Why does my hollow chisel mortice blade stick in the mortice?
ofc
| Posted in General Discussion on
I have a General International hollow chisel mortiser with new General International bits and chisels. However, the chisels stick in the wood when drilling holes. This makes it sometimes very difficult to pull the bit back out of the hole after it is drilled. I noticed in the video that the chisels (and bits) seemed to come back out of the wood quite easily. Very different than mine.
Am I doing something wrong? Or, is there something wrong with the geometry of the chisels? Or … ?
Thanks for any help that someone can give.
Oliver
Replies
Holding down the stock in a rock-solid manner will make a huge diff. Cleaning up the outside faces of the chisel like you would the back of a plane iron will also help. On larger chisels you might want to relieve the outside of the chisel up away from the cutting edge for less friction in and out.
It’s also about the rigidity of the setup, when using hollow chisels on a press drill that same problem occurs unless the table is supported and the piece solidly clamped.
You gotta hold the work piece down solid and a bit of dry lube on the chisel makes a big difference.
The why it sticks is really quite simple, you really have to listen very carefully and the sound of the machine will probably drown it out , but, when your making your cut the wood cells are screaming "Hold on,Hold on,Hold on!" Of course in their native language which is very similar to Algonquin.
I keep a block of paraffin near and every once in a while I simply plunge into it. This seems to help but the advise from MJ and Gulfstar is right on as well.
I've had a few instances where I had to use force to lift up on the handle, but usually it comes out easily.
I don't know what it could be. Maybe polish and the outside of the chisel :-)
Polishing the outsides made a huge difference in mine; no more problems.
Thanks folks, I will make sure that I hold down the workpiece and will polish the faces of the chisel and add some lubrication to the outside of the chisel. I may even listen carefully to the wood. ;)
If it's a bench top machine, they are notorious for lack of holding strength and machine rigidity. ANY racking or movement of any kind can contribute to the binding issue.
I agree with the others, hone the outside as you would with any chisel back.
Lubricate the chisel, I use renaissance wax on mine.
This is all assuming your machine is aligned properly
The big difference between a bench top machine and an industrial floor-standing model, and I've used both, is that the latter holds the work securely and does so on a carriage that can be moved left and right for the length of the mortise. In other words, once secure, your work can be moved easily left and right and remains stuck down, and it is easy to remove the chisel.
The bench top machines I've seen don't lock down the work and in fact need to be fairly loose so you can push the stock back and forth between plunges. The floor standing model is hugely better for just this single difference. It also uses a foot pedal rather than your arm for the motion, and the counterbalancing is such that it pulls the bit up. The strength of your leg is such that it is easy to store excess energy in a spring or counterweight, and that pulls the bit out.
Unfortunately, floor-standing machines are huge and expensive. Get a Domino and keep it in a drawer instead. You can get the same result with no elaborate scribing of the mortise--just a centerline.
Not all floor models are foot operated, mine for one, is not
Also there is no counterbalance as such on most models today, just a gas strut (like on a car hatch) that raises the head.
Mortisers with the features you mentioned are not that common any more. There are industrial models with many advanced or automatic features but for most people, you still need to pull the level.
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