I debated a long time about whether to make the quill per the Chaddock’s original design based on the A3 magneto bearings, or to redesign the quill around a matched set of ABEC-7 spindle bearings. The A3 bearings are for a 13mm shaft and have a 30mm outside diameter. The smallest ABEC-7 bearings I have are for a 15mm shaft and have a 32mm OD. There is no way to fit 32mm OD bearings in the original 1-3/8″ quill body diameter, so moving to ABEC-7 bearing would also mean moving up to a 1.5″ diameter quill body. Fortunately a 1.5″ quill body can be squeezed into the existing wheelhead casting.

The quill started with a 4-3/4″ long piece of ∅1.3750″ ground 17-4PH H900 stainless. This is a heat-treatable stainless pre-hardened to approximately 170,000psi tensile strength and 40HRc. Don’t let the hardness scare you, it actually machines beautifully with carbide tools. The extra inch length on the blank is because I plan on making the end caps at the same time.

I’m going to start with the end caps first since I can use thread wires to gauge the external 1.25″-32 thread. These can then be used to gauge the internal thread in the body. To start, the blank was dialed-in on the 6-jaw chuck. I ended up with no discernible needle movement on my tenth indicator.

After indicating, the blank was drilled ∅5/8″ approximately 1/2″ deep.

The face was cleaned up, and the thread boss was turned to ∅1.247″ and the thread relief cut.  The 32 TPI thread was then cut.  Maximum pitch diameter should be D – 0.64951905*P = 1.25 -0.64951905/32 = 1.2297 so measuring over ∅0.018″ wires, I was shooting for a measurement of PD – 0.86603P +3W = 1.2297 – 0.86603/32 + 3*0.018 = 1.2566″.

With the outside completed, a 0.031″ grooving tool was used to bore the cap ID, cut the internal labyrinth grooves, and add the inner bearing race relief.

The end cap was then parted off 0.02″ long. I usually part almost all the way through and then finish with a hack saw.  This keeps the part from falling into the chip tray, and keeps the bit from snagging as it breaks through.  I repeated this process for the second end cap.

I plan on using the quill body as a machining fixture to finish the end caps.  Before I can do that, I need to go ahead and cut the spanner grooves on the end caps so I can tighten and loosen them on the body.  I made a simple arbor to center the end cap and pull it tight against an 11/16″ collet in a hex collet block.

The collet block and end cap was then set-up in the mill and the six spanner slots were cut.  This was repeated for the second end cap.

With the end caps prepped and ready, I moved back to the lathe and indicated the now shorter body blank back in true.  I pre-drilled 3/8″ and followed with a 39/64″ drill through.

I used a 1/2″ boring bar to face the end of the part and establish my dataum.  I then proceeded to finish the ∅5/8″ and ∅7/8″ features including the radius and chamfer.  At this point, I left the bearing race and thread area undersize at ∅1.160″ with 0.005″ left to take off the shoulder as well.

Next, I used my 1/32″ grooving tool to bore the ∅30mm bearing seat to an easy push- fit on the actual race and take the finish cut on the back face.  With the bearing bore established, I then used the grooving tool to bore the ∅1.206″ minor thread diameter and add the thread relief groove.

Threading the ID was a tedious process as there is very little support under the sharp-V insert tip and therefore they break very easily.  To account for this, I took 0.002″ off the diameter at each pass and snuck up on the finish size at 0.001″ off the diameter for the finish passes.  With the end cap threaded on, I ended up with no discernible radial movement of the end cap and only 0.0007″ of axial end-play on the threads.

With the threads completed on this first end, I could then use this as a fixture to finish the end caps.  The end cap was fitted and tightened down.  Since I still had my zero from facing the body, It was easy to back off 7/64″ and take the facing cut on the end cap.

Now that the end cap was faced to length, I could trepan the labyrinth groove.  These last two steps were repeated for the second end cap.

To finish the quill body, the part was rotated and re-indicated in the lathe.  I again used my 1/2″ boring bar to cut the ∅30mm feature for the spring box and bearing seat.  This was a close slip-fit on the bearing race.

The 1/32″ grooving tool was back to establish the 1.206″ minor diameter and cut the thread relief for the 1.25″-32 thread.

This was followed by the same tedious threading operation as before.

The last operation on the Quill Body was to add the oiling hole. The screw I used had an undercut head which was great as it allowed me to add a 4mm x 6mm O-ring to seal the screw.