Gallery, Projects and General > Project Logs
Getting a tacho drive fixed on a classic racing bike
John Stevenson:
John,
Why not part true the OD of the boss up with a left hand boring tool, [ no joke they do exist but John probably knows that and has some ]
John S.
PS Did you check the pitch when in imperial ?
bogstandard:
John,
Actually, I was just about to remount it to do just that, I have just been scribing around the takeoff fitting to give me the size I should go to.
But I am using a standard cutter facing inwards and running the mill in reverse (I knew I would get to use that feature one day).
John
ADDED LATER
Just had Stew down to visit and we put it up onto the table. It won't work, can't get enough all round depth to clean it up, so it will have to be done with a normal cutter and eyeball.
bogstandard:
Not much to show this time, as I have been doing other work on this part and the engine.
Because I couldn't use John's suggestion of using an inner cutting boring tool, I had to mount the cover onto the RT and do the job freehand using a ball nosed cutter to shape the boss and weld area so that it would look like it was part of the original cover casting.
It didn't take more than about ten minutes once I got the RT fitted up with a mandrel to hold the cover and get it centralised.
A bit of work with a small drum sander in the mini drill soon had it basically to shape and blended in nicely.
It was at this time I had to make some phos bronze bushes to fit this cover and an internal hole in the crankcase as well. The kick start had been removed years ago, but all the operating mechanism had been left in. It was now the time to get the engine modded to remove it completely, and save a few pounds in weight. So now the gear lever shaft has it's own internal and external support bearings rather than relying on the kick start mechanism to do the job.
So after that, I got this bit reworked by banging out all the dents, and blending out the scratches it had picked up during it's life. Then onto the buffing machine to get everything blended together using a hard sisal mop and some heavy cutting soap, then back to the mini polisher to blend the bits I couldn't get at.
So this is after the first polish of the ali engine covers. As you can now see, the original welded on boss looks like it has been part of this engine since it's manufacture, I even managed to shape some of the weld to run up the boss like an extension of the cast on centre line, making it look even more like it was part of the original casting.
I can't do any more to this at this time. The other day I replaced the bearings in the crankcase, and I am still waiting for another one to fit. Without it, I can't assemble the crank in the case and carry out the machining on the two bits that this post is all about.
A good shower needed now, I look like Al Jolson, from all the buffing I have done.
Bogs
John Stevenson:
Mammeeeee, the sun shines east [ on a good day ] :wave:
John S.
bogstandard:
You've just reminded me John, so I have popped out to the shop and got my notes.
Readings when I checked my lathe for doing imperial threading.
I decided to check using the 16 TPI I already had set up. Which should give 0.0625" movement per revolution.
No of turns on chuck Saddle movement
2 0.124"
4 0.249"
8 0.498"
16 0.998"
24 1.498"
32 1.998"
40 2.498"
48 2.998"
So it looks like there was a minute amount of backlash to take up at the beginning, then after that, everything was absolutely perfect. So now I know that at least I can cut 16 TPI and know it is correct. I think I will do a few more different settings, just to see if it is still as accurate.
John
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