There are many ways to mortise a door, to take a lock body.
One way which I really like is to use an electric mortising machine with a vacuum port. It's cuts clean, fast and accurate, however the initial investment to get set up with one of those machines is between $2,500 - $6,000.
Let me introduce you to another way of mortising, which is very similar but far less expensive.
You can mortise using the TIDY TRADIE Router Jig, a large plunge router and a special long reach cutter.
Note, this is advanced routing! Extra caution must be taken when handling the router.
Plunging to a depth of 100 is possible using a large plunge router and a 160 long 16 wide cutter. This requires you to use either a shorter cutter to begin with, using a second router with a shorter cutter or even pre-drilling the mortice pocket.
These pictures will explain why and you can watch the video at the bottom.
This shows the Festool 1400 with the 160 cutter fully inserted into the collet. It projects out from the base by 36. The router jig is 20 thick, therefore a depth of at least 16 needs to be removed from the door using one of the methods mentioned above. This is if you have a 20 copy ring that fits flush into the base.
This shows a 20 copy ring fitted to a Trend universal base which is 8 thick, leaving a projection of 28. Therefore a depth of at least 8 needs to be removed from the door using one of the methods mentioned above.
The length shown with the cutter fully inserted is 97, giving a maximum plunging depth of 77. Once the mortice cut-out is complete, the cutter can then be extended out from the collet.
With the cutter secured at least 30 into the collet, it now projects 56 from the base.
The maximum plunge depth is now 103. Extra care needs to be taken when plunging and cleaning up the cavity sides.
Because the dust extraction from the router jig is so effective, plunging this deep is much easier than you think.
It is hard work on the arm muscles if you're attempting this vertically but preferably you would have the door on edge in secure door stands.
Pivot mechanisms which go into the ends of doors are the hardest to do, but it's a great arm work out!