Third-party Longer Mortise Bit for DF500

Bohdan said:
I think that the real question is, if you break the joint, exactly what breaks.

Will it be the domino or will it be the surounding wood. If the domino breaks then a deeper one would have made no difference. If the surrounding wood breaks then a deeper domino may have helped but if the domino pulls out then maybe you didn't use enough glue or it wasn't long enough.

Has anybody seen any tests that tested domino joints to destruction.

This?http://www.finewoodworking.com/item/7592/readers-respond-to-our-joinery-shoot-out
 
I don't remember seeing the FWW test result but the video suggests it is similar to the Wood test.  Their tests stressed the joints the same so they should get similar results.  That test is representative of the back leg to the seat support joint as the video shows.  At least it is when somebody leans back.  But that isn't the only type of stress the chair sees.  It may well be the peak stress, however.  The conclusion is that a lap joint is the strongest, mortise and tenons are strongest when the tenon is 1/2 the wood thickness (not the more typical 1/3), biscuits not very strong, etc..  Dominos did not fare well in the Wood test but that was at least partially because they used a much smaller joint than the traditional mortise and tenon joints.  Surface area of the joint makes a significant difference, in other words.  Same reason the lap joint was strongest.

If you only occasionally need bigger mortise and tenon joints you could cut them more traditional ways.  They are much slower but work well.  I use a benchtop hollow chisel mortiser, for instance, that will cut joints about 3 inches deep and as wide as you want (it's maximum chisels are 1/2 inch but you can cut overlapping holes easily).  It costs around $250 - much cheaper than Dominos.  Even cheaper is to just drill and chisel.  But a benchtop mortiser is much faster than drilling and chiseling - but much slower than using a Domino.
 
OK, probably stupid thought, but here it is:

Any change you could use the DF 500 and for those (rare) occasion you need bigger tenons, deepen/widen the mortise with a OF1400 (has also max. depth of 70mm) ?
 
threesixright said:
Any chance you could use the DF 500 and for those (rare) occasion you need bigger tenons, deepen/widen the mortise with a OF1400 (has also max. depth of 70mm)?

Yes this would be possible.  Using a router and/or drill press, you could increase the depth of the mortise.  The Domino 500 drills 28mm deep maximum.  Lets round that to 30 and 60mm total Domino length.  For the Domino 700 Festool sells 80 and 100mm length Dominoes.  So you would need to drill/rout an extra 10 or 20 mm of depth on each side[bottom] of the mortise.  Aligning the router or the drill press would not be easy, but could be done.  I am sure you can buy 8 and 10 mm drill bits and router bits that are long enough to go 40 or 50mm deep in each mortise.  I'm sure Europe has them.  You might have a little problem with aligning everything so the extra 10 or 20 mm depth you drill/rout may not be perfectly aligned and smooth with the original Domino mortise.  So likely you would need some Epoxy filler for the last 10 or 20 mm of the Domino to take up the excess space and looseness.  Since Epoxy is strong and hardens when dry, I don't think this excess space would affect the overall strength of the joint.  And you would get the full benefit of the 80 or 100mm long Dominoes in the 8 and 10mm size.

Now whether this deepening makes sense, I don't know.  Lot of extra work for likely minimal if any extra benefit, strength.  Probably better to just add a couple extra 50mm long Dominoes to each joint and not worry about going deeper.  Just go with more tenons, not deeper tenons.
 
RussellS said:
threesixright said:
Any chance you could use the DF 500 and for those (rare) occasion you need bigger tenons, deepen/widen the mortise with a OF1400 (has also max. depth of 70mm)?

Now whether this deepening makes sense, I don't know.  Lot of extra work for likely minimal if any extra benefit, strength.  Probably better to just add a couple extra 50mm long Dominoes to each joint and not worry about going deeper.  Just go with more tenons, not deeper tenons.
Thanks Russel, thats bring up a interesting point, which is: I would assume a longer tenon would given a lot more strength, then more tenons? I don't know the math behind it, but instinctive. I would rather choose a few longer ones.

