Minnie on the cheap!

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NormanV:
I've also done the final drive gear with its centre. I was lucky to find a lathe change wheel of the correct DP and it was a simple job to machine it down to the correct thickness and bore it to size.
The keyways were a bit of a faff. I did them by putting a parting tool sideways in the lathe toolpost and racking it backwards and forwards taking a light cut each time. I tried it first on a piece of scrap, it was a hell of a struggle taking a lot of effort to pass the tool through the hole plus it kept digging in. I gave up and tried to make a broach, I tried to do it rough and ready and it was unsuccessful so I went back to the parting tool. After I had adjusted the gib strips it was better so I attacked the first keyway. It was still hard work but I got there. The second keyway was a doddle, I reduced the feed to one thou. for each cut and it sailed through, no dig ins. Well next time I have to cut a keyway I'll know how to do it!

awemawson:
When broaching keyways in the lathe I first turn up a peg that fits in the centre hole flush both sides. I then drill a hole that is slightly smaller diameter than the intended keyway at the intersection of the peg and the gear leaving a D shape in both.

Then removing the peg I broach away. This way there is much less material to remove and the hole tends to guide slender tools.

NormanV:
That's a good idea, I will file it away in my memory for the next time, thanks.

tom osselton:
When I get a cut like that I put a piece of cigarette paper on it the blood holds the paper and drys like a second skin.
We learned to make keyways like that years ago in shop making a jackstand for a car it was external though down the side of the threaded rod. Its best to have a through hole though unless you have grooved the inside to clear the tail chip.

NormanV:
Tom, I don't smoke but that is no reason to not keep a stock of cigarette papers. I need to get some.
When I used to smoke(50 years ago) they cost 2d. I think that they may be more expensive now!
I managed to buy some involute gear cutters at a good price, They needed sharpening. This was my first opportunity to use my Harold Hall grinding jig. It was a fiddle to set it up but it did the job.

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