Last week I was working on some knobs for the cradle hangers/locks and reground my skew chisel to help reduce catches.

In an effort to reduce the waste of the walnut, I turned all of the knobs from a single blank. This is great for keeping multiple objects symmetrical as they are all in view at once and there is less waste because you only need to chuck two ends for the entire thing.

Of course, it seems with every positive point there is a counter point and this is no exception. These knobs are mounted with dowel bolts and hanger bolts. They needed to have pre-drilled bases for the bolt installation. To accomplish the drilling, the knobs needed to be separated. Separating them means there is no waste to hold/chuck the knob for drilling. Further, the knobs were rounded on the end so setting them flat on the drill press was going to be iffy, at best. 

I needed a way to hold the knobs accurately and without damaging the turned/sanded surface. I tried some various padding for my Nova chuck but nothing worked- short of making a new set of wooden jaws similar to the ones I was using for the salt cellars. That seemed like an awful amount of work just to drill 8 holes.

I finally settled on a modified jamb chuck, with a worm gear clamp.

The chuck is made from a piece of 4 x 4 turned round. One end turned down to fit into the Nova chuck, the other end hollowed out using a bowl scraper. The hollowed end was also turned down some, using a roughing gouge, to allow the worm gear clamp to fit. Also, the slots were cut to permit compression around the knob.

Even with this setup, the knobs did not initially align perfectly with the bit. It takes a little fussing back and forth to get it aligned with the lathe center axis. It would have been faster if I had a wobble edge finder but using the edge of the tool rest worked OK for this application.

Once each knob was setup, It was a simple matter to advance the bit to the patented depth stop.

I initially intended to turn 6 knobs- 2 identical smaller diameter for the locking mechanism and 4 identical larger knobs for the hanging mechanism. The key word here is "IDENTICAL". Turns out that wasn't the case. So, I started with my jamb chuck/compression collet for the smallest diameter and then slightly increase the opening when necessary until all 6 knobs were drilled.

The 2 smaller knobs are the locking devices and the others are the hanging sets. They all need a little touch-up sanding but they went together well.

Next up- finishing! But first I need to clean and dust the shop.

Safe Turning!

---

Lew Kauffman-
Wood Turners Forum Host

Time traveler. Purveyor of the world's finest custom rolling pins!

If you are not dead set on drilling on the lathe you can try a method I used lately.

On a squared up piece of 2 x 4 drill a hole partially through with a Forstner bit slightly less that the diameter of you knob.

Round over the entrance of your hole with a round over bit to match the curve of your knob.

Chuck up your pilot bit in the drill press.  Use the indentation in the bottom of your hole to center your jig and clamp it to the drill press table. 

Place you knob upright in the jig and drill your pilot.

Because of the small size of the pilot bit, the danger of not clamping the knob is very low.  Small pieces of double stick tape could be used to increase the hold.

Lew,

In your post you mention a Wobble Edge Finder.  I have heard of them but have never used one.  Could you please explain how they work and there usefulness in lathe work?

Greg,

Thanks for the idea! I sometimes get tunnel vision when working on a project- which usually causes me more work than necessary!!

As for the Wobble Edge Finder, I used to help out in the Machine Shop at school where I taught. They had some of these-

Apparently, this is only one type of edge finder but I thought it might work for what I was trying to do. This particular device is designed to shift when contacting the edge of the work piece. The correct usage is to have the finder spinning and the work piece stationary. My thoughts were to reverse this- holding the finder in a sliding bracket and move it close to the spinning turning and adjusting the turning until it didn't cause the finder to shift.

What I did do was turn my home made short tool rest so it was perpendicular to the end/edge of the exposed knob. Then slid the banjo in so the end of the tool rest contacted the knob- but not locking down the banjo. Rotated the lathe by hand so the off centered knob would hit/miss the edge of the tool rest. Finding the "high/low" sides and using a small tapping device (ie- mallet) adjusted the knob position until I could "hear" the knob rub the tool rest for a 360° turn. At that point I snugged down the worm gear clamp and did a test at normal speed- with the tool rest pulled back. If it looked good- drilled the hole.

Hope this helps.

Lew

Greg Coleman said:

Lew,

In your post you mention a Wobble Edge Finder.  I have heard of them but have never used one.  Could you please explain how they work and there usefulness in lathe work?