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! 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.