LumberJocks

M&T

  • Advertise with us

« back to Joinery forum

Forum topic by drcodfish posted 03-10-2016 08:32 PM 581 views 0 times favorited 7 replies Add to Favorites Watch
View drcodfish's profile

drcodfish

120 posts in 418 days


03-10-2016 08:32 PM

Joinery Kings, your advice is requested:

I am building a mission style desk using Q-sawn white oak. I have the wood and recently bought a new unused but no longer in production power mortising machine (Steel City). I have a Grizzly hybrid table saw and an old but in great condition Grizzly Table saw trenon jig. I have not yet used either the mortiser or the tenoning jig, but plan to do some practice work with these this weekend before I dive into the spendy wood.

Obviously, being a mission style design there is lots of M&T joinery in this project so I have a few questions for the joinery wizards here:

1. Is the Tenon jig worth using? It appears to me to take a fair amount of set up to use this thing, however there are a few assemblies where I will be making many repeated tenons (same dimensions on multiple identical pieces)—that seems to me to be the greatest opportunity for efficiency. But what about the set up time involved for tenons of different dimension? Wound it be better just to use the dado set on the table saw?

One nice thing is that almost all of the desk assembly calls for 3/4” stock. I am starting with 4/4 S2S stock, have dimensioned some of the lumber and my 12” Grizzly planer is working fine and the cheapo Harbor Freight 6” joiner is doing it’s job as well (knock wood). The wood does not show as much figure as I would like but it is very clean (no knots or rot) and displays almost no warp, twist, bow or cupping.

2. Any advice on using the mortiser would be appreciated. It looks to me to be almost brain dead simple, but it is also obvious that precise set up will be needed. Again, the fact that almost all of the stock needing M&T joinery is 3/4” helps reduce the number of set ups and bit changes required.

I am a little intimidated, but really excited about undertaking this project. It represents a big step up for me from smaller projects (boxes and such) to real furniture. Where are the booby traps I need to be watching for?

Yikes, fasten the seatbelts!

-- Dr C


7 replies so far

View Fred Hargis's profile

Fred Hargis

3947 posts in 1959 days


#1 posted 03-10-2016 08:58 PM

I have a tenon jig, like the smooth cheek cuts I get but I still do most of mine with a dado set on the table saw. I get close, and then fit them with a shoulder plane. I think it may just be a personal preference thing, and I’m not sure there is much different in set up..at least for me. Maybe you should try a few both ways and see if one appeals to you more than the other. No opinion on the mortiser since I don’t have one.

-- Our village hasn't lost it's idiot, he was elected to congress.

View pintodeluxe's profile

pintodeluxe

4859 posts in 2279 days


#2 posted 03-10-2016 09:08 PM

1. Is the Tenon jig worth using?

No, probably not. I am a proponent of using a good quality dado blade to make tenons. There is less setup involved, and repeatable results are pretty easy to achieve. The thing I don’t like about tenoning jigs is there are too many setups to cut a single tenon. First cut the tenon cheeks, then reset saw and cut large shoulders, then to the bandsaw to cut the side shoulders. Plus, working with long workpieces standing on end has always bothered me.

With a dado set and a trustworthy miter gauge you can easily and quickly cut your tenons. Heck, if the cheeks and the shoulders have the same offset you can cut all sides of the tenon with only one tablesaw setup.

2. Any advice on using the mortiser…
Get a diamond cone sharpener and some fine diamond sharpening files. Use the cone first, then polish the outside of the chisel with the files to remove the burr.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View conifur's profile

conifur

955 posts in 617 days


#3 posted 03-10-2016 11:09 PM

When useing the mortiser make sure your drill bit is low enough below the chisel. Also on the mortises lets say you are using a 3/8 chisel and the mortise is 1 1/5”’ long, you cut ever other spot of 3/8, then go back and cut out the remaining, that way you have support on all sides of the chisel for many of the cuts.

-- Knowledge and experience equals Wisdom, Michael Frankowski

View runswithscissors's profile

runswithscissors

2192 posts in 1491 days


#4 posted 03-10-2016 11:34 PM

I have never found it a problem to make all the mortise plunges in linear sequence. I understand the theory—that you might be inviting chisel flex—but not in my experience. On other hand, I rarely use the 1/4” chisel for 3/4” stock, preferring the 5/16” instead. Still leaves plenty of meat on both sides of the mortise, but gives you a stronger tenon.

A TS tenoning jig can be modified to make beautiful and very quick tenons with a shaper or router table. Needs a bit as long as the tenon will be. If you should try this, feed with the carbide, not against it. In other words, a climb cut. It will want to pull the stock into the bit rather aggressively, but it’s not hard to control as long as you brace yourself for it. The advantage is you get very clean tenons, with virtually no tearout.

