Harold Hall

Workshop Projects


Reference to photograph. 2 shows that the moving internal dimension jaw moves along on top of the main mounting member, there being just a very small clearance between the two. This arrangement helps to avoid damage to the caliper if too much pressure is placed on the control buttons as it will support it if that happens. I was though pleasantly surprised just how robust the mounting was.


It is though absolutely essential that the caliper is perfectly horizontal else strain will be placed on the unit as the saddle moves left and right. To ensure that this is possible there are two screw positions (X and Y) shown in the mounting arm though only one is required, which one being determined on  initial assembly. The purpose is to jack up either the left of right hand edge of the arm as is found necessary to set the caliper horizontal.


It is also vital that the caliper is parallel with the lathe's axis else similarly strain will result on the caliper if this is not so. This will be set by moving the caliper's head slightly under the clamp.


Both these requirements can be tested by setting the caliper's depth bar in the fully out position and with that done use the saddle to push the bar back in. If there is an error the end of the bar will be seen to move on the side of the cross slide. Typically, if there is an error such that the caliper is closer to the lathe's axis at the outer end then the end of the depth bar will move away from the axis as it is being pushed into the calipers main arm. It will of course be necessary to carry out these tests each time you add the milling head to the lathe.


Series Seven owners will have noticed that it was necessary to remove the top slide clamping screw as it would foul the bar clamp assembly. This though is of no consequence as the top slide would be removed when the milling head is in use, though closing the large hole with a plug is a good idea and is one item I still have to make. However, if the top part of the clamp is removed the screw can fitted allowing the lower portion to remain in place when the lathe is being used for turning.


Having completed the fitting of the digital caliper it has become obvious that it would have significantly helped in machining the horizontal mill engine

and will be a worthwhile addition for future projects.