Stepped Stud - Stator Bolt?

[NorthernJordan]

Hi All,

I've had a few issues recently with bolts coming loose on the stator plate, and stripping the threads in the casing.

I'm thinking a stepped stud would be a good repair, as there would be less screwing in/out of aluminium.

Can I use a M8 to M6 stud? I can get these made at work and have the taps to do the job.

Jordan

[Knowledge]

M8 sounds a bit too chunky, as the thickness of the engine casing at that point is a bit narrow and gets narrower behind the gasket face.

I would have thought that an M7/M6 stepped stud would be better, and no harder to manufacture.

[Warkton Tornado No.1]

The holes do tend to get ‘baggy’ in that area but rarely do they need little more than a thorough clean out & fresh M6 studs securing with a good thread locker. Beware of hydraulic lock, though.

Tapping M6 to M8 in the casting will work but there is not a lot of meat remaining around the holes & the casting can very easily crack. You can buy double ended M8 to M6 conversion studs but I wouldn’t choose them.

If you have access to engineering supplies, the better solution in alloy is to tap & fit an M6 thread insert such as Helicoil.

Many engineering firms fit these from the outset of making an alloy part, not just as a fix.

[NorthernJordan]

I'm going to go for the M7/M6 stepped studs. I'm really doubting there is enough meat there for an M8. Everything is massive at work so it all get a bit limited when you go small!

I've ordered the M7 tap and will order studs now.

[drivera]

As Warkton says why not try a helicoil , you can pick up kits from unithread for not much cash and once you have the steel thread inserted it wont wear out if you keep inserting/taking out the studs ?

[NorthernJordan]

Once the studs are in, you don't have to remove/insert them, you just tighten a nut and washer up.

I'm not a big fan of helicoils either...

[Warkton Tornado No.1]

Post by NorthernJordan » Fri Oct 07, 2016 12:44 pm

Once the studs are in, you don't have to remove/insert them, you just tighten a nut and washer up.

I'm not a big fan of helicoils either...

Presumably you’ll just be replacing three studs & will continue using M6 socket screws/bolts to hold the stator in place. That is, unless there’s room behind the flywheel for nyloc nuts & washers...

Those particular holes are the three most subject to wear, but I’m sure you have it all figured out.

[xenia1]

The helicoil is by far the better option, tap them out larger and after a while you'll have the same problem. Steel to steel wont wear like steel to alloy..

[steve t]

Helicoil is the way To go got me out out of the sh@t loads of times in the last 25 years not just lammies I know some people don't like but I think there ok and not badly priced plenty on ebay

[Knowledge]

I must admit that my thread stripped, so I drilled it deeper and re-tapped it. It is now secured with a very long bolt, but it works.

I only remembered this at the weekend when I was testing some stators I had built.

[Warkton Tornado No.1]

Post by Knowledge » Mon Oct 10, 2016 4:42 pm

I must admit that my thread stripped, so I drilled it deeper and re-tapped it. It is now secured with a very long bolt, but it works.

I only remembered this at the weekend when I was testing some stators I had built.

I think many of us have done something similar. I have used longer, M6 studs on occasion. I have even Helicoiled the end plate stud holes ‘down’ to M6 (same pitch as M7) so that I could use much higher grade socket fasteners as I was struggling to find decent M7 nuts @ some point years ago

However, with the benefit of technology/engineering becoming much more accessible within the realms of DIY, I reason that advice given by the majority of us is our best advice, often with the benefit of hindsight.

There are ‘get-you-home’ bodges & there are ‘best-engineering-solutions’

Unfortunately, the choice often comes down to cost.....

[NorthernJordan]

Well I've gone with stepped studs and nuts... We'll see how I get on!