So I have this little spindle that I wanted to make some accessories for,
and checked the size a couple of different ways, and came to the conclusion
that the thread is 5/16-32.

I tapped the hole with a new tap, and was ready to fit the part.. Ahh****,
no Worky.

The thread checks sure looked correct. I wondered how far off a 0.75mm pitch
was, and it isn't 32 TPI but 33.866.

I didn't have much more than 1/2" of thread to examine, and the 32 TPI tap
even matches the 0.75mm pitch fairly closely.

--
WB
..........

"Wild_Bill" wrote in news:HeRor.293664$5f3.191913
@en-nntp-12.dc1.easynews.com:

So I have this little spindle that I wanted to make some accessories for,
and checked the size a couple of different ways, and came to the conclusion
that the thread is 5/16-32.

I tapped the hole with a new tap, and was ready to fit the part.. Ahh****,
no Worky.

The thread checks sure looked correct. I wondered how far off a 0.75mm pitch
was, and it isn't 32 TPI but 33.866.

I didn't have much more than 1/2" of thread to examine, and the 32 TPI tap
even matches the 0.75mm pitch fairly closely.

Counting the threads in 1/2" is sufficient to tell the two apart: 16 if it's 32 tpi, 17 if it's 0.75mm
pitch.

"Doug Miller" wrote in message
. ..
"Wild_Bill" wrote in
news:HeRor.293664$5f3.191913
@en-nntp-12.dc1.easynews.com:

So I have this little spindle that I wanted to make some accessories for,
and checked the size a couple of different ways, and came to the
conclusion
that the thread is 5/16-32.

I tapped the hole with a new tap, and was ready to fit the part..
Ahh****,
no Worky.

The thread checks sure looked correct. I wondered how far off a 0.75mm
pitch
was, and it isn't 32 TPI but 33.866.

I didn't have much more than 1/2" of thread to examine, and the 32 TPI
tap
even matches the 0.75mm pitch fairly closely.

Counting the threads in 1/2" is sufficient to tell the two apart: 16 if
it's 32 tpi, 17 if it's 0.75mm
pitch.

Where ever possible I use a thread gage. If it doesn't fit cleanly that
isn't it.

"Wild_Bill" wrote:

So I have this little spindle that I wanted to make some accessories for,
and checked the size a couple of different ways, and came to the conclusion
that the thread is 5/16-32.

I tapped the hole with a new tap, and was ready to fit the part.. Ahh****,
no Worky.

The thread checks sure looked correct. I wondered how far off a 0.75mm pitch
was, and it isn't 32 TPI but 33.866.


I feel your pain. I have a 5/16-36 tap here for the Hornady lock and load tool for
determining the OAL for seating a given bullets against the lands or more often a bit
behind.

Then there is the tap I *thought* would be the right size to make a holder for my other
rear aperatures for my AR. Wrong tap. Need to figure out correct one.

At least I was 50% on my recent special tap buy, beats zero.

Williams rear aperature sights use a 7/32-40 thread just to add content.

http://www.jtsmach.com is a good place for decently priced special taps.

Wes

On Fri, 4 May 2012 09:50:33 -0700, "Bob La Londe"
wrote:

"Doug Miller" wrote in message
...
"Wild_Bill" wrote in
news:HeRor.293664$5f3.191913
@en-nntp-12.dc1.easynews.com:

So I have this little spindle that I wanted to make some accessories for,
and checked the size a couple of different ways, and came to the
conclusion
that the thread is 5/16-32.

I tapped the hole with a new tap, and was ready to fit the part..
Ahh****,
no Worky.

The thread checks sure looked correct. I wondered how far off a 0.75mm
pitch
was, and it isn't 32 TPI but 33.866.

I didn't have much more than 1/2" of thread to examine, and the 32 TPI
tap
even matches the 0.75mm pitch fairly closely.

Counting the threads in 1/2" is sufficient to tell the two apart: 16 if
it's 32 tpi, 17 if it's 0.75mm
pitch.

