Hollow Chisel Mortiser

[rick7938]

My latest project is going to require 88 mortise and tenon joints. After pondering this for a few minutes, I elected to empty the mad money stash and bought a hollow chisel mortiser and tenoning jig.

Does anyone have any good "Lessons Learned" tips for using these two new gadgets that may save me some heartaches?

Thanks for any help or feedback.

 

[McRabbet]

If they are all blind mortise and tenon joints and you've got a good sized stash, I'd recommend a Festool Domino!

 

[walnutjerry]

My latest project is going to require 88 mortise and tenon joints. After pondering this for a few minutes, I elected to empty the mad money stash and bought a hollow chisel mortiser and tenoning jig.

Does anyone have any good "Lessons Learned" tips for using these two new gadgets that may save me some heartaches?

Thanks for any help or feedback.

I assume you have already bought a mortiser. READ all the instructions about set-up. Pay special attention to the bit/chisel set up and the part about having the chisel parallel to the fence. Take the time to get the fence set to where the mortise is dead center of the material to be mortised. Keep bits and chisels sharp. Nibble out about 2 widths of the chisel with alternate cuts until you reach the depth desired then you can go to the bottom adjacent to that hole with one plunge.

I like to do the mortises first and fit the tenons to the mortises, much easier than the reverse.

Use a couple scrap blocks same thickness as material in your project for the trial and error set up.

Jerry

 

[Ozzie-x]

Good advice from Jerry. One of the most overlooked things with a mortiser is that most folks take for granted that it's adjusted properly from the factory, which is never the case - the factory usually only assembles them and send them away. Take the time to go through your new mortiser and set/adjust everything properly, and you will be much happier with it. Here's a shortcut for a good primer on mortisers from our own beloved Tom Hintz.

http://www.newwoodworker.com/setupmort.html

There's several cone shaped sharpeners out there for the inside of the chisels, however some of them are pretty rough. I've never seen anyone mention the outside of the chisels, but it takes two surfaces to make an edge... One tip I've learned is to lightly hone the outside of the chisels and they will work much better. The factory chisels have pretty bad mill marks on the outside sometimes. I use ~1500 grit and slick them up, but be very careful to not remove much material or you will change the dimensions of your mortises. I also keep wax on the chisels while I'm using them. The bits can also be pretty ragged from the factory and I usually sharpen those with a small jeweler or gunsmithing type file before I use them. Just because they're new doesn't mean they're sharp, sharpen them before you use them and you'll get better results. Also make sure to leave plenty of space between the chisel and the bit when you put them in the machine.

Jerry hit on several good points in cutting the mortises. I cut the mortises first also, because the size of the mortises are pretty well set by the chisel. Cut the tenons last and you can tailor them to the mortises. It may be my eyes playing tricks, but sometimes it looks like the chisel "bows" or leads out in harder woods when cleaning out the "mortise middles", especially after you've cut several mortises and heated up the bit. :-( For this reason, I first cut both ends of the mortises, then the chisel is supported equally by wood on all sides and goes straight into the wood. The ends are usually the most important for fit. Then clean out the "middles" and if the chisel trails off some side-to-side, it's probably no big deal as long as it maintains the horizontal edge lines. Jerry also made a good point in that sometimes it's a good idea to "nibble" the mortises or make partial cuts. This is particularly good if your mortiser is not a hoss, bad chisel, very hard wood, etc. Partial cuts really slow down the process but often make for a much better job and preserves your tools better also.

Hope this helps, just my windy 2 cents.

 

[Travis Porter]

I agree with everything posted, good advice. The one hard lesson I learned that hasn't been posted here yet is to be sure to leave adequate space between the bit and the chisel for chip removal. Otherwise, the bit will heat up and break off. I learned this after breaking 3 drill bits and you can't buy the bits without the chisels.

 

[junquecol]

I agree with everything posted, good advice. The one hard lesson I learned that hasn't been posted here yet is to be sure to leave adequate space between the bit and the chisel for chip removal. Otherwise, the bit will heat up and break off. I learned this after breaking 3 drill bits and you can't buy the bits without the chisels.

It's called the 10 cent trick. Put a dime (flat ways) between the chisel and the housing on the mortiser. Insert bit all the way into the chisel and tighten the chuck. Remove the dime, and move chisel up into mortiser, and retighten. This gives clearance to the bit. You can spray the bit with "Pam" prior to inserting to help chip flow upwards. Woodworkers Supply sells just bits in their "Big Book of Woodworking" ( catalogue). These are listed to fit their premium grade mortise chisels, but probably will fit others as well.

