Marking out for 3 bolt holes.
I have drilled through holes to suit M6 bolts and am now counterboring for the head of the socket head capscrews. For counterboring I first drilled the 3 holes in most of the way with the appropriate sized drill with the normal cutting angle on the end, therefore the holes are now partially counterbored almost to full depth, then I resharpened the drill to have a flat end. I only hand sharpen on the bench grinder, no sharpening jigs or anything so I just use an engineers square to sight across the end of the drill to check for squareness and flatness. Once the drill has a flat end I grind both cutting edges to give a little front clearance then use it to complete the counterboring. It's easy to align the flat end drill in the previously partially counterbored holes. The flat bottom drill is used to remove the angled material that is at the bottom of the hole from the previous drill which was the same size as the flat ended drill. There is only a little bit of material to be removed with the flat ended drill and it is best done with a bit of an aggressive cut so chatter won't have a chance to start. It pays to set the stop on the drill press so the depth is correct and no chance of the drill pulling in and cutting too deep. Once I make a flat bottom drill I'll often buy a new drill that size so I can keep the flat one for future use, I've built up a reasonable collection of them now. This counterboring using the two drill(same size) technique shown here is being done in a normal bench drill press. With just a little bit of care there is no problem and an excellent counterbore is achieved with nil or minimal expense. The ring under the clamp is an old inner race of a roller bearing just being used for clamping purposes.
Have finished the drilling and counterboring and am now pressing the location ring into it's recess.
The locating ring is a neat fit into the pulley of the lathe, I have it all clamped together and am spot drilling the pulley, the drill is the same size as the through hole so must only spot the pulley as the pulley has to be drilled with a smaller drill.
The spots on the pulley are now being drilled for the tapping size for M6x1.
Starting the tap in the job with the tap held in the drill chuck, Turning the chuck by hand.
Finish tapping through using tap handle.
Lathe pulley and spindle handle, you can see where the location ring locates. When I was working out the PCD (Pitch Circle Diameter) for the holes I had to make sure that the holes didn't break into the vee of the next pulley down, there are three vees on this pulley.
Test assembly on the lathe, I now only have to make the turning handle for the end of the arm.
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