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small.planes
06-26-2009, 05:20 PM
Evening all,
Im in the planning stages of a new project. Im going to have to make a crankshaft (EN24T I think) with bigger throws than I can turn on my lathe.
Short of buying another lathe (not allowed - SWMBO!) I do have a s*dding great milling machine at my disposal.
Ive seen some CNC mill-turning videos on utube etc where they coordinate the axes to do all the throws in one setup.
I dont plan to do that (manual machine), but if I setup as though I was turning it with offset centers using a dividing head and tailstock
I think that I should be able to mill the journals by rotating the dividing head.
I cant see any problems with this approach, but I like to check Ive not missed something obvious....

And does anyone know how a rolled fillet radius is produced, or if you really have to grind finish a crankshaft?

cheers

Dave

JCHannum
06-26-2009, 05:34 PM
In one of the Phil Duclos engine builds, he machined the crankshaft on the milling machine. The only caveat is that ends of the flutes on most end mills are ground on a slight angle and are lower in the center. This can produce a barrel shaped journal unless the end mill is passed across the throw while rotating the crank.

Another method of turning on the mill is to use the boring bar, turn the cutter in and reverse bore the OD. This works very well on odd shaped parts that cannot be chucked up in the lathe.

An end mill with a radius on the end of the flute can cut the shoulder radius, and grinding is not necessary on most engines.

small.planes
06-26-2009, 07:04 PM
In one of the Phil Duclos engine builds, he machined the crankshaft on the milling machine. The only caveat is that ends of the flutes on most end mills are ground on a slight angle and are lower in the center. This can produce a barrel shaped journal unless the end mill is passed across the throw while rotating the crank.

:) Hadn't considered that, although Im not certain yet (details to be worked out) but I think Ill be using an insert mill to get the length to get between the flanks of the counterweights.


An end mill with a radius on the end of the flute can cut the shoulder radius, and grinding is not necessary on most engines.

Thats what I thought. This is a blown race engine (aiming about 200Hp/L) so reliability is important (to finish first, first you have to finish) but it wont do mega amounts of running between teardowns, so inspections will be frequent.

Dave