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Triumph TR6 - thread tapping size for oil sending unit

Hi to all in TR6 land

I'm midway through a very busy week off. have spent most waking hours (and some sleeping hours!) working on the car I have sandblasted tons of small pieces with great sucess and I'm picking up the frame to take to the welders tommorow. Also have the head at dynamic in Toronto getting redone The only snag so far is the oil sending unit. I removed it this afternoon to make painting the block easier and to repace with a new one but the thread got buggered up a little at the first thread. the problem is I dont know if its 1/8 pipe thread or a machine thread size. the oil sending unit is buggered or I'd use that in a die to tell me what tap to use Any advice or wisdom would be appeciated. I suppose I could wait until I get the replacement oil sending unit but I was going to plug the hole while I painted the block. thanks for any advice John OMeara
jh omeara


My opinion is for you to wait for the new sending unit. Plug the hole with something for painting.

HP
HP Henry Patterson

John
It's 18 tpi and I'm pretty sure it's 3/8" BSP [British Standard Pipe Thread]
Ron
R. Algie

I don't have a sender unit or block at the house to verify the actual size, but then remembered that I had brought home my handy dandy Aeroquip Port and Connector Identification Kit to identify and inventory a bunch of AN/AS/MS fittings for my brother in law. From that, here are the values for BSPT (British Standard Pipe Tapered)

inch dash nominal male female
size size thread thread thread
size OD inch ID inch
1/8 02 1/8-28 3/8 (.38) 11/32 (.35)
1/4 04 1/4-19 23/64 (.52) 15/32 (.47)
3/8 06 3/8-19 21/32 (.65) 19/32 (.60)

Here are the values for NPT (National Pipe Tapered)

inch dash nominal male female
size size thread thread thread
size OD inch ID inch
1/8 02 1/8-27 13/32 (.41) 3/8 (.38)
1/4 04 1/4-18 17/32 (.54) 1/2 (.49)
3/8 06 3/8-19 11/16 (.68) 5/8 (.63)

Yea, I know that 5/8 is not really .63, but given the way the diameters are measured on tapered threads, two place accuracy is good enough. Thread diamater measurements are taken about half way down the taper. The quick and dirty way to get a feel for the tube and dash size is to measure the thread diameter and subtract 1/4" in both cases. These two standards are close and it is easy to mix them up if not careful. Both rely on thread distortion for sealing purposes so don't screw up with these things.
SteveP

And here I had hoped that it would keep the table format thanks to careful spacing, etc. So much for wishful thinking......

In order, from left to right, are the the corresponding table column headers.

The first fractional number is the nominal tube or pipe size.

The second number two digit number is the tube or pipe dash number size in sixteenths of an inch.

The next fractional number with dash and two digit number is the nominal thread diameter and thread count per inch.

The next fractional number and the corresponding two digit decimal number is the male thread OD.

The last fractional number and corresponding two digit decimal number is the female thread ID.

Get out those calipers and thread gauge and have at it.
SteveP

Ignore my last post I measured the wrong sender unit!!!
Ron
R. Algie

This thread was discussed on 24/03/2005

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