A Clarkson Deadlock Mandrel

John Fawcett makes a custom mandrel for these cutters.

This short article was prompted by a request in MEW from Geoff Garrett asking about some cutters he had and did not know what they were. They were indeed Clarkson Deadlock cutters, easy for me to identify because I had used them many times in industry and had several in my “armoury”, photo 1.

However, I had only one size of mandrel which suited the larger cutters I had: 1½” & 2” diameter these have a spigot diameter of ¾” and a ¾” x 12 BSF thread. The other cutters I have are 1” diameter these are threaded ½” Whitworth with a corresponding ½” bore for location on the mandrel. I had somewhat perilously used these with VERY light cuts mounted on a “temporary” mandrel made from a ½” Whitworth bolt, photo 2. Now was the time to remedy this and make a properly manufactured mount and thus reap the befit of being able to use the cutters to the best advantage.

Not having the ability to use CAD after some careful measuring and a sketch I produced a working drawing the longhand way — tech drawing! Figure 1.

I had a No2 Morse taper blank in stock, purchased some years ago it was much larger on the blank end than most of the ones available, it came from Myford Nottingham, I see they still sell them today. As an aside I don’t understand why most other suppliers have such a small blank end? The cost of a larger one would be minimal and increases the possible uses greatly IMO.

First job was to drill and tap the Morse taper end to accept a drawbar, this was ⅜ BSF. I chose this size to match the other original mandrel, photo 3.