

Given a desired tap depth, is there a formula for the drill depth?

Along those lines, here is a ditty I use for tapping.
R8, R9 establish the relationship between drill and tap depths in subroutine
L200, and get passed to the Z's in the drill/tap cycle, preserving the
relationship.  This also minimizes the error of changing one, and not
changing the other.

I have chosen a drill depth 50% greater than the tap depth.
Normally, I would assign these numbers to V variables, and later pass those
on to R variables, but with no real calculations, this isn't really
necessary here.

Feel free to critique the tapping code, as I have no idea why shit is the
way it is, just that it works.

N13L200

N14#R8=.48'    tap depth

N15#R9=1.5*R8'    drill depth

N16M17

N21M30

N22( MAIN PROGRAM

N31M6T21( #21 DRILL

N32L201

N33G0X0Y0Z3.H21E2M3S1500

N34Z1.M8

N35Z0.1

N36G83G98R+0.1Z-R9F7.5Q0.45(   <------   R9

N38G80

N39(

N40M6T20( TAP, 10-32

N41L201

N42G0X0Y0Z3.E1H20

N43Z1.G4P500

N44G0G90G80M90S2000.2M5

N45G84.2

N46Z0.4M8

N47G84.1G98R+0.1Z-R8S1000.2F31.25(   <---------  R8

N49G80M9

N50Y4.

N51M6T2


--

Mr. PV'd

Mae West (yer fav Congressman) to the Gangster (yer fav Lobbyist):
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Re: Drill depth vs. cut tap depth in blind hole
Proctologically Violated wrote:
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http://www.rose-training.com/tandp/aug06.htm

--


Regards,
Steve Saling
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Re: Drill depth vs. cut tap depth in blind hole


Proctologically Violated wrote:
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PV:

    I generally make the cut tap depth 2/3 of the drill depth for blind
holes.  Essentially identical to your drill depth being 50% greater
than your tap depth.

    I've got a whole slew of "hooks" to pull threads out of blind holes,
from modified saw blades down to paper clips with small hooks on them.
  Also have a series of air nozzles going down to .050" OD to try and
blow them out.

    Trapped chips in blind holes is the ONE best reason for switching to a
form tap.  Then you can run the form tap right down to near bottom, I
generally go down to the depth of the outer dia. of the drill's cutting
lips.
    When engineers get crazy with their full thread depth callouts I'll
often modify form taps to cut full threads to within .030 of  the
bottom of the hole (after helical milling the hole to get a flat
bottom).  That last little bit usually has to be done by hand.
    
    There's always the option of thread milling, no problem with trapped
chips, and you don't have to drill the hole much deeper than your
thread depth. Those puppies seem to cost about 10 times what a tap does
though.  Snap a couple of those off and you'll be depressed for the
whole day.    :)

--
BottleBob
http://home.earthlink.net/~bottlbob


Re: Drill depth vs. cut tap depth in blind hole
BottleBob wrote:

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Crochet hooks. They're available in numerous sizes.

Store them next to the lipstick for sticky collets for a little feminine
touch in your tool box. I keep my silly putty for proofing mold
engraving in the same area too. :)

--
Black Dragon

Your chances of getting hit by lightning go up if you stand under a tree,
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Re: Drill depth vs. cut tap depth in blind hole

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Interestingly, I've found Vaseline to be much more useful than lipstick...

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Re: Drill depth vs. cut tap depth in blind hole
Bipolar Bear wrote:

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In that case, store them next to the Vaseline for sticky collets for a
little bi-curious touch in your tool box...

--
Black Dragon

I finally got it all together...
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Re: Drill depth vs. cut tap depth in blind hole


Black Dragon wrote:
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BD:

    Well now, that's a real machining TIP that I've never heard before.
Someone should start making a list.    <g>

    Actually, thinking about it now I've got like a .125 Dia. stainless
rod that I've modified the end (which resembles a knitting needle tip),
that I use for yanking thread chips out of larger holes.

