sharpening spoon bits

[bill howes]

I picked up some older spoon bits and would appreciate any advice on sharpening particularily the larger one.
Thanks

[harry strasil]

You really don't have a spoon bit in the group, memory fails me on the pictured ones names.

[george wilson]

I forget the name also. But,being in the house for 2 days with a new furnace smelling the place up has me feeling like I had a stiff drink. I don't seem to quite know what I am doing.

Anyway,I used to use those in the museum. Not often though,as I was making musical instruments,and just the occasional piece of furniture. Sharpen the large one by honing the outside of the end of the bit as little as possible to make it sharp enough to cut. Trouble is,you will have to sharpen it again and again,so leave as much metal as possible so you don't soon get the cutting edge below the centerline of the rotating cut.

These bits are usually started by drilling a shallow hole the size of your bit with a center bit so the hole will be accurately located,without the bit wandering at the start. I think I might have also seen the hole started differently,but that is how I have used them,but I'm not a chair maker.

I recall early on in my career in the museum,in fact in the first month or so,I was very keen to find appropriate tools. Bits were hard to find locally. However I came across a pawn shop close to the river in Richmond which had a box with about a cubic foot of NOS bits like those. Never used,never rusted German made bits. I bought several. I should have bought them all,but did not have the cash on me. Unfortunately,there was soon a flood which wiped the place out. I also recall they had a nice black Les Paul guitar laying in its open case on the floor a few feet from those bits. No doubt it was totaled.

[Jack Curtis]

You really don't have a spoon bit in the group, memory fails me on the pictured ones names.

Shell bits. Spoon bits look like this: 50k6506s1.jpg

[bill howes]

Thanks. I take it that the difference is whether the side of the bit is sharp or not?

[Jonas Andersson]

As I understand with spoon bits you have to reforge the cutting edge after some sharpenings?

I found a nice blog post about the topic: http://www.fullchisel.com/blog/?p=106

[bill howes]

I did search the net and end up more confused than normal. I do know its ok to play the flute while wearing braces
. The bit that puzzled me most might be a nose bit.
There are various descriptions for sharpening flute/ gauge bits from burnishing the inside to just sharpening like a gouge There is mention that Michael Dunbar describes sharpening of bits in his book on restoring old tools and f an article in fine woodworking vol 43:0-72 1983
I don't have access to either so if anyone does and its helpful please let me know

[harry strasil]

Spoon bits owe their unique design to the fact that old chair makers used green wood for the legs and the spoon bits could be used at an angle all around the hole to make the hole wider at the bottom than at the entrance, as the spindles were made of dry wood with a bulb type end on the tenon and were pushed into the wider at the bottom holes in the greenwood uprights and then when the greenwood dried and shrunk, you had a glueless extremely tight joint. And they are impossible to remove the stretchers without either breaking off the stretcher tenons or splitting the uprights.

I always thought the Cook style bits had been overheated in some way and the flutes destroyed.

[Roderick Gentry]

Thanks. I take it that the difference is whether the side of the bit is sharp or not?

On spoon bits, the point is pretty much central. When you start one up, it cuts a conical hole that is about 25% the overall diameter. If you want to start it up at a particular point you have to offset it from the center point you want to have, by half the initial circle size, and as it cuts the first circle it will circumscribe the center point, which you hope you estimated correctly (easy once you have cut a few holes).

To sharpen the bit, the main deal is to get on it before it goes dull. The geometry is such that the forward cutting edge is slightly proud of the trailing edge. If you do not hone both sides of the bit the cutting edge works down to the point where it no longer takes a shaving. I haven't used mine in a while, but it seems like it would be an ideal thing to use a leather/diamond strop on.

The type of bit that you have, is basically the same deal, it just doesn't have a point/end to start on.