Hi All,
A question: is it equivalent to use loose tenons as opposed to integral tenons? I am building some complex cabinets and it is easier for me to make mortises on a home-build jig. So, are loose tenons as strong as integral tenons? Or are there times when one or the other is better?
Replies
FWW did a semi scientific study some years ago and the verdict was the loose tenon wasn't signifigantly weaker. Been using loose tenos and slot mortisers for 25 years and wouldn't do it any other way. The only time I would say it's better is if you are doing historical reproductions and only for the historical accuracy. Loose tenons are certainly faster and more accurate as you are making the same slot in the mating pieces. Also the router or slot mortiser will give a better slot as far as consistency and quality of the inside finish versus using a chisel mortiser or certainly a chain mortiser which is considerably rougher.
Great, thanks Rick. I was hoping that was the answer.
I believe it was issues # 111 and 148 the test was redone. I have both issues myself. Not sure if it was reprinted elsewhere.
http://www.taunton.com/finewoodworking/store/pages/fw_toc_148.asp
http://www.taunton.com/finewoodworking/store/pages/fw_toc_111.asp
All of the tests I've seen support the fact that 'loose tenons' are extremely strong and shouldn't pose any problems for what you propose to do. It's actually pretty amazing how strong these joints are when you see the stress they are put under in the tests. It's hard to imagine that any kind of abuse around the home would ever match some of those conditions.
Rick
Rick in Cowichan Bay, B.C. - 50km north of Victoria, B.C.
My Website: http://www.rickswoodworking.ca
I use the Beadlock jig for making loose tenons. Works great and is easy to use. I never had any tenon fail yet and the fact that all I need is a drill and some tenon stock makes it a no brainer for me.
I've just fininshed a set of mirrored doors using floating tenions, and the doors are solid as a rock.
Mike D
I second the Beadlock. Stronger than the surrounding wood, and so ridiculously easy that it feels like cheating.
Talbino,
Whether it's easier to make integral tenons vs using "loose tenon" construction is pretty much up to the wood worker. Using a Wood Rat or a Leigh router jig it is just as easy to do it either way.
It's actually just as easy to cut tenons on a table saw or with a router in a router table as to make mortises in all your pieces, then mill the floating tenon stock to match the mortises. It's just a matter of gaining the experience with the equipment.
In any case, a loose tenon/mortise joint is probably strong enough for any application a woodworker could normally use with the possible exception of a very heavy door. Even then, the fact that it is possible to show greater strength, in destructive testing, for the "true tenon" design, a loose tenon door would probably outlast the maker if done well.
One slight caution - a tenon milled to be the right fit for the mortise in the long grain piece, will be looser in the mortise of the end grain piece (the "false tenon" part of the joint). The same router bit will take out more of the end grain than long (side) grain.
You can ignore the looseness and expect the glue to fill the gap. A PVA glue such as Titebond I or II probably will give all the joint strength ever needed.
Or you can mill the tenon stock to properly fit the end grain piece, glue it in place and slightly shave/scrape the protruding section with a cabinet scaper or chisel (don't sand it) to fit the long grain piece.
I made a lot of furniture with loose tenon construction and never had a problem (I used the second method to make the tenons fit.) I also thought loose tenon construction would be easier to do. Then I decided to do it "properly." After a while, it took no more time (possibly less) to cut the tenons on the table saw, made to fit my router mortises perfectly (side to side). I still had to chop the round ends of the mortises square. At first I thought that was a hard thing to do. After a while, it becomes ridiculously easy to very quickly chop them exactly the right length and perfectly square.
Then I built a router jig that cuts the tenons exactly the right thickness and exactly the right length and gives me either rounded ends or square ends. True tenons that fit my routered mortises absolutely perfectly, every time, with no further attention after using the router.
I router the mortises using a router in a table and stop blocks on the fence. I make the tenons first, then adjust the router table fence to get the mortise properly positioned in a test piece. The whole process is much faster than using a loose tenon method.
And there is something very satisfying about pushing the (integral) tenon piece into the mortise piece and (if the 2 pieces are the same thickness) having the sides line up to less than a ten-thousandth.
The jig I made is from Taunton's, "Ingenious Jigs & Shop Accessories," 1999, pp 69-75, "Router Fixture Takes on Angled Tenons."
Yes, it cuts angled tenons. It's as good as a $600 Wood Rat or a $1000+ Leigh jig for what it does. It's not as versatile as a Wood Rat - it won't do dovetail joints (that's a whole other discussion) but it makes incredibly accurate M&T joints. Cost of materials is well under $50.
(Warning - at least half the projects in the book are so compelling you may get side tracked for a while doing nothing but making jigs!)
Have fun, whatever method you use.
Rich
Thanks Rich. Good tip.
Tony
"One slight caution - a tenon milled to be the right fit for the mortise in the long grain piece, will be looser in the mortise of the end grain piece (the "false tenon" part of the joint). The same router bit will take out more of the end grain than long (side) grain."
Been using slot mortisers for 25 years in commercial shops and this is absolutley not true. Mortises in stile and rail are exactly the same size. If the piece is held firmly the mortise will not be oversized.
