Stripped thread

[breakwellmz]

Hi.
Whilst carrying out an oil change on the Mastif,i`ve stripped the thread in the crankcase of one of the two screws securing the oil pipe.
None of the usual warning,it just kept turning without tightening up!(Possibly it stripped on removal)
Anyway,i`ve got to repair it!
I did think the screws seem a little short.
The holes in the case are 20mm deep,the oil pipe boss nearly 5,plus washer.Almost 25mm.The attachment screws are just 16mm long.
Any thoughts on how to repair would be MUCH appreciated!
At the moment i have looked no further than Helicoil type kits,but the inserts themselves don`t seem long enough to me.Fortunately(?)it is the upper on the two holes,that doesn`t have a frame tube in the way!
I`m sure i`m not the first to have done this(Or the last!)
HELP!!
All the best.

[Bill Jurgenson]

helicoil is fine. Some think TimeSert is better but it is also MUCH more expensive. I use and have been using Helicoils for many years now.

[Linegeist]

The last time this happened to me (on a previous machine), it was on a Sunday and nothing was open to get any bits. So I experimented and improvised.

I found, like you, by measuring with a piece of thin rod that the threaded hole was significantly deeper than the 5mm diameter stud actually penetrated and that there remained a substantial amount of unused (and unstripped) internal threading in the alloy crankcase. Armed with this knowledge, I carefully cleaned out the stripped hole with a syringe, a small paintbrush, and brake cleaner until perfectly oil-free. Then I cut a suitable length of threaded stud from stock that was about 1/2" longer than the OEM allen bolt previously fitted. I fitted two nuts to one end of the stud piece and locked them up, then coated the stud end that was going into the hole with Araldite. I carefully wound the stud in by the locked-up nuts until it bottomed (if you use too much Araladite, it'll form a hydraulic lock at the end of the blind hole and stop you winding it all the way in) and then left it to set for a few hours. Then I popped off the nuts.

From there, it was a simple matter of reassembly, using a nut and washer where previously there'd been a machine screw. The nut tightened up to the correct torque, and the repair remained in service for several years until I stripped the engine and, in a fit of perfectionism, helicoiled the repaired hole. Interestingly, I needn't have bothered. That blasted stud fought every centimeter of the way out............!

[breakwellmz]

Hi.
Thanks for that.
I thought of putting my own stud in,but there is not enough room on the plate to fit an M6 nut.
UNLESS i make up a packing piece the same diameter as the head of the Allen screw!
I`ll take a look at that.

[jimc]

Helicoils are available in several lengths, shouldn't be an issue.
It's helpful to make a guide block from aluminum stock or hardwood to assure straightness
when drilling etc.