Are there any 'rules-of-tumb' when it comes to the thickness and length of these tenons?
 
Widening or making the mortises thicker is not an issue with the DF500 joiner. You simply make the first cut as usual and then reposiiton the joiner (without changing any other settings) against the same reference surface to do a second cut to widen the mortise. To make it thicker, adjust the fence (higher or lower) -- and again keeping all other settings unchanged) -- and cut again.

I am not giving up, and am still hoping someone might come up with either a commercial or homemade solution that can mill mortises deeper with the DF500 joiner. Hey, even someone has come up with a prototype that can address the kickback problem with a circular saw, that I am sure few ever thought of.
 
threesixright said:
I would assume a longer tenon would give a lot more strength than more tenons? I don't know the math behind it, but instinctive. I would rather choose a few longer ones.
Are there any 'rules-of-tumb' when it comes to the thickness and length of these tenons?

I am sure there are engineers who deal with foundations on buildings and houses who have the math to determine the optimal number and depth of foundations (tenons).  I believe on the Gulf coast in Miss. and Lou. they build houses on marshy soft ground by driving poles into the ground to establish a foundation for the house.  I suspect these people could tell you whether its better to drive six poles 40 feet deep or twelve poles 20 feet deep.  But I'm guessing it may be like someone wrote at the beginning of this thread.  If a post driven 2 feet into the ground is unmovable, unbreakable, then what is gained by driving it 3 feet into the ground?  If its 100% perfectly strong enough, then no need to waste effort making it stronger.

For rules of thumb about Dominoes, I assume they are the same as mortise and tenon, slip tenons, loose tenons.  The old 1/3 scale for thickness.  1.5" thick leg, make the tenon 0.5" thick.  Roughly, give or take.  I prefer thicker tenons personally.  As for length and width, kind of the longer and wider is better theory.  Within some logical restraints.  Unless you carry things to wacky extremes, just making things so they look right will be perfectly good.
 
ChuckS said:
DF700 users can buy third-party cutters and use the 700 like a DF500. Is there anyone out there
producing and selling longer cutters that we can use a DF500 with longer Dominoes like the 8mm x 22mm x 80mm, or even the 100mm?

Please share the source if anyone knows about such cutters for DF500. Thanks.

Chuck

Hi chuck hey next reader
Intention to inform.
The bit would look outside the mouth we know that for sure.
What we dont know is how much breaking power is applied to the tenon what wood is used and what glue.
To resolve your first question properly...

We drill in the done holes from the df500 with a drill the holes deeper and then take a chisel and cut the "V" that stays between the holes.
That works good for us.

Now how to calculate the maxload for a tenon there are several methodes to an end.
Search for the wood and search for the max loads it can handle. Then caluclate from there the dimension needed.

What gives strong tenons is how wide the domino is ,  how thick the walls are that hold and then the deepth.

No selfmade domino will carry much load especially when he is slim and long.
He must be thick and long burried into a thick corpus of wood.
The next question would be are the forces in a sher motion or is a leveraction applied to the tenon.
But here you have to calculate what happens.

A good basis is 1:1:0.5
20mm wide x 25mm long x 10mm thick.
Before you try deeper holes widen the cut and add wider dominos that will produce a supirior tenon then one with a deeper hole.

Remember wide/brother dominos carry more than longer. Why because of leverforce applied to a 20mm stick isnt doing anything but leaveraction applied onto a 200mm plank delivers (yes until both break but a plank is 10 times wider so it must deliver at least 10times more!)
To give more strenght to a join we widen the domino holes and applied glue that gives us the best results.
Have fun doing it
 
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Wooody said:
Snip.
Hi chuck hey next reader
Intention to inform.
The bit would look outside the mouth we know that for sure.
Snip.
Yes, the opening (width) of the mouth on the DF500 machine is sure a concern. I haven't checked how much wider the DF700's is than the DF500's.

