For the key, you can file up a bit of mild steel to fit. You might be saved by Bill Chugg (see current offer of help) over the lefthand threaded bolt.

Try these people for the bolt, they sell a range of left hand thread saw blade bolts.

Power tool centre

Martin C

Ps I would be wary of a home made bolt. What would happen if it snapped during use? 

Edited By Martin Connelly on 15/04/2020 18:46:52

Obviously it would be far better to use the proper part or at least proper thread, but I investigated the pitch error over 20mm if you treat a 1mm pitch as 25tpi (with 60º angle).

1mm = 0.0394 inch, so 20 turns = 0.7874 inch.

25tpi = 0.040 " pitch = 0.800 " over 20 turns.

Cumulative error = 0.013 " so possibly too much.

Nevertheless I'd still prefer a proper replacement, for the reason Martin suggests. The machine may be a badged clone, or its present incarnations may still use the same small parts, so spares might be fairly easy to find. M8 x 1mm is an ISO Metric Fine standard, but left-hand?

Key steel is a slightly higher carbon content than mild steel and comes in square and rectangular sections to match standard sizes. Bit of grade 5 bolt probably ok.

The key should only be used for location. The drive should be taken by the clamping forces of the bolt.

I agree with VE.

I ran a competition Rally Car engine with NO key in the Cam pulley to get the valve timing correct and forgot about it until the end of season strip down. No problems.

Roger

During my apprenticeship I was taught that for cutters larger than 1/4 inch wide you keyed the cutter, for cutters under 1/4 inch wide you keyed the arbor.