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    Have you ever found a machining related use for tampons?   :)

--
BottleBob
http://home.earthlink.net/~bottlbob


Re: Drill depth vs. cut tap depth in blind hole
BottleBob wrote:

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Count me out! I've had my fill of lits for a while. :)

Quoted text here. Click to load it



New? Or used? <g>

--
Black Dragon

The magic of our first love is our ignorance that it can ever end.
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Re: Drill depth vs. cut tap depth in blind hole


Black Dragon wrote:
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BD:

    Yetch!  I'll NEVER get that imagery out of my mind now.  :(

--
BottleBob
http://home.earthlink.net/~bottlbob


Re: Drill depth vs. cut tap depth in blind hole

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In the oil patch, a box of feminine napkins are usually around for soaking up
blood from
an injury.  As far as tampons, any drive by shooters near your shop? ;)

Wes

Re: Drill depth vs. cut tap depth in blind hole
snipped-for-privacy@lycos.com wrote:
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Do you remember the old TV show "Combat"?
I was just a kid but recognized the "bandages" they pulled out of their
kits.
RR


Re: Drill depth vs. cut tap depth in blind hole
wrote:

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From James Harvey's book I use a drywall screw.  Works even better if
you grind off the head and use them in a cordless drill.  1/4-20 or
bigger anyway.

Thank You,
Randy

Remove 333 from email address to reply.

Re: Drill depth vs. cut tap depth in blind hole


Randy wrote:

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Randy:

    I made a cork-screw looking chip remover, a pain to make and didn't
work all that well anyway.  Wish I had thought of the drywall screw
idea, sounds like a winner.

--
BottleBob
http://home.earthlink.net/~bottlbob


Re: Drill depth vs. cut tap depth in blind hole
BottleBob wrote:
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It works ok but does anyone make them with a left-hand thread?
RR


Re: Drill depth vs. cut tap depth in blind hole
Randy Replogle wrote:
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Randy, How about running the drill in reverse?

Best,
Steve

--


Regards,
Steve Saling
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Re: Drill depth vs. cut tap depth in blind hole


Garlicdude wrote:
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GD:

    Probably wouldn't work well.  It would tend to PUSH the chips DOWN
rather than pull them up the thread spiral.  Think corkscrew in reverse.

--
BottleBob
http://home.earthlink.net/~bottlbob


Re: Drill depth vs. cut tap depth in blind hole
BottleBob wrote:
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Bob, Running in reverse would LIFT the chips up, but the screw wouldn't self
feed into the chips.

Best,
Steve

--


Regards,
Steve Saling
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Re: Drill depth vs. cut tap depth in blind hole
Garlicdude wrote:

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"Lift" meaning chips/strings unscrewing themselves out of the hole?
Probably so. I was thinking about a left-handed screw biting screw into
the mess and unscrewing it. Instead of a right-hand screw running
backward to unscrew the mess, how about something like a phillips
screwdriver bit or maybe a drill blank with a left-hand drill type tip
or spade tip ground into it?
RR


Re: Drill depth vs. cut tap depth in blind hole


Garlicdude wrote:
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GD:

    Right after I hit the send button I thought GD was probably joking and
I took him too literally.


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    Now from THIS response it seems likely that while you have me on your
hook, you're wiggling it a little to watch me squirm.

    But for your "squirm" watching pleasure, I'll continue.  :)

    If you take a regular right-hand screw and stick your thumbnail  in
the thread (simulating a chip), and screw it clockwise (like screwing
it INTO a hole), your thumbnail will travel UP the screw like a chip
would.  But if you turn it in reverse (like UNscrewing it) your
thumbnail will move DOWNWARD.
    
    Now having said THAT, IF you could displace the chips sideways INTO
the existing threads you "might" get a lifting assist by the threads
themselves.  BUT, thread chips are usually crammed down in the hole
below where the threads end, so that's an ify situation.

    I don't have any access to any chips, threaded holes, screws, or
anything else right now to actually test this.

    
--
BottleBob
http://home.earthlink.net/~bottlbob


Re: Drill depth vs. cut tap depth in blind hole
BottleBob wrote:
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Bob, Not trying to hook you, but watching the screw flights on a large wood
screw it appeared to me that the flights would lift chips out of the hole.


Best,
Steve

--


Regards,
Steve Saling
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