Mortise Question

[Dan Hulbert]

I have 320 M&T joints to make on my current project. Does anybody have a good way to clear chips out of ¼” wide by 1 ½” deep mortises? I use a hollow chisel mortise machine and punch the ends first, then I work from right to left to finish the mortise, chip ejection slot is to the right.
I’ve been spending as much time digging the chips out of the mortise as I have been drilling them in the first place. There’s got to be a better way.
Thanks

[Neal Clayton]

probably why there were a lot of chainsaw mortisers being used in the old days when machines first came into production shops ;).

[Leo Vogel]

Dan - when I was doing a lot of mortises with my hollow chisel mortise machine, I always had my airhose next to the machine. I would blow out the chips with the hose. Not too bad, but I can't imagine doing it without the airhose.

[Matt Day]

I wish I could help you, but i struggle with the same thing and did just this past weekend cut some for breadboard ends. Sharp bits/chisels will at least help make the process easier and hopefully limit burning/clogging for you. Blowing chips around with 100psi of compressed air might help, but that sounds messy!

[Neil Brooks]

All I can add is ... I feel your pain.

Last night, I had to bang out a couple dozen, on my Grizzly mortiser.

I spent as much time ... using a utility knife ... clearing out the chunks that would jam up the bit, as I did cutting mortises.

I would agree that .... a well sharpened bit ... and maybe a light touch of beeswax -- replenished regularly -- on the end OF the bit ... can't hurt.

I've got the tip of the bit extending 0.125" beyond the chisel points. What I haven't yet done is shrink that gap a bit. It MAY reduce the opportunity for substantial chunks to jam things up....

Good luck !

[Russell Sansom]

Have you tried drilling a relief hole in one end and working away from it? That's worked for me depending on mortise dimensions. A very good vacuum with a small nozzle works pretty well, too, depending on dimensions. You almost have to make a special nozzle ( say, 3/4" diameter ) and put it on an arm...like a gooseneck. I have the great big Fein shop vacuum that can do this

Compressed air might be the answer and probably for 320 mortises ( ! ) the only sensible answer. Be careful, though. You can damage your eyes very seriously. In a metal shop it's very bad form to use air to clean machines, though it's been done in half the shops I've had anything to do with. Projecting a thumbnail-shaped particle into your eye is a terrible way to ruin your day.

[Peter Quinn]

I usually like the chip ejection slot facing forward on a chisel mortiser. To the left or right and the chips go back in the hole instead of up and out as they should. A vacuum with small nozzle or compressed air, or both, is about the only way I know to get the junk out of the slot. I can tell you its much easier with a slot mortiser, as gravity is in your favor rather than against you! I hog slots on the bridgeport mill at work and use compressed air with a stiff flex hose that can be aimed at the slot. There is a dial type regulator at the outlet that sets the air speed. I stand to the right and blow to the left to minimize chips in the face, and wear good goggles to protect the eyes. It creates a chip storm that must later be cleaned up. I have also rigged up a vac at the machines head and used an occasional blast of air to clear the slot. This seems to get less effective as the slots narrow.

[David Prince]

You could try doing all the mortises with a hand chisel and see what takes longer! :D LOL

[glenn bradley]

When I use the Mortise Pal I have a shop vac whip-hose with a narrow nozzle hanging from a bungee nearby. I connect the vac to a deadman's switch. Plunge the mortise, step on the pedal and poke the nozzle near the hole, repeat.

[Dan Hulbert]

Thanks for all your suggestions. I did buy a new bit for this project and am having no trouble getting the chips out of the bit. I'll be giving the small nozzle on the shop vac a test run first, then try blowing them out with air. I really don't like blowing chips around with compressed air, but if it will speed things up, it may be worth it.

[Frank Drew]

I used an air gun with my slot mortiser; chips go everywhere but it's better than the slowup of recutting the same material (now in chip form) over and over.

[Stephen Cherry]

I vote for the forward facing slot also. First do the ends. Then work from one side to the next, leaving half a chisels worth of wood unplunged between the plunges. Then go back and get the missed areas. Then once more from one side to the other to clean everything out. With the sliding table, this goes pretty fast.