Where ever possible I use a thread gage. If it doesn't fit cleanly that
isn't it.


I have, on occasion, re-tapped an existing hole for 1/8 pipe from 28
tpi to 27 tpi - use lots of dope!

After revisiting and examinating the threaded area, the threaded section
spans about .380".

The measuring "errors" were due to due to an assumption that the thread
pitch was 32 TPI.
Not being aware that a metric thread was so close to 32, I jumped to the
conclusion that it was 32.

--
WB
..........


"Doug Miller" wrote in message
. ..

Counting the threads in 1/2" is sufficient to tell the two apart: 16 if
it's 32 tpi, 17 if it's 0.75mm
pitch.

I'd used a digital caliper, 5/16-32 screw, and an Enco/India gage, and the
thread count wasn't obvious over the short section of thread.

I've been aware of the close aproximation of 5/16" and 8mm as far as wrench
sizes and fastener diameters, although just not familiar with the 0.75mm and
other fine thread pitches (apparently there is also a 0.5mm pitch but don't
think I've encountered that).

The threads mated eventually, after running the tap thru the part
supplemented by
a little pushing and pulling applied to the tap.

I'll make another workpiece when I get the correct taps and use the goofy
one for something else, 'cuz in HSM metalworking, there really isn't much
that needs to be scrapped.. nearly everything can be repurposed.

--
WB
..........


"Bob La Londe" wrote in message
...
"Doug Miller" wrote in message
. ..
Counting the threads in 1/2" is sufficient to tell the two apart: 16 if
it's 32 tpi, 17 if it's 0.75mm
pitch.

Where ever possible I use a thread gage. If it doesn't fit cleanly that
isn't it.

Also, being able to tap a hole slightly oversize, to accomodate SAE
fasteners in place of sloppy metric threads is handy.
I don't understand how tapped threads turn out grossly oversized on China
equipment, but it's fairly common, IME.

--
WB
..........


wrote in message
...

I have, on occasion, re-tapped an existing hole for 1/8 pipe from 28
tpi to 27 tpi - use lots of dope!

Howdy, Wes.. I haven't seen much of your presence lately.. and my news
reader missed this reply, but I saw it in the Goog threads.

I definitely wouldn't want to be making similar threading mistakes on
valuable parts, that's for sure.
Luckily, my error was a cheap lesson.. well, this time anyway.

Yep, JTS has a lot of inventory.. I discovered them when they began listing
a limited amount of tooling on eBag years ago, and they've been a fairly
popular supplier.
Their taps and reamer inventory covers sizes that many other suppliers don't
stock.

--
WB
..........


I feel your pain. I have a 5/16-36 tap here for the Hornady lock and load
tool for determining the OAL for seating a given bullets against the lands
or more often a bit behind.

Then there is the tap I *thought* would be the right size to make a holder
for my other rear aperatures for my AR. Wrong tap. Need to figure out
correct one.

At least I was 50% on my recent special tap buy, beats zero.
Williams rear aperature sights use a 7/32-40 thread just to add content.
http://www.jtsmach.com is a good place for decently priced special taps.
Wes

wrote:
On Fri, 4 May 2012 09:50:33 -0700, "Bob La Londe"
wrote:


"Doug Miller" wrote in message
. ..

"Wild_Bill" wrote in
news:HeRor.293664$5f3.191913
@en-nntp-12.dc1.easynews.com:


So I have this little spindle that I wanted to make some accessories for,
and checked the size a couple of different ways, and came to the
conclusion
that the thread is 5/16-32.

I tapped the hole with a new tap, and was ready to fit the part..
Ahh****,
no Worky.

The thread checks sure looked correct. I wondered how far off a 0.75mm
pitch
was, and it isn't 32 TPI but 33.866.

I didn't have much more than 1/2" of thread to examine, and the 32 TPI
tap
even matches the 0.75mm pitch fairly closely.


Counting the threads in 1/2" is sufficient to tell the two apart: 16 if
it's 32 tpi, 17 if it's 0.75mm
pitch.

