The Rat was setup for the cutting the pins and some test pins made. I maybe could have spent much more time faffing about with the settings to get it absolutely spot on but I was happy enough with what I achieved. There are a few very very small gaps which seem to be due to a slightly different angle cut wrt the tails. This can only be altered by messing about with the pivot point on the Rat (Centre Plate -> Button Settings) so that the angle of the pins are cut differently. Anyway, I have what I have now!
I think I also messed up which way round the boards should have been put in the Rat, i.e. the relative board orientation has ended up being different but I am not a pro so am not going to get too upset on this occasion! It still looks good to me.
For those who don't know, the board with the tails already cut is placed in the marker position (left hand clamp) on the left hand side of the Rat. When I first cut the dovetail cutter through a thin piece of ply, I then moved it from the cutter position (right hand clamp) to the marker position where I marked the profile of the DT cutter onto the front face of the Woodrat. This is then used to line up each further cut. When cutting the dovetails, a marking jig is placed in the marker position (this is just a vertical piece of wood clamped in the marker position with another piece of wood attached to this with a hot melt glue gun or similar, 90 degrees relative to the vertical piece. The top surface of which is aligned with the top surface of the Woodrat when clamped in position.). This is used for making pencil marks on which are relative to the left hand side of the marker position clamp (fixed fence). At this point in time the Rat is not moved east/west, so that the position of the cutter is maintained relative to the marker position. We can now mark pencil lines relative to the cutter position on the marking jig, then when the cutter position is moved east/west, we can align the cutter relative to the original starting cutter position of the dovetail bit. Hope this makes sense!?!!
Cutting the remaining dovetails along the width of the board is then worked out in your head based on the diameter of the dovetail bit and the spacing you wish to achieve between DTs. The half DTs at each end of the board I worked out to be 11mm from the edge of the board (at the base of the DT cutter), so this is just over half the diameter of the DT bit (15mm diameter) plus a bit more. Then I calculated 15mm for the next piece of wood to remain and then I moved another 7.5mm because of the dovetail bit giving 33.5mm from the side of the marking jig or left hand fixed fence (this was marked on the top surface of the marking jig). Then the first cut could be made. The board is then flipped around in the cutting position 3 more times to cut at both ends of the board and two sides (one cut from each side edge). This saves time and saves losing accuracy. The next cut position is then calculated and the board moved along east/west and the flip and cut process repeated.
Once the two side panel boards are cut the pins can be setup which is where the centre plate comes in and the aluminium north-south guide rails are removed because we want to pull the router through at an angle relative to the front face of the Rat. The centre plate forms the pivot point from which the router is pulled through at an angle. One of the side boards with the DTs cut can be placed in the left hand marker position clamp and aligned with the previously marked dovetail profile (which is marked in pencil on the front face of the Rat). To calculate the button position in the centre plate you use the given formula which is [ (DT Bit diameter + Straight Bit diameter)/2 x Slope = Button Setting ], for me I was using a 6.35 mm straight bit (upward spiral) so this gave (15+6.35)/2 x 6 = 64, where a 1:6 dovetail bit was used.
The spirals (left & right) were then setup using a sliding bevel set to the angle of the 1:6 DT bit. I used a Veritas 1:6 dovetail marking template to setup the sliding bevel. This is then laid on the woodrat base plate against the side edge of the router plate (which is positioned roughly angled) and the other face of the sliding bevel against the front edge of the base plate. Then the position of the router plate is kept still whilst the spiral is tightened up. Then do the same for the other spiral.
Now you are ready for a test cut (of a pin). It may take a few goes to get it spot on but once you have made soem further small tweaks to the button setting and/or the spiral settings you can cut pins until your heart is content!
I hope this helps someone out there, you never know...?
Apologies to those of you who prefer hand cut dovetails, I do do these occasionally but I didn't want to ruin my son's cabinet on this occasion as I am no expert at hand cut DTs (yet)!
cheers
Steve