[Russell Smallwood]

Soooo....

Just to be contrarian. When I do something with lots of M&T joints, like the stiles on an arts and crafts headboard, I make a pattern out of hardboard and use an upcut spiral bit with a guide bushing.

Takes a while to make the hardboard jig, but if the parts are all the same, then you can build stops into the jig and avoid having to do all that layout to boot. Clamp the jig to the workpiece and go.

If you do it this way, you can use whatever dust collection is built into the router. Of course you have the extra step of making the tenon's round or the mortises square but...

[Cody Colston]

I always set up my chisels with the ejection to the right. I use a thick rubber band to attach the shop vac nozzle near the bit and it gets nearly every chip. I use a dime to set the bit extension below the chisel.

[Dave Cav]

My Newman T-20 (old arn) mortiser has a built in chip blower, so I'm afraid I can't help....


but I would try a vacuum cleaner set up to blow. This is one application where high volume at relatively low pressure might work better than an air hose. Also, I have my chisels set up to eject to the front.

[paul dyar]

I use air, but it is to keep the chisel cool. Use vacuum to get the chips out.
Paul

[Matt Kestenbaum]

+ 1 for Russell's suggestion -- use a router and 1/4" upcut spiral ...you could event use the hollow chisel mortiser to square up the ends.

[Kirk Poore]

My Newman T-20 (old arn) mortiser has a built in chip blower, so I'm afraid I can't help....


but I would try a vacuum cleaner set up to blow. This is one application where high volume at relatively low pressure might work better than an air hose. Also, I have my chisels set up to eject to the front.

As Dave says, an integrated blower would work best (I never have this problem on my Greenlee), and a shop vac probably second best. If the shop vac isn't working well enough, but your shop vac can be set up to blow as well as suck, you might be able to set it up to blow the chips off the work as they are generated. This will keep the chips from falling back into the slot.

Kirk

[Floyd Mah]

I just completed the frames for 18 windows, each had at least a dozen M&T joints, from 1/4" by 7/8" to 1/4" by 2.5", ranging from 1" to 1.5" deep. So, at least 200 mortices. I think you are correct to position the discharge slot from the mortice chisel to the right and cut from right to left. When the discharge slot faces the previously cut space, the cutting goes very easily (the chips aren't compacted and then drawn up the bore of the chisel. Otherwise each cut takes a lot of effort). Make a cut on the left to establish the end and then work from the right.

I did some of the slotting using a horizontal router table, with a sliding bed to allow me to clamp the workpiece and a screw to allow me to advance the depth of the cut. The mortice chisel probably worked just as fast as the router with the difference that you feel like you had a couple of days at the slots in Reno. The only difference is that the bottom of the mortice is likely to be flat with the router. I made a custom clamp which allowed me to rapidly clamp and release the work from the mortising machine (Harbor Freight tool, cost less than $100 after a coupon).

The key to clearing the slots was compressed air. As someone else mentioned, watch out for the flying chips. Also, use a 1/4" chisel to pry any material that doesn't come out. Vacuum doesn't work as well to clear the chips, leaves chips almost always. Also, I made a probe out of a short length of 1/4" inch steel to check the depth of the mortice because I found that sometimes my technique with the morticing machine varied and I didn't plunge the chisel deeply enough. Light tapping and twisting with the 1/4" chisel was sufficient to deepen the high spots. The router technique did not make the process of clearing the chips any easier. I wouldn't bother with getting an upcut bit just for the reason that it's easy to clear most of the chips with whatever technique you choose, but it's the last chip that refuses to come out easily that gives you the problems. Just blast it out with air.

Since you are making that many joints, do consider a clamping jig so that you can position the pieces quickly and in a repeatable fashion. Also, with the mortising machine that I had, the depth stop was a collar on the shaft with a thumb screw to lock it in place. That didn't work very well, as I progressed, the collar would slip and my cuts were getting deeper. What I did was cut a length of scrap wood (reaching from the bottom of the collar to the deck of the machine underneath) to place under the collar to keep it from descending and tied it in place with a piece of wire. Also clearly mark the waste with a pencil to avoid cutting the wrong stuff. I advanced the drill bit approximately the thickness of a dime beyond the cone of the chisel and that seemed to make chips that did not clog the chisel.

