Chasing threads with a greased tap

[MisterCinders]

I am concerned that my spark plug threads are wearing and/or cross-threading. With all the tuning and re-jetting, I am in and out of those plug holes quite a bit.

Ordinarily, I screw the plugs in lightly by hand and use a wrench only for the final turn. My plugs usually spin right in to a stop and then need barely a single turn for full tightening.

Lately, at least one of the plugs will spin in to a finger pressure stop but, instead a firm turn to finish, feel like they want to give more. IOW they are willing to take a level of torque that is more than hand pressure, but not the usual full stop.

Before I push that issue and strip something, it seems that cleaning up the threads with a tap would be best. I found some threads about doing this without removing the head (which I don't want to do), and they suggest using grease on the tap to capture any cutting bits or shavings.

How exactly does this work? I think it means to apply grease to the bit and go in and out gradually to drag the shavings up the threads instead of pushing them down into the cylinder. Is that right? What other steps should I take?

TIA

[Agemax]

yep, greasing the tap will catch any tiny bits of swarf or shavings in the fluted part as you run the tap through. just do it slowly and carefully and in stages, removing the tap regularly to remove any bits that do get caught up in the grease.

[Wallowgreen]

Put a timesert in one side of my 250 using the grease method. Works a treat so long as you use plenty of grease and, as already mentioned, remove the tap regularly to clean off the grease and apply fresh.

250 fired right up afterward and has been running great ever since.

Good luck.

[bwringer]

DON'T USE A TAP!

Use a thread chaser -- it is designed to gently clean up existing threads. A tap is designed to remove metal to create new threads.

[Johno]

Use a thread chaser

Check this previous thread

http://www.thegsresources.com/_forum/showthread.php?t=195089

[oldpara]

I agree with Bwringer, use a thread chaser. (Or use what you want)
It will reform/cleanup the threads more than recut the threads.
If you have or can get a GO/NoGo guage for that thread size work that in and out a little at a time slowly, lubed well.

[argonsagas]

Yes, a thread chaser is better if there is sufficient material available.


Grease is really a good way to avoid bits of falling metal however, and if you need to use a tap, then that is the way to go.

Use a soft grease and fill the flutes in the tap with it so everything that is removed will be trapped in the grease.