Ron's Bridge Notcher

[Phillip Ford]

Very impressive Ron.  Thanks for sharing this.  I don't think I completely 
understand how it works.  A few questions interspersed below.


>Well, here they are. There are a lot of ways to build something like
>this, and a good percentage of them would work. I designed this around
>partly what I had on hand, partly what I could buy without spending
>thousands, and what I thought I was capable of producing with the
>equipment I have in the shop. I started with an old router, and went
>from there
>
>
>The carriage runs on 1/2" rods, with linear bearings embedded in
>the Baltic birch sandwich everything is bolted to. The cutter and hold
>down height relationship is fixed, with both mounted on the slide rods.

I'm not sure what you're calling the hold down and what is being held 
down.  The bridge?  Is the hold down that vaguely L-shaped wooden 'foot' 
that is attached to what I'm calling the stop block?  And is that thing the 
stop block?  It looks like it would stop the cutter table travel and 
appears to be adjustable.

If that thing is the hold down and does what I think it does, and the 
cutter height is fixed relative to it, then the depth of cut is always the 
same.  Correct?

>
>Since the slide bearings and hold down mount are very close together on
>the rods, it's quite rigid. An old die set from a salvage yard, and a
>pneumatic ram harvested from junked data processing equipment twenty
>years ago provide the lift mechanism to press the bridge against the
>hold down from below.

So, you step on the foot switch and a pneumatic cylinder lifts the lower 
table (with the bridge on it) up against the hold down?  What sort of 
pressure are you using?

>  The big threaded rods front and back are height
>adjustments for different height bridges.

With the pneumatic lift table why do you need this?  Is the travel of the 
table limited?

>1101: Cutter (2" shaper, Grizzly), hold down, lift table, and the arbor
>I made out of a chunk of steel plate, a piece of water pipe, and a
>couple of bearings. Have you ever tried to find an arbor?

How did you decide on cutter diameter?  Is a typical notch about a 1 inch 
radius?

>1098: This is a slam suppressor. It's used on thinks like big cedar
>chests and the like to let the lid down slowly under hydraulic control.
>Since I'm doing a climb cut into the bridge top, this prevents the
>cutter from climbing on top of the bridge and eating me. A very good
>thing.
>
>..........It ain't pretty, but the silly thing works about as well as I could
>have hoped. Oh yes, the highly sophisticated cutter feed consists of
>grabbing the router handle, pressing the trigger switch with my index
>finger, and pulling against the slam suppressor resistance until the
>carriage hits the stop. Very high tech.
>
>And there you have it.
>Ron N
>

I don't understand how the bridge is positioned in the machine.  How do you 
insure that the edge of the cutter is aligned with the inside bridge pin 
hole?  That the cut is square to the line of the three (or however many) 
bridge pin holes (in other words, how do you insure that the bridge isn't 
skewed)?  How do you position the bridge so that when the cutter table hits 
the stop the cutter is at the center of the bridge pin holes?

Any possibility of a couple of pictures with a bridge in the machine?

Phil Ford