Yes, those are the push-in kind, although I don't know about having to mortice them. (Mortising isn't that difficult.)

My problem with them is that there's always the possibility of them falling out over time, since they rely on those little teeth to stay in place, and when you insert/remove them a few times for repairs, or during the course of window renovation, they are bound to get loose and wobbly, perhaps?

The company that sells them didn't have instructions; they sell them as replacements. It seems to me that mortising very hard, old wood in a window channel is difficult, and it would be even trickier to do a curved edge.

If I have to mortise - learn to mortise - I will buy the pulleys with squared edges. But I am trying to avoid that part of the job.

Drill the correct hole for the top and bottom and then cut between the holes.

Good brad point bits cut clean (the ones with actual cutting spurs on each side of the point).

Keyhole saw or a portable jig saw if you are careful (use a fine tooth blade).

Thanks, Brickeyee. I understand the part about cutting the hole for the pulley mechanism. It is the mortising for the rim that concerns me.

Are brad point bits similar to Forstner bits?

Long ago I was working on an old house that had this style of pulley, and the original carpenter had whittled a peg to pass through the hole (which lined up with the backside of the jamb) providing a failsafe in case the serrated teeth worked loose. But it depended on the jamb thickness being agreeable.
Casey

" I understand the part about cutting the hole for the pulley mechanism. It is the mortising for the rim that concerns me."

If the metal is tapers thing enough there is no real mortise needed there.

"Are brad point bits similar to Forstner bits?"

Brad pints are less expensive and better in hand drills than Forstner bits.

they have a more standard twist drill body, but a tip optimized for clean wood cutting.

A central spur for location ad cutting spurs at the outer edges of each flute (similar to an auger bit).

Good ones cut nice holes, cheap ones tear like a split point pastern twist drill.

My favorite Forstner-type bit are the sawtooth-edged ones by Bormax. They cut as cleanly as a forstner but more aggressively, and work well freehand outside a drill press. They are also $$
Casey

No need to mortise. I have these pulleys on all of my windows and have replaced a few. As long at the opening for the pulley is the right size, they will sit flush with a very slight reveal. The reveal will not affect the window operation

Diane

"My favorite Forstner-type bit are the sawtooth-edged ones by Bormax. "

Not really a Forstner any more (there is an old Forstner patent, long expired, that defines the bit).

The toothed ones fail at the one very special thing the bit is good at, drilling overlapping holes at an angle to the wood surface.

Brickeyee - do they make brad point bits in larger sizes? The largest I'm finding is 1/2 inch.

Try Woodcraft.

They go to at least 3/4 inch.

Use a LOW RPM DRILL.

Here is a link that might be useful: woodCraft Brad point bits