Frankly, unless things have changed drastically since I was in the shop
(entirely possible!), the thread designation would be something like 1/4-28
UNF (n)A (2A or 3A) I have no clue why it would include SAE (that's
understood by the NF in UNF), and the LT means nothing to me. If you
discover something significant in the LT designation, I'd appreciate you
posting the information. The only thing that comes to mind would be the T
standing for truncated. That's typical of the no-go.
It's a lubrication fitting thread used in automotive and machine tool
applications. Think zerk fitting.
IIRC, it's a tapered thread so there is no "go/not go" ring gages per se.
You would need a set like those used on an NPT thread that not only do
go/no go but also check length.
I would try Johnson Gage <http://www.johnsongage.com/
They are truly the thread gage experts.
The threads are the same, but the fit is better.In the aircraft business-
most lube fittings require
a 3b fit. Holes are drilled smaller than for a normal 2b fit. This allows
more thread to engage
with the fitting. We use the same tap (after testing in a test piece ). If
by chance we screwed up and
a 3b no-go gage would screw in a certain number of turns, usually 2 turns
or more (depending on the depth of threads required) it would receive a
reject tag and need to be redrilled and threaded for an insert.
Hope this helped.
I don't know much about gaging, just what I use for reloading, but when
I have a question, I find that the tech support at vermont gage is very
I email them directly from their website at
they also have tech articles and questions from others answered, so you
may find what you are looking for already there.
Now, if I can just get my loading bench cleaned off.
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