I’ve been cutting tenons on the tablesaw using 2 dado blades with spacers in between them to match the size of the mortise. I mentioned this on a post once and was told by many that this was an unsafe practice. Matter of fact, I asked Freud if their box cutter set could be used that way and was told it was unsafe and would send me to the emergency room!
I’ve been watching Garrett Hack’s video series on making the small cabinet and what do I see?, he uses two blades to cut his tenon in one pass too.
Now I’m really curious about this, I saw someone do it years ago and have done it for a long time using automotive shims and washers. How many of you do that as well, and if you do, has it ever caused an accident or kickback?
Replies
As with many things, the level of safety depends on the details of how something is done, and with what. The safety factor of using the dual-balde method to cut tenons might also be affected by the design of the tenoning jig and how well the stock is held in place. For example, if the side retention screw isn't tight, the added force of the second blade might force the top of the piece toward the rear of the saw, pivoting it out from under the retention screw. At that point, it's "projectile time". A secondary retention block clamped in front of the work piece would reduce that risk. Feed speed would likely be a factor, as well.
The bottom line is that an experienced woodworker can often safely execute a technique that should never be recommended to a novice. For that reason, manufacturers are loathe to recommend such techniques, lest they incur legal liability when an injury takes place.
How large are the tenons, are you using a tenon jig, do you make the cheek cuts first and use single blades or are you stacking cutters for the complete width? A long tenon may be too much for a box joint set, I think the tips are thick, 1/4" which is quite a bite. The tips are also offset from the blade body. Without a securely clamped, accurately set tenon jig, tuned saw and experienced operator, the work can get pinched between the blades and that could be disaster. The blades are set high and no guard can be used. There is a lot of potential for a problem and there are other ways to do the task that may have lower risk. Personally, it's not a method I use but that's my choice.
I'm talking about tenons anywhere from 1/4" to 5/8" if needed. Most are in the 3/8" and maybe 1 1/2" long. I checked the other link for a discussion on this too. I have a Delta, cast iron tenonning jig and use 5/8" diameter thick washers of automotive quality. To fine tune the cut you can get a set of metal shims. Yes, it does take some time to initially set things up but you only need to do it once for each size then wire them together for future use. I generally cut them a whisker over-size and true them with a rabbet block plane.
The one thing I may add for safety would be a dedicated throat plate.
Two blades for a tenon thing . . .
here is a thread here on Knots :
http://forums.finewoodworking.com/fine-woodworking-knots/general-discussion/blades-tandem
You might ask these guys (at least you will be accessing a larger audience).
http://forums.delphiforums.com/burl/messages/?msg=804.1
This dual blade set up has at least one advantage; if the wood is not perfectly thicknessed , 2 x 4s or some such, and one is going off one face for a reference and one has many tenons of the same size to run then the dual blade thing is quick to use. Make or buy a solid sliding jig to back up and GRIP the work.
" . . . not perfectly thicknessed , 2 x 4s referenced off one face" ? When the heck would a person do that ? You may ask.
See the photos of my panel cutting table (FWW project ).
Rather than nail it together, as the FWW article suggested, I made it with big "O monster tenons. That way I could practice making big "O monster tenons and I could knock this cutting table down and fit it easily in my MG. ( one never knows when one might have to do that )
: )
Cutting table
Roc,
Not to steal this thread, but when I saw the photos of your cutting table I almost swallowed the toothpick I always have in my mouth. It is identical - right down to the color of the folding metal table legs - to one I made for my shop.
As you're certainly aware by now, it's a very handy little thing to have around. The top of mine doesn't break down though; I glued the mortises and tenons.
Interesting how great minds sometimes converge on things, isn't it?
Zolton
It's all a matter of perspective
Zolton,
> little thing<
Doesn't seem like a "little" thing in my shop. It is all I can do to get it out of the laundry room, through the door way and around the bend into my shop. It is my own fault though; if I didn't have so much crap in my shop I could store the cutting table in the shop. Maybe in the future I will unload some stuff. If I do, that will be about the time I need some of that stuff back though.
Norm would be proud of me. Never throw anything away.
: )
materials and transport
Good thing you didn't use walnut, oak, or curly maple for your table, Roc. Otherwise, you might have to upgrade to a Morgan to transport it. ;-)
Upgrade to a Morgan
Works for me . . .
If you have an extra one in your stable I would be willing to keep it exercised for you. Of course it would mean remaking my cutting table but that is a burden I am willing to bear for the sake of the common good and keeping up a high standard of chic.
This forum post is now archived. Commenting has been disabled