 

[walnutjerry]

I agree with everything posted, good advice. The one hard lesson I learned that hasn't been posted here yet is to be sure to leave adequate space between the bit and the chisel for chip removal. Otherwise, the bit will heat up and break off. I learned this after breaking 3 drill bits and you can't buy the bits without the chisels.

Good point Travis-------------when I bought my mortiser the guy demonstrating told me to set the bit below the chisel by the thickness of a dime. That has worked well for me. I turn the slot in the chisel toward me so the chips do not cover up the mortise layout.

Jerry

 

[GeorgeM]

I have the Powermatic. It has the spacer build in for the spacing and it works great.

 

[cpowell]

If the mortises are to be centered in the stock then I will usually set the fence as close to center as possible using cutoffs from the stock. I make the mortises using side 'A' against the fence then flip and re-mortise with side 'B' against the fence. It is difficult to find EXACT center. Usually the second pass is simply shaving a little from the morties sides.

I always mill all of the stock at the same time to ensure they are the same dimension. I will always leave room for an off-cut to use for mortiser setup.

I try to clamp as many pieces of stock as possible then mark the mortise locations at the same time. This ensures any marking error is consistent for all of the mating stock. It isn't necessary to mark the mortise sides, just mark the Start and Stop locations. You will need to mark the full mortise on your practice stock. Once the mortiser fence is set for the practice stock you just need to run your project stock through.


Chuck

 

[Alan in Little Washington]

A couple things I found-

Mortising some hardwoods can require a bit of force on the handle. If you have to put all your weight on the handle, something is wrong (bit depth, bit or chisel sharpness, etc.) and you are going to break the chisel or mortiser unlrss you correct it.

To repeat- make sure your fence is aligned. I had recently remounted my cross slide vise to my mortiser and hadn't checked the the alignment of the vise faces (fence). They were not parallel to the chisel. One of the heavy solid oak shop doors I made last year had a few rails that were not coplanar with the rails- the mortises were angled- a lot of planing and sanding fixed it, but my door is thinner than intended.

It is a good idea to lap the outside of the chisel, especially if it has heavy milling marks. It really doesn't matter if your chisel is not exactly 1/4", 3/8" or 1/2" etc. since you should cut the mortises first, then cut the tenons to fit the mortise. And if you cut centered mortises by doing the flip method, cutting from each face, the mortise may be wider than the stated measurement anyway.

The direction of chip slots is a personal preference- some have it face front, some have it face left or right in the direction they are cutting- chips can hide your layout stop line. Others have it facing where they started (assuming they cut the same direction each time)- this dumps chips into your mortise.

Having a A DC or shopvac hose handy to vacuum out the mortise as you go and clean the area around the mortiser is nice.

Cross slide vise- I modified and mounted one on my mortiser, but the jury is still out. It has limitations. It is heavy, L-R movement, throat, and height capacity can be restricted. A lot of the cross slide vises out there are crap and don't slide as easily as they should. I removed the left-right crank as being too slow, but moving the vise left and right manually is not as easy as I would like. I will eventually replace or modify part or all of this rig.

 

[sediener]

I got the delta tenoning jig and had to re-set it for left tilt saw. Either there is either enough play in where the guide attaches to the base plate or the block of wood I attached to the fence wasn't parallel because my tenons came out slightly angled. If you look down on them from above they looked like this // (off by a few degrees) instead of this ||. It wasn't blatant enough to notice in test cuts for some reason but when I went to dry-fit, it showed up. It is obvious to me now, and may already be to you, but check that your jig is parallel to your blade before cutting especially if you have to re-set it for a left tilt saw.

- Steve

 

[McRabbet]

One can only presume that you also checked the blade tilt angle....

 

[sediener]

One can only presume that you also checked the blade tilt angle....

It was not tilted as though the blade wasn't at 90 degrees. If you looked straight at endgrain of the tenon, it was like |\\| instead of ||||. It is probably user error because what I think happened doesn't really make sense. Maybe the guide in the t-track wasn't fully adjusted and let the jig twist as I pushed it through. I'll be using it again soon and hopefully figure out what is going on.

- Steve