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My major interest is in wooden hand screws, commonly called clamps. These fit into a general Taxonomy .
The collector is faced with the problem,
Where did this come from?This field guide is intended to provide some guidance.
The first question is
factory made or
Clue 1: Factory made clamps tend to be better made, with less tear-out at the holes in the jaws, with better surface finish, with more uniform chamfering. However, there are exceptions.
Clue 2: Factory made clamps almost always have two distinct
spindles, while craft made sometimes have a single
spindle that can be used in either position. (One known
exception is Hempe , who made wooden clamps under its own mark, and for Craftsman, and apparently for A and A.)
Clue 3: Factory made clamps usually have a maker's mark that includes the town and state, while craft made often have just a name, or initials, with no location.
Clue 4: Craft made clamps have hand made threads, as do early factory made. Later factory made clamps have machine made (lathe cut) threads. I'd like to quote from Tom Conroy, talking about the threads found on plough planes, as the principles are the same:
Someone asked about what tools were used to cut the screws on plough plane arms. I can at least contribute a bit about the toolmarks involved.
The relevant mark is the end of the thread at the bottom, where cutting stopped. When a hand screwbox is used, the cutter is a v-shape like a v-gouge or a bruzz, and the bit cut out breaks off crossgrained as you go along. At the end of the thread the broken-off surface framed by a v-cut is quite apparent. Large screwboxes (over 1-1/4" diameter/ 4 t.p.i.) have two v-cutters, one making an initial cut, the second (180 degrees away from it around the circumference) widening the cut; both these cutters leave a v-and-broken-off mark like the above, but at opposite ends of the diameter, and the bigger one is interrupted by continuation of the smaller lead thread. I have examined a fairly large number of old woodenbookbinders' tools, say from late 19th century until after WWII, and in every case where I looked for a toolmark it has been from a screwbox.
Where a router jig system like the Beall is used, the cutter is a conical router bit, so the tool mark (in the same location as that for a screwbox) is a negative half-cone shape.
The commonest lathe systems are hand chasing, or with a special bit for a screwcutting lathe. I have never observed these in operation, but in lathe cutting screws you go over the screw repeatedly, taking small incremental cuts. I would guess that if the end of the thread fades out gradually, and that this would indicate the use of a lathe. I have a screw-arm tongue plane that has screws that fade out gradually, and I suspect that hand chasing was used for this, if not a screwcutting lathe (fine, shallow grooves, large number of turns per inch suggests hand chasing to me, as big screws suggest a screwbox or even hand cutting). On my tongue plane, though, I wonder if the end of the thread may have been neatened up after it was completed.
St. Roy's instructions on hand-carving screws are clear, and I've done it three or four times for tool repairs, but there are a couple of points to add:
In general, my experience is not only did each [plough plane] manufacturer have a different screw size and pitch, but that each manufacturer would have had a number of screw boxes in different variations, and would use them indiscriminately. Why not? Standardised screws were only needed for precision machinery, and were not adopted widely even for metal screws until the late 19th century. I've measured at least a dozen Hickok binders' finishing presses in more or less the same size and design (from anywhere between the 1880s and the 1950s), and they varied completely erratically from 3.5 to 4.5 and from 1-1/8" to 1-3/8". No one would ever have thought of just ordering a replacement part for these. It all makes the repairs more fun. Tom Conroy
- Don't assume that the thread will be 60 degrees; it probably won't. A more obtuse angle is common with wooden screws, to decrease the danger of having the thread chip out. The idea would be to give a wider base. I was surprised to see a reference to Acme threads for wooden screws, since this strikes me as a bad idea for the same reason: the Acme thread has a wider base than a square thread, making it stronger than a square thread, but it is narrower than a triangular thread, the form that is common for wooden threads. Acme and square threads only make sense for metal screws, not for easily-chipped-off wooden threads.
- For a plough plane, hand chasing may be the simplest way to go. Hand chasing tools don't look like a big deal to make, and they are appropriate to the fine thread for plane arms. Of course, that means learning another high-skill-simple-tools technique, i.e. chasing, but surely galoots don't object to that? And making your own hand-chasing tools gives you the versitility to respond to a plethora of pitches.
- Handcarving threads isn't that skill-intensive, though it makes demands on time and patience; and it too gives versitility. Someone gave a good brief summary earlier, and as I said St. Roy's instructions are good, but I have one important point to add: be prepared to do a lot of detail hand-fitting to get the thread to work, by some variation of carbon-paper-and-scraping. Try screwing your "completed" thread into the hole and it will probably hang up (if it doesn't, you overcut). So screw it in again with carbon paper wrapped around it, and carefully pare away the high spots. That should gain you another turn or two. Repeat forty or fifty times until the screw works well and evenly all along its length. Not a lot of skill involved, but patience; oh, yes, patience.
- I have used the wooden-tap style, made by a friend in 1-1/4"/4 t.p.i. for binders' tools, and it works very well in the bigger size; I'm sure it would be the easiest way to go in working new nuts. Tap the nut with the outside oversize to reduce the danger of splitting the nut while tapping.
My focus is on factory made.
There are distinct regional variations - all the Rhode Island
manufacturers share some aspects amongst themselves, while the
Massachusetts manufacturers share other aspects. In addition,
each manufacturer has its own distinct
look, so that
(after a while) you can spot them at a distance.
The usual characteristics to check are the type and location of chamfering on the jaws; the shape of the handles of each spindle; the shape of the tip on the through spindle. I have outlines and photos of each characteristic; just follow the links!
I will treat jaws together. In my experience, users rarely break up a pair, although married pairs can be found.
Note, however, that a wooden clamp is made of two distinct jaws, which cannot substitute for one another.
If the jaws bear a legible maker 's
mark, or dealer 's mark or label, or an
owner 's mark, then the question is,
the spindles go with the jaws?; Otherwise, the question is,
Who made this?
Stopped spindles , or terminal spindles, have a stub end to fit into the pit of the stopped jaw; so they belong in the end hole of the jaws. But they are sometimes used as substitutes for lost or broken through spindles. Even when they are in the right place, they are easily switched from clamp to clamp.
Through Spindles , or central spindles, have a shoulder to press against the stopped jaw, so they belong in the middle hole of the jaws. But they are sometimes used as substitutes for stopped spindles (after a bit of damage is done to the tip). They are less easily switched from clamp to clamp.
These can be easily switched between the two positions on a clamp. They have both a shoulder, and a stub. The presence of universal spindles is usually a mark of a craft made clamp.
There are several related pages, that discuss clamps as things:
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