Making an M18x1.5 thread cleaning tap

[Just for fun]

I screwed up the other day working on my Bronco project. I welded in a O2 sensor bung to my header reducer and got it a little too hot. The threads look ok but have kind of a mill scale look to them. I could probably force the sensor in, but I would rather clean up the threads.

So, my plan is to make a cleaning tap. I'll turn some stock to M18x1.5 and then mill 3 slots length wise and then heat treat. Since I have never did any heat treating before (I'll watch some YouTube first) will it distort the threads? The other thing is, I'm not sure what I have for stock, will 12L14 work? Other than that, I probably only have mystery metal. Or maybe a larger US bolt that I could turn down.

I don't think it will take much to clean up the threads, maybe even turning an M18x1.5 and a couple slots would do it without even hardening.

 

[benmychree]

You need to use a material that will harden with heat treatment; 12L14 is not that metal. Material from a high grade bolt might do it.

 

[aliva]

try using 4140

 

[Just for fun]

Thanks, I did look up heat treating 12L14 after I posted and seen that it was a no go. I might see if I have a large bolt to turn down and thread. Like I said I don't think it will take much. But then again...... If it doesn't work on the first try, I may have to resort to buying a piece of 4140, it never hurts to have extra stock anyway,

 

[Just for fun]

If I buy some 4140, I want the Annealed stuff, right? I see online metals has Heat treated stuff also.

 

[ChazzC]

Thanks, I did look up heat treating 12L14 after I posted and seen that it was a no go. I might see if I have a large bolt to turn down and thread. Like I said I don't think it will take much. But then again...... If it doesn't work on the first try, I may have to resort to buying a piece of 4140, it never hurts to have extra stock anyway,

For quick & dirty, why not start with an M18-1.5 hard bolt?

 

[Jim F]

Lisle makes a thread chaser, $16 bucks.

 

[Nutfarmer]

Grade 8 bolt with a cut off blade slot ground a little deeper than threads in four places. Looks kind of like a tap , but the flutes are just slots

 

[pontiac428]

If the bung is stainless (the only way to build an exhaust system) then a chaser might really make a mess of things- use a tap. If it's steel or cast iron, it'll be fine. You're going to want to use sensor-safe anti seize for certain if chasing removes any passivation to save trouble down the road.

 

[Huub Buis]

Just for cleaning up a steel thread once, even a not hardened steel tap will do.