Halfa, a DOHC inline Twin

[Roger B]

That was a tough bit of material preparation 

At that point I might have used the facilities at work although I try to do all my engine work with my own tools.

[vtsteam]

re. smaller drill ... good tip!

[Hugh Currin]

Ron:

Good progress and nice work. Did you use any lubricant for drilling? If not that might help.

I've been real hesitant to get my fingers too close to spinning milling tools. Years ago I lost the very tip of a finger to a facing mill. The feeling is coming back but still not quite right. SO, I now use the handle of my cheap chip brush to clear chips from drills. The bristles still give out before the handle, but my handles look a little chewed up. Your mileage may vary.

Thanks.

[RReid]

Thanks vtsteam!
Thanks Hugh!
I did try squirting on some WD-40. It seemed to help when drilling on the mill, where the spindle speed was higher. On the drill press it didn't seem worth the extra mess.

You're quite right, I don't go near the mill spindle with fingers when it's running. But on the drill press the space is not so confined, and the drill bit in use was too small to do any real damage, especially to a gloved finger (gloves with a smooth plastic-ey fingertip, not fluffy). I normally use a brush, but it was completely ineffective in this case.

[RReid]

Once I got the cylinder block all finished off to size, I next wanted to get it and the upper crankcase half joined together. To do this I would drill through the crankcase and into the block, then tap them both while clamped together for a pair of 4-40 screws. I started with the set-up below, with the block exactly centered on the crankcase half.


Unfortunately the mill head interfered with the top of the vise by just a tiny bit, but that prevented me from lowering the head enough to execute my plan. So I used a long 1/16” bit to pilot drill the two holes. With a couple of pins in them to hold the alignment, I rearranged things to this set-up.


With this set-up I was able to get the drilling/tapping done. In the photo you can see one of the screws already in place. The the drill chuck holding the tap is in a loosened collet, which holds the tap vertical while allowing me run it in by hand.


Next up was to pilot drill for the crank bearings and the cylinder bores. With both crankcase halves and the block all fastened together, I mounted the assembly to the tilting angle plate, which itself was mounted all nice and square to the mill table. Starting with it set up at 90 deg, I carefully located and center drilled the crank centerline, then drilled and reamed right through to 0.3125”. This is smaller than the diameter of the bearings, but I did this because that's the largest reamer I can use here (it has to drop down through the spindle and into the collet, not enough head room to insert it normally) and so that a bit of drill rod will be a good fit for use in clocking in on the lathe later.




Now, with the assembly rotated down to horizontal, the cylinder centerline should be directly over the crank centerline and be directly under the spindle. Lo and behold, it actually was!


So I then proceeded to drill/ream through the block in the two places, also to 0.3125”.




The next plan is to open up those cylinder bores on the lathe to accept the cylinder liners. I don't have a long enough bar for the boring head to do this job on the mill. This is where those reamed holes and the drill rod comes into play.


Although the image above shows the crankcase half attached to the block, I soon found it more convenient to remove it and just concentrate on boring the block. The hole through the crankcase can be opened up later, their diameter is not critical as long as they're not smaller than the block bore where they meet. I got one bore completed, the other one is scheduled for tomorrow. I did drill it out to 1/2" before proceeding with the boring bar.

[Kim]

It's fun watching you work, Ron!  I forget you're doing all this on Taig equipment!  You and Chris make those small tools look so capable! 

Kim

[john mills]

I would keep fingers well away from drill or any cutting tool however small they may be with a glove it ca grab and pull your hand it be for you know.i unwound a lady in the factory i worked in 40 years ago the rubber glove dragged her hand in see was glad i came to turn the power off and unwind to release her hand lucky it was a flat belt that did stop turning but it still tore tenant from the fingers.the chips often look after them selves . use proper coolant it works.recently using a bigger drill a contract wanted to use his fingers to move chips
told him what to do get his hand away the swaff would look after it self and was not a problem.just a habit some people get .
John

[Jasonb]

Unless I read it wrong the drill chuck is being used as a tap wrench and turned by hand, can't see anything wrong with that.

Engine is coming along nicely.

[Zephyrin]

very nice start with this engine, from the personal design to the machining, great!
by the way, the mill and the lathe too, you are using looks rather small.

[RReid]

Kim, John, Jason, Zephyrin - Thank you all for your support, comments, and concerns!
Also a late Thanks to RogerB. Missed you last time around, sorry. No workplace machines available to me anymore!

by the way, the mill and the lathe too, you are using looks rather small.

Yes, the Taig machines are small, but like the similarly sized Sherline tools can do a good bit of work. To give an idea, here are some basic specs:

Taig Lathe
Spindle Nose 3/4-16 Thread
Center Height 2.25 in (5.7 cm)
Swing over crosslide 2.375 in (6 cm)
Length of Bed 15.5 in (39.4 cm)

Taig Mill
Spindle Nose ER16
Travel in Y axis 5.5 in (14 cm)
Travel in X axis 12 in. (30.5 cm)
Travel in Z axis 6.0 in (15.2 cm)
Maximum Z-distance to table 9.0 in (23 cm)

[RReid]

Today I finished up boring the block to accept the cylinder liners. Just repeating the same steps as yesterday. With that done I also opened up the holes in the crankcase that the conrods pass through, and drilled the block for the coolant in/out and to pass through the web between the cylinders. Now it is starting to be somewhat more “engine” looking.

[Brendon M]

Looking great so far

[steamer]

Making quick work of that so far Ron.   Ball bearing crank?

[vtsteam]

Looking great! That long drill and pinning method was really good to see    I probably will have to do the same thing.

Speaking of small lathes, I really enjoyed seeing what R.L. Tingey accomplished with a Unimat (and his modifications to it) in the late 70's Model Engineer magazines (looking up....vol 143 I think). He seemed to really stretch the capacity of that lathe in clever ways, and built some really interesting stuff with it like a valveless twin steam engine. Always admired those articles. Similar work being done here! 

[vtsteam]

Wait, I think center height is half that, isn't it?