This should accurately contour the bridge's foot to the shape of the table once it is roughly chiselled to shape. Use a piece of paper to plan out the exact location of the remaining strings.
Make sure you leave the front lip of the saddle alone, to 'stop' the string cleanly, don't round it off. How do I know what strings to use? Several of the mandolin family of instruments have different tuning possibilities.
Instead of drilling holes in a straight line and angling the saddle like Martin does on most modelsCollings angles the holes to match the saddle. This page will, hopefully, help answer some question and clarify some terms.
Place the fence to center the bit in the slot. Mark the string locations on the bridge or saddle with cutting bridge slots pencil or knife.
Angle the back of the groove towards the tailpiece with the break angle of the string. The right ball is in a slotted hole, pushing against a non-slotted pin.
It is unlikely on a mandolin, that the bridge should need to be pushed back by more than 3mm. This gives you the approximate height of the top of the bridge saddle as a starting point.
NB with a shelf bridge, almost all the adjustment needs to be to the bridge foot, though if you are careful, you can shave down the shelf itself a little. An extra pair of hands is useful here! On the left, we have the inside of a non-slotted hole.
It depends on the sound you are looking for, and it may take several different bridges to achieve what you want. Then will be the time to check the bridge slots and the level of the strings.
If the hole were truly non-slotted, the string would actually dive into the bridge IN the pin, creating even less of a break angle.
It's not a huge difference, but you can see that the ball on the left is trying to push itself into the groove in the pin. I like to have just a little "push" on the pins to help hold them in place, but you can definitely feel the string "click" into the plate.
The bridge on the left is slotted but not ramped, and the bridge on the right is slotted and ramped.
Do so often now, as outlined in step 4. Slotted Bridges There's some confusion and many questions about slotted bridges.
There is a MUCH larger overall groove on the right and the ball will, over time, work its way into that groove. The scale length of an instrument, is theoretically defined as twice the distance between 0 or nut if there is no 0 fret and 12th fret.
You can cutting bridge slots them up just a little to more closely match the angles, and thus create a little more even pull on the saddle.