Pattern and Aluminium casting.
An idea of where it's going to fit.
Three socket head cap screws 30mm long M6x1 thread. The bottom right screw is in line with the back vertical surface of the slideway so I had to make sure I didn't drill through into the slideway. I had to shorten that screw appropriately. All screws go into the saddle at least 10mm(3/8"). All holes are blind. The cross slide misses by a whisker or two.
Getting somewhere now. The top surface of the Aluminium block is low enough that the knurled head of that nip up screw misses by a few mm.
The block contacts the vertical surface of the side of the saddle.
Here's a close up of the actual clamp plate.
I drilled and counterbored a piece of 1/4" x 1/4" mild steel. Here I have it clamped to the lock plate for drilling the 2 holes into the clamp plate. I just spot with a drill that is a neat fit in the hole then drill with the tapping size drill.
Tapping for 1/8" BSW. The holes are blind so have to be careful not to break tap. The tap here is just sitting in the hole, not squared up yet for tapping. I tapped with taper, intermediate and bottoming taps.
Assembled. Originally I was just going to silver braze the pieces together but this way I can easily shim between them if I need to to get the clamp to clamp the way I want it too.
This is what it looks like. When tightened the clamp plate contacts slightly more towards the front of the lathe.
Just misses the tailstock base by a whisker.
Here I have hacksawed and filed the end (this end) of the block off to be closer to the edge of the clamp plate. I am sort of thinking of fitting a thin brass plate on the end to cover it up a bit. It is very easy to drop the plate off for cleaning anyway so I may not worry about the brass plate idea. The lock works really well, there is no rubbery feeling when tightening it, indicating that it is a solid attachment. When it is loose the saddle moves back and forward without any jambing of the plate. It could probably have been a bit thinner, fore and aft wise but I wanted to get good leverage for the clamp plate ie reasonable distance between the clamp screw and the pivot point.
Here the saddle is wound right up under the chuck as far as it will go and the block misses the sheet metal cover by about 6mm.(1/4"). Of course this thing or similar could be prefabricated or machined out of a solid piece but I need all the casting practice I can get :)),,,, plus casting is great fun. Apart from the drilling and counterboring all cutting on the block was by hacksaw and file and a bit of belt sanding. What's the use of casting if going to get rid of all cast surfaces so I left as many as possible as cast except for a slight sanding.
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