Try “tenon jig” in the search box at the top of the LJ window; you’ll see many ways to do this.

Another way to sharpen mortising chisels is with a sanding cone. I got mine at my local hardware store. You can buy a rubber mandrel (1/4” shank) for it. Cones come in several grits, including very fine. Works well.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View JBrow's profile

JBrow

819 posts in 386 days


#5 posted 03-11-2016 05:22 AM

drcodfish,

I am no joinery wizard and I agree with the advice you have already received. But some points not mentioned are perhaps worth consideration.

Mortises:

Since you are using ¾” thick material, perfectly centered mortises would be nice when it comes to using a dado set or tenoning jig. By cutting the mortises twice the mortises can be centered. Once the mortises have been cut, flip the work piece around and re-cut the mortise but with the opposite work piece face against the fence. This method requires a quality set of chisels with minimal flex since the second cut is a paring cut.

If your design incorporates through tenons, the mortises are accurately laid out on opposite sides. Then only cutting midway through the work piece on the first pass and then finishing the mortise by cutting it from the opposite side will eliminate ragged mortise edges that can result from tear out. Alternatively a pair of stop blocks will keep the mortises aligned and eliminate the need to lay out the mortise on two sides.

Tenons:

The only advantage I can think of in using a tenoning jig over a dado set is that the tenoning jig produces smooth cheeks on the tenons, important only if the end of the tenon will be exposed in a through mortise and tenon joint. Using a shoulder plane to remove the score marks left by the dado set and end up with a perfect fitting tenon is a challenge. However, the tenoning jig may be difficult to use on the long rails of the desk. A workpiece sticking straight up 5’ can be unwieldy, plus you need adequate ceiling height. A 5’ long rail would require a ceiling height of 8’.

One problem I have encountered when cutting tenons with a dado set is that sometimes the shoulders were not dead flush all the way around. I finally figured out that the slop in the mitre gauge traveling through table saw’s mitre slot was mostly the problem. When I register the mitre gauge against one side of the mitre slot during setup and throughout all cuts this problem was mostly solved. If there is slop in the tenoning jig riding in the mitre slot, this problem could occur.

If the tenoning jig is used, the first step is to establish the length of the tenon. This step makes cutting the cheeks with the tenoning jig later easier and accurate. This is done with the sharp crosscut blade on the table saw along with a scrap backer board to reduce tear out. The blade height is set to the depth of the shoulder on the faces of the work piece. A “scoring” cut is made on both faces which establish the face shoulders with the work piece faces lying flat against the table and using the mitre gauge set square to the blade. The edge shoulders are established similarly, with the edges flat against the table using the mitre gauge. If the shoulders on the edges are a different measurement from that of the faces, the blade height must be changed, but the distance from the end of the work piece remains the same (length of the tenon). This is confusing so I including a sketch to illustrate what I am talking about.

The last thing to mention, even though you are probably already planning to do this, is to cut a little extra stock. The extra stock can be used for test cuts to dial in perfect fitting tenon.

View conifur's profile

conifur

955 posts in 617 days


#6 posted 03-11-2016 07:19 AM

Forgot this, do your mortises first then make the tenons to fit the mortise, make the tenons a bit fat and work them to fit size. Make the tenon about an 1/16 shorter then the depth of the mortise and on the tenon champher all edges a touch with a bench chisel.

-- Knowledge and experience equals Wisdom, Michael Frankowski

View drcodfish's profile

drcodfish

120 posts in 418 days


#7 posted 03-13-2016 05:38 AM

OK: After a day of experimenting/testing and set up of machines and jigs I think I am zeroing in on how I will proceed with this project.

The mortising machine is going to be my friend, not a perfect tool but will be much better than trying to hand cut all these mortises. There is need for a little clean up with a chisel but goes fairly quickly (with a sharp chisel).

For the tenons I have tried a coupe things.

I cut my first few with a dozuki, and then a few with the table saw. The TS produces better shoulder cuts, the dozuki does ok but not very uniform cuts.

I spent some time setting up the tenon jig (getting it square and plumb on the table saw). It makes very nice cheeks and I can see doing production work with this (at least for this project) Cutting the shoulders is the last thing I need to figure out.

I am inclined not steer clear of the dado: My dado set is pretty rough and I can see I would be doing a lot of chisel work to clean up the cuts, and it is the shoulder cuts which make or break the M&T joint: Done right and the joint is pretty much invisible, but get these cuts off a bit and it will look bad. I think I can make a jig for uniform shoulder cuts on the TS. I will try to post some pics tomorrow.

-- Dr C

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

HomeRefurbers.com