Thread Chaser or Tap?

I’m an idiot, there I’ve said it.

I’ve managed to damage the first couple of threads on one side of my pivot bearing axle when I was drifting it out to replace the bearings last night. At the moment, it’s looking like I might be struggling to get a replacement so I’m starting to wonder about trying to salvage the situation.

I have used a tap and die set before, c. 1985 ‘O’ Grade Metalwork, Denny High School. I think I got a ‘C’ in the end.

I’m aware that a Tap is primarily designed to create new threads, so at the moment I’m looking at these thread chaser things, designed to repair the existing thread. However, the problem is that I can’t get the bolt to catch the first couple of threads that are damaged and I believe the Chaser would have the same problem as from what I’ve read about them, they need to catch those first couple of threads?  So, in this situation, would / should I be using an M6 tap to repair the damaged M6 thread?

Any advice would be gratefully appreciated

Cheers

Craig

I usually start with a right angled pick. Get it in thete at a clean bit of thread, and work backwards, picking out/pushing back any loose bits of thread. It’s usually pretty successful.

Is the hole blind? Any chance of getting in from the other side?

Sounds like you’d have more luck with a tapered tap.

Other options might include drilling out the first couple of threads if there’s enough further down to hold the bolt. Or, if it’s fully threaded from one side to the other, running some threaded bar through from the good side.

Or drill out entirely and helicoil

What I think you should do:

Submarined +1, can you clean out the thread a bit with a pic?

If not then if there’s enough thread left deeper in the hole then countersink it until you’re down to decent threads.

What I would actually do:

Brute force the tap into the hole and cut whole new threads.

That won’t always work in a blind hole though, if your taps are tapered they won’t bite into the threads further down which may/may not mean you end up with missaligned threads that the bolt may just strip out.  You’d need a tap designed to bottom out in the blind hole.

I’ve got o do the leaf spring mounts on the Midget at the weekend, I suspect someone has at some point tried to force a M8 bolt in to a 3/8 UNF hole ………. wish me luck!

I damaged a thread like this as well.  What I did was get a pal who is a really good mechanical tech / engineer ( RAF trained) to help.  He cleaned it up with a pick and a thread file, filed a taper on a bolt of the right thread and cleaned up the thread with a die and then used that bolt to clean up the thread.

I consider myself a decent mechanic but I knew I was in danger of damaging this further so got help

Got any photos?

Got any photos?

I think what you mean is This Thread is Useless Without Pictures.

This Thread is Useless Without Pictures.

:good:

There should a clapping emoji

Is the thread accessible from the other side? Run a tap through and it will re cut the thread straight. If you only have access from the damaged side run a spiral point tap through, it’s tapered so should pick up the good thread. If not drill out thread and helicoil.

I think what you mean is This Thread is Useless Without Pictures Pitch-ers

Ftfy

I think what you mean is This Thread is Useless Without Pictures Pitch-ers

Yes that was the joke…

Your pedantry is lame AF

You want one of these https://www.ebay.co.uk/itm/362687224152

Don’t think a thread file won’t work because they’re designed for OD, not ID i.e. bolt threads, not nut threads

Can you get in from the other side? Picture would help, you surely have a bit of thread to get into, it’s just part of the diameter that’s ruined, not the whole thing right?

Thread chaser would be better than a tap as you risk making it even worse. Helicoil might also work but depends on how much meat there is, again, a pic would help