Replies

1. 
   Telemike | Jul 20, 2005 08:03am | #1

   Some of the magazines I've read (including FWW) have had mortiser articles the last few years.

   I have a drill press attachment gathering dust and a cheap benchtop (gift) mortiser that I use. I've learned the following:

   1. The drill press mortiser is only so accurate given all the moving parts in a drill press: head, quill, table, and mortising attachment.

   2. If a piece has multiple mortises, slide it forwards and cut each mortise with the piece pointing in the same direction. With my mortiser, I made some symetrical door mortises and flipped the stiles end for end to cut the mortises. Since the pressure of chisel made the mortise cut slightly off perpendicular to the table, flipping the piece end to end made the mortises off in complementary directions on each piece and the doors I was making were warped. Take my advice: Don't flip a piece end for end; mark the mortises on each end and slide the piece along the table and the errors will be insignificant rather than adding together.

   3. Leave the cutting edge of the bit about 1/16 below the chisel. Run the bit slowly and feed slowly. Wax the bit and keep the exit chute in the chisel clear. Don't overheat or your bit will loose it's temper.

   4. Lee valley sells some diamond cones that are perfect for sharpening the chisels.

   5. Cut each end of the mortise first, then remove the stock in the middle.

   6. Yes, it takes some pressure to cut the mortises. The bigger the chisel, the higher the pressue. It is probably unrealistic to use more than a 1/2" chisel with a drill press attachment or even a small bench top mortiser.

   7. If you're making through mortises, clamp the workpiece to a sacraficial piece of wood to prevent blowout on the exit hole.

   All of these bits of advice were accumulated the hard way.

2. 
   JimE921 | Jul 20, 2005 08:12am | #2

   I got some cheap ones and had a heck of a time with them. I don't know about where the auger should be but I had to polish the outside of the mortise or what ever it is called and sharpen the auger and the mortise cutter. It helped but I still have to apply a good amount of pressure. For me it seems that the larger the mortise I'm trying to make the harder I have to pull on the handle. Now I know that I have made a fool of myself but regardless of that I will be back to see what others have said.

3. 
   joinerswork | Jul 20, 2005 03:32pm | #3

   brian,

   The advice you've gotten so far has been good.  I'll add that you might want to check that the outside faces of the chisel are parallel.  I've seen ones that were tapered, thru incorrect machining or sharpening (careful to hone the whole outside face, not just the bottom inch or so), so that they wedged tighter the farther in they were pushed.  Polishing the outside faces of the chisel will reduce friction. And sharpening the cutting surfaces helps too.

   The speed I use is just a bit slower than I'd use for a drill of comparable size. Other shops I been in like higher speeds, experiment to see what works best for your machine. Feed rate is also important--it's easy to "choke" a small (1/4"-5/16") mortise bit.  Feed slowly enough to allow chips to be ejected.  Resinous woods such as pine are a real problem, as the chips tend to stick together.  It seems to me that extending the bit too far below the chisel yields a bigger chip, and increases clogging.  On the other hand, too tight to the chisel, and overheating is more likely.  I drop the bit down about 1/32" or a little more.  No more than 1/16, even on large (1/2" or bigger) chisels.

   In addition to punching the ends of the mortise first, I recommend leaving a space slightly smaller than the chisel on each side when punching out the center portion.  Then come back and punch these spaces out last.  This equalizes the stress on the chisel, and yields a more uniform mortise.  It will tend to walk towards the unsupported side if you just nibble from one end of the mortise to the other.

   Regards,

   Ray

4. 
   WillGeorge | Jul 20, 2005 05:29pm | #4

   and I was only trying to drill into pine!!

   Soft wood is HARD to Mortise.. Hardwood cuts MUCH better...

   I like you HAD one of those I used for many years till I got my routers and my Jet Mortise.. I use the routers most of the time..

   I have 'looked' all over for some text on auger dept to the chisel and I have never found anything specific...

   I 'think' (gets me in trouble) you want the auger to cut about 1/2 of the circumference of the hole and the chisel just cuttin' behind it..

   I think it is sort of a 'ART' I never got !

    

1. 
   brianmexico | Jul 20, 2005 10:36pm | #5

   Thanks to all,

   I appreciate all the advice that's learned the "hard way", and I'll be sure to try and take the steps afore mentioned by all. If someone could give me somekind of an idea for RPM's it would help to hone in on that ideal speed. I have the thing set snail speed now because it seemed to me to be the proper way to run the thing, I'll step up the speed a bit and see what happens.

   Is the general preferance toward the mortisers like the ones featured in the review that FWW just did or do the router jigs win the battle for ease of use???

   Brian

1. 
   AlbionWood | Jul 21, 2005 01:54am | #6

   Brian, the motor speeds on benchtop mortisers - which use exactly the same chisel/auger tooling - are either 1750 or 3500 rpm. General consensus seems to be that it doesn't really make a difference. My little Jet BT mortiser runs at 1750. It sounds like you may have your drill press running too slowly for good chip ejection. I used a drill press mortising attachment before I got the BT mortiser. The drill press flexes too much, as someone else noted, causing the mortises to drift away from vertical. One thing you can do to make it easier: use only the 1/4" chisel. It is far easier to push in than the larger ones. I just make multiple passes if I need wider mortises. The other big problem with the drill press is keeping the fence parallel to the face of the chisel. I don't have any solution to that.I also use a plunge router with an edge-guide for a lot of mortises; it gives a much better result. The BT chisel mortiser is mainly for deeper mortises and faster setup.Now it is time for Rick to remind us that slot mortisers rule!"Everything should be made as simple as possible, but no simpler."  A. Einstein

   http://www.albionworks.net

5. 
   Steve50 | Jul 21, 2005 03:18am | #7

   Brian,

   Take a piece of plastic laminate scrap (if you don't have any go to a cabinet shop and they will probably give you some) and cut a u-shaped slot into about a 2" x 3" piece.  The slot should fit around the round shank portion of the square chisel.  Place your chisel in the holder using the laminate scrap as a shim between the chisel and holder and tighten the chisel in the housing.  Remove the laminate scrap.  Then insert the bit into the chisel as far as it will go holding in place with a scrap block of wood over the tip (fewer holes in the fingers) and then tighten your chuck.  Loosen the setscrew for the chisel and insert fully into the holder.  This will give you the correct clearance between the chisel and bit.

   Steve