crankshafts

[cessna]

Hi, I seem to have a lot of trouble machining small multi cyl cranks. Is it possible or feasible to cut the excess material away then use a type of tool post grinder to finish the journals?
Your thoughts?
Terry

 

[gbritnell]

Yes it can be done. The hardest part is trying to find thin enough grinding wheels to get between the cheeks of the crank and move back and forth a little.
gbritnell

 

[ddmckee54]

Would an abrasive cut-off disk work, or would that be too coarse of a grit?

Don

 

[cessna]

Thanks for the replies, the one I am presently cutting is roughly 1/4" wide between the throws, I have been cutting the excess out with a parting tool and finishing with a 3/16" tool that has a tiny slot in the middle of the cutting edge, I don't have good luck with the parting tool , it needs so much stick out, I have the tip just a hair below center but it will every once in a while grab and twist everything. It just seems there must be a better way. Looking at tool post grinders in various forms here on the forum, I wondered if they would work.
Frustrated!!
Terry:wall:

 

[MachineTom]

A tool post grinder will always leave a radius, size based on grit of wheel. And most TP wheels are 46 -60 so the radius is not small. Google to find radius.

 

[lohring]

See http://www.homemodelenginemachinist.com/f31/multi-cylinder-crankshaft-machining-tutorial-5011/

Lohring Miller

 

[Charles Lamont]

A tool post grinder will always leave a radius, size based on grit of wheel. And most TP wheels are 46 -60 so the radius is not small. Google to find radius.

Journals and crankpins should always have a radius where they meet the webs anyway.

 

[texta]

have a look at the grinding wheels that are used on chainsaw electric sharpeners , they are about 4"dia and only about 1/8" wide , the one i have has a 7/8" arbour and is good for 7800rpm .

johno

 

[LongRat]

have a look at the grinding wheels that are used on chainsaw electric sharpeners , they are about 4"dia and only about 1/8" wide , the one i have has a 7/8" arbour and is good for 7800rpm .

johno

That's a very useful bit of advice - thanks for posting.