WoodRat Addition

[SketchUp Guru]

I just thought I'd post a couple of images showing an addition I made to my Rat. Maybe someone here might find it useful.

First, a SketchUp drawing of the Rat with my planned addition. It's simply a piece of T-track attached to the top left end. There are a couple of stops that can be set to limit the travel of the East-West carriage. They contact whatever is clamped in the marker postion. Click on the pictures for larger views.

My main reason for adding this to my Rat was to reduce the chance of getting a misalignment between pieces when cutting dovetails. Although I cut them differently on the Rat, these stops could be useful for box joints, too. I could also see doing something with the stops to use them for cutting mortises and tenons.

I ended up with a different sort of track than the one I drew. This one has a flange on the back side with mounting holes drilled. since I had this stuff on hand, I ended up using it.

Again, because I had them, I used a couple of cam locks from Lee Valley. All the knobs I had were much larger in diameter and I didn't want the knob to interfere with the work.



And finally, here's the first joint out of the Rat using the stops.

I colored the ends of the pins with a marker so they'd show. The joint is tight and perfectly aligned. I think if I were going to glue the joint I'd back the button setting off by a tenth of a millimeter or so.

 

[Philly]

Great idea ,Dave-and well implemented.
Keep up the good work,
Philly

 

[Adam]

Good stuff!

Adam

 

[RogerS]

Hi Dave

Snap!

https://www.ukworkshop.co.uk/forums/viewtopic.php?t=4622&highlight=

Roger :lol:

 

[Alf]

Also snap here (about the eighth piccy). 'Cept the left hand one's removed or else it tends to get walked into... #-o Think I got the idea from Roger in fact.

Cheers, Alf

 

[SketchUp Guru]

Philly and Adam, thank you.

ALF and Roger, I knew it wasn't original. I always invent stuff that have already been invented. Remind me to tell you about the time I invented the wheel.

I remember seeing your additions to the Rat in the past and they must have been residing in the back of my mind. Thanks for that.

 

[LyNx]

Looks a good idea, even though i don't know how the rat works

Quick question, how do you stop any breakout of the timber when cutting the dovetails? And how are the dovetails marked on the rat?

Andy

 

[RogerS]

Philly and Adam, thank you.

Remind me to tell you about the time I invented the wheel.

.

:lol: :lol:

Dave, how do you 'register' (for want of a better word) against the stops? I find that I still have a fair bit of fiddling around swapping between left and right side tracks especially if I'm working with the mortice rail. In an ideal world I guess I'd mount a continuous length underneath the 'Rat that didn;t get in the way of things.

Roger

 

[SketchUp Guru]

Andy, I didn't experience any breakout when I made these cuts but you can back up the work with a piece of scrap if you want.

As to how they are marked, you can see part of a dovetail mark on the face of the Rat at the left edge of the tail board. That mark was made by making a cut in a thin piece--I use some 1/8" thick pine left over from a project--then the thin piece is moved over to the marker position and the dovetail shape is traced witha very sharp pencil onto the face. If you don't move the carriage when moving the slat, the pencil mark is at a fixed distance from the bit.

You mark out the joint on the board that will get the pins and clamp that in the left hand clamp. I just make a mark for the center of each pin and align that with a centerline drawn in the tracing of the DT bit. there's no rules about how you mark them out.

Actually, I have started doing an intersting think I got from Mike Humphreys. He tapes the two tail boards together and cuts the tails in one go. He cuts the socket for the first half pin. Then he flips the work end for end, cuts, rotates, cuts, flips, cuts. When he is done with that, he has all the corners cut. Then he moves the carriage for the next socket and repeats the process. This procedure, while it sounds like a lot of work ensures symmetry in the joints and any set of tails and pins should fit together.

 

[SketchUp Guru]

Roger, so far I have only used the stops for cutting dovetails. Since both stops are on the left side of the Rat, I haven't had any issues with swapping.

The method I used when cutting the test joint is as follows:

1. Make the mark as per the manual.
2. Mark out the joint on the pin board. In this case I only marked the center of the center pin.
3. Place the pin board in the marker position. tail board is in the cutter position.
4. Track the carriage to the right to align for the first half socket. This time I aligned the edge of the pin board with the top left corner on the mark. You can kind of see that in the photo.
5. Set the right side stop against the right edge of the pin board.
6. Track the carriage to the left and position it for the right side half socket. See below for an adjustment to this procedure.
7. Set the left side stop against the pin board.
8. Cut the sockets. Doesn't matter which direction you track from but I went left to right because that's the way I started doing them.
9. After all the sockets are cut I marked out the pins ala Aldel's method. In this case that was more to give me a visual idea of how I was doing as I went along. I think it is good practice, though.
10. Insert the tail board in the marker position, pin board in the cutter position and then track the work using the stops as the limits.

Hope all that makes sense. Maybe it was more detail than you want.

Oh, the change in the procedure. is this: Mike Humphreys' method of flipping and flopping works very well. I think I would only set the stop on the right for the first cut since it would serve for making all of the cuts at the corner.
Dave

 

[RogerS]

Andy

Check out Aldel's site for everything you ever wanted to know about the 'Rat

http://www.aldel.co.uk/

Roger

 

[Alf]

Remind me to tell you about the time I invented the wheel.

Drat, you too? #-o :lol:

Andy, vis-a-vis breakout, one way to avoid it is hopping over the board and coming in from each side. Particularly easy with the plunge bar.

Cheers, Alf

 

[SketchUp Guru]

ALF, was that you standing in front of me in the que at the patent office?

Hopping over does work, too.

 

[GCR]

Thanks Dave. Always interesting to see the 'Rat in action.

Bob