Machining model crankshafts

[JPR428]

Hi,

First of all I hope I got the right forum for my question.

I have been reading about different ways of machining crankshafts for model engines. My own interests are in model steam engines and I have always made my crankshafts by machining all the crank pins and webs separately before silver soldering everything together, hopefully keeping everything straight and aligned.

So I was wondering, is it possible to make a crankshaft from one piece of steel on a benchtop cnc mill with a 4th axis.

As a more general question, is it possible to "turn" a shaft on a 4th axis mill with an end mill and how do the results compare to a lathe.

Thanks.

[Shotout]

I looked at this with my father in law's redwing hit and miss engine. For his shaft it was possible to offset a 4 jawed chuck to turn the ends leaving a billet in the middle. By then transferring it to a mill he could indicate in on each shaft end, vertically as well is X and Y and then center drill the billet to be mounter in between centers. Saw part of the billet away and the use a grooving tool to turn the center of the shaft, however it was a lot easier for me to make him one to demonstrate the process of making it in pieces and jigging it to hold it in position to solder it. I can't answer the 4th axis question with any authority as all my 4th axis work has been in index mode, however the drive/encoder of the 4th axis will determine how true of an arc you can produce on your shaft. Deflection on the scale of his engine would be a serious consideration as well.

[Mcgyver]

the short answer is no, because the bottom of endmils are not flat.....the bottom teeth slant a few degrees upward toward the centre so that they have clearance. So even if you could live with the finish, each pin would be a bit pregnant in the middle.

Why not turn it in the lathe? there are many not-to-difficult ways to do this from solid. Here's the most complicated i've done, a three throw crank turned from solid (except the counter weights which were added afterward). anytime you turn a crank you have to make a fixture giving you the required centres for each pin - the secret is turn the pins first as as each is turned fill in the gap with a peice of very close fitting packing to maintain the rigidity of the shaft