Anyone ever hear of a 1/8-28 NPT tap or die?

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  #1  
Old 06-03-03, 05:11 PM
MikeVB
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Anyone ever hear of a 1/8-28 NPT tap or die?

I have a compressor with a 1/8-28 NPT fitting and I need to find a way to convert it to fit into a standard fitting such as a 1/8-27 NPT or a 1/4" NPT. Any idea who sells one of these?

I have looked into it and the only 1/8-28 I have found is a 1/8-28 BSP (British Standard Pipe) tap but it differs from our 1/8-27 NPT in that it has a 55 degree pitch in the threads where ours is 60 degrees. I put a 28 TPI thread pitch gauge on this fitting and it fits perfect and appears to have the same pitch threads as the gauge so I am assuming it is 60 degrees.

Any ideas?

Thanks

Mike
 
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  #2  
Old 06-03-03, 09:59 PM
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Mike:

I've never had to be concerned about the thread pitch on a pipe thread as NPT is a standard pitch.

What make of equipment is this thread on and where was it made?
 
  #3  
Old 06-03-03, 10:06 PM
MikeVB
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Greg,

It is a Jun-Air silent compressor and they are made in Denmark.

They are very quiet and very expensive.

Jun-Air Compressors

I wonder if they tooled a 1/8-28 just so people would have to buy their air lines?

Mike
 
  #4  
Old 06-04-03, 06:59 AM
NutAndBoltKing
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Smile Whitworth's

I believe your 1/8-28 fitting is a Whitworth Thread.

Can't see it, so I could be wrong, but I think it's BSPP, British Standard Parallel Pipe, not NPT.

Looking for a tap or die?

Whitworth Thread taps and dies are available almost anywhere, on-line from e-taps.com
 
  #5  
Old 06-04-03, 05:12 PM
MikeVB
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Re: Whitworth's

Originally posted by NutAndBoltKing
I believe your 1/8-28 fitting is a Whitworth Thread.

Can't see it, so I could be wrong, but I think it's BSPP, British Standard Parallel Pipe, not NPT.

I took the fitting to work today and had our machinist look at it.
He said it is metric and is not pipe threads. He said it is a 9.5 x .9 M according to the measurements.

Mike
 
  #6  
Old 06-04-03, 08:00 PM
MikeVB
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NutAndBoltKing,

The male fitting coming out of the compressor head and the male fitting that connects to the air tank measure .380" and .378" respectively on my dial calipers.

The braided air hose that connects them has a measurement of .345" I.D. on both ends.

Both my 28 TPI standard thread pitch gauge as well as my .9M metric thread pitch gauge fits the threads.

Mike
 
  #7  
Old 06-04-03, 09:53 PM
NutAndBoltKing
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Happy to see you found the correct thread sizing for your piece.

I couldn't see it, so I went by your statements that you had a 1/8-28 fitting on an import. It's been my experience that 1/8-28 BSP, either BSPP or BSPT, appear on imports; and 1/8-28 BSPs are Whitworth's 55 degree thread form. Whitworth thread is VERY close to many other types - it even appears to be a match or at least looks to be interchangeable with them - but are not.
 
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