I was starting to make a drill sharpening jig which required a slot to be milled at a precise angle, so I set up a pair of toolmaker’s buttons on the mill table to use a sine-bar to set the angle. When I came to use the dial indicator to set the buttons parallel to the table, I realised that holding the dial indicator in the spindle required that the spindle had to be prevented from rotating in order to be able to obtain a satisfactory reading. This required a lot of head scratching and thinking as to how I could build a spindle hold without altering the machine itself.
I hesitated to call this a spindle lock, as that would suggest that the spindle was well and truly locked and should allow quite a bit of torque to be used. This is not the case – it merely serves to hold the spindle from rotating whilst the DTI is used. Similarly, I did not call it a spindle brake, as this might imply a method of bringing the spindle to a stop whilst it is rotating, so I decided to call it a spindle hold.
My first and primary objective was to make it such that no alterations were made to the milling machine at all. I found that I could not achieve this objective fully, as I did end up having to drill an access hole for the screw to operate the spindle hold. I considered that a single 7mm diameter hole in the plastic cover over the motor and spindle was acceptable. Otherwise, there are no irreversible alterations to the milling machine.
Although the dimensions given for the items for this spindle hold are sized to fit the Warco WM16 milling machine, I am sure that there are clones of this machine onto which it would fit directly. If you have a larger or smaller machine of the same general design, then a quick look under the motor/spindle cover will allow a check to be made whether it is feasible to fit it to your machine, photo 1. If it looks like photo 1, then your machine should be suitable. The spindle hold will be fitted to bear on the vertical part of the tachometer ring (just below the part with lots of small holes in it).
This design is for light duties only – the ring on which the friction pad operates is held on to the spindle by two M3 screws – so if you screw the locking star knob down too hard, you may well displace or damage the tachometer ring which will cost you a lot in spare parts! As can be seen from photo 2, the only visible alteration to the machine is the star knob used to press the friction pad against the tachometer ring. The tachometer ring is directly attached to the spindle with the M3 cap head screws and can be used with a small friction pad curved to fit the recess under the perforated disc to hold the spindle. The finished spindle hold is shown in photo 3, with the cover removed to show the details.
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