Kiwi Crankcase – a different approach

[Mike Ginn]

I am always hesitant when suggesting that there is a different way to machine a well-established casting. I am sure someone will point me to a post made years ago which describes the same process! That said, the method of holding the rear crankcase casting described by ETW and more recently in the excellent instructions from Vince Cutajar and others, is based on holding the casting in a 4 jaw using small blocks of wood. I decided I wanted a more secure method so came up with a method based on glues and fillers! I have found this approach ideal for milling thin plates and awkward shaped castings in the lathe especially where the cut is intermittent. I have never found that the styrene filler leaves deposits if it is knocked off with a hammer. It can, however, be burned with a flame if necessary. The card and wood glue method requires at least 2 thicknesses of stiff card so that a knife will separate the card. The separated part is them boiled in water for about 5 minutes to soften the glue. If glue deposits remain, then these may be scrubbed when the part is hot.

The attached shows the 2 methods in action.
Mike

 

[methuselah1]

Those are two very good ideas for the mental arsenal! I can't remember how I made the rear cover, but I do remember how I did the rear case- and thinking it was the dodgiest bit of chucking I had ever done! I used strips of lead, folded double, between the jaws and the casting, and took things really easy. The lead deformed to both the jaws and the work, and all was well.