Expansive Auger Bits, Part 3

In parts 1 and 2 of this series, the Irwin #2 and Clark Expansive / T&L Co. bits were featured.  This time, it's the Irwin #22.  Its form is very similar to the #2.

Irwin #2 at top, #22 bottom

Unlike for the other two expansive bits, I've got both the long and short cutters for the #22.  The two bits in the above picture have a lot of similarities.  While they were probably made a few decades apart, they have the same thread on the lead screw, the same overall length and the same relative position of the main body's radial cutter.  The main difference is how the adjustable arm is clamped.

The Irwin #22 close up

Irwin #2 top, #22 bottom

The #2 clamps the adjustable arm using a screw (turned from the front) that squeezes together the main body, that has a kerf cut into it, and this in turn pushes the dovetail of the adjustable arm into the dovetailed way of the main body.  The #22 has a very different mechanism.

"Wheel" removed

The lower edge of the wheel is in a wedge shape ...

... that matches a wedge shape where it resides in the main body

When the screw is tightened (from the back side), the wheel is pulled down into its seat.  The gear teeth on the wheel mesh with the teeth on the adjustable arm.  The toothed edge of the adjustable arm has an angle that matches the wedge angle of the wheel.  As the wheel gets pulled down into its seat, the adjustable arm is forced up into the dovetail way of the main body.

As wheel gets pulled down (red arrow), adjustable arm is
 forced against main body (yellow arrow)

There seems to be poor machining of the mating surfaces of the adjustable arms and the main body.  In the following pics, the long cutter is installed.

Right side showing gaps in the dovetailed ways

Left side showing some gaps at dovetail ways (red arrow), but also
it appears the adjustable arm is making contact with the main body at the yellow arrow,
which does not allow the dovetails to fully seat. 

I've been frustrated at attempts to eliminate the gap between the adjustable arm and the main body.  After spending several hours over the last two days studying it and trying some judicious filing, I can't get the gap to close.

Here is what happens when I use the bit to bore a hole.  I get into the cut several turns, and then things start bogging down.

Using the small arm to bore (approx) 1 1/4" hole.
Shavings clogging the works.

This is what's left when I pull out the bit and remove most of the debris

I can't be certain that this is what starts the bit on the road to poor performance, but that's what I think it is.  I'd love to be able to film the cutting action close-up, but that's far beyond my tech capabilities.

My thinking is that this model is simply a poor design that was poorly machined.  In the next photos, look at how the adjustable arm is supported when making the larger diameters for each arm.

Short arm at minimum diameter setting: wheel contacts arm in center of arm

Short arm at maximum diameter setting: wheel contacts arm only at right end of arm

Long arm at minimum diameter setting (about 1.5"): wheel contacts arm in center of arm

Long arm at maximum diameter setting (about 3"): wheel contacts arm only at right end of arm

An indication of the poor support of the arms when at their max diameter setting is that I can jiggle the short arm when it is fully tightened.  My thought is that with only a small part of the toothed edge of the adjustable cutter being supported, just a little torque can knock these cutters out of whack.

For comparison, here is a picture of the Irwin #2 with long cutter arm in place at maximum diameter setting.  The arm is supported from its right end to where it exits the main body.

Irwin #2 at max diameter: arrows show where arm is supported by wedge

I found a fix to the problem of the short cutter on the #22 jiggling even when tightened.  By adding a 0.005" shim behind the cutter, the bit could be tightened sufficiently.

Bottom line is this: I don't think the #22 is a good design, nor was it machined well.  I doubt I'll ever use it, as I can use the other two.  But the cutters will fit into the T&L Co. bit (even with the teeth), so it might be worth keeping just for those parts.

Expansive Auger Bits, Part 2

Last time I discussed how expansive bits work and showed the sharpening of the Irwin #2.  Today's post will cover the Clark Expansive bit from T&L Co., New York.  BTW, I could find zero information on T&L Co.  My guess is that they were a hardware store or distributer who put their own name on a tool made by a bigger name company.

The markings on the tool

This one was found with only the small cutter

When tightened, there is a good size gap where I'm pointing

This bit (left) compared to the Irwin #2

This Clark expansive bit is made differently from the Irwin.  The clamp (lower left) is a separate piece, and tightens the adjustable arm into the dovetailed "way" when a screw is tightened.  On the Irwin #2, a slot is machined in the body of the bit and the screw has to bend the metal to force the adjustable arm into the dovetailed way.

Notice the difference on these two bits where the adjustable arm dovetails into the main body.  With the Irwin #2, the adjustable arm just fits much better into the dovetailed way.  With the T&L Co. bit, there is some slop, and this leads to a large gap (about 1/32") between the radial cutter of the adjustable arm and the main body.

I sharpened the adjustable arm's radial cutter and spur like I did on the Irwin #2.

Used a dowel wrapped in 220, then 600 grit sandpaper to work on this concave area.
You can see at the cutting edge where a previous owner cut a much more severe angle at that edge.

Used a very fine file and extra fine diamond paddle to dress the front edge of the spur.
Also removed the burr from the outside with VERY light passes of the diamond paddle.

Then I got to the cutters on the main body.  This one differs from the Irwin #2 in that it has a spur on the main body.  In effect, it could be used to cut a 7/8" diameter hole by removing the adjustable arm and boring with the main body of the tool.

Radial cutter (red arrow) and spur (yellow arrow).
The radial cutter was very dull and needed files and diamond paddle to get it sharp.
Note the "escapement" for chips to go after being severed from the wood.

Look at the shape of the spur.  Clearly it has been sharpened too much or very badly.
I went very carefully to sharpen it without losing any more height.
Note how this radial cutter and spur are cantilevered out from the base of the lead screw.

Before I did anything with the dovetailed ways to reduce or eliminate the gap, I tried out the tool on a 2x4.  It cut very nicely and left clean walls on the (approx. 1 5/16") hole.

Red arrow: adjustable arm's spur cutting the circumference.  Radial cutter not yet cutting.
Green arrow: main body spur cutting a 7/8" circumference
Yellow arrow: a thick chip coming through the main body radial cutter escapement

OK, so here's what I'm discovering.  The thick chip in the above photo is coming towards the camera.  It is coming through the main body escapement and doesn't even get near the gap (clearly seen just below the chip in this photo) between the adjustable arm and the main body.  So it doesn't get clogged in that gap.  I bored a couple of holes with this bit and didn't get any clogs.

Smooth walls on both long and short grain

Here's a chip that came off one of the radial cutters - not sure which one

Here's the only chip that got caught and it was inconsequential

While this bit cut nicely, the hole got a little larger at the exit than at the entry.  So, just like with the Irwin #2, the adjustable arm slipped a little.

Just wanted to add a little more about chip clogging.  I noticed a big difference in the position of the main body radial cutter between the Irwin #2 and the T&L Co. bits.  Look at these pics, both of which have the adjustable arms in the same orientation.

Irwin #2 main body radial cutter

T&L Co. main body radial cutter

The Irwin #2 main body radial cutter forces chips into the location where, if there was a gap, they would get caught.  As we saw a few pictures ago, the T&L Co. bit expels chips away from the seam between adjustable arm and main body.

This Irwin #2 radial cutter forces chips down towards the seam between the
adjustable arm and the main body.  There is no gap, so all is safe.

I don't know about you, but I find this fascinating.  I wonder if the manufacturer of the T&L Co. bit knew something that Irwin didn't.