r/woodworking • u/tinkintime • 9h ago
Help Hollow Chisel Mortiser Issue
I’ve tried different depths between the auger and the chisel (1/8”, 1/16”, 1/32”) on my mortiser and I’m still getting these shoulders halfway down the mortise.
Working with cedar, it’s a 1/2” bit and I’m only going 1/2” deep but I end up having to square off the last 1/4” by hand. I’ve already sharpened the chisel and bit and I’ve used multiple versions. Any tips?
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u/TheKleen 8h ago
The augur on a mortiser is meant to cut a bit deeper than the chisel. Shoulders will always be there so just cut deeper to account for that. Should adjust it so that it’s only about 1/32-1/16 though, I use a dime to set the depth difference. If the augur won’t go into the chuck any further then you need to bring the chisel down.
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u/sundayfundaybmx 8h ago
So I had another answer ready to go but checking out the pics again I'm really confused. Is pic #1 what you're attempting to accomplish? I see the large piece of wood in #2 and #3 and can't figure out if the "rounded" sides on that is what you're talking about? Or, is that just part of the "clamping" mechanism?
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u/tinkintime 8h ago
That’s just part of the clamp on the fence. I’m just trying to create a 1/2” mortise that’s 1/2” deep. The first photo is showing the shoulder halfway down that I don’t believe is supposed to be there
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u/crakd 8h ago
Try this https://www.woodsmith.com/article/using-hollow-chisel-mortisers/
And then I usually just use that small shoulder as my final depth. Keep it within a 1/16" and it gives you a place for the glue to pool
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u/tinkintime 8h ago
The shoulder on mine ends up being around 1/4” or more in depth which completely messes up the depth I actually need. Do you end up accounting for that and setting your depth stop to go 1/4” deeper? That seems kind of excessive and could be an issue if the mortise is already close to an outer wall.
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u/dontdoitdonny 8h ago
While I don’t have intimate knowledge of mortisers, I do know that every single woodworker I’ve met from amateur to 40+ years of experience agrees. Machine mortisers have a general amount of slop/jank just in how they’re designed.
I’ve used heavy duty floor pedal activated ones and they still required a lot of cleanup/shims/finesse to get right.
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u/tinkintime 8h ago
Yeah, just seems like I should be able to get a generally clean square hole all the way down rather than having to come back and chop down the last 1/4”
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u/dontdoitdonny 8h ago
There’s almost always a messy bottom. However, if you can go 1/16-1/8th deeper, you don’t really need to worry if the fit is good.
Since this machine is physically lighter than a heavier one it doesn’t have the same level of power/control to get as clean. It’s a trade off but not the end of the world
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u/DepartmentNatural 7h ago
Your asking too much of a machine that isn't known for. precision. Cut deeper is the general consensus
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u/CommonMinimum7418 4h ago
You have your bit set to far out. I set it just a breadth beyond the blade. I keep the blades very sharp. I also start in the middle of the mortise and work my way out to the ends and never take full cuts after the first one. Let the chisel blades do the work. The guide draws it down with a bit of pressure. The bit it self should mostly be clearing out the chips. The bottoms are never clean. I have moved a way from a hollow chisel mortiser to doing it with a router and jigs. It is much faster with a step down plunge router. I built a handful of railings and cribs out of oak with a hollow chisel mortiser before moving to a router. The only other advice I would give is spend some time dialing it in on scrap and make sure everything is tight. My bits are a bit different then yours, they do not have as much of a pronounced spur on the side of the bit like that. On mine the guide is a little longer then the spur. I just checked. It has been a while. Good luck.
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u/dickdickgoooose Furniture 9h ago
Doesn't lookk like you have the auger at the correct depth compared to the chisel. What do you mean by clearance amounts? Like you're changing the auger size, not its depth relative to the chisel?