crossflow crankshaft thread sizes.

[itsaboattime]

Re: crossflow crankshaft thread sizes.

Been following this thread and I'm kinda blown away. .006 of an inch?!?! Holy crap.
Gotta hand it to you guys, you know your stuff.

 

[schematic]

Re: crossflow crankshaft thread sizes.

You an amateur or a pro like etracer ?
I'm just a home-shop metal cruncher, but a 54" x 10" Atlas lets me do some pretty cost-saving repairs at home....

I'm just a hobbyist. Had lathes at home for the last 40+ years. I learnt early in life the value of a lathe! I certainly don't have the experience that etracer has, so I really appreciate his input too! What threw me on this endeavor was the fact that the threads looked original to the naked eye which sent me down the path of trying to find the right nut.
Cutting oversize threads was relatively easy. I used a 7/16x14 tap as my cutting tool. Lined it up and made one .003 pass.
Thanks for all your guys interest

 

[Tim Frank]

Re: crossflow crankshaft thread sizes.

I'm just a hobbyist. Had lathes at home for the last 40+ years. I learnt early in life the value of a lathe! I certainly don't have the experience that etracer has, so I really appreciate his input too! What threw me on this endeavor was the fact that the threads looked original to the naked eye which sent me down the path of trying to find the right nut.
Cutting oversize threads was relatively easy. I used a 7/16x14 tap as my cutting tool. Lined it up and made one .003 pass.
Thanks for all your guys interest

How did you set that up?
I'd have chucked the nut in a three jaw, and single-pointed it with a boring bar....which would have included 1/2 hour+ messing around with change gear combos to get it right....

I like the idea of using a 14 tpi tap as the cutting tool, just not sure how to set it up so that the threads would index properly.

 

[schematic]

Re: crossflow crankshaft thread sizes.

Hi Frank
Yes you have to set your gear box to 14 threads per inch. Then engage the saddle until it near the chuck. Stop the lathe when its close. Never disengage the feed screw once you start. Insert the tap in the turret and mesh with the threads(as in picture).Lock in place. Zero the hand wheel then move it in .050 or so. restart the lathe in rev rotation to back it out of nut. Stop lathe. Back hand wheel out .053 Restart lathe until tap has done its job. The tap serves as a rigid boring bar, and since its taper, it cuts progressively with no chatter

 

[Tim Frank]

Re: crossflow crankshaft thread sizes.

Hi Frank
Yes you have to set your gear box to 14 threads per inch. Then engage the saddle until it near the chuck. Stop the lathe when its close. Never disengage the feed screw once you start. Insert the tap in the turret and mesh with the threads(as in picture).Lock in place. Zero the hand wheel then move it in .050 or so. restart the lathe in rev rotation to back it out of nut. Stop lathe. Back hand wheel out .053 Restart lathe until tap has done its job. The tap serves as a rigid boring bar, and since its taper, it cuts progressively with no chatter

View attachment 200109

Got it! Thanks for the explanation and setup pic.
That is so slick i may have to find something to damage just so that I can fix it....