Rick,What kind of a bit did you use in the slot mortiser? And what speed does it turn.?I think the differences in machines and bits has a lot to do with it.My experience was with a router and a standard, 2 flute, carbide, straight, 1/2" and smaller bits. I had always intended to try an end mill, or other bits to to the work, but didn't bother because I stopped using loose tenon construction.I experimented with slowing the router down, but I got the best results at its normal high speed setting, so I did most of the work that way. The mortises in end grain were always a hair oversize. And the effect was greatest in oak, less so in maple. I'm sure the pieces did not move in the clamp during the operation.Rich
Typical is around 3,500 rpm in a slot mortiser. The lower speed in nice for horizontal drilling and doweling. HSS spiral 2 flute endmills designed for aluminum work great. Four flutes bog down. Less teeth is better like a rip blade for long grain. I've always had both mortises in rails and stiles exactly the same. You can tell by the fit and I've put a caliper to them. I know lots of shops using slot mortisers. Yours is the first mention of this oversize thing I've heard in 35 years.
Rick,You seem to keep missing the point that we are apparently comparing using a (metal cutting) HSS end mill in a slot mortiser at about 3500 rpm to using a 2 flute straight, carbide tip wood cutting router bit in a router at 15000-2000 rpm. Not an apple to orange comparison, but maybe a Granny Smith apple to a Golden Delicious comparison?You know of lots of shops using slot mortisers. Fine. No argument there whatsoever. I'm not disputing for an instant your experience with slot mortising. I said in the earlier post that I was going to experiment with end mills in the router, but didn't. I wish I had had a slot mortiser, but all I had was a router and I was giving advice to someone who was contemplating the SAME technique.I'm sorry that this is the first time you have heard of getting an oversize mortise in 35 years. But that's exactly what happened every time to me using my set up. I WAS NOT USING A SLOT MORTISER. The router technique at high speed produced slightly larger holes in end grain than it did in cuting into the side of long grain. Fact.Now you can say, in 35+ years you have heard of ONE case of oversized mortises, but the stupid guy was USING A ROUTER, NOT A SLOT MORTISER!Rich
I know of others who have slot mortisers with routers and they don't seem to have any problems with oversize slots in endgrain. I set up the Robland mortiser and router for a friend and personally tested it. I used a standard straight flute router bit and it was consistent. I'm going to check again and bring a caliper.
Edited 11/3/2006 3:04 pm ET by RickL
Don't use a caliper. Mill a tenon piece to fit properly in the side grain mortise, then test it in the end grain mortise.Rich
I'm well aware of the loose fit properties but will use a caliper to apply real numbers to the situation. My background is furniture making with the servicing of machines for a dealer so I have machined straight edges and precise measuring tools for the quick tuning up of machinery such as planers, jointers, sliding panel saws.
Just to add fuel to the fire, I've had success using a shop-made slot mortiser set-up, combined with the horizontal routing attachment for my shop-made router table. Loose tenons fit just as tight in end grain-cut slots as long grain-cut slots using the setup I have. I'm using a 2 flute spiral carbide upcut bit with my DeWalt DW621 plunge router that I have mounted as follows:
I made the slot mortiser based on plans I found in FWW #174. Here's a link to that article for online subscribers:
http://www.taunton.com/finewoodworking/Workshop/WorkshopPDF.aspx?id=24110
Instead of the router attachment suggested in those plans (angle iron and an aluminum router baseplate), I chose to modify my router table. I built the table from plans I found in Woodworker's Journal (Vol 27, Issue 1)
http://www.woodworkersjournal.com/plans/index.cfm/plan_details/5/61/1482
Those plans include an optional horizontal routing attachment that I made when I built the table. I put two threaded inserts into the base of the FWW slot mortiser so that I could firmly attach it to the horizontal routing attachment with two bolts. I also attach the base to the router table itsself with wood screws.
Unfortunately I don't have any pictures of the set-up in action, and it's all sitting in storage in California as I type this from my new home in Germany (I'm in the Air Force). Here is the best picture I can find on my hard drive of my router table. You'll see the horizontal routing attachment and shop made mortiser covered in sawdust below the table.
Muzhik,Thanks. Looks like a good setup and it's good to know that a router using a straight bit does not necesarily produce different size holes in side vs endgrain.I can't repeat my previous set up, and I don't rout end grain anymore. My router jig was somewhat different than yours and I'm pretty sure the work was held tightly and accurately positioned. I consistently got a loose fit in the end grain with a tenon that fit the side mortise tightly. I had a Craftsman router then, I have a Bosch now. Mabe there was excessive run out which affected an end grain cut more than a side grain cut. I don't know.Rich
I'm not sure. It may be as simple as the bit itsself. I can imagine a less-than-new straight-cut bit would hog out/tear out more material in an end grain cut than it would shear off in a long grain cut. A new spiral upcut bit may just be the key.
Edited 2/5/2007 7:05 am ET by Muzhik
Here’s how to find the router jig article Rich14 is referring to: go to the top of this page and click the Workshop tab. Go to the nearby search window and paste this title in: Router Fixture Takes on Angled Tenons. Click go. Click on the article in question, second one down on the list. You do have to be a member of the site to open the pdf of the article.
Thanks, Rick.
That was a great "use of the site" tip.
Mike D
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