Dominator HT Pinion and Camshaft Woodruff Keys

Once upon a time you could purchase these keys as a set. I believe there were 5 keys in the set which cost a massive £2.00. In recent years I have obtained those for my needs as single items and generally found some fettling was needed for a snug fit. Often, on the larger keys, the ends also had to be chopped off so they dropped deeper into the crankshaft slots.

Hi Alan I too am building a 1960 Dommie 99 and, like you, have fallen foul of the ‘oversize Woodruff key’ issue. I ended up grinding and filing 3 out of the 5 keys to make them fit into the slots in the various shafts. I even bought a complete set from one of the usual suspects but they too were oversize. I think that’s what we get for now living in a time where precision isn’t particularly popular with the mass parts retailers.

Good luck.

Regards 

Tony

Maybe they were match fitted in the works? They need to be snug, and how quickly did the cutting tool stay within a tight enough tolerance to allow keys to be interchangeable? Remember...in car factories, "standard" pistons often came in four graded sizes...a, b, c and d. As the boring cutters wore, the bores on successive motors got smaller and they fitted the next size down the sequence until they ran out of sizes and reset the machine. You can always make a big key fit a small slot...it's a good thing they don't sell them under sized.

Before I put on my Big Boy Pants to buy my first Norton, I had a couple of Jap stinkwheel tiddlers. With the casual ignorance of Yoof, I ignored the fact that the woodruff key I had bought for the flywheel mag was a Very loose fit in the keyway (probably wrong key altogether), thinking doing up the nut at tight as I could would be fine. Then after a few weeks, that rattle just got louder......Eventually I could put it off no more: thankfully the crank itself was undamaged, but I had to get a new flywheel (and the correct key) from another dealer.....

I would not be too surprised to learn that the set of replacement keys for Dominators are now metric in size.

While there is no excuse as to why the keys supplied by the big suppliers don't fit, they don't have to be particularly precise in their size. They should only be there to act as a locator, and in many cases don't need to be there at all. That is why they are made from relatively soft mild steel.

If they are being relied on to provide the drive/power transmission, then something is wrong - there are things called drive keys for that job, a different animal as to shape and material. On our engines, that is what the tapers do/ should be doing.

Keyways for cam drives started to disappear in the car world from around 1985-86, instead relying on the shape of the bolt heads and proper torque to keep everything in place and that is the norm now in most engines made as cutting key slots and fitting keys costs time and money.