Shadow Build

[John H]

The tricky step is measuring and getting the last .0005". If it comes to that I will make an expandable lap to finish it off. Or use the Sunnen hone.

[John H]

Picked up this little guy cheap so I can cut metric threads. I don't expect much accuracy with it but may be surprised. It didn't come with any tools or accessories.

Lathe finished.JPG (164.58 KiB) Viewed 24979 times

[Lotus54]

That is around the size of mine. Does ok for small stuff- been really handy for making bushings, spacers and bearing drivers etc. plus I have learned a lot about using it and things that matter for the machine.

I thought I would use it to cut threads a lot- but I’ve still not done it. Ha it is a metric machine, so should be ok. But I suspect operating the half-nut is a lot clunkier than on a better machine.

[John H]

I was confused how the half nut works with metric threads. On downloading a manual I now see that the thread dial cannot be used. Instead, the half nut must not be disengaged. The tool is withdrawn and the motor is reversed. The thread dial is only for inch threads only. That will take some time getting use to.

[Lotus54]

Hmmm, I’m not sure mine works that way- I’d better check the manual. Could be.
I was going to try it out the other day- but had other stuff to do and didn’t.

I’ve never tried cutting threads, so need to learn how before I really need to do it (without a tap or die that is)

[John H]

One flywheel is bored to 1.0605 so I won't take a chance on another cut. The rest of the day was spent making a special bore lapping tool. Closest piece of tubing I found was actually a 3/4" pipe nipple 6" long. It is actually undersize for what I need but after cleaning it up, one end was machined to 1" to fit inside a R-8 x 1" collet which fits the mill. The other end was turned with a 2º inside taper. I then saw cut the tube in quarters, then made a tapered plug to drive into the taper just enough to enlarge the diameter so it could be turned down to 1.060. Now I have a perfect parallel surface to lap the flywheel bore.
Medium lapping compound will be used and if needed the tapered plug can be driven in further to expand the lap. This is where a 3-point micrometer would be really nice have.

IMG_5413.JPG (164.4 KiB) Viewed 24968 times

[John H]

I corrected my numbers I posted in the last update. The crank pin is 1.0635 and the finish bore is 1.061. Anyway, it's finished and the lap worked great.

Crank lapping.JPG (216.93 KiB) Viewed 24955 times

Before the crank can be assembled, the new rod races have to be pressed into the rods then honed to fit the bearings on the crank pin. This will be Sunnen hone job. It's a slow process, maybe because I'm slow.

Crank assembly ready.JPG (289.02 KiB) Viewed 24955 times

[ATinkerer]

Slow to get it correct is usually quicker than fast and having to do it three times before it is the correct size.
Less expensive also, less material used.

[John H]

Yes, I keep reminding myself of that. For instance, before checking to see if the flywheel pin bore was good enough for the 1.005" oversize pin set I had pressed the races in the rods. Well that didn't work because the new pin set is a different mfg, and the bearing rollers are a different size. The races have to be changed out for the new 1.065" oversize pin set.
Before they can be pressed in though, they need 4 oil reliefs ground in the outer edge to better lubricate the face of the rod.

Rod race oil groove.JPG (187.76 KiB) Viewed 24934 times

The easy part now is pressing the races into the rods. They are about .060" wider than the rod so I try to get the .030" even on both sides. That's controlled by another jig.

Press rod races.JPG (231.12 KiB) Viewed 24934 times

[John H]

I didn't have a chance to hone the rods today. I did add 1/4" holes in each flywheel that will be used to keep them lined up when the big pin is pressed in. The old way was to use a straight edge on the outer surface for alignment. That works well if both flywheels are the same diameter, which in this case they were not. So to the lathe to take a skim cut and now they are the same. I used the bore lap to line up the crank pin holes then used the straight edge to line things up before drilling the 1/4" holes. The rod is tungsten carbide so should hold things true.

carbide allignment.JPG (285.35 KiB) Viewed 24919 times