Just received my new Powermatic Mortiser and have questions

[Joe Cowan]

I bought the Premium bits from Lee Valley in the 1/2" and 7/8" sizes. The instructions for set up have me adding a chuck extension if I am using short shank bits. It says these are extra long bits, but I want to make sure. I would think I would need short shank bits for this tool, as this is a bench top mortiser. Below I will show what I bought from Lee Valley. Any advice appreciated.





Premium Hollow Mortise Chisels & Bits











http://www.leevalley.com/US/images/item/woodworking/drilling/04j1104-dsp.jpg






Made from special carbon steel, these excellent-quality chisel-and-bit sets from Japan are attractively priced. The chisel bodies, accurately ground and hardened to Rc47-51, have polished outside faces and smoothly machined inner bevels. Designed for efficient chip ejection, the drill bits have well-ground cutting tips and spurs, and are extra long (between 8-3/4" and 11" overall) for compatibility with a variety of mortisers.

[Stephen Cherry]

I've always cut off the inner bits at the correct length. In any case, have a bowl of Wheaties before using those bits- they are pretty big.

[Joe Cowan]

I've always cut off the inner bits at the correct length. In any case, have a bowl of Wheaties before using those bits- they are pretty big.


I will be using them on cypress for my first project which is soft, but get your point for sure.

[Michael Heffernan]

I have those same chisels and a PM benchtop mortiser. They work fine; no need to cut them down. 7/8" chisel? That's mighty big for this mortiser. What is the shank size? The largest I've got and used is a 5/8" chisel.

[Joe Cowan]

I have those same chisels and a PM benchtop mortiser. They work fine; no need to cut them down. 7/8" chisel? That's mighty big for this mortiser. What is the shank size? The largest I've got and used is a 5/8" chisel.

Not sure the shank size, but the mortiser came with a bushing to receive the 1/2" bit I have, as well as a 2nd bushing that receives this 7/8" chisel.

[Gary Muto]

Joe,

I have those chisels (4 pc set) and use them on a smaller mortiser. The bits are long so that they can be cut down to fit smaller machines. I only took off a small amount and it was easy with a hacksaw. View the instructions http://www.leevalley.com/US/shopping/Instructions.aspx?p=54295

It covers shortening bits and also setting proper bit/chisel clearance. I recall it was a little more humerous previously. It read something like; "If you chisel bit turns blue due to excess heat, you will need to look in a mirror to identify the problem". Something like that anyway...

Good Luck and Enjoy.

[C Scott McDonald]

Have you used the cone sharpener with any luck?

[Kent A Bathurst]

Sharpen frequently - just like a bench chisel or plane iron. The cone sharpener works as advertised. I "paint" the inside with a Sharpie so I can monitor my "verticality" skills with the cone and cordless drill.

Hone the outside just like a bench chisel. One word from the "Lessons Learned" folder: Be very careful that you do not change the geometry of the HCM sides. By this I mean that you want to be sure you never change it from flat along its length to a situation where the last bit - 1/2" - 1" - is every so slightly narrower than the body. When this happens, you can still make the plunge, but the body gets stuck on the sides of the cut and you cannot get the HCM back out without a hammer on the wood and cusswords filling the air.

It is possible, especially with softer woods, to over-muscle the plunge. You want to make it a steady, smooth plunge that does not create chips faster than the drill/chisel can clear them. Chips clogging the HCM cause the "Blue Steel of Death" by overheating.

Flight instructions:
1. Set the HMC with the chip slot on the left or the right side.
2. First plunge with the slot at the end of the mortise.
3. Move away from that end, so that the chips can eject into the previous plunge.
4. Work your way across the mortise - as you approach the other end, skip a plunge and go to the very end end. Clear it, and then back up to clear the bit that you skipped. This gives you a cleaner mortise end. Believe it or not, there is enough force in play that if you don't do this, that last plunge will not end up dead-nuts vertical - you get a slight angle - the force moves the HCM off-line as you plunge, unless it has wood mass on all 4 sides.Wouldn't have believed it until I saw it.

I have a small dispenser bottle with a pad on the end - full of camellia oil - that I use on planes. I also swipe this on the sides of the hollow chisel before each mortise (not each plunge). Seems to help - virtually all of my mortises are in very dense QSWO, so YMMV.

Thousands of mortises on my PM 719 over 13+ years. It doesn't have the machine hours of, say TS/planer/jointer. But it plays in almost every game. Wouldn't be without it.

One last observation on the LV HCM - I like them a lot. Beware, though: they do not [or, did not when I last inquired] have replacement drill bits available - you have to buy an entire HCM set. Sharpen the bit as well as the HCM, and remember plunging too fast and/or chronic overheating are very efficient methods for snapping the bits. DAMHIKT.

[Gary Muto]

Have you used the cone sharpener with any luck?
I've used the Rockler Hollow Chisel sharpener kit. It comes with a handle and 2 cones. I use the handle instead of a drill for more control. Honing the outside of the chisels is very important too. I just use an coarse/fine oilstone for that and it polishes nicely.

[Ken Fitzgerald]

I use 2 sharpening kits. One from Woodcraft which is really reamer similar to what people handloading bullets use. First I ream a hollow chisel. Then I use the Rockler kit which consists of 2 diamond hones and handle.

I made my version of Norm Abram's porch swing last year out of white oak. There was between 40 and 50 mortise and tenon joints. I sharpened before I started and another time midway through the project.

For a mortiser to work well, it's imperative that the hollow chisel be sharp as stated just like a chisel or hand plane.

I also sharpen the bit with a jewelers file.

When both are sharpened properly, a mortiser is a joy to use!