Tapping threads in engine to u.s standard

[Cavi Mike]

For starters, 1/4" is only .014" larger than 6mm, I don't know what any of you heard.
1/4in = .250"
6mm = .236"

You're not going anywhere with .014". You've ruined your threads, that's all there is to it. You'd need to go to 5/16" or run a 1/4" Heli-Coil insert.

 

[Cavi Mike]

The tap on the left is an M6x1, this is what the holes originally were. On the right is a 1/4-20, what you've just cross-threaded into your motor.

The green lines indicate where the threads will line up and you'll have something for the screw to hold onto. Orange will be partial threads and red are completely missing threads from where the 1/4" tap simply cut away the M6 threads and left you with nothing.

 

[alec]

Well from the looks of the threads they are complete and pretty good. You can dump over the idea all you want but in the long run it worked and that's all that matters

 

[Al.Fisherman]

For starters, 1/4" is only .014" larger than 6mm, I don't know what any of you heard.
1/4in = .250"
6mm = .236"

You're not going anywhere with .014". You've ruined your threads, that's all there is to it. You'd need to go to 5/16" or run a 1/4" Heli-Coil insert.

Hey, no argument here, I'm all behind you 100% on this. It's a no brainier.

 

[Cavi Mike]

Well from the looks of the threads they are complete and pretty good. You can dump over the idea all you want but in the long run it worked and that's all that matters

From the looks of what? You can't see inside that hole. And I will dump all over this because it's a really stupid idea and it won't work for long - I guarantee it - and THAT is all that matters.

*edit* And since this picture I took of the taps wasn't enough to convince you, I'll make a block at work tomorrow and cut it in half so you can see just how terrible your threads are.

 

[Al.Fisherman]

any input on this?

Isn't it funny, how people ask for your input, then wants to argue with you? Wonder where he got all of his experience from? Sure wasn't from anyone that knows their s^^t.

 

[alec]

Actually I got my info from my grandfather who is a grand craftsman. He can cast and machine engines from scratch and make every part on a motorcycle. He's even created replica .50 Hawkins rifles by hand. I didn't argue all I said is that it worked for me and the threads are strong.

 

[alec]

For example when I first showed him the engine, my grandfather had the coolest ideas to fabricate special mounts which he explained the design and other stuff to align the chain and other stuff like that. He knows his stuff. Once again I'm not trying to be argumentative.

 

[alec]

Also do you really think the OEM threads are any better? All of mine were almost nonexistent because its s#@% China quality.

 

[tooljunkie]

this looks like one o them agree to disagree scenarios.
i have ran a metric die down a standard bolt,curious what the threads would look like.
similar result would be when tapping a metric hole to standard.threads are fugly.
i wouldnt expect to ever get it apart,as galling is almost a sure thing.
as a last resort,yes i would do it,but i prefer to go up to the next bolt size.

heli-coils are the strongest repair in crappy cast aluminum.