First run of new PM mortiser.

[T.J.]

I'm working on a split-top Roubo bench ala Bench Crafted. In the planning process, I decided accuracy and looks were more important to me at this time than doing the wood work by hand.
So, I decided to invest in a bench top mortiser. I can't justify the floor-standing version right now, but I did want to buy the best one I could manage. All the reviews pointed me toward the Powermatic.
Though it hurt my heart a little to bring in this foreign made machine, I'm happy so far with the quality.

Does anyone have this same machine and could offer any advice on optimal use? In my first few mortises so far, I've learned:

1. The gib has to be fairly tight and only loosened enough to allow the arm to move the head. I had some slop in it at first which cause the bit to shift over the second half of the travel. I've got that fixed now.

2. Having the chisel size match my desired mortise is better than using a smaller bit and taking two passes to get the desired width. I've done that on the first two mortises and the result is serviceable, but I have ordered the 5/8" bit (my mortise size) from Lee Valley and will continue when that comes in.

NOTE: I have three mortise chisels to start (JET brand 1/2, 3/8, 1/4, I think.), but the 5/8" will be from Lee Valley.

[Steve N]

Good quality bits usually come sharp, but all that shearing action makes them dull pretty quick. Lee Valley has good sharpening stones, and you'll need a good flat stone to lap the backs.

See the cone sharpeners



A how to


Setting the gap between chisel and bit is very important. LV instruction sheet Open the link and look for "INSTR" on the first line

Beyond properly set bits that are VERY sharp, the next big thing is work holding and positioning. Many use an XY vise. I like sized blocks of wood and just hand hold the stock in place, pushing in to hold it firm, using a sized block of wood the space where I want the mortise is assured. Plus I find it can be used on almost any size of stock.

Beyond that the machine itself is just a lever arm, that allows you to push and shear with the chisel what isn't drilled away with the bit.

[T.J.]

This is great. Thank you, Steve.