DP Mortising

[Michael O'Sullivan]

I am using my Grizzly DP to do some 1/2" x 3/2" morticing through 4/4 hard maple.

Two issues have come up.

First, especially on the initial penetration, it is dang tough to extricate the morticer from the wood. The mallet-banging that is required has taken off the chuck itself the last couple of times. Any suggestions?

Second, the morticer has a tough time ejecting all the cuttings. This leads to high friction and super-high heat as the bit rubs against the chisel attachment. I have the DP set to about 500 rpm for a 1/2" bit. Will increasing the RPM help?

Thanks/

[Steve Rowe]

Michael,
I have two suggestions:

Hone the sides of the mortise chisel just like you would the back of your chisel or plane iron. Most chisels have machine marks that cause resistance during insertion and extraction.
From what you describe about excessive heating, it doesn't sound like you have adequate clearance between the bit and chisel. When I had a hollow chisel mortiser, I used a piece of laminate with a slot cut in it as a shim to hold the mortise chisel down 1/16" from the chisel holder. Use this to set the bit height. When bit is set remove the shim and raise the mortise chisel to the holder and tighten. This should give you the correct clearance.Hope this helps,
Steve

[Jim Becker]

Also make sure the bit projects below the chisel by about the thickness of a nickel...the bit does the work and the chisel is only for cleaning the edges/squaring the mortise.

You may want to get some honing cones to sharpen your chisels if you have not already done so...even new ones are quite dull and that's going to cause binding and crushing of fibers. It's even worse in softer wood, believe it or not.

I'm a little confused about your extraction issues...the hold-down should keep the material on the table as you raise the chisel/bit with the quill handles. Even with the short arms on a DP handle (as opposed to a dedicated mortiser, you should have enough leverage to lift the cutters if the material is held in place by the hold-down arms.

[Michael O'Sullivan]

Thanks for the suggestions

[Michael O'Sullivan]

I finally threw in the towel on the DP mortising attachment and bought a Steel City benchtop mortiser. Wow! What a difference. The DP version actually yanked the chuck out of my DP -- twice. After the second time, I just stopped using it.

The SC is much smoother. Even with the 1/2" chisels, the heat/smoking factor is very manageable, and the cuts are nice and clean.

My one question is, when measuring the extra distance that the bit should be set down (i.e. protrude) from the end of the chisel, what reference point do you use? Is it from the tip of the bit, from the lowest (i.e. closest to the tip of the bit) part of the first cutting flute, or from the highest part of the first cutting flute? I feel like I have the bit protruding too far, but I would like to know what others do.

[Paul Murphy]

After making the setup error of not having the drill bit properly extended, I now do as Lee Valley suggests, which is pretty much what other posters mention. Just thought you might want their excellent setup instructions for further pointers. I also need to try to hone the exterior of my chisels as Steve suggests, I too get quite a bit of resistance to removing the chisel from the mortise.

http://www.leevalley.com/wood/page.aspx?c=2&p=53252&cat=1,180,42240,53317
http://www.leevalley.com/html/04j1016ie.pdf
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(04J11.04 to 04J12.25)

Basic Installation

Improperly setting up the chisel and bit in the holder can result in excessive heat build-up that can damage both the bit and chisel. Fortunately, proper set-up is quite straightforward and easily mastered.

1. Disconnect the power to the machinery.

2. Insert the shank of the chisel into the chisel holder with the chip ejection slot facing either right or left.

3. Position the chisel shank so that a space of approximately 1/32" is left between the base of the holder and the shoulder of the chisel (it is traditional practice to use a dime for spacing). Clamp the chisel in position using the thumbscrew located on the front of the chisel holder.

4. Insert the shank of the drill bit up through the chisel until firmly seated against the mortise chisel and then secure the bit by tightening the drill-press chuck.

5. Loosen the thumbscrew located on the front of the chisel holder to unclamp the mortise chisel.

6. Push the chisel upward to remove the 1/32" space created in step 3 and retighten the thumbscrew.


This set-up provides the necessary clearance between the mortise chisel and drill bit for proper operation.

Shortening the Drill Shank

The length of the bits (between 8-3/4" and 11" long overall) makes them compatible with a variety of mortisers. However, they may be too long for some mortisers. Fortunately, the shanks are soft enough to be easily docked if required.

1. Follow steps 1 to 3 above.

2. Insert the shank of the drill bit until bottomed out in the chuck. Tighten chuck.

3. Rotate the drill bit until its cutting spur lines up with one of the front corners of the chisel. Since the spur is curved, it is important that the apex of this curve coincides with the chisel tip. Eyeballing this is perfectly acceptable, but there should be no major misalignment.

4. Measure the distance from the cutting spur to the chisel tip. This is the amount that needs to be removed from the drill shank’s length. Add 1/8" to this measurement, so that the drill doesn’t bottom out in the chuck. Use a black marker to mark the amount of shank to be removed.

5. For easy clamping, we recommend making a pair of hardwood jaws for your vise. Cut two pieces of hardwood, approximately 1-1/2" X 2" X 3/4" and clamp them together. Drill a hole the same diameter as the drill shank through the two pieces. This is most easily accomplished with a drill press.

6. Install the drill bit in the hardwood jaws and clamp in a vise.

7. Cut the shank with a hacksaw, file the surface smooth, and apply a small chamfer around the end to remove any burrs.

8. Return to step 4 of "Basic Installation".


Realigning the Chisel Holder in a Drill-Press Chuck

If the chisel and bit emit a loud grating noise during use in a drill-press mounted mortising attachment, the chisel holder may need to be realigned with the drill-press chuck. This is accomplished as follows:

1. Loosen the drill-press chuck and remove the drill bit from the drill press.

2. Loosen the thumbscrew located on the front of the chisel holder and remove the mortise chisel.

3. Slightly loosen the handle on the chisel holder enough to allow the holder to be pivoted left or right as needed. Do not remove the holder.

4. Insert the quill alignment pin, small-diameter end first, through the bottom of the chisel holder and into the drill-press chuck. You may have to manipulate the chisel holder slightly to allow the quill alignment pin to fully seat inside the drill-press chuck.

5. Tighten the drill-press chuck to secure the alignment pin in the chuck.

6. Tighten the thumbscrew on the front of the chisel holder to secure the alignment pin to the chisel holder.

7. Tighten the handle on the chisel holder to secure the holder over the split ring collars on the quill.

8. Loosen the drill-press chuck and the thumbscrew located on the front of the chisel holder to remove the quill alignment pin.

9. Reinstall the mortise chisel and bit as described above.


For complete installation, set-up and usage information, please refer to the operating and installation instructions included with your mortising attachment.
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