Where to put water temp sensor?

[DanEC]

Looks like I'm going to need a 5/8 inch NPT threaded hole for the sensor. I hope Sears has an appropriate tap and drill bits of 1/2 inch dia.

[tirod]

That's an awful big tap. NPT isn't exactly the same as OD thread or root diameter, it's the nominal dimension for the inside of the pipe itself. 5/8" NPT is big - bigger than half inch water pipe. Which would mean adding the wall thickness and threads, too. That makes 3/4 pipe over 1" hole size.

Plus, I'm not sure how available 5/8" NPT is. NPT- National Pipe Thread Taper- ANSI B1.20.1

FWIW.

[patrickt]

I don't know if you're putting Smiths gauges in there, but I think my Smiths sending unit is UNF thread....

[DanEC]

I have a standard water hose nipple that has a nominal diameter of 5/8 inch on the exterior of the threads - but it might actually be sized as something else - I'm not sure. I'm going to take the nipple down to Sears this afternoon and try to match it up against a tap - see if I have any luck. And then if I can match it up I hope the tap notes the size of drill bit I will need.

UNF threads - huh? Well, I guess they generally have screwed into the standard NPT hose nipple manifold opening or there would be a whole cottage industry built up around re-tapping out Ford intake manifolds. I will visually compare the nipple to the sending unit threads and see how they match up. But yes, they are Smith gages.

Thanks

[patrickt]

Originally Posted by DanEC

UNF threads - huh? Well, I guess they generally have screwed into the standard NPT hose nipple manifold opening or there would be a whole cottage industry built up around re-tapping out Ford intake manifolds. I will visually compare the nipple to the sending unit threads and see how they match up. But yes, they are Smith gages.

This page says that UNF threads can only be used with other UNF threads....
McMaster-Carr

[patrickt]

If it was me, I'd call Peter up at Nisonger and ask him just what the deal is with the funky thread. I know he sells his Smiths stuff with your choice of either 5/8 UNF or 3/8 NPT temperature sensor fittings... so it just might make a difference. Certainly worth the price of call before you start carving. Orrrrr, you could do like the rest of us and just jam the threads in good crossways, use a lot of leak-b-gone goo, and torque it down like crazy.

[DanEC]

Originally Posted by patrickt

This page says that UNF threads can only be used with other UNF threads....
McMaster-Carr

I don't think these are a fine thread tapping. I'm beginning to suspect they may just be a standard coarse UNC tapping (non-tapered) opening.

[patrickt]

Originally Posted by DanEC

I don't think these are a fine thread tapping. I'm beginning to suspect they may just be a standard coarse UNC tapping (non-tapered) opening.

Dunno... but all the Smiths stuff at Gauge Guys comes in BSP and UNF. Smiths Classic Gauges

[patrickt]

This is from Caerbont. I think I remember Bob, Peter, or Doug telling me they built the Smiths gauges that were in my car.



Source: Water Temperature Sender

[DanEC]

Well I didn't remember it looking like a fine thread fitting but maybe it is and the large diameter is throwing me off. Don't work with 5/8 inch bolts every day. Anyway, I will match it up and come up with something that works.

Thanks

[patrickt]

Originally Posted by DanEC

Well I didn't remember it looking like a fine thread fitting but maybe it is and the large diameter is throwing me off. Don't work with 5/8 inch bolts every day. Anyway, I will match it up and come up with something that works.

ehhh, I'd just sink it in a pool of JB Weld.

[DanEC]

I double checked it when I got home and it looks like a 5/8-18 UNF thread adaptor. So much for my 61 year old brain cells. The hieater nipple does look to be slightly tapered so it is probably a NPT piece - but I'm banking on the manifolds being a straight UNF tapping. No luck at Sears but I found a tap and 37/64 drill bit at McMaster-Carr and ordered it. So, with a little luck the JB Weld can stay put away.

[DanEC]

One more question on this subject. I received my UFC 5/8 inch tap from McMaster Car today and it mikes out at .63 inch on outside of the cutting edges. The temp and oil sender fittings mike out at .66 inch OD. Does a .03 inch interference fit seem unusual for a treaded fitting like this? I assumed they would be closer in diameter or identical and I definately don't want to accidently crack this old intake.

Thanks

[patrickt]

Originally Posted by DanEC

One more question on this subject. I received my UFC 5/8 inch tap from McMaster Car today and it mikes out at .63 inch on outside of the cutting edges. The temp and oil sender fittings mike out at .66 inch OD. Does a .03 inch interference fit seem unusual for a treaded fitting like this? I assumed they would be closer in diameter or identical and I definately don't want to accidently crack this old intake.

Thanks

Maybe this? Unified National Fine Thread Chart

[DanEC]

Well, it's not 11/16 inch. I wonder if the sending unit is 17 mm which converts to .69 inch? I may just have to get a 5/8 -18 die and turn down the sending unit so that it matches the tapped hole and doesn't crack the intake.

I talked to Doug at ERA. I should have done this first I guess. He said he usually does this with a 3/8 inch NTP tap. So, I guess it's back to McMasters.