Martin Cleeve Swing Clear Retracting Toolholder

[egaParticipant @ega]

MichaelG:

Thanks for the link to the PM article describing the single tool slot version of the device mounted direct to the cross slide.

I see that the tool post was intended to be rotatable around its holding-down screw thus presenting the cutting tool either normal or parallel to the lathe axis. This apparently raised the question of the tool post’s resistance to unintended rotation and the suggestion of increasing the friction between it and the mounting surface with a fibre washer; another idea would be to substitute a stud and nut for the screw and interpose a thrust bearing between them.

[egaParticipant @ega]

Having first upgraded the topslide micrometer dial as per the article in MEW 328 – thanks to Pete Barker – I have now had the opportunity of trying out the Hemingway/Martin Cleeve swing clear tool post. Considering the overhangs inherent in the design it performs surprisingly well. I would agree that it’s best suited to repetitive screwcutting and boring.

The bulk of the down thrust on the cutting tool is taken by the height adjustment screw on the topslide surface and I therefore made mine of brass. Despite this the cast iron began to show signs of indentation and I fitted a thin piece of gauge plate to prevent this. If I were making it again, I would consider trying to get the screw closer to the tool point; in its design position it is rather too close to the holding down cap screws for the tool bit (they could be substituted by grub screws).

The design calls for a vee groove in the “floor” of the boring bar slot but given the customary top and bottom flats on modern insert bars I thought this unnecessary (and difficult to produce). The angle of the insert is, of course, affected by the use of the height adjustment screw which, however, did not seem to prevent satisfactory use with a 10mm diameter bar. I have made split clamp holders for the smaller bars which can then be rotated in the holder so as to get the desired insert angle.

Swapping topslides on the Super Seven is fairly quick and I shall keep the swing clear on its own slide handy in case the fancy takes me to use it. In the meantime, the trusty GHT four way indexable toolpost will no doubt continue to meet my modest needs for general turning. The great man intended it for 5/16″ square tool bits with appropriate packing but it also works well with 10mm square holders modified to bring the insert to correct height and changing between four tools is all but instantaneous.

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