Good luck.

[Kirk Poore]

I just completed the frames for 18 windows, each had at least a dozen M&T joints, from 1/4" by 7/8" to 1/4" by 2.5", ranging from 1" to 1.5" deep. So, at least 200 mortices. I think you are correct to position the discharge slot from the mortice chisel to the right and cut from right to left. When the discharge slot faces the previously cut space, the cutting goes very easily (the chips aren't compacted and then drawn up the bore of the chisel. Otherwise each cut takes a lot of effort). Make a cut on the left to establish the end and then work from the right.

...
Good luck.

Floyd, I agree with most of what you're saying, but we need to realize that having the discharge slot "trailing" the direction of work means that it will dump some of the chips down inside the mortise rather than clearing them out of the mortise and then a few falling back in. Working from left to right in this case will keep more of the chips out of the mortise at the cost of more resistance since there is no place for them to go except up and out. I don't have a hand driven mortiser, so I don't know if the additional resistance will be worse than clearing the chips with compressed air.

Kirk

[Floyd Mah]

There is a real difference when working with a hand driven mortising machine. It's not a big deal if you are plunging the chisel for a few mortises, but when you multiply 300+ mortises by the six or ten plunges per mortise, you begin to notice the difference after only a few minutes. It's like the frequent discussions in this forum about hand-cut vs. template guided dovetail joints. One box is easy to make using hand-cut joints, a chest of drawers, or a large piece of furniture will drain all of the creative juices out of you if you insist on hand-cut joints. In this case, of course, you could try using the opposite arm to pull, or use a Mark Twain/Huckleberry Finn approach and trick someone else into doing the work for you. I realize that you are blowing more chips out, but this work is done by the compressor.

[Kirk Poore]

That's kind of what I was afraid of. I went from hand chopping to an autofeed industrial mortiser, and neither end of the spectrum has the middle range's problem. Well, Dan, good luck with the compressed air...

Kirk

[Forrest Bonner]

When I had only 96 M&T joints to do, I decided to use loose tenons joinery. You then only make mortises all the same and make the loose tenons in bulk then cut to size. I used a router with an upcutting bit and an accurate jig to locate the mortises. Yes, the mortises are round ended, but that does not detract from the glue surface all that much. If you want more loose tenon contact you can round-over the edges on a router table. Still making the tenons by batch then cut to length. The slight mismatch allows for a small bit of play for adjusting the fit at glueup.
Forrest

[Dan Hulbert]

You have all given me a number of methods to try to make this project move along. Unfortunately, I work long days Monday thru Thursday so I won't get to try them out until Friday.

For those who may be wondering, this project is making interior shutters for 6 sliding glass doors and 4 large windows. Each opening will have four folding panels, each folding panel has three inset panels and all are rail and stile construction. This is what happens when the wife wants to control the sun pouring into the house, but hates curtains. :)
I'm using poplar for the frames that started out at 6/4 rough and has ended up about 5/4 milled. I'll be using 1/4 plywood for the panels and will eventually be adding stopped bevels around the interior of each panel.
I'm a one-off hobbiest, but my wife has tremendous confidence in me. This kind of production work is unllike anything I've ever attempted before. My previous big project were 2 Morris Chairs and two Adorondak style chairs.

Happy Holidays to all, and thanks again for your thoughtful advise.

[Ronald Blue]

I think air will be the way to go. Something we used to do when in the metal working trade was setup a fixed air line that is aimed at in this case the mortising bit. Install a small ball type valve and turn on just enough air flow to assist in clearing the chips away. You could use some small copper tubing for simplicity and ease of obtaining. A small direct stream of air at the point of operation could do wonders and not require a huge volume either. You could also use a regulator to control the flow. A really neat system is snap together plastic line called loc line. Here is a link to it. Good luck and let us know how it goes. http://www.modularhose.com/

[Bobby Knourek]

There is a special grind that you can put on the twist of the mortise bit.
This grind will help the bit grind the chips while in the barrel of the chisel
into smaller pieces and help them eject with minimal vacuum or blowing.

BK.