Thread: Trying to plumb my brake system?

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Since pipe threads are tapered, it doesn't take much to cause the results you are having.

It seems to me that the standards for manufacturing of these threads are all over the place. There is also something known as "tolerance stackup". All manufactured things have a high and low range on their acceptable size. Get one part on the small side and another on the big side and you get just what you are experiencing. There are also different classes of fit for all threads. Some are intended to fit better than others.

If you are sure that both parts are 1/8 x 27 pipe, then you may have to buy a 1/8 pipe tap and tap the threads a little larger. I've had to do that many times. Just be very careful. Pipe thread size can sneak up on you. Very easy to get the female part oversize. Just take care not to get metal shavings inside what you are tapping. Grease packed in the flutes of the tap will help trap cuttings.

I know that sounds bad considering that both parts are supposed to go together, but that's the reality of building anything, especially cars. Many parts that are supposed to "bolt on", simply don't. That's a fact of car building life.

Here's an example. I have 2 parts out in my shop that are listed as fitting a stock Mustang II front end. One is an aftermarket spindle and the other is an aftermarket adjustable ball joint. They are by different manufacturers. Both parts will work on a stock front end just barely, but they will not work together. I'm going to have to ream the spindle to fit the ball joint.