cafebike

There is broken allen in FSA crankret arm. I need to know what exactly size is allen screw?
I needed use 5 inch allen but I am not sure what exatly size is.
I need to remove it by drill and screw extractor( any knowledge what sizes I should use).
Any help how to remove destroy screw please let me know.

wschruba

There are a few possibilities, but without a picture (or more precise description), we can't really help you.

Was it the fixing bolt for the crank (3 common sizes)? One of the chaining bolts (again, 3 commonly used sizes)?

Dsprok

Local bike shop may be best.

Troul 

cut off the arm & replace it.

Hoopdriver

I'd first grind the screw stub flat with an abrasive rotary tool. This will allow you to drill without the bit wandering. If you have a crank arm puller, I would use the outer part to form a guide for your drill bit. You will have to make a sleeve out of a length of wood dowel with a through hole the diameter of your bit. Screw this on to your crank and it will perfectly center the bit in the stub. If you have already removed the crank, put it back on.

If you are talking about chainring bolts, just drill them from the front and they will separate. No need to extract.

Good luck.