Any tips on hollow chisel mortiser problems?

  • Advertise with us

« back to Power Tools, Hardware and Accessories forum

Forum topic by tallpaul posted 03-26-2012 06:16 PM 7143 views 0 times favorited 17 replies Add to Favorites Watch
View tallpaul's profile


27 posts in 3723 days

03-26-2012 06:16 PM

I have a Delta dedicated mortiser, which has shortcomings, but won’t be replaced any time soon. I’m having this problem: After making the plunge, I find that the chisel binds in the work, and lifts the lumber off the machines little table. There is an adjustable hold down to allow me to retract the chisel, but the force is strong enough to cause the hold down to slip. It’s held in adjustment by a set screw, and cranking down harder on that will likely lead to stripping it.

I’ve tried waxing the outside of the chisel, which seems to help a bit. I’ve tried retracting a few times during the cut, to clear more of the sawdust out. These things help, but I think that I’m missing the real solution.

Any thoughts? Thanks!

-- tallpaul

17 replies so far

View Viking's profile


880 posts in 3162 days

#1 posted 03-26-2012 06:23 PM


Have you sharpened the chisel? If chisel is dull the sides of the mortices may not be as smooth as you would like.

Good luck.

-- Rick Gustafson - Lost Creek Ranch - Colorado County, Texas

View Richforever's profile


757 posts in 3687 days

#2 posted 03-26-2012 06:27 PM

The hold down on my Jet mortiser is really poor also. I’ve tried putting a small wedge between the hold down and the piece being mortised. It helps a little.

-- Rich, Seattle, WA

View waho6o9's profile


8165 posts in 2544 days

#3 posted 03-26-2012 07:49 PM

The wood whisperer had an article on mortisers and it just might help you.

View dbhost's profile


5705 posts in 3199 days

#4 posted 03-26-2012 07:54 PM

The hold down on my HF mortising machine is beyond pitiful. I built a new table with T track, and rigged a U clamp sort of gizmo that I just turn the star knobs down on to apply better hold down pressure on the work piece. It’s kind of a jury rig, but it works for me.

-- Please like and subscribe to my YouTube Channel

View Bertha's profile


13521 posts in 2660 days

#5 posted 03-26-2012 08:30 PM

You’re not alone. The work grabber on my JET has a silly little screw, too. What always confused me is why on earth they didn’t provide a little cutaway on the fence to allow the holder to approach the base? I don’t know about y’all, but I mortise stuff thinner than 2 inches or so. I’m tempted to make a new contraption. Mine slips even with brand new ubersharp chisels and I’ve tried waxing too.
In typical dumba$$ fashion, I hold it down with a vise grip. Just like duct tape, so many uses for a vise grip:)

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View Rick  Dennington's profile

Rick Dennington

5807 posts in 3161 days

#6 posted 03-26-2012 11:21 PM

Huuuummm….something sounds up with that…!!

I have an old Delta model 14-650 Type II, and it’s about 15-16 years old….I’ve never had the problem you’re describing here….I don’t know if you have a newer Type 1 or not, but I’ve heard they had a few problems with them…(?). One thing you have to do to keep the chisel from binding is to make sure the chisel and bit are just perfectly straight… if you don’t, and if it’s cocked a little bit to one side, it’ll bind up…I’ve never had any trouble with the hold-down on mine making the wood want to rise up…I just tighten the set screw down just enough to let the wood slide…not loosely….and a straight chisel….One thing I did do to improve the machine was I bought a bigger table from Rockler a couple of years ago…It has the t-tracks

with rollers that push the wood into the fence, yet lets it roll along…...don’t know if they even make it anymore, but it sure works good….here’s a picture of it…..Hope you get yours figured out, and you other guys, too…..just try squaring the chisel and see if that helps…..

-- " At my age, happy hour is a crap and a nap".....

View davidroberts's profile


1027 posts in 3453 days

#7 posted 03-26-2012 11:46 PM

this may be to obvious, but how far do you extend the bit beyond the chisel. at least an 1/8th, and 3/16 would not hurt. much more and you’ve got holes in the bottom of your mortise. if the auger doesn’t have a chance to clear chips, the chisel will bind in the mortise. also the sharpening idea is always true. woodcraft sells an hollow chisel sharpening kit for about $15, or so. i haven’t looked lately at the current price. i bought mine a few years ago on sale.

rockler discontinued the mortise table.


