Hi All,
My 260 has one of Mal's slotted cross slides fitted. I decided to take advantage of the t-slots and made a solid toolpost mount to replace the topslide when its features aren't needed.

I started by making a spigot to the same dimensions as the one on the topslide. It has 6mm extra length to allow it to be shrink-fitted into a bore in the block.

I took a 125 long piece of 100x50 1020 mild steel. Milled it to the same thickness as the topslide and squared up all faces. Mounted the block in a 4-jaw chuck and bored a 6mm deep pocket slightly smaller than the OD of the spigot.
Heated the block to 200C in the oven and cooled the spigot in the freezer. I was hoping the spigot would drop easily into the hole. However it got half way in and froze. I raced out to the workshop and gave the spigot a few whacks with a hammer with a piece of aluminium to protect it. Thankfully that coaxed the spigot the rest of the way in. The M12 cap screw provides peace of mind.

I also made a ⅞" AF nut with an M12 thread, as I wanted to use the same ring spanner that I use on topslide nut. That nut has a 9/16" thread, but I don't have a 9/16 tap.

So far it's working well. The real test will be parting-off stainless steel.
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