Cross slide riser and center drilling attachment


Recently, I wanted to do some machining on the top side of a 2 inch diameter piece of brass stock held in my three jaw chuck. I was using the vertical milling attachment and quickly found that it didn't have the vertical reach to clear the top of the workpiece.  I decided to make a riser that bolted securely on top of the top slide. Rather than just use a nice piece of brass as a slab to add height, I decided to combine a second project with it and design a center drilling jig for round stock right into the front side of it. The results worked wonderfully well and are below.

This first image shows the completed riser with the clamping attachment in place. You'll notice the screw and retaining washer for the clamping jaw are completed here but are not in the rest of the shots.
Derbyshire riser and center drilling attachment
The unit mounts to the cross slide with two full width custom T-nuts seen below.

Riser/center drill rig parts
You can see the recess milled in the clamping bar and the shortened 8-32 set screw with the tip machined clean of threads to stop it from rotating when it is being clamped down. You can also see the full length T-nuts.
Riser/center drilling rig parts 2
The clamping head mounts when I want to use the riser in its center drill function. It has four positions achievable by flipping it over and using it on either the left or the right side.
center drill jig in place on cross slide
When mounted, the full width V-groove sits at absolute dead center for the headstock making it so easy to drill perfectly centered holes in many different diameter round parts. I've machined centerline indicators in the riser as well to add to quick set up and accuracy. Here I'm drilling the center hole for making several replacement cross-slide nuts for the bottom slide of the cross slide. I've replaced the top nut (you can see the posting on this site) and will be pressing out the bottom nut for replacement as soon as these are done.

Derbyshire drilling attachment in use

Below are additional shots of drilling and tapping.

Derbyshire drilling rig in use

Derbyshire drilling attachment in use

Derbyshire drilling attachment in use for tapping
I combined using the center drilling attachment with the custom headstock crank handle (also displayed on this blog) for some very easy hand-driven tapping. You can really feel any resistance this way and carefully tap without any breakage. I disconnect the upper lead screw for this operation so that the cross slide could easily drift towards the tap at its own rate.
Watchmakers lathe hand crank in use with center drilling attachment on cross slide








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