The Classic Design, and What It Can Do
Scratch stocks are used whenever a cut is required for which a dedicated plane (often a plough or moulder) is not available, or whose purchase cannot be justified for a small job. The cutter for a scratch stock is made from middling hard steel, such as a broken or worn out handsaw, and is simply filed to shape.
(Jan 19, 2005) I have discovered that blades for hand held circular saws provide good stock material; they're a little thicker and more chatter resistant than handsaw blades, and easy to find at car boots sales etc. You want the non carbide tipped kind, since the body of the tipped blades is not such good steel.The cutting action is (of course) much slower than a "proper" plane, which is why the plane makers stayed in business.
For a long time I've had (and very occasionally used) a simple "L" shaped scratch stock. The cutter is placed in a kerf in the long arm of the "L" and the screws tighten down to keep it in place. This design has the merit of being quick and simple to make - so much so that it is common to find old toolkits with a stock for each cutter.
The "L" design does have some limitations though. Adjusting the cutter is a loosen-move-tighten deal. This makes it difficult to adjust (for example) the offset of the cutter from the fence without having to (re)adjust the depth and orientation of the cutter.
Another issue is twisting. Since the cutter tends be not to be in the middle of the stock, a "grab" tends to result in the stock twisting. If the fence stays in contact with the edge of the workpiece, this twisting can cause the cut to move off the desired line.
Ideas And Features From Other Tools
Having decided to build a better scratch stock, I reviewed my various (several!) OLDTOOL references for design ideas.
Many instructional texts give scratch stock ideas. The common refinements over the humble "L" are longer bodies, shaped handles, and moveable fences.
Garratt Hack espouses a minimalist design , with a fence which holds the blade, but no body (and hence no depth stop). The blades used in this design are made large enough to serve as the body, projecting from the fence.
The catalogues list several commercial
variations on the scratch stock theme,
including stringing and ploughing routers in both
wood and (later) cast iron, and
"beaders" including the popular
Stanley #66, the more elaborate Preston Beader
and the more current
Lee Valley beading tool.
Most of these share quite long bodies, with a
semi-central cutter position,
and a moveable fence. There are divergent solutions to the cutter
holding problem including wedges, screws and
clamps. The Preston Quirk router even
has fine adjust on the cutter depth.|
Historically, there have also been "Windsor beaders" which are quite specialised in their purpose, but highly desirable. The two famous types are by "Poole & Williams" and Kendal & Vose", both made in repro by Kansas City tool works. The former allows multiple blades to be assembled to make a complex composite cutter, The latter has a round blade with multiple mouldings around it,
If you don't wish to make your own scratch stock, you can buy a new one:
My final solution is a plain, moderately
long body, with a moveable fence. Construction
was straightforward. The simple body is composed
of 2 similar pieces, 8" long. The mortise that the fence
bolt runs in is a simple dado in each half; the
screws that both align the 2 body pieces and
clamp the cutter are actually ¼" machine bolts,
engaging nuts inset on the rear face. The 20 TPI
threads of the machine bolts are much finer than
a woodscrew, allowing the cutter to be clamped
very positively. The body sits in a wide shallow
groove (2mm) on the upper surface of the fence; a coach
bolt with a wing nut provides for adjustment of
the fence position.|
The body length allows twisting forces to be resisted; it also allows a fairly central cutter position to minimise the generation of such forces in the first place. The moveable fence allows the cutter depth and orientation to be adjusted with the fence moved well out of the way. The fence can then be moved to its final distance from the cutter as a final, easy step. These separate adjustments are far easier to perform than the all-or-nothing of the "L" stock.
Fence length proved to be interesting. The first fence I made was a moderate 40mm long. This stock was (in hindsight) the worst possible! It was long enough that a twist of the stock caused the fence length to act as a lever, transforming the twist into a movement of the cutter towards the edge of the workpiece. And yet the fence was not long enough to guarantee that such a twist would not occur. Simply increasing the fence length to 80mm gave enough fence/workpiece contact to prevent all twist, resulting in perfectly accurate cuts. However, the large fence made the stock rather cumbersome in use.
(Dec 11, 2007)Derek Cohen made an auxilliary fence for his Stanley #66Consequent to the observation that the length of the fence acts as an error magnifier for twist, I made an essentially zero length fence, by putting a small radius on a 10mm fence. This does nothing to resist twist occuring, but does minimise its consequences. The stock with this fence is almost as accurate as with the 80mm fence, but is much easier to handle.
(Aug 1, 2006) This is a good design for beading and stringing; for making larger, more complex cuts you really want the cutter clamped all around which is easily done in the classic 'L'.
The CuttersAs with most handtools, time spent sharpening is well repaid both in ease of use and final result. In the case of my 2.5 mm groove cutter, the end face (all 2.5mm x 0.75 mm of it!) was made true, square and mirror polished using my monster jig and it works well. As an experiment, I created a moulding cutter for the (oldish) skirting board in my house. I tried using it both straight from the file, and after honing with SiC paper wrapped around (various...) profiles.
The conclusion? Yes - honing is well worth doing. What's more, with their 90 degree edge bevel, the edges last pretty well, even though saw steel is tempered much softer than blade steel.
On to the scratch stock itself...
The standard (but not well known ;-) advice for plough and rebate planes (start at the far end and work back) is definitely applicable to scratch stocks.
Take short strokes, and run right off the end. If you don't, you'll leave a little bump at the end, which is very difficult to remove. As your work progresses, you can track your start point backwards. In this way, the difficult end cut is performed in the easiest possible way, and the cutter is always working the grain "downhill". It is rather difficult to work all the way to the near end - I found the best way is to treat it the same as a mirror image of the far end, cutting on the pull stroke.
The cutter is partially self limiting for depth of cut - it just isn't effective enough to really dig in. In addition, it's easy to run the body on its leading (or trailing) edge, and control the depth at which the cutter is presented to the work by twisting the body on it's main axis. This technique allows the cutter to be gradually lowered into the cut as work progresses.
(19th Mar 2007)I thought simple scratch stocks were never made commercially, but last Saturday I bought one - second hand, of course. The fence adjuster nut is threaded 1/4" x 20 TPI (BSW) and the blade holding bolts are 3/16" x 24 TPI (BSF). The blank blades are 0.050" (1/20") thick. The stock is 20cm long, 23 mm deep (top to curved bottom), and 21mm thick (front to back).
Apart from the narrow fence, the design is remarkably similar to mine. If anyone knows who the manufacturer was, I'd love to know.
(mar 2007) Some people with more catalogues than me say it's by Tilgear)
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