Where ever possible I use a thread gage. If it doesn't fit cleanly that
isn't it.



I have, on occasion, re-tapped an existing hole for 1/8 pipe from 28
tpi to 27 tpi - use lots of dope!

Sounds like you re-tapped 1/8" BSPT? or BSPP?, which was adopted as the
international standard, to 1/8" NPT. Maybe a good move in the US as the
fittings are likely far easier to obtain as long as the application is
not demanding.

"Wild_Bill" wrote in message
...
I'd used a digital caliper, 5/16-32 screw, and an Enco/India gage, and the
thread count wasn't obvious over the short section of thread.

I've been aware of the close aproximation of 5/16" and 8mm as far as
wrench sizes and fastener diameters, although just not familiar with the
0.75mm and other fine thread pitches (apparently there is also a 0.5mm
pitch but don't think I've encountered that).

The threads mated eventually, after running the tap thru the part
supplemented by
a little pushing and pulling applied to the tap.

I'll make another workpiece when I get the correct taps and use the goofy
one for something else, 'cuz in HSM metalworking, there really isn't much
that needs to be scrapped.. nearly everything can be repurposed.

Sorry, I saw that you did check it after I made my post.






WB
.........


"Bob La Londe" wrote in message
...
"Doug Miller" wrote in message
. ..
Counting the threads in 1/2" is sufficient to tell the two apart: 16 if
it's 32 tpi, 17 if it's 0.75mm
pitch.

Where ever possible I use a thread gage. If it doesn't fit cleanly that
isn't it.

"Wild_Bill" wrote in message
...
Also, being able to tap a hole slightly oversize, to accomodate SAE
fasteners in place of sloppy metric threads is handy.
I don't understand how tapped threads turn out grossly oversized on China
equipment, but it's fairly common, IME.



I threw away a whole set of Chinese taps a couple months ago because they
were all larger than their marked sizes.





--
WB
.........


wrote in message
...

I have, on occasion, re-tapped an existing hole for 1/8 pipe from 28
tpi to 27 tpi - use lots of dope!

On Sun, 06 May 2012 00:17:34 +0100, David Billington
wrote:

wrote:
On Fri, 4 May 2012 09:50:33 -0700, "Bob La Londe"
wrote:


"Doug Miller" wrote in message
. ..

"Wild_Bill" wrote in
news:HeRor.293664$5f3.191913
@en-nntp-12.dc1.easynews.com:


So I have this little spindle that I wanted to make some accessories for,
and checked the size a couple of different ways, and came to the
conclusion
that the thread is 5/16-32.

I tapped the hole with a new tap, and was ready to fit the part..
Ahh****,
no Worky.

The thread checks sure looked correct. I wondered how far off a 0.75mm
pitch
was, and it isn't 32 TPI but 33.866.

I didn't have much more than 1/2" of thread to examine, and the 32 TPI
tap
even matches the 0.75mm pitch fairly closely.


Counting the threads in 1/2" is sufficient to tell the two apart: 16 if
it's 32 tpi, 17 if it's 0.75mm
pitch.

Where ever possible I use a thread gage. If it doesn't fit cleanly that
isn't it.



I have, on occasion, re-tapped an existing hole for 1/8 pipe from 28
tpi to 27 tpi - use lots of dope!

Sounds like you re-tapped 1/8" BSPT? or BSPP?, which was adopted as the
international standard, to 1/8" NPT. Maybe a good move in the US as the
fittings are likely far easier to obtain as long as the application is
not demanding.
All kinds of oddball stuff comes to light saturday mornings. Some
useful, some just interesting.

Meh, not a big deal, Bob. Like I mentioned in my reply to Wes, it was a
cheap lesson.

--
WB
..........


"Bob La Londe" wrote in message
...

Sorry, I saw that you did check it after I made my post.


"Bob La Londe" wrote in message
...

Where ever possible I use a thread gage. If it doesn't fit cleanly that
isn't it.