-- Better woodworking through old hand tools.

View Johnnyblot's profile


319 posts in 2243 days

#8 posted 03-27-2012 12:09 AM

My best advice- and this worked for me when I had the same problem, is to polish all four sides of your chisel to a mirror finish. I used my water stones. Same as you would to the blade in your plane. It worked for me, and that was with some cheapo Chinese chisels I bought from ALDI’s [local store, cheaper than Wal-Mart even]

-- Gossamer shavings just floating around the back yard….-Bandit

View tallpaul's profile


27 posts in 3723 days

#9 posted 03-27-2012 02:44 AM

Okay folks….looks like I need to sharpen/hone the outer faces of my chisels, and to make sure they are square to the table and fence.

Nothing looks too far out of square, but I might need to shim and otherwise jury rig everything square.

Thanks for the suggestions!

-- tallpaul

View bruc101's profile


1200 posts in 3509 days

#10 posted 03-27-2012 03:32 AM

I just put some Renaissance wax on my chisels before I start. Sometimes though the first cut will be a little more difficult raising the chisel out of the board and I’ve never had any problems with my Delta mortiser. The hold down works ok without any problems.

-- Bruce Free Plans

View WoodKutter's profile


29 posts in 3434 days

#11 posted 03-27-2012 03:45 AM

Hi TallPaul,

What I’ve found found to be the biggest cause of binding on the return stroke of my mortiser is the lower surface of the hold down is not square to the chisel. When it is resting on the work it looks square but when upward pressure is put on it, it will flex up just a little bit. Doesn’t take much to bind the chisel. You have to find a way to hold the work piece firmly down on the table and not lift up. The hold down systems on the small Jet and Delta models are not the best.

Gary S

View philip marcou's profile

philip marcou

264 posts in 2564 days

#12 posted 03-27-2012 06:03 AM

Are you using genuine Delta chisels? If you can look at good quality chisel sets such as Multico or most industrial standard chisels you will observe that they are ground very slightly smaller in the middle meaning that the sharp end cuts a slightly bigger four sided hole-which facilitates penetration and withdrawal (of the chisel).(!)
You can use a belt grinder (first choice) or an ordinary belt sander to “waist” a hollow square chisel,but be sure not to grind anywhere within about 10mm from the sharp end, and it only requires a very small amount eg 4 thou or so.
WoodKutter has mentioned a common cause of binding on withdrawal and this is made worse when the hold down provided is of poor design (like on many diy type machines).
Also, if the chisel is not sharp enough and the augur projection incorrect the the sides of the “hole” will be rough and this will make withdrawal more difficult-and some woods make this situation worse.
Wax is good, and some timbers demand it no matter how well set up everything is.

View Johnnyblot's profile


319 posts in 2243 days

#13 posted 03-27-2012 01:08 PM

The Clip by Mark S- the Wood Whisperer says it all.

-- Gossamer shavings just floating around the back yard….-Bandit

View hairy's profile


2656 posts in 3499 days

#14 posted 03-27-2012 03:06 PM

Is it hard to move just by itself? A bad gas cylinder could cause some of that. When you pull down on the lever, the gas is compressed. It is there to assist coming back up.

Remove it from the top to test. It should be hard to compress.

It’s the same idea as on a hatchback or trunk lid on a car.

-- My reality check bounced...

View tallpaul's profile


27 posts in 3723 days

#15 posted 03-27-2012 06:56 PM

Thanks for your suggestions, all. I spent fifteen minutes polishing my chisel, and I did see a lot of improvement. I was skeptical that such a minor change would help, but it seems to be doing the trick. I still think the hold down on my Delta machine is crap…will have to look for something better as a modification in time. A simple screw down clamp would be worlds better. It seems these basic mortisers haven’t evolved much over the years, but there is lots of room for improvement without adding much cost. Looks like the high end floor standing machines have some better features though!

-- tallpaul

showing 1 through 15 of 17 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics