Drill bit size

I need to know what size drill bit to use on the nut and trigger for the pivot point on the crossbow? It show's 3/16 of an inch, but I would like to here from you guys. Who been doing this for awhile. The nut size is 1 1/2" diameter, trigger is 3/8 x 3/8 any help here thanks.

with 3/8 in. trigger stock, a 3/16 drill is about right.  Anything larger leaves too little metal on both sides.  Anything smaller gives you a pretty thin pivot pin.  I use 3/16 machine bolts to hang my triggers... that lets me inlet a nut on each side of the stock, so the trigger is well supported.  My apprentice, Lightly, prefers to line the passage with brass tubing and hangs the trigger on a 3/16 in. steel rod, either stainless or hardened music wire.  That gives her a slightly stronger pivot pin, but it's more trouble to remove in case you need to re-surface the distal end of the trigger.  Six of one, half a dozen of the other.  It's one of the few places we differ in mechanical details.
Geezer.

Post script.  3/16 machine bolts work out to no. 12/24 machine screws. One can heat the 3/8 in. trigger stock where you intend to insert the pin and flatten it a bit side-to-side with a hammer.  That gives you a slightly broader trigger at the critical point, so you'll have more metal on each side of the hole.  In fact, many of the medieval triggers I've seen were more like 1/2 inch wide where the pivot pin goes thru, but I consider that overkill for a lightweight bow (say under 200 lb) and it increases the labor required... that matters a lot to me when I'm making bows for sale. With heavier stock, I either have to charge more or eat the difference myself. Geezer

Geezer, I like the way you explain your thoughts. I can see where lightly is coming from also. I'm kinda dumb but, I agree with her. Reason being , if your shooting enough to wear out the brass liner, your gonna need to rebuild a lot more than the tickler. She is on to this stuff. Just think a weeks work --- to maybe an hour.He,He.But seriously , there are a lot of ways to skin a cat, especially here. There is a fantastic mix of thoughts from you older timers at the hobby.

Geezer back again!  yes, the whole question comes down to a combination of speed of assembly and serviceability versus ultimate strength and appearance.  Lightly is a very meticulous crafts-woman who wants everything to look perfect.  By and large, she's successful at that. There's no doubt her finished product looks prettier than mine.  On the down side, it takes her 3 times as long to build a bow and if/when it requires service, which does happen now and again, disassembly and re-assembly takes her longer as well. Real medieval bows went a step further.  About the only screw you'll see in a medieval bow holds in the bolt-clip, assuming there IS a clip. They riveted everything together. It looks cool and is very strong, but God Forbid you ever have to take your riveted bow apart! 
I work on the assumption that any and every bow may come back for service and I jolly well want to be able to get in there, fix it, and get the bow back to my customer.  Lightly... well she just takes longer.  Smartass....

PS: the wear on the trigger probably won't be at the brass liner anyway, though I do like the idea of reinforcing the wood where the pin goes through.  The greatest wear is always at the distal end (fore-end) of the tickler and the sear-plug. If you harden those, they wear more slowly of course, but they do wear. I usually use mild-steel allthread rod for the sear-plug, squared off and slotted on the bottom end for the tickler to work against, and I use ordinary mild-steel square-section 3/8 in. bar stock for the tickler itself.  Occasionally I use stainless allthread for a sear-plug for stronger bows... that makes a harder sear-plug, which means the end of the trigger wears faster.  From a service/repair point of view, it's actually a lot more trouble to remove a tickler and heat/re-work the distal end to stretch and resurface when it becomes worn.  It's much easier to remove the roller-nut, slightly heat the sear plug (yeah, I put a bit of super glue on them) and then unscrew the sear-plug to replace with a new one.  So all things considered, I would prefer to replace a sear-plug rather than re-surface a tickler-end. Again, it's as much a business decision as anything.  Your mileage may vary.  Geezer.

My friend it's great talking to you. I have a question of sorts .If you use stainless in the wheel is there any way practical that you could mount it on the distal end also, without losing the benefit of stainless. Maybe ,over thinking this?Do you like hard on hard or, only one end hard? I'm dumb here.Don't know what's proper for the job on hand.

Hard to hard lasts longest of course.  Somebody on this group recently passed on a simple formula for a quenching agent that will substantially harden the mild steel used for tickler/triggers. One could harden the allthread as well, or if you're not building too strong, you can go with un-hardened mild steel. They'll stand up either way to thousands of shots.  If you go with the softer metal, just take a look at your sear now and again to see it's not wearing too much. Hard on one and soft on the other surface guarantees the softer surface will wear much faster, so you probably don't want to go that route.  Don't worry about it too much unless you're planning to use something like aluminum.  Years ago I made a lot of bows with brass triggers and brass sear-plates set in hardwood (maple boiled in petroleum-wax) rollers. Indeed the bows were light, only @ 70 lb. draw, but they stood up amazingly well. Some of those old wooden rollers are still in service 20 years later, though I can't really recommend doing it that way.  In fact, I did one bow with oak roller and brass trigger that drew @ 120 lb. and the customer shot for years that way. Again, I can't recommend it, but it DID work.
Geezer.

And of course, you could use stainless steel 3/8 in. bar stock to make your tickler as well.  It's much harder to bend, even hot, and a real bugger to drill, but it would be strong, wear-resistant and look mighty nice.  Though of course stainless doesn't heat-blue with a darn.  Just do it polished.  Geezer.

Thanks Geezer for reply, so I see the roller nut should be 3/16 also right? No word on the roller nut.
I'm using delrin for the nut.

If you're using a round roller nut in a 2/3 round socket, the diameter of your center pin isn't terribly important.  Actually you don't need a center pin at all to make the lock work, but if there's nothing at all keeping the roller in, there's a chance it will hop out on release, leaving you searching the grass and cursing.
Lots of medieval/renaissance bows simply ran several turns of stout cord through the center of the roller and under the stock to keep the nut in place. For a tied-in nut, I generally make the hole 1/8 to 3/16 diameter.  And of course you can fit a metal pin instead. A good stout pin will make your roller run a bit faster, at least when the bow is new, but in time, your pin may take a bend, in which case, it may actually slow the roller down or even jam it.  In that case, you remove the pin and put in another.  Generally speaking, on rounded north/central European bows that get a bound roller, I just tie the sucker in. If the lock fits correctly, the string will last for years.  For square-section Western and Southern European bows, I usually use one or two small metal pins hidden beneath the lockplates that fit into the center-passage by a quarter-inch or so. They're just long enough to keep the roller from hopping out on release, and are thin enough to offer no resistance to rolling.  I only use a full width roller-axle if my customer absolutely insists.  
Does that make sense?  Geezer.

Yes Geezer that makes sense to me thanks for your help on the nut and trigger.
Euell