Failure of a thread on the gear housing.

May 2019

A thread on the gear housing that enables attaching the blade/strimmer guards has failed, so guards are only held by the other two screws.

Spoke to ?? on ?? who suggested taking to shop and not to try it myself as it needs specialised work. ?? Although I said I was pretty sure I could do it, it was reiterated that I could not it and should not try. I said I would send an email but never got around to it. Continued using for another few stretches of hours.

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July 2019

1. 2nd July Spoke to Guy on 2nd. This conversation was a little more practical and confirmed the bolts were 5m but no info on the thread width|TPI
   Looks like 32TPI (0.8mm)
2. 2nd July Ordered a 5mm helicoil kit after confirming thread was standard 0.8mm
3. 5th July Collected 5mm helicoil kit £21 from
4. 6th July Repair successful

Although it is labelled as 'Made in Australia' it adds "Parts sourced from Korea and China or USA"

The repair.

• I had reservations about the short length of the coils, thinking it will not provide enough grip and that there was only one medium tap that would not tap the full depth. However given the first the second didn't matter as much.
• Ok drilled out the existing thread in the gear housing, without going through the shaft. A stop could be used to avoid the danger. Further a smaller, less powerful electric drill could be used to aid handling.
• The tapping went ok and stopped when it reached the bottom, and like previously said the depth was well over what was necessary for the length of the helicoil. The tapping was old-school 1/4 turn, back up 1/4, forward 1/4 to free and clean the cut, backup a whole turn to move the swarf. After a few turns it occurred to me so add a little grease|oil to the tap.
• Screwed in coil with tool and used the provided punch to snap of the spur used for purchase during insertion. Ensured the coil was a thread lower than flush.
• Assembled guard and all seems good. Only then did I realise I could have added the coils to all three bolt holes.

Have now emailed Stihl

Hi further to two telephone conversations I had with your technical team.

The background is I bought an FS460 some five years ago to clear paths some 1km long a few times a year, altogether I have used the machine 98 times measured by full tanks over the five years, so not much. Yet I had have a two thread failures and a rider cup replacement.

The rider cup replacement seems understandable if not totally acceptable as I variously use a bladed cutter, a shredder and the strimmer head.

This continuing change of the guard for the cutting head has no doubt been instrumental in the thread baring. Still it seems a week point in design - cast alloy head that isn't really fit to have the guards changed some 45 times over 5 years. ?? Sure it's not a simple event as the heads are being vibrated viscously.

I have spoke to you before about the thread in the handle stock baring and that one of the guard screws lost it's hex star fixing screw ability.

All problems apart from the rider cup are associated with aluminium parts that give way very early on as they cannot withstand repeated fastening|unfastening

The other issue, over which I did go back to Radmore Tucker was that the strimmer thread keeps snapping and no solution there.

Pity! as the machine is useful but not reliable in these circumstances of handle adjustment for storage and guard swapping for alternative cutting tools.

Would appreciate some useful feedback.

The link below goes to my website where I detail, in this instance, the problem with the gear housing guard holding bolt hole.

Gear housing guard holding bolt hole problem

Thank you

Roger Lovejoy