I found this in my tap drawer and I don’t know where it came from. It’s 1/8-27 NPT made by L.S.I. model 8156-A. I’ve never seen one like this, where the narrow end of the tap is on the shaft side. It’s 8 inches long. What’s it for?
Upside down backward NPT tap.
- Thread starter Etchase
- Start date
JSGAuto
Well-known member
Removing a machine setup. Taping from the back side thru a hole.
Or, adding a thread on the inside of a box.
We've used tools like that before.
Or, adding a thread on the inside of a box.
We've used tools like that before.
Jawn
Well-known member
...or possibly aligning the tapped threads to a hole on the other side of a device?
Thanks for all the help. It seems it is used (as Randall Thompson described so well below) in double wall boilers where it provides access and alignment, (2) general avoidance of obstructions like in a box, and/or (3) to utilize a single set up from one side, but needing a fitting from the other side. There is a tool for everything. It is not a bottom tap, nor home made or modified.
How do you buy one of these things?. I tried searches for back, pull, reverse, boiler tap and other terms to no avail. I can’t find L.S.I. Is it possible McMaster Carr doesn’t sell something?
How do you buy one of these things?. I tried searches for back, pull, reverse, boiler tap and other terms to no avail. I can’t find L.S.I. Is it possible McMaster Carr doesn’t sell something?
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oldtractors
Well-known member
Randall is wrong. It is not a staybolt tap. I have no idea what it is for. The tap would have to be fed in from the far side, and if there is enough room for that long of the tap, it seems like there would be enough room to just use a regular tap.
I believe what he was saying is that they used that particular tap to align the threads in the outer was accurately with the hole in the inner wall, not because the access was limited to the outer wall.
JSGAuto
Well-known member
It could be custom (or semi-custom). We use machinery specific tool vendors for such things. You are not going to find it in a catalogue.
I can give them a sketch of a tool, have a quote in a day, and usually 2 weeks later have my custom tool.
I can give them a sketch of a tool, have a quote in a day, and usually 2 weeks later have my custom tool.
mike93lx
ALLIANCE MEMBER
If mcmaster doesn't have it, you can't possibly need it 
WWheeler
Well-known member
And yet so often when they do, I can't afford or at least bring myself to pay what they are asking for it so I wind up shopping for the same item elsewhere.If mcmaster doesn't have it, you can't possibly need it