Did look up the drill & tap charts found on 'net.

I did find a store that supply 37/64" drill for 3/8-18 NPT tap but boy
that is only an HS drill costs 30 CDN !? (snap-on canada) but does
have both taps there but no 45/64" drill for 1/2-14 NPT tap. Sheesh.

The plan with these is occasional job. Like cleaning up 3/8 NPT
thread on a engine head aluminum is very soft. Other times have to
make a brass threaded sleeve with 3/8" female thread out of male brass
1/2 NPT plug and drill out the ruined plug hole (this happened already
to mine and in process asking here now) to size and tap with 1/2-14.
This 3/8-18 NPT hole is used either for coolant temp sensor or a 3/8
NPT plug, but this location also is useful for purging air out of
cooling system & filling with coolant after any service that required
coolant drained. I can anneal the brass plug with propane torch or
stove top coil glowing orange for a short time.

But I wonder is this possible to use available drill bits (1/2" for
3/8-18 NPT tap in annealed brass and 1/2-14 with bit larger drill bit
for aluminum) and really go slow & gentle and frequent backing up on
tapping with plenty of cutting oil?

Depth is around 50% for 3/8-18 otherwise any deeper the tip of sensor
would hit the thermostat. Doesn't matter for the brass sleeve because
I will cut it to length after drilling & 3/8-18 female internal thread
cut a 1/2-14 NPT plug.

The key is to get these taps within canada and hopefully use readily
available drill sizes.

The key is to get water-tight seal using telfon tape, not for
precision job.

Merry-xmas & Cheers,

Wizard (Jason Pero)

If you really don't want spend the money, I'd keep looking, if I were
you. You must have a source in Canada like Harbor Freight or MSC or
ENCO or J&L or ?. Some machinery suppliers even carry a line of
inexpensive (you get what you pay for) drill bits.
Maybe even drop into some local machine shop and ask if they've go
the sizes you need that have been shortened by repeated grinding or have
buggered up shanks.
Actually, I have used such needs over the years as a excuse to get
sets of things like drill bits by the 64th, etc.. Over the years
you'll never remember the cost, but you certainly will remember the
times you needed a size you didn't have, late at night or on a Sunday.

Pete Stanaitis
---------------

Jason D. wrote:

Did look up the drill & tap charts found on 'net.

I did find a store that supply 37/64" drill for 3/8-18 NPT tap but boy
that is only an HS drill costs 30 CDN !? (snap-on canada) but does
have both taps there but no 45/64" drill for 1/2-14 NPT tap. Sheesh.

The plan with these is occasional job. Like cleaning up 3/8 NPT
thread on a engine head aluminum is very soft. Other times have to
make a brass threaded sleeve with 3/8" female thread out of male brass
1/2 NPT plug and drill out the ruined plug hole (this happened already
to mine and in process asking here now) to size and tap with 1/2-14.
This 3/8-18 NPT hole is used either for coolant temp sensor or a 3/8
NPT plug, but this location also is useful for purging air out of
cooling system & filling with coolant after any service that required
coolant drained. I can anneal the brass plug with propane torch or
stove top coil glowing orange for a short time.

But I wonder is this possible to use available drill bits (1/2" for
3/8-18 NPT tap in annealed brass and 1/2-14 with bit larger drill bit
for aluminum) and really go slow & gentle and frequent backing up on
tapping with plenty of cutting oil?

Depth is around 50% for 3/8-18 otherwise any deeper the tip of sensor
would hit the thermostat. Doesn't matter for the brass sleeve because
I will cut it to length after drilling & 3/8-18 female internal thread
cut a 1/2-14 NPT plug.

The key is to get these taps within canada and hopefully use readily
available drill sizes.

The key is to get water-tight seal using telfon tape, not for
precision job.

Merry-xmas & Cheers,

Wizard (Jason Pero)

KBC Tools 1-800-668-5616
http://www.kbctools.com/canada/home.cfm

1-001-037 37/64 HS IMPORTED JOBBER DRILL $6.51

1-050-045 45/64 HS DRILL STUB SM $19.41


"Jason D." wrote in message
...
Did look up the drill & tap charts found on 'net.

I did find a store that supply 37/64" drill for 3/8-18 NPT tap but boy
that is only an HS drill costs 30 CDN !? (snap-on canada) but does
have both taps there but no 45/64" drill for 1/2-14 NPT tap. Sheesh.

The plan with these is occasional job. Like cleaning up 3/8 NPT
thread on a engine head aluminum is very soft. Other times have to
make a brass threaded sleeve with 3/8" female thread out of male brass
1/2 NPT plug and drill out the ruined plug hole (this happened already
to mine and in process asking here now) to size and tap with 1/2-14.
This 3/8-18 NPT hole is used either for coolant temp sensor or a 3/8
NPT plug, but this location also is useful for purging air out of
cooling system & filling with coolant after any service that required
coolant drained. I can anneal the brass plug with propane torch or
stove top coil glowing orange for a short time.

But I wonder is this possible to use available drill bits (1/2" for
3/8-18 NPT tap in annealed brass and 1/2-14 with bit larger drill bit
for aluminum) and really go slow & gentle and frequent backing up on
tapping with plenty of cutting oil?

Depth is around 50% for 3/8-18 otherwise any deeper the tip of sensor
would hit the thermostat. Doesn't matter for the brass sleeve because
I will cut it to length after drilling & 3/8-18 female internal thread
cut a 1/2-14 NPT plug.

The key is to get these taps within canada and hopefully use readily
available drill sizes.

The key is to get water-tight seal using telfon tape, not for
precision job.

Merry-xmas & Cheers,

Wizard (Jason Pero)


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"Jason D." wrote:

Did look up the drill & tap charts found on 'net.

(snip)

Some years ago, I drilled some holes that were to be pipe tapped in a
later operation. I got the drill size (don't remember the NPT
involved)from a standard pocket guide. The guy who was to tap them said
I drilled 'em wrong, his pocket guide called for a bigger drill. We
showed this to the foreman, who checked his own reference, which listed
a third size! With NPT, the hole is a cylinder, the thread is tapered,
so going up or down a drill size is not likely to cause a problem.

David

David R. Birch wrote:

Some years ago, I drilled some holes that were to be pipe tapped in a
later operation. I got the drill size (don't remember the NPT
involved)from a standard pocket guide. The guy who was to tap them said
I drilled 'em wrong, his pocket guide called for a bigger drill. We
showed this to the foreman, who checked his own reference, which listed
a third size! With NPT, the hole is a cylinder, the thread is tapered,
so going up or down a drill size is not likely to cause a problem.

I picked up some surplus tapered reamers apparently designed to ream
holes prior to tapping for NPT. This makes the tapping much easier on
both the tap and my arm. Could the smallest of the drill sizes you
encountered be intended for use prior to reaming?

Ted