1/4" or 1/8" NPT probe,what did you choose and why?

[fencebuilders]

Another choice to be made on the gauge install. Any one with a quick/clear synopsis between the two size probes? Thanks

 

[KKlepfer]

I used the 1/4 because if I stripped the threads I could always retap w/ the 1/8th. This doesn't seem logical. One would think 1/8 is smaller than 1/4, but for some reason in my head 1/4 is smaller when it relates to NPT. Oh well, in any case I used whatever one is smaller.

 

[Gary - K7GLD]

Readout response time can be MUCH faster with the 1/8 probe...

 

[rbattelle]

1/4 inch NPT takes a 7/16 tap drill. That's a big hole to drill. IIRC, 1/8 npt uses 5/16... more resonable in my book.

 

[nickleinonen]

Originally posted by rbattelle

1/4 inch NPT takes a 7/16 tap drill. That's a big hole to drill. IIRC, 1/8 npt uses 5/16... more resonable in my book.

11/32" is actually the size needed for the 1/8" npt. 5/16" will work sorta, but you'll be carving a lot out with the tap

 

[ThomasLawrence]

I used the 1/4 because if I stripped the threads I could always retap w/ the 1/8th.

1/8" NPT is smaller than 1/4" NPT (almost exactly half the size )



Now, the OD of an 1/8" NPT fitting is actually a little bigger than 1/4" (pipe sizes reflect the ID of the pipe). However, the OD of a 1/4" NPT fitting is over 1/2".



At any rate, the general consensus is to use an 1/8" NPT probe



-Tom

 

[ThomasLawrence]

11/32" is actually the size needed for the 1/8" npt.

As long as we're splitting hairs, 11/32" is the recommended hole size for 1/8" straight pipe threads. Most probes use a tapered thread, which, "technically", calls for a letter Q drill, . 332". 21/64" is the closest fractional size, at . 328" (. 004" isn't going to matter in cast iron, or darn near any other material. You'll probably hog the hole out by a few thousandths anyway with a hand drill). 11/32" will leave a hole . 343", which just means the fitting will sit a little deeper in the manifold (because of the tapered threads).



In the end, cast iron being as soft as it is, either 5/16", 21/64", or 11/32" will work.



-Tom

 

[nwjetboat]

My X-monitor came with 1/4" NPT pobe. I am with most of this crowd, and would like to use an 1/8" coupler.

Does anyone know if BD makes 1/8" version? Because of the connector to the x-monitor, I cannot simply buy another T/C and use it.

Did everyone with X-monitor use the 1/4" style?

 

[RankRam]

I used the 1/4" and have had no problems.



Also I'm very happy with the X-Monitor.