Sacrificial Fences...

Questions and comments concerning the assembly of the Jointmaker Pro

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Sacrificial Fences...

Postby John » Mon Mar 16, 2009 3:09 pm

This may seem like common sense, but since I have repeated this mistake no less than 50 times, it is probably worth sharing...

The proper sequence for attaching a sacrificial fence to the left and right fences is as follows;

1. Loosen the metal fences--remove fence if necessary.
2. Slide a sacrificial fence onto the dovetail nuts on both metal fences.
3. Position and tighten the dovetail nuts.
4. Tighten the metal fences after setting for your particular angle.

If you don't loosen the metal fences first, the sacrificial fence may be hard to remove/install due to irregularities caused by humidity, warpage, etc.

Also, don't forget that after you have taken the time to dial in a particular angle of the fence(s), use a pencil and scribe a line on the table tops if you want to repeat said angle later without the trial & error of another setup. Works great! If you are like me (flakey memory), note on the table what the angle is--i.e., 8:1 dovetail)

Lastly, if you want to make your own sacrificial fence, you don't necessarily have to use the dovetail nuts--take them out and use the screw holes in the metal fences for wood screws. (If you want to add additional screws, the fences are aluminum and you can drill and countersink as needed.)

If you lose a dovetail nut, don't worry--we have replacements for $321. each.... (just kidding folks...we don't have replacements).

Lastly again, if you do make your own sacrificial fence(s) jigs, etc. make sure you put a small chamfer on the bottom of the fence where your stock intersects the fence and the table for dust/waste clearance.

--John
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Postby Cory » Mon Mar 16, 2009 8:03 pm

One thing I learned in making a few dovetails is that whenever you change the angle of the metal fences, you have to loosen the sacrificial fence.

This is because the 2 inside boltholes aren't slotted, so turning the fence with the fence tightened will try to pull the tables together or push them apart. Loosening the sacrificial fence allows the metal fences to slide apart, not forcing the tables.

I'm describing it poorly - just try it out and you'll see.
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Postby John » Mon Mar 16, 2009 8:55 pm

Cory;

That is exactly right. Now what is the underlying trig principle involved?

This is a WAT question...Woodworking Aptitude Test question.

John

:D
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Postby Cory » Mon Mar 16, 2009 9:44 pm

Hmm....
soh cah toa (amazing what still sticks after all of these years)

I'll use cosine because I'm comparing the relative length of the adjacent and hypotenuse segments of the triangle.

Ok, lemme get out my TI-85...

cos( 8 ) * 4.25 =4.20863929215, so an 8 degree turn pulls the tables together about 4/100ths.

hows that?
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Postby John » Mon Mar 16, 2009 9:57 pm

Cory:

Be honest now...TI85?

How 'bout a Pickett Slide Rule... ? I hauled one of those around on my belt for two years in the 60's...tough to get date with that thing tagging along...

You pass--next stop: differential calculus--and if you are not careful I will throw in an organic chemistry question--or two.

John
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Postby Cory » Mon Mar 16, 2009 10:10 pm

Yup, TI-85. I didn't even use those weird stack-based HP calculators. I'm a bit of a youngster among the woodworkers I know...
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Advances in Technology

Postby BobStrawn » Tue Mar 17, 2009 10:05 am

Fortunately these days we have computers and don't have to lug slide rules around anymore! Instead we can use our computers to go here, http://www.antiquark.com/sliderule/sim/n909es/virtual-n909-es.html

The page even works if you download it, so there is really no excuse for carrying a slide rule anymore!

Bob ^_^
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Postby John » Tue Mar 17, 2009 11:11 am

Bob;

THAT IS COOL! Wow, what memories. I can remember sitting in physics exams working this thing with sweat all over my hands while trying to ignore the war protests outside. What a decade--and it was the same decade I discovered woodworking.

Thanks for sharing--I am going to send this to my son as further proof that his math life is gilded.

You TOO Cory!

John
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Here is the mother load!

Postby BobStrawn » Tue Mar 17, 2009 3:40 pm

Even more fun, http://www.antiquark.com/sliderule/sim/index.html
is a range of slide rules, even a zip file to download them with!

We had mad skills at being able to keep the decimal point in our head back then as we sailed through calculations on slip sticks.

Then I was corrupted by a TI-59.

Bob
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Sacrificial Fences

Postby MikeDaum » Tue Mar 17, 2009 7:36 pm

I discovered a helpful little trick to help in removing the sacrificial fence from the dovetailed keys. Depending on how much force you use to tighten the fence, the metal dovetail key can dig into the wooden dovetailed slot and make it hard to slide off, even after loosening the bolts completely.

The solution: After loosening the bolt holding the fence to the dovetailed keys with a few turns, simply push the allen key into the bolt toward the fence. This forces the key to release from the wooden slot. You will hear and feel it release.

Mike
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Postby John » Wed Mar 18, 2009 9:42 am

Mike;

Thanks for sharing--we also posted this trick on page 16 of the manual--works like a charm.

John
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Re: Sacrificial Fences...

Postby jegeering@yahoo.com » Sun Nov 13, 2011 9:15 pm

Hi,

I am building my jointmaker now. How hard should it be to get the sacrificial fence onto the dovetails? Should it just slide on or does it need to be tapped / banged into place using a rubber mallet?
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Re: Sacrificial Fences...

Postby Michael » Mon Nov 14, 2011 10:05 am

They should slip on with no assistance from a mallet.
Try further loosening the dovetails nuts if the it is difficult to slide on.

Let us know how it works out.


Thanks!
Michael
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