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If you're reading this then maybe you're a muppet like me and have overtightened your brake mount bolts on your expensive fork once too many times (preventative tip: buy a torque wrench!)...
I recently did exactly that and thanks to many posts on this site and others I found the engineering marvel that is HeliCoil! So I decided to go it alone and buy a kit and fix it myself - it's pretty easy to DIY - and I posted a howto here.
(1) First you need to get the kit - I went for the branded original from Screwfix - my post mount screws (like most) are M6 size - which dictates the kit to buy.
(2) Other things that are useful/needed:
- Depth gauge (but could use end of screwdriver at a push)
- Drill (speed adjustable is IMPORTANT)
- Tape (to mark required depth on drill bit and thread tap)
- Hex keys etc
- Some wd40
- Threadlocker (I use locktite 222)
(3) Measure depth of post hole in fork
(4) Mark depth on drill bit and thread tap with Tape
(5) Here goes - DRILL into existing post hole to remove old thread
- I used WD40 as lubricant but the Fox fork lowers are Aluminium Magnesium alloy which is very soft
- Line up drill bit as straight as possible
- GO SLOW with the drill - less is more - take your time
(6) Remove waste from hole with vacuum cleaner/WD40 wash
(7) Tap new thread with Thread tap bit
- Again line up as best possible
- Start slow, keep constant and slow rate of turn
- When at depth, reverse drill direction and slowly reatract bit from hole
(8) Another clean with WD40 and hoover
(9) Put HeliCoil on insert tool, apply threadlocker, screw into hole
(10) Insert tang remover tool, hit with hammer (very little force needed)
(11) Hoover out tang
(12) Refit caliper, apply threadlocker, torque correctly as usual.
Hope this helps!
Or, if you're in Surrey, pay Surrey hills cycleworks a few quid, and they do it for you😁
Done properly it’s an incredibly satisfying job. No way I’d want to pay somebody else to do it!!
Great step by step guide thanks.
One thing there about tapping the thread, I would think you'd be better with a hand held tapper than attaching it to a drill, and I was always taught to do it 1 turn in, back off half a turn and so on to get a good finish. Perhaps this is out of date!
ooh this is interesting
Don't suppose you're in Manchester Reevo and fancy doing one for me too?
Nice one, I did this recently. Very satisfying.
I can't stress the hoover/wd40/CLEAN OUT THE SWARF thing enough.
Thanks! I don't need to do this, but I know what the thin part of a Vernier caliper's for now. Not sure how I never knew that.
tis good but very brave of you using the tap in a drill. i would have done it by hand.
Nothing wrong with using a drill for tapping. If you have a good drill it is very easy to control. You can even set the max torque. I've tapped hundreds of threads like that. The softer the material the better it works. It's easier to keep straight than a hand tap, too. No need to go right to the bottom of the hole though, that's where you risk stripping it, just go deep enough for the helicoil
One thing there about tapping the thread, I would think you’d be better with a hand held tapper than attaching it to a drill, and I was always taught to do it 1 turn in, back off half a turn and so on to get a good finish. Perhaps this is out of date!
When I did the hose screw I just hand reamed then tapped.
It’s much much softer than steel so you can get away with more than 1 forwards 1/2 back though 2-0.5 is normal for mild steel from what I remember.
When I drill 7075 cranks I find you need to back off further to clear the crud and really slow to prevent melting. Tapping for pedal inserts again hand reaming works fine and quick.
Nice write up, I did this a couple of months ago after some heavyhandedness. Took the forks off and clamped em in a vice though. As others have said, tapping by hand seems the way to go (and yes very satisfying when it works!).
Would an old bolt thru type adapter bolted on to the undamaged thread help line up the bit and keep it straighter well drilling.
Also threadlock on caliper bolt might undo the helicoil, I always use grease torqued up correctly and never had a caliper bolt come loose.