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  #11 (permalink)  
Old 09-12-2011, 05:26 AM
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Default Re: A new joint?

I don't find that exact joint in any of my books so it's wide open to your naming of it.
A couple of points:

You could create a 1/2 lap joint to the exact fit you want using your KerfMaker (no gaps) and you wouldn't need to remove all the stock you did in your mock ups making a stronger joint.

A sliding dovetail would also make a very strong joint for your application.
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Old 09-12-2011, 06:26 AM
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Default Re: A new joint?

Thanks for your research, Ron. I'm a little surprised that the joint doesn't exist - it seems pretty obvious, and easy to do with hand tools.

I think for my purposes this will be stronger than sliding dovetails, and less wobbly than a half-lap joint. The mitered shoulders really add a lot of strength and rigidity. You should try one!

Should I sell naming rights? Who wants a joint named after them?
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Old 09-12-2011, 06:36 AM
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Default Re: A new joint?

Quote:
Originally Posted by hasslefactor View Post
It's nice to see your process, Peter.

I found this link a couple days ago. Maybe you'll like it, too:
The Project Gutenberg eBook of Woodwork Joints, by Unknown.
Cool, Laurie! My joint is a variation on Fig. 40: The Project Gutenberg eBook of Woodwork Joints, by Unknown. - the "cross halving joint edgeways". So maybe this one is a "mitered cross halving joint edgeways"?

Let's make one at the WIA! Rutager's always up for these things, too...
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Old 09-12-2011, 06:49 AM
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Default Re: A new joint?

"Fig. 55 shows the elevation and end view of a "Cross Halving Joint" with housed or notched shoulders. This joint is seldom used in actual practice. The separate parts are given in Fig. 56.

The notched shoulders are in only one of the pieces and they're square shouldered but it's close in principle.
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Old 09-12-2011, 07:15 AM
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Default Re: A new joint?

The notched shoulders are in only one of the pieces and they're square shouldered but it's close in principle.[/QUOTE]

Is that called the "Peter Principle"???
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Old 09-12-2011, 05:13 PM
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Default Re: A new joint?



"I'm working on a table that will have stretchers joining the legs diagonally across the bottom of the table. The stretchers will be quite wide (4-5") and will cross at right angles under the table."

So, this is a square table?

The deeper the miter the weaker the stretcher.

I'd go no more than 1/8" deep. At an 1/8" deep in a 3/4" x 4" stretcher you're now down to a cross section of 1/2" x 2" maximum, slightly stronger than a nominal 1x2.

[In the top board, the one with the slot in it's underside. The other board will be substantially stronger since compression in it's upper half will be maintained.]

The mitered shoulders provide some mechanical resistance to twisting and glue will improve that but glue won't add any deflection resistance. So, keep the mitered shoulders shallow.


How long are the stretchers?

The JMP would be great at cutting the mitered shoulders if the pieces are short. That brings up the Achilles heel of the JMP, it uses the stationary machinery principle of moving the work across the tool and the tool can only support small work pieces.

Someone needs to come up with some low friction outriggers to support longer stock on the JMP. Since the throw on the JMP is short they could be pretty fine without costing too much.
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Old 09-12-2011, 05:28 PM
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Default Re: A new joint?

The stretchers will be about 20" long - it's a small table. I agree with your conclusion that the mitered shoulders be kept shallow - I'd come to the same conclusion myself. I wouldn't go much deeper than 1/8", as you say.

You've identified the main problem I see with the JMP - you can't work big pieces on it. How would you build a cabinet or desk? A frictionless outrigger table would be a good start. Maybe use those leftover bearings to make a sliding outrigger table. Could you keep things square? It would be nice to join them mechanically somehow.
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Old 09-12-2011, 06:50 PM
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Default Re: A new joint?

Here's my evolutionary plan for the JMP.

1. Lock the table and slide the saw blade.
Can't be done unless the blade is radically shortened or you abandon
the tilting trunions or make even more radical changes to the overall design.

In Europe there are several portable table saw designs that slide the saw
carriage rather than the stock. They even have tilting arbors. But that would
never pass UL here. So...

2. Shorten the saw blade by making it round A fine circular Japanese
blade would be amazing. But we can't go back to the sliding table idea
because it still only supports short stock, it just isn't the best (Festool) way.
None of the other BCT tools work that way either.

