Helicoil Excercise

Last week I noticed that the brake pad ‘pin hanger plug’ was missing from the rear brake calliper. This was no surprise because I knew that the threads in the caliper were stripped and so far I’ve kept the ‘pin hanger’ and plug in with Loctite. Fortunately, the 'pin hanger' itself was still there.

I’m about to undertake my first attempt at helicoilling. I bought a kit for size M10x1.0x1D (you’ll need to look it up). Anyhow, the helicoil inserts wouldn’t in fit into my ‘test hole’ so I tried it out on a M10x1.25x1.0 hole and it fitted. The kit obviously came with the wrong size thread pitch Helicoil. Doh!

My new OEM ‘plug’ has arrived and I’m waiting on delivery of some M10x1.0x1.0D and M10x1.0x1.5D helicoils. The depth of the threaded hole is 15mm so I’m hoping that the 1.5D helicoil will do the job.

We all know how easy it is to strip threads in alloy and this excercise will give me, and others, some confidence in helicoilling. I'll let you know how it goes.

On the other hand I could be looking at a new rear calliper. Yikes!  

"Anyhow, the helicoil inserts wouldn’t in fit into my ‘test hole’ so I tried it out on a M10x1.5x1.0 hole and it fitted. The kit obviously came with the wrong size thread pitch Helicoil. Doh!"

Just to clarify, your "test hole" was tapped out with a 10mm metric fine thread ?

Well, that's where it gets complicated. The thread diameter is 10mm, the pitch is 1.0. I'm assuming that 1.0 is classified as a metric fine thread pitch.

Pitches of 1.25 and 1.50 seem to be more common.

(I've edited my post from 1.5 thread to 1.25) Test hole.

Are you saying that a 1.0 pitch can vary depending on whether it's a fine thread or coarse thread?

From what I can remember @ 10mm a pitch of 1.0 is metric fine, pitch of 1.25 is an Asian fine(where ever they use them) and a pitch of 1.5 is standard.
I can confirm that Monday when I contact my supplier.

Be safe, be seen!

I suppose you can always rely on Honda to choose a 'not so common' option!

BTW, your supplier? Are you in the mech business?

There are better thread repair kits Heilcoil tend to be a onetime use thing as they can crack when loosening bolts over time. Ever hear of Time-sert repair kits? It's a threaded insert and they work very well but kit price is over a $100 US and each one is specific to that size and thread pitch. Google it. Hope it goes well.

Was, retired now(but still potter), always been in maintenance since I started my apprenticeship @ 16 yrs old, motor trade, agricultural, plant hydraulics, electrics, self taught electronics, building computers, diagnostics(scanners), fabrication and fitment mig tig and arc, I could go on lol.
So I know a few things and where to get em!

I also try to learn something new each day. keep the grey matter active.


Be safe, be seen!

I did look into time-sert kits but the price is prohibitive. I'm hoping that a helicoil will suffice as there is very little torque required for this job.

I know that helicoils can be removed with a tool called a 'jiggery-pokery' but I'm hoping I won't need one of those.

I have been sat here pondering your problem as I have the same issue with a spare rear caliper for my Burgman.
So.
15mm wide strip, cut from a drinks can(thinner the better) long enough to roll into a tube, see where I'm going...
Insert tube into damaged hole, screw new pin into whole, should go tight, then screw cover in and finally trim excess drinks can tube.

Seems to work ok in my case.

Worth a try, I'm happy its tight enough for road use, not sure I would trust it if the hole had been cleaned out with a drill, but the remains of the thread lock the "bodge" tight.

Hope this helps.

Be safe, be seen!

Well, my new helicoils have arrived and they fit using my test holes. After doing some more measuring I'm ready to go. My biggest fear is making sure I drill the hole out perpendicular (accurately) as I'm doing this in situ!

If I mess it up I could well be using your drinks can method.

I had to Helicoil a 6mm starter bolt hole on my Burgman today, not the easyist place to work on.
Pictures save a lot of typing.






All is now well "in the hood"


Be safe, be seen!

I'm sorry to say that my helicoil excercise was 'almost' successful.

The opening coil managed to 'jump' a thread while installing it. The hanging pin went in OK but it wouldn't go all the way to the blind stop. Consequently, the pin head stopped short. It is sitting almost at the edge of the hole and so there is no room for the plug to go in. This is due to the taper of the tapping tool.

All is not lost though. The hanging pin is a 'very tight fit' so I can't imagine it falling out due to vibration, or whatever. It's certainly doing its job. I'm happy with the repair but I'll look out for a second hand rear caliper when the mood takes me. So, for now, job done.

Bought a used rear caliper today so that's my next project, but there's no rush