Quick Change Toolpost for Storebro

[Hawkeye]

In the 1950s and '60s, the Storebro Bruk 185-GK lathe came with a QCTP that was quite heavy and well made.
   

You'll notice that the centre section is large, with no features very close to the mounting bolt. I take this to indicate that the topslide on this lathe was made the same way as the earlier model like the one I just set up in my shop. There is a large post cast into the topslide, which is split into four segments. This post is a slip fit into a socket inside the toolpost. The bolt is tapered and expands like an inside collet when the nut is tightened.
   

In order to make a QCTP that can fit on this lathe, it is necessary to work around this large post. In the Bergman toolpost supplied with the 185-GK, they used a rotating cam to pull in a dovetail section, which in turn pulled in the toolholder. Too many loose parts for my tastes. Some have made units with the clamping device in one corner, which serves to tighten two dovetail slots. I like this better, since the tightening force acts in the same direction that the work forces will try to push the toolholder.

On with the build. First, you take a piece of metal a bit bigger than you need.
   

Then you remove everything that doesn't look like the part you want. Unfortunately, the scarf joint on my bandsaw blade let go during the fourth cut. I had to finish with the portable.
   

I used the lathe to face the larger surfaces, then went to the horizontal mill to true up the rest. Even with the mill running at the correct cutting speed, cast iron can burn. Note the spark trails.
   
   

After the light show, I went back to the lathe and faced the remaining surfaces. Then it was time to create the socket to fit the topslide post. It took a awhile, especially as I was getting close to the ideal size. Nailed it.
   
   

Tomorrow, dovetails. Once the toolpost is done, I'll need a long bar of steel to cut the individual toolholders out of. There are at least 12 different sizes of cutters I'll need to mount. For some sizes, I'll want several copies. I should plan on 20 holders.