Halfa, a DOHC inline Twin

[Kim]

Nice setup, Ron.  Creating the setups can take more time than the actual machining of the part sometimes.  But it's the time in the setup that makes it easy to do the machining!   

Kim

[RReid]

Thanks Kim, and I agree completely. Taking time on the set-up is always time well spent. And when I try to cheat I usually come to regret it!

With the first set of bores done, I now had a flat surface that could serve as the z-axis baseline for the other three sets, with the help of a suitable stand-off of known length.


Working slowly and carefully to avoid a screw-up, especially when it came to turning the part around and re-aligning it, I got 'er done. Next is to flip it over and do the combustion chambers and valve bores.

[Dave Otto]

Making good progress Ron, looks nice!

Dave

[vtsteam]

That's coming along great! 

[Admiral_dk]

Lovely Headjob Ron - great progress 

Per

[RReid]

Dave, Steve, Per - Thanks guys!

Cutting in the combustion chambers went fine, no disasters and the I found bottoms of the holes drilled previously in the expected locations (sigh of relief).
Started with the head upside down and horizontal to form a “roof”.


Then back onto the tilting table, still set as before, to form the “ramps”, perpendicular to the axis of motion of the valves, and into which the valve seats will be formed. You can now see why I wanted to be sure that angle setting was rock solid and couldn't be knocked awry.

[jcge]

I can well imagine your relief, when finding those valve holes in their expected locations !
Lovely work
Regards
John

[Brendon M]

Geez, hard to believe this is only a few months work! Great work so far

[simplyloco]

 
John

[Hugh Currin]

Nice work. How did you finish the bottom of the combustion chamber? I'd anticipate some "gouging" at the corners that don't meet at 90 degrees. Did you use a ball mill for the corners? What ever you did it sure looks nice.

Thanks.

[RReid]

John (jcge), Brendon, John (simplyloco), and Hugh - Thank you very much, guys!

Hugh - I used a 1/8" bullnose end mill with a 0.020" corner radius. I learned about this type from a discussion between Steamer and Crueby about them in one of the latter's threads. Wanting to try one, I got a 1/4" version with a .060" radius and have found it very effective on many jobs already on this build, leaving nice rounded corners but still with a flat when you need to span across an area with repeated passes. So I got the little one for this job, and as you say it was great for minimizing the "nicking" at the intersections.

[RReid]

Another sigh of relief day. I got the six coolant channels drilled in the head without hitting any of the features they weren't supposed to hit. Four holes lengthwise, 2.1” long and 2 crosswise on the same plane 2.7” long, to form a flow grid with one entrance and one exit at opposite corners (after a bit of plugging). You might not think drilling 6 holes could possibly take anyone most of the day, but I managed it.


None of the holes were drilled through. The two on the left will get plugged, and the two in the middle bottom will also be plugged, leaving the front and back (top and bottom in the pic) corners for inlet and outlet.

[vtsteam]

Ron, it must be satisfying to have them all work out, especially after a day of careful setup. 

[RReid]

Yes Steve, satisfying it is. Hope you are staying warm!

[vtsteam]

Trying to Ron. It's -12 F and still dropping at the moment (nearly 10pm, eastern) and winds are 16 gusting to 32. We've got another day of this stuff to get through, and then Sunday it's supposed to go up to 41F