I have used the template set (Irwin, IIRC?) and it worked well. It's trickier perhaps in the enlargement scenario. I usually just use a plywood template clamped down really well. You don't want it shifting. You just need to get a 1/4" start for the new bore, then you could take off the guide. I recommend drilling from both sides to prevent tearout, or back up the cut with a scrap of wood, but drilling both sides also improves the precision.
Casey

There is a special hole saw arbor that allows two cutters to be mounted.
The smaller cutter matches the existing hole size and guides the larger cutter.

You can also bore a piece of 2x lumber with the larger cutter and then clamp it to the door to control the larger cutter.

Don't have the locksmith prep the door. The locksmiths I know refer this sort of thing to us carpenters. If you follow Casey's advice you will do a better job yourself.

The store-bought jigs are pretty lousy. We have a Porter Cable set that has no value other than the box to keep the bits together. I recommend using thin plywood templates and drilling from both sides.

Can I assume that 1/4" plywood would work for templates? I think I can do this. I believe the secret will be to measure carefully, do a practice cut with the hole saw, make sure the templates are tightly clamped, drill from both sides, and DON'T RUSH!

I'll go ahead and order the hardware. I'm also going to replace the leaded glass (it's in bad shape) and strip and refinish the doors. I have an oil-based stain which matches my other wood and I'm going to find a post I saw here about finishing with non-tinted base paint.

I'm sure I'll be back posting here for help with this project. I'm nervous about having the front doors removed for the time it takes to refinish.

Thanks, everyone!

"Can I assume that 1/4" plywood would work for templates? "

Thicker works better since there is no drill bit to hold the saw centered, and there is a decent amount of torque present when the teeth start to cut.

Starrett call it the 'oops arbor' for enlarging holes.

Oops arbor

Here is a link that might be useful: oops arbor

The enlarger arbor is concentric, and I wasn't clear whether that was the condition at hand; the plywood template allows the new hole to be placed eccentric to the old hole, or wherever. The thing would be to make sure the new hole matches the new lock's backset value.
Casey

Yes -- the backset of both the deadbolt and handleset latch are now 2 1/2", and I need to maintain that. I like the oops arbor, but I'd also need to purchase two hole saws (1 5/8" and 2 1/8") to enlarge the 1 5/8" hole to 2 1/8" -- right? If I carefully measure, I should be able to use the plywood template and a single 2 1/8" hole saw to enlarge the hole concentrically. If the oops arbor is more foolproof, I should go with that. Which do you guys recommend?

I would not trust thin plywood to make sure a 2+ inch hole saw did not skate on the surface without a center pilot bit.

Even with a low RPM drill, there is a lot of torque if the hole saw grabs unevenly as it starts to cut.

I agree against using 1/4" ply, should be half-inch.
Casey

IMO the opps-arbor is by far your best choice. You should back up the hole with a piece of pine or other wood to minimize tearout when you exit the hole. With the opps-arbor, your backset would remain the same. As far as hardware, either choice would be good.

"You should back up the hole with a piece of pine or other wood to minimize tearout when you exit the hole."

Drill part way through (about 1/2) and then finish form the other side.

I ordered the oops arbor and a lockset hole saw kit, both by Starrett, so they should be compatible. Thanks so much for all of your input on this.

Here is a link that might be useful: Lockset Hole Saw Kit

Make sure you use a LOW RPM drill.

If you spin a hole saw fast it will burn and if you press to hard when boring it can grab.

My oops arbor and hole saw kit arrived today. My dummy door will go to a millwork shop tomorrow for a replacement astragal. The glass company should come by Friday to measure for replacement reed glass in the windows. The handlesets should arrive next week.

I need to strip the finish from both doors, drill the new cross bores, stain and finish, install hardware and rehang. I hope I'm up to the task and can figure out how to do all of this without leaving the doors off overnight.

I might as well start stripping them now, while they're still hanging. I can remove the doors early on "the big day", remove the hardware and strip the inaccessible places (top, bottom, sides and behind hardware). I'll need to stain 6 sides (1 hour minimum dry time) and apply paint as a clear finish (bobsmyuncle posted about it in another thread) - 2 coats front & back and 3 coats on edges. I need to get to the paint store to buy oil-based exterior paint for deepest color without pigment. I hope the dry time of the paint won't preclude me from finishing in one day -- I'll have to wait for one side to dry before putting a coat on the other side.

I think I may try to have the glass installed after I finish everything else. If I don't damage the trim pieces which hold the glass, I can stain and finish them separately, then reattach when the glass is installed. I should be able to stick 1/4" plywood in the windows until the glass is installed.

Sorry to go into so much detail, but if anyone is still reading this, do you think this plan will work?

Thanks!

Here is a link that might be useful: Paint as a clear finish