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Tapping a Tappered Thread

Posted: Thu Jan 16, 2020 4:24 pm
by 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.

Re: Tapping a Tappered Thread

Posted: Thu Jan 16, 2020 4:55 pm
by Exminiman
Oneball wrote: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.

Re: Tapping a Tappered Thread

Posted: Thu Jan 16, 2020 5:01 pm
by 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 ? :shock:

Re: Tapping a Tappered Thread

Posted: Thu Jan 16, 2020 5:08 pm
by 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.

Re: Tapping a Tappered Thread

Posted: Thu Jan 16, 2020 6:13 pm
by Exminiman
This thread, sorry for the pun :D

Is quite good, need to get about halfway down

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

Re: Tapping a Tappered Thread

Posted: Thu Jan 16, 2020 6:24 pm
by Oneball
Exminiman wrote:This thread, sorry for the pun :D

Is quite good, need to get about halfway down


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

Re: Tapping a Tappered Thread

Posted: Thu Jan 16, 2020 7:44 pm
by Ronnie
As Spider say's the taps are tapered pictures here >>> https://www.google.com/search?q=bspt+ta ... 9&bih=1252

;)

Re: Tapping a Tappered Thread

Posted: Thu Jan 16, 2020 8:43 pm
by Oneball
Thanks I was going for a 6AN to 1/4 NPT union as it’s a Yank mobile.