TOOLS – A MORSE TAPER TAPPING TOOL

Geoff describes another simple-to-make and highly useful workshop addition.

Here is a little weekend project which creates a most useful tool. I made mine in 1996 and it has been in use very frequently ever since, in fact I would not like to be without it. Its most obvious use is in the lathe but I also use it in the pillar drill and in my mini milling machine.

The basis of the construction is a number two Morse Taper shank. Mine came from a basket of old tools at an antique (bric-a-brac rubbish) shop. The donor drill had obviously had a hard life, the working end was very short and the web of the drill was very thick. Reclamation attempts on an off-hand grinder had not had the desired effect and so it had ended up where I found it.

The shank was in quite good condition with only minor bruising which was easily stoned out. The drill shank close to the Morse Taper was soft and so readily sawn off.

The other main item of course is the drill chuck and here it is important that it has a screwed socket, not a Jacobs Taper. I have several small drill chucks with screwed sockets and they are all threaded 5⁄16-inch UNF.

Construction

We start construction with the handwheel, I made mine in aluminium and after many years of use I think that, due to its lower mass and therefore inertia, there is a better ‘feel’ when tapping very small holes. I used it to tap six 10BA holes in ¼-inch thick gauge plate from which I made the two cam rings for a radial i/c engine and I had no breakages.

Set a piece of 1 ¾ -inch diameter material to run true in a four-jaw chuck, with sufficient protruding to enable a length of ¾-inch to be parted off (ultimately). Take a very light cut to just clean up the outside diameter and knurl about a ¾-inch length.

Next machine what will become Face A, ensuring that the ¾-inch diameter face has a good finish.

Centre drill (BS 3), follow by a 7mm diameter drill to a depth of about an inch – a bit wasteful, but necessary to ensure a fully formed thread for the final thickness of ⅝-inch.

Tap the hole 5⁄16-inch UNF, supporting the tap with a centre in the tailstock and making sure that contact with the centre is not lost throughout. Finally part-off to 0.7-inch for finishing later.

The next item to make is the threaded stub, for this I used a 5⁄16-inch UNF cap-head screw. These are made from high-tensile steel and have rolled threads of excellent quality. As a bonus the material machines beautifully.

Cut off a threaded length of 1¼-inch. Dress the burr from the cut end for safety, but there is no need to machine it – yet. Clean it with methylated spirits or wash it with washing-up liquid.

Screw the original bolt end of the threaded stub into the handwheel from the unfinished side (what will be Face B) to a penetration of ½-inch, in other words still underflush on the finished side (Face A). Coat the remaining protruding threads with high-strength anaerobic adhesive and screw it into the handwheel to give a protrusion from Face A of ½-inch. Set aside to cure.

Whilst the handwheel assembly is curing, the Morse Taper arbour can be modified. If it is to be made from a salvaged drill, then the first job is to cut off the drill section.

The unknown bit is knowing where the transition from the hard

“Due to its lower mass and therefore inertia, there is a better ‘feel’ when

tapping very small

holes...”

drill shank to the machinable taper shank occurs, this is most easily established using the corner of a file (my taper shank came from a 9⁄16-inch diameter drill and the ‘soft’ section extended about ⅝ths of an inch from the top of the Morse taper).

Cut off the drill with a hacksaw leaving a short parallel section. Mount the Morse taper shank in the headstock spindle taper and clean up the sawn end (the ½-inch shown on the drawing is purely arbitrary – it happens to be what mine is).

Next mount the Morse taper

shank in the tailstock and centre drill (BS3) from the headstock, followed by a 4.5mm diameter drill. Being a rather deep hole it is best to drill to depth in very small steps, clearing the swarf at each step. Keeping the drill free from trapped swarf thoughout improves the chance of achieving a straight hole. Follow by reaming 3⁄16-inch diameter, running the reamer slowly, with cutting fluid and again clearing swarf as for drilling.

Finishing assembly

The handwheel assembly will be finished when screwed into the Jacobs chuck and to facilitate this the chuck has to be mounted in the lathe. Put a piece of ⅜-inch diameter mild steel in the lathe’s three-jaw chuck with about 1¼-inch protruding. Carefully turn a diameter which is just under the capacity of the Jacobs chuck and long enough to fully engage with the chuck jaws. Do not remove the component from the machine.

Make sure the threads in the back of the Jacobs chuck and those protruding from the handwheel are clean, then screw the two together tightly using the chuck key to give adequate grip. Now slide the Jacobs chuck onto the mandrel in the lathe chuck and tighten the Jacobs chuck. Face A can now be completed and the centre hole drilled and reamed as for the Morse taper shank.

Release the drill chuck from the mandrel in the lathe and finally take a 2-insch length of 3⁄16-inch diameter silver steel and secure it in the handwheel assembly with highstrength anaerobic adhesive.

Job complete – it may have taken longer to read this than the actual time taken to make the tool (or it may seem that way), if so, I apologize but hope that you will find it as useful in your workshop as I have.