787 confirm bottom case bolt sizes and thread

[kmarts]

So I have my crank case split at the moment and I'm cleaning everything for reassembly.

I believe the two bolt sizes are M10x1.5 and M8x1.25, correct?

When I went to run the bolts through a die to clean the threads the M8's run through as expected but the M10's seem to bind after a few turns. I put a thread gauge on them and they're definitely 1.5 thread.

I then tried tapping the block holes and it was the same thing.

I experienced this when I went to clean the threads on my exhaust manifold to pipe thread holes and bolts.

What's up with this? It seems to be only M10 bolts and holes I'm having an issue with... am I doing something wrong?

 

[Dr Honda]

Put the 10mm and 8mm bolt threads together. I'm thinking they are both 1.25 pitch.

 

[racerxxx]

M8 X 1.25 and M10 X 1.5 is the correct thread pitch.

There are different classifications of taps so who know what you're working with. I know when I tap the cases I'm removing a little material. I assume they're using a tighter tolerance tap classification than we use at work. As far as chasing the screws, just use a wire wheel, so much faster and easier. Or use a drill and scotch brite. Put the head of the screw in the drill and put the scotch brite around the threads and squeeze. Or put the head in a vise and put a wire wheel on your drill and go around it.

 

[Dr Honda]

Thanks for the verification on that. It's been a while since I had those bolts in my hands.

 

[mikidymac]

Bench grinder with a wire wheel is to only way to clean Seadoo engine bolts. You can also get thread cleaning taps that will not remove material like the cutting taps will.