3. So we've got a small circular blade sliding (just a foot or so which allows
a tilting arbor design within a small footprint) on rails and the work is stationary.
And we know UL won't approve it if it has a power cord. So....
wind it up with a spring motor governed by a flywheel. A simple mechanical
link to a foot pedal can provide starting/stopping of the flywheel/arbor.
With one hand on the work (but not in the path of the blade) the other hand
pulls a lever that slides the saw carriage forward and back. Let off the power
pedal to save the drive spring on the way back. Oh, forgot to point out,
this provides full depth cutting in one pass, if the spring motor is up to it.


Just looked up spring motors and found this wonderfully written
description of the repair and maintenance of a Victrola spring motor.

'Victrola motors will tolerate an astonishing amount of old grease, but a good
starting point for any repair is to clean the motor. It's perfectly acceptable, and
sometime miraculous, to spray everything in the motor with a lethal dose of WD40."



This serious looking mechanism is an Edison Triumph three spring motor.
"The Triumph was certainly one of the most powerful machines Edison ever
manufactured, and was billed as playing up to 16 records off a single winding."

The apparent weight, mechanical and manufacturing complexity of that Edison motor
lead me to think of using the guts of a cordless portable circular saw. Don't know if UL
would be involved in that but I doubt BCT would be interested. Looking at more spring motor
stuff I learned that in the 19th century there was an effort to make a spring motor tram
that didn't get very far. The spring motor was the problem and an interesting substitute
was proposed, compressed air. I like that idea but a small compressed air motor is noisy.
A small hydraulic motor (I think they're very quiet?) driven by remotely compressed air
(the noise is out in the garage) would be cool.


So.. yea, it can get complicated.

Here is a short history of early peddle powered machines.
We could do a little better these days. Electricity is awesome!
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  #19 (permalink)  
Old 09-12-2011, 08:00 PM
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Default Re: A new joint?

Quote:
Originally Posted by MichaelKellough View Post
Here's my evolutionary plan for the JMP.

1. Lock the table and slide the saw blade.
Can't be done unless the blade is radically shortened or you abandon
the tilting trunions or make even more radical changes to the overall design.

In Europe there are several portable table saw designs that slide the saw
carriage rather than the stock. They even have tilting arbors. But that would
never pass UL here. So...

2. Shorten the saw blade by making it round A fine circular Japanese
blade would be amazing. But we can't go back to the sliding table idea
because it still only supports short stock, it just isn't the best (Festool) way.
None of the other BCT tools work that way either.

3. So we've got a small circular blade sliding (just a foot or so which allows
a tilting arbor design within a small footprint) on rails and the work is stationary.
And we know UL won't approve it if it has a power cord. So....
wind it up with a spring motor governed by a flywheel. A simple mechanical
link to a foot pedal can provide starting/stopping of the flywheel/arbor.
With one hand on the work (but not in the path of the blade) the other hand
pulls a lever that slides the saw carriage forward and back. Let off the power
pedal to save the drive spring on the way back. Oh, forgot to point out,
this provides full depth cutting in one pass, if the spring motor is up to it.


Just looked up spring motors and found this wonderfully written
description of the repair and maintenance of a Victrola spring motor.

'Victrola motors will tolerate an astonishing amount of old grease, but a good
starting point for any repair is to clean the motor. It's perfectly acceptable, and
sometime miraculous, to spray everything in the motor with a lethal dose of WD40."



This serious looking mechanism is an Edison Triumph three spring motor.
"The Triumph was certainly one of the most powerful machines Edison ever
manufactured, and was billed as playing up to 16 records off a single winding."

The apparent weight, mechanical and manufacturing complexity of that Edison motor
lead me to think of using the guts of a cordless portable circular saw. Don't know if UL
would be involved in that but I doubt BCT would be interested. Looking at more spring motor
stuff I learned that in the 19th century there was an effort to make a spring motor tram
that didn't get very far. The spring motor was the problem and an interesting substitute
was proposed, compressed air. I like that idea but a small compressed air motor is noisy.
A small hydraulic motor (I think they're very quiet?) driven by remotely compressed air
(the noise is out in the garage) would be cool.


So.. yea, it can get complicated.

Here is a short history of early peddle powered machines.
We could do a little better these days. Electricity is awesome!
Great stuff Michael!
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  #20 (permalink)  
Old 09-12-2011, 08:31 PM
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Default Re: A new joint?


Peddle powered sliding table circular saw.
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