8mm or 10mm for pivot

Evening all!

So I've bought an 8mm bolt and a 10mm bolt to cut down to use as the pivot-bar of my tickler, I think the draw weight will be about 150lb. I can't really see much of a difference between them and so was going to use the 8mm bar as this will give me a slight advantage in the carving I am planning to put into the side plates but the advantage is marginal and I wouldn't want to compromise the bow.  Is 8mm sufficient, or 10mm, or should I go with a different size altogether?

I think 8mm would be stout enough for 150lb. I've used smaller rods without issue- usually 3/16 inch, which is less than 5mm, I believe.
Gnome

For bows under 200 lb. draw (most of mine) I use a 12/24 machinescrew, supported at both ends by nuts inlet into the stock.  That comes out to about 3/16 inch.  8 millimeter is about 32/100 of an inch... that should be plenty strong for your project.  Geezer.

That's great info., thanks both, I think I'll go for a 5mm bar in that case.  Geezer, you anchor yours with captive nuts?  I was going to use an interference fit so the mechanism could be easily dismantled for tuning and maintenance; is this approach unwise?

I use captive nuts so the pin can't wallow out its passage thru the stock.  My journeyman/former apprentice, Lightly, uses 3/16 in. diameter 'music wire' mounted thru thin brass tube to line the passage for the same effect.  She glues her pins in place.  They can be knocked out fairly readily, but generally stay in place quite nicely.  I prefer using machine-bolts thru captive nuts because I find them easier to assemble/disassemble without glue. Of course it's a bit more trouble to drill oversized holes and hammer in the nuts.  So It's a matter of choice.  The whole point was to have a trigger pivot pin that was strong enough, required the minimum hole thru the trigger/tickler, and wouldn't work itself loose after thousands of shots.
You have to remember I'm making several dozen crossbows a year that go to a wide variety of users.  What might work out just great in your personal bow, may not be optimal for field repair at an outdoor event in the middle of nowhere.  For me mechanical accessibility is really important.  Medieval bows almost invariably used thicker trigger pins, thicker triggers (thru the middle anyhow) and riveted them in place over washers, so they couldn't be disassembled.   Geezer.

Hi, I usually use 6mm silver steel on my crossbows. With metal side plates the sheer strength it more than adequate. I also run the nut in a saddle  with a thread through the hole in the nut rather than having a pivot rod. I have used this on medieval crossbows up to 250lbs draw with no bending.

Thanks guys that's been a huge help