EDM, Wow!

I purchased a '73 750 about 2 years ago and have finally got to working on it; I'll cut to the chase (no pun intended). I striped the engine and split the cases, they were covered in all kinds of crap that mixes with oil. The timing cover was off when I purchased the motorcycle, but when I cleaned the timing side I saw that three of the 1/4-20 cover machine screws had been broken off just flush with the casting and that some PO had tried to drill them out and given up; the timing side engine case does not have a lot of meat around these fasteners and I just didn't feel competent setting heli-coils.

I took the engine case to a small service near by and discussed the repair, I trust this guy with the highest regards. He called me the next day and told me that the repair was complete, which amazed me, as I'm not in a hurry and expected to see the repair completed in 2-3 weeks.

When I saw the case I was amazed, no heli-coils, instead he had used a very sophisticated EDM machine and had turned the broken-off screws into plasma leaving the factor threads completely intact, wow! I was skeptical, but ran a new 1/4-20 fastener into holes and was impressed that they felt as tight as any other of the tapped holes.

If this old hat to you gurus, I apologize for wasting your time, if not and you would like to use this service just PM me and I'll give you his contact.

Likewise for broken taps. As you may have already experienced, broken taps do not lend themselves to being drilled out. However, an EDM with a hollow electrode can effortlessly removed the core of the tap, leaving the flutes to simply fall out of the threaded hole once the electrode is retracted. Fun stuff!

Nathan

Them's some nice wire cutters, alright...

Excuse me for my ignorance, but what does EDM stand for ? When I google EDM, all I get is Electronic Dance Music. :roll:

Peter R said:

Excuse me for my ignorance, but what does EDM stand for ? When I google EDM, all I get is Electronic Dance Music. :roll:

Click to expand...

Electrical Discharge Machining.

Try Googling E.D.M. and learn.

https://www.youtube.com/watch?v=NALJONqLwtk

A little long-winded, but good video of the process.

And you can have a lot of fun in your spare time! This fork brace used wire edm for the body and wire/sinker edm for the logo.And yes, it's on my Norton

The Turbocharged Offenhauser 159 of the 1970s were largely finish machined using EDM. The Offy engines utilized a one piece cylinder head block design. For anybody interested the Book " Offy, Americas Greatest Racing Engine by Kenneth E. Walton, is a terrific read; great pictures, drawings, and interviews with the engineers that designed and built these engines.

Thanks for that - much appreciated !

Found one !

http://edmvic.com.au/