Thread cutting advise / tools

Hi ALL, to start with, I hope your all doing as well as you possibly can in the current situation and I wish you all the best

I have this valve here:



One side has a thread of 1/4" sae, this is the side I need to work with, what I need to do is drill and tap a plastic block, screw this in and try make a tight seal, as I have no access to the other side / inside of the block, any tips on the best way to do this to get a good tapered seat for this to seal on. also what size/type drill bit and tap would need

I also have a pressure gauge that I might need to use with this, the gauge has 1/4 bspp thread with a small aluminum sealing washer, again need advise on drilling and tapping, as this has flat seal do flat drill bits exist for doing this kind of work




Thanks

The thread that you have labeled "SAE" seems to be a straight thread, NOT TAPERED. Tapered (pipe) threads are used for sealing, not straight threads. From the looks of your fitting, it is probably some kind of compression or flare (tubing) fitting. The seal is intended to be made at the tip which is tapered (chamfered). You probably need to work with that area for your seal and just use the threads for mechanical holding, as they were intended. I am not sure what you are doing or what you are sealing in (gas, liquid, or ??) or the pressure involved. Those may have a lot to do with how you make your mating hole. You could consider things like a simple mating taper (conical surface), an O-ring, rubber washer, or just a lot of pipe sealing compound. I don't think making a mating surface is a job for a drill press: it should be done in a lathe or milling machine with the proper tooling.

Another thought is to remove that fitting and use one that is more suited to your needs; probably one with pipe threads on both ends.

Flat drill bits do exist. They are called counterbores and will have a pilot section to guide them so you need to drill that pilot size first: you are going to need a central opening anyway. There are other (better?) ways to do this but they require a milling machine or a properly clamped set up on the drill press. An end cutting milling cutter could be used in these set ups.

7/16-20 UNF, 45 degree flare

Thank for the info guys, on the 7/16-20 UNF, whats the "20"

The fitting is the same as an aircon, fridge/freezer gas recharge valve, pressure wise, nothing, its vacuum I'll be pulling through it but only down to -15 psi and its only to test for leaks, the plastic block will also have a ball valve. Im just a little confused about drill bit and tap size as there are so many out there, would like to buy new both the drill bits and taps for both, Ive tried looking on charts but that confuses me

Thanks again

20 threads per inch. And good luck getting below 0 psi... Atmospheric pressure is 14.7....complete vacuum is 0. Using relative pressure as you are, 14.7 psi below atmospheric (or -14.7) is as far as is possible.

Thanks for the info, yes I understand about the atmospheric pressure, I'll be using a 0 to -1 bar gauge and a couple of small ball valve taps.

Im sorry that Im only an amature that wants to build a little project for a hobby and Im not on the level that you guys are at, I can understand your frustration when an idiot like me pops up and starts asking questions, I'll do my best to keep the questions to a minimum if that's OK

Thanks again

deltap said:

7/16-20 UNF, 45 degree flare

Click to expand...

IIRC, 45 deg. is for LP gas and NG. 37 deg. is for JIC which is used for hydraulics up to 5000+ psi.

Since the seat is a smaller diameter than the minor diameter of the thread, you could make a 45d spade drill for the seat, then tap the threads.

liteace said:

Thanks for the info, yes I understand about the atmospheric pressure, I'll be using a 0 to -1 bar gauge and a couple of small ball valve taps.

Im sorry that Im only an amature that wants to build a little project for a hobby and Im not on the level that you guys are at, I can understand your frustration when an idiot like me pops up and starts asking questions, I'll do my best to keep the questions to a minimum if that's OK

Thanks again

Click to expand...

It's all good. We all started somewhere. Besides, you must be near world record in lurker status. 10 year member with 5 posts?Now that's what I'd call keeping it to a minimum!

Anyways, watch what plastic you use, some are not good for vacuum apparatus usage.

Its that grey plastic, same as whats used on drainage pipes, the reason I use it, I have loads of off-cuts from a factory that make the pipes, Ive used it before and it worked but before I have plastic hose with pipe clips. I could do the same again but as I have loads of time at mo so I'd like to build something a little better

Thank

liteace said:

Hi ALL, to start with, I hope your all doing as well as you possibly can in the current situation and I wish you all the best

I have this valve here:

View attachment 283508

One side has a thread of 1/4" sae, this is the side I need to work with, what I need to do is drill and tap a plastic block, screw this in and try make a tight seal, as I have no access to the other side / inside of the block, any tips on the best way to do this to get a good tapered seat for this to seal on. also what size/type drill bit and tap would need

I also have a pressure gauge that I might need to use with this, the gauge has 1/4 bspp thread with a small aluminum sealing washer, again need advise on drilling and tapping, as this has flat seal do flat drill bits exist for doing this kind of work

View attachment 283509


Thanks

Click to expand...

I had a similar situation and because of it aircon not cooling, it was still necessary to have the right pressure. I was thinking of using an O-ring, a rubber washer, or just a lot of pipe sealing compound.
This must be done on a lathe or milling machine with the appropriate tooling. Remove this fitting and use the one that is more suitable for your needs; possibly with a pipe thread at both ends. Here are the best ways to do this, but they require a milling machine.I was more lucky in this case, I was helped by my friend, who is a pro in this