Both the depth and width (as well as thickness) of a tenon matter in a loose tenon joint. Width alone doesn't cut it. When I want to have a deeper mortise (than the one that a DF500 can mill), I can't just use a wider mortise (e.g. by overlapping cuts or milling in the widest setting) instead.

Case in point: Wide tenons (illustrated in blue) wouldn't give the joint strength needed for connecting these two structural parts as deeper ones (in red) did.
 

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ChuckS said:
DF700 users can buy third-party cutters and use the 700 like a DF500. Is there anyone out there producing and selling longer cutters that we can use a DF500 with longer Dominoes like the 8mm x 22mm x 80mm, or even the 100mm?

Please share the source if anyone knows about such cutters for DF500. Thanks.

Chuck
 
Deeper Mortises?

several choices

Chisels

DF700

or a router

Leigh FMT

mortise machine Horizontal or vertical

I have done  more than a few with a router and am perfectly satisfied with the results; Getting hung up on using something it was not designed for is an effort in futility
 
ChuckS said:
DF700 users can buy third-party cutters and use the 700 like a DF500. Is there anyone out there producing and selling longer cutters that we can use a DF500 with longer Dominoes like the 8mm x 22mm x 80mm, or even the 100mm?

Please share the source if anyone knows about such cutters for DF500. Thanks.

Chuck

Last year I went as far as sending crude shop drawings of a long DF500 bit to Vortex Tools. They gave me a quote of $375.00 for a prototype . We both decided that carbide was too fragile for the extended cutter. Vortex sent me to WL Fuller. WL Fuller primarily uses HSS for most of their products, but they can combine carbide cutters with HSS. Vortex only works with carbide. I was interested in adding 3/8"-1/2" to the overall length, no point in adding more than a 1/2". I had a project that was using draw-bore dowels in the corners of cabinet doors. We were using the extendable tenon, cope and stick bits from Freud. We set up the Domino in a bench cradle, and used the Seneca Dock Plate to cut all the mortises. The idea was to make an 1-1/2" mortise in two cuts, the first cut was max depth with 6mm Domino cutter, then switch it out with the longer bit and finish the cut at 1-1/2".
Extra, Extra care is required because the extended cutter is exposed when making the second cut.
I never had the extended bit made, I ended up finishing the mortise with a bench top mortiser, which was a real pain. The Domino really excels here because of the dust collection. I'd be interested a few bits if the concept got legs.
E.
 
Coincidentally, I asked the same question about extending the depth a few weeks ago. To answer this question, some context is needed.

I am in the process of building two single beds. The wood is Jarrah, which is hard, heavy, and strong. The 26mm wide rails are 5”/125mm and join with a 55mm short post at each corner. Ordinarily, I would have built the ends with mortice-and-tenon joints, but the boards are only long enough to fit using loose tenons. I decided to make the 10mm mortices with the Domino DF500.

I have not made loose tenons before, so was concerned about the depth they needed when secured in the rail. Keep in mind that I have been building furniture for 30+ years, and I know what to do with traditional joinery.

Finally, it dawned on me, with the help of a little research supplied by an experienced woodworker, that …

1.  The tail- and head end of the beds (which are the fixed joinery) do not experience the stresses of the side rails (which are secured with shallow 10mm mortice-and-tenons and bed bolts).

2. A depth of 28mm will be sufficient into the 55mm post (it is half the width), recognizing that the loose tenon is shop made from Jarrah and 110mm wide. Wider is better, along with a tight sidewall fit.

3. The depth of the mortice into the rail can be the same as the depth into the post, noting that the loose tenon is also 110mm wide. For extra security, any movement will be eliminated by adding two pins (from the inside) to the joint.

I will post photos of all this once completed.

Regards from Perth

Derek
 
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