An inline 6 cylinder OHV engine

[gbritnell]

With the drawings far enough along to get started I ordered aluminum for the block, 1144 steel for the crankshaft and rectangular Durabar iron for the head.
It been a long time since I did a multi-cylinder crankshaft that isn't in a flat plane so figuring this is going to be the hardest part this is where I'll start.
I chucked the 1.25 bar up and turned and center drilled both ends. On one end I cut a true diameter so that I could indicate it true in the 4 jaw chuck.
The O.D. was then turned to 1.23 diameter.
gbritnell

[gbritnell]

The next step was to mount the blank in the mill vise. The bar was set on a parallel high enough to achieve the depth of cut needed to rough out the center journals. A stop was also positioned to allow rotating the piece while keeping the registration. The slots were first cut with a .187, 2 flute endmill followed by a .25, 4 flute with a small radius on the corners. The depth was taken to .010 shy of the finished diameter.
gbritnell

[gbritnell]

The next step was to remount the bar in the 4 jaw chuck and indicate it true to cut the journals to .3125 diameter.
gbritnell

[gbritnell]

I have found in the past that it's easier to mill stock away on a crank blank then to tentatively dive in with a cutoff tool. Needing a fixture to rough out the throw journals and later on for finishing the counterweights I made one up from aluminum. Each journal has it's own clamping bearing which should be more than enough to hold everything in place while milling.
I made the end journals .438 diameter for 2 reasons, one, to give more gripping surface for the offset blocks when turning the throws and two, to allow enough stock to cut 3 flats at 120 degrees so that the part can be indexed accurately.
The fixture was moved to the mill and the blank was indicated true and clamped tight. As with the main journals I first went in with a .187 endmill to rough them out followed by the .25 endmill to finish up the sides of the cheeks. This way the only material that will need to be removed will be from the journals and not the sides.
gbritnell

[Don1966]

George I just love your photos great details. I plane to pull my chair up and watch this take shape. Awesome George. 

Don

[gbritnell]

You can see in the last photo that there are 2 different steps, on the first and last throws and all of the center throws. I have calculated the required depth relative to each reference flat while rotating the blank to the various positions. With this I will end up with a .332 square from which the .312 journal will be turned.
gbritnell

[Kim]

Hi George,
This is fascinating!
Thanks for taking the time to post your construction pictures and explanatory text.  I'm going to learn a lot from watching your build!
Kim

[ths]

Hi George, this is very instructive, thanks.

Hugh.

[steamer]

Nice one George!....I really like that approach!....I'm going to do that with the Wallaby!

Dave

[b.lindsey]

Great starts George and as always your pictures and descriptions are like a textbook on how to do things right!!

Bill

[ozzie46]

   Oh Boy! Another great thread from George. Got my learning ears on. Thanks George.

 Off to a great start.

  Ron

[Dave Otto]

Nice fixture George; and the crank is also taking shape and looking good.

It will be fun to watch this engine progress.

Dave

[maury]

George, as always, Excellent Work! I just tuned in, and already have a question. I have made crank shafts this ( or similar too) way, and have always found it very precarious to cut the journals with a cut off tool. It may be my inexperience or my equipment or my tool...
The question is what speed/feed/depth of cut do you use to prevent catching? Also, is your tool on center or below?

Thanks,
maury

[gbritnell]

Hi Maury,
I use the thinnest cutoff blade I have, .062. I make sure the front edge is square to the sides so that when I set the tool I know that the journal will be cut parallel. I put a small notch in the face so the tool loading is reduced. (bifurcated)  I definitely put the tool on center. Putting it below is asking for trouble. As far as catching I just go very slowly and work back and forth as I'm infeeding. The nice thing about milling the webs first is that you don't have to cut them on the lathe. 
gbritnell

[tvoght]

It's really great to see this project!

You mention cutting flats on the end journals for indexing the throw journals. Just to make sure I'm following correctly, are the flats on the journal to the right in the photos? A little hard to see.
What are the flats referenced to? Are you setting up the indexing for one in the photo with the indicator?

--Tim