Harold Hall
Three simple modifications to my Advanced Grinding Rest. Harold Hall
With the many tooling items I have made over the years and that have been published as projects for the home workshop, it was inevitable that with their continued use beneficial modifications would surface. For the grinding rest on this page I am suggesting three that can easily be done to an existing rest or incorporated into a new build. For details of the rest see here
Modification One
The original design, Photograph 1, used 8mm thick material for the two Side Arms (20) but being so thick they had little flexibility to cope with even very small differences in the width of the parts at either end, also if the sides of these were very slightly off parallel. The result was that securing the setup took more torque than was easily applied with the provided handles.
The modification consists of reducing the thickness of the arms to 3mm, Photograph 2,to provide some flexibility, and whilst this has the required effect there is no noticeable reduction in the rigidity of the assembly as a whole. See the drawings for Modification One for the details.
Modification Two
As rotation of the Lower Lock Screw (5) is prevented by being keyed into one of the side arms, the position that the Locking Handle (11) when tightened is dependant on the angle of the side arms at the time. Typically, this can be a problem if the arms are tilted back as the locking handle may contact the workbench before it is fully tightened.
For the mod therefore, the lower lock screw is made without a key to engage the slot and rotation of the screw prevented using the screw H9 on the assembly drawing. The drawings for the modification should make the requirements for the parts clear but the following process is essential for the success of the result.
Assemble the lower half of the rest using the modified parts and arrange such that the lower Locking Handle (11) becomes tight when below horizontal by about 30 degrees. With that done, drill though both the Lower Arm Spacer (18) and the Lock Screw (5A) using a drill size for tapping M3. Dismantle and tap the Lower Arm Spacer M3 and open up the hole in the Lock Screw to 3.5mm diameter. Reassemble and fit the M3 screw (H9) and with that done the handle will always tighten in the same position.
Note, the screw is above centre in the Lock Screw to ensure that it is always assembled the same way round.
Metalworking
Workshop Projects
1
2
All pictures can be clicked on to provide a larger view