Tapping a Tappered Thread

[Oneball]

I need to fit a union into a diff case. How do I tap a tappered thread? Most of the procedure will be as per normal but how do I know how far down the tapper to go is there a diameter based on the union I’m using or something similar.

[Exminiman]

I need to fit a union into a diff case. How do I tap a tapered thread? Most of the procedure will be as per normal but how do I know how far down the tapper to go is there a diameter based on the union I’m using or something similar.

Dont take this as gospel, others please chime in, but I think the thread in casing is actually tapped as parallel and plug or fitting you screw in is tapered- or other way round.

[Spider]

I measure the dia of the fitting at 5/8's to 3/4's of the thread length and then measure the tap for that same dia. I'll then put a mark on the tap with a felt tip marker and tap to about 2 - 3 thread short of that and test. If need be, go a bit more.

If there's more than one hole, after getting to that happy place on the first hole, I'll mark the tap with some tape while I have it in that first hole.

The taps for Taper Threads are Tapered.

There's likely a better and proper method, but the few that I do, that's all I've done.

Is this for an Air Locker on the diff ?

[Oneball]

Thanks both.

It’s not for a Mini, it’s for a diff cooler on a Corvette race car I’m building, thought I’d ask here as you all generally know what you’re doing. Will still be racing the Cooper but thoughtd I’d see what power but no handling is like.

[Exminiman]

This thread, sorry for the pun

Is quite good, need to get about halfway down

https://www.pistonheads.com/gassing/top ... 3&t=972367

[Oneball]

This thread, sorry for the pun

Is quite good, need to get about halfway down


https://www.pistonheads.com/gassing/top ... 3&t=972367

Thanks.

[Ronnie]

As Spider say's the taps are tapered pictures here >>> https://www.google.com/search?q=bspt+ta ... 9&bih=1252

[Oneball]

Thanks I was going for a 6AN to 1/4 NPT union as it’s a Yank mobile.