On Sunday, October 15, 2006 10:20:30 PM UTC-7, blueman wrote:
I need to mortise out a door to accept a Baldwin mortise lock.
I know that the tolerances are really tight (with errors being pretty
disasterous) and that locksmiths typically use a router with a fancy
mortising jig.

However, I have not been able to find the jig in the local tool rental
shops, so I was wondering whether there are any reliable alternative
approaches or sources for a good jig?

Thanks

Yes there is but you need patience.

I had a chinese mortise lock set my friends got in China of all places.
First of course you will need to router your outer flange area that will hold the mortise lock in place.
Next, I was able to go to Home Depot and buy a 5/8" dia hole drill bit for my drill. I installed the bit on my drill with the shaft at it's "utmost extended portion" of the shaft. (I used a drill with a hand tightened chuck). Usually the lock set has a pattern so I marked were my lock set was going to be using this pattern. You have to make sure your drill is at a 90 degree angel at all times while drilling the gap out. I had to use about 7 holes befroe I was done.
Next, I got a very sharp wood chisel and a hammer and cleaned up the edges going deep into the wood. Get a vacuum cleaner to clean out the hole from time to time so you can see what you are doing.
It may be rugged but if you are careful you will get the mortise hardware in the gap easily.
Next using your stencil pattern mark your holes, drill the holes then install the lock.
Taa Daa!
Mine turned out pretty god.