This article by Heartwood Director Will Beemer first appeared in Timber Framing #107, March 2013.
PINS hold our craft together. They distinguish our frames from other types of post-and-beam construction. Not all pins—and many workers call them pegs—are created equal, and some may do more work than others depending on their location. Ideally, frames should be designed as much as possible to avoid tension joinery in which pins have to resist loads in shear.
In a well-designed frame, we use pins mainly to draw joints tight and hold them together during assembly (comealongs are thus seldom required) as well as to keep them tight after erection as the timbers shrink. This can be accomplished through drawboring— offsetting the pin holes in the tenon and the mortise a calculated amount such that the joint is drawn tight as the driven pin trans- fixes the tenon, a technique requiring a tapered pin, or one tapered for part of its length. (See “A Boring Essay,” in Timber Framing #67, also collected in the Guild’s newest book, Timber Framing Fundamentals, pp. 207–9.)
A thorough discussion of the relative merits of riven (split) pins shaved to an octagon, lathe-turned cylindrical pins, and octagonal pins sawn on a table saw is beyond the scope of this article, but it’s fair to say that the advantage of riven pins over turned or sawn pins is that the grain of the riven pin is predominantly continuous for the length of the pin, not necessarily the case with the others.
Continuous grain helps shear capacity, which translates into flexibility without breaking while a pin is driven. Riven pins are also less likely to split if they are struck imperfectly. I would guess, however, that most timber framers use turned pins. If the pins aren’t required to do much work, turned pins are sufficient and less expensive than paying for the labor to rive and shave pins.
Pins are split out from a clear log round (or billet) by quartering, then riving 4-pin blanks, then further riving individual squares and, finally, shaping with a drawknife. Favored species in our area of New England include white oak and black locust (both good for rot resistance), red oak and hickory. These are all very straight- grained woods (certainly over the short lengths that pins require) and will split easily and true in the absence of knots or twisted grain. Other possible species are white ash, Osage orange, yellow birch and hard maple (the last for interior use only). Whatever the species, splitting true is best assured by obtaining a round from the branchless butt (lower end) of a tree. Since log butts usually have a bit of flare, loggers or sawyers may be willing to sell off a foot or so to have the log fit better on the saw carriage. Of course, you can also buy a long, clear log a foot or more in diameter and cut it into short lengths for a decade’s worth of pins.
The billets should be sawn square to the axis of the log and 12 to 14 in. long. The outer few inches are usually waste (with their sapwood, bark and susceptibility to uneven splitting), but even with the remainder you could get about 100 1-in. pins from a 12-in.-diameter round. Pins should be 4 in. or so longer than the deepest framing timber anticipated, since the point will taper and you’ll want that extending out past the face after driving.
The blanks will split out better if the log is green; the finished pins themselves should be semi-dry when the frame is assembled so the frame’s green timbers can shrink around them. Usually enough time elapses for pins to dry between the making (say in winter while watching soap operas) and the frame assembly. End-seal the log butts if they’re going to sit for awhile. Quarters, if they have dried out before shaving, can be “reconstituted” by soaking, as can square blanks. Red oak works well even if dry, so if the stock must sit around for awhile, that would be the species of choice. White oak and locust are a little more difficult to work when dry, and all the other woods mentioned get much more difficult, so they should be shaped green. Make pins immediately after felling if using white ash, as that species, with very little free water, starts to split on its own very quickly, making riving difficult. When making pins from green material, aim to make them slightly over- sized compared to dry ones (but no more than 1⁄32 in.) such that they snug up a little sooner along their length in a test hole.
To rive the squares that will be split and shaved into pins, lay out a grid on the end of the log using a framing square or other gauge. Draw crossing perpendicular lines through the pith of the log, even if off center, to quarter it. (An ink pencil works well on a wet surface such as might be presented by a green billet. Ink pencils, available from skinboats.com and leevalleytools.com, are also good for scribing wet timbers.) Then draw lines parallel to these outward at regular intervals to make a grid of squares; each of these blanks will yield (theoretically) four pins. The size of these square blanks should be ⅛ in. less than twice the diameter of a pin. In other words, to make four 1-in. pins, lay out a grid of 1⅞-in. squares. The pins resulting will be slightly less (1⁄16 in.) than 1 in. across the flats, but slightly more across the corners. For other sizes, use 1⅝-in. squares for ⅞-in. pins, 1½-in. for 13⁄16-in. pins, etc. The 1½-in. module is handy since the tongue of a framing square fits the grid; for other sizes make up a template to draw lines parallel to your original lines though the pith. If 13⁄16 seems an odd size, we do see it a lot in old buildings, and there is a substantial difference in heft between it and a ¾-in. pin.
It’s of interest at the outset to assess the growth rings of the log as well. Relatively speaking, fast-grown ring-porous hardwoods such as oak and ash are generally stronger than slow-grown examples of the same species, since the rate of growth is reflected in the amount of denser latewood put on each year. In these species, wider growth rings, as seen at right, mean stronger pins. (See R. Bruce Hoadley, Understanding Wood, 1980, p. 131.)
Put the log on a solid surface or raised block—you’ll smack it pretty hard in the next step. Place the froe, the classic, ancient riving tool, on a line through the pith and split the log in half. Don’t try to enter the log all at once; start on the outside edge with the froe on a slight angle.. Pound it on the tip to get it started and then level it out as you pound it down near the handle into the end of the log. The split should start before the froe is all the way into the log (a good sign) and simply torquing the handle often gives enough leverage to open up the piece. If the log is wider than the froe, remove the froe before going too far and go to the opposite corner and start again. If the log is too stub- born or wide to get a good split started, try splitting off some of the outer circumference, or use a splitting maul or wedge (or a glut) to get the split started, as with firewood. A good straight-grained billet
14 in. long, however, should be split easily by a proper froe with gradually tapered sides (see discussion below). If the log fights back and doesn’t want to split, it probably has unseen knots or twisted grain and really doesn’t want to become pins.
Once the billet is split for the first time, the work, now with shorter cuts, should get easier. Take the two halves and split them in half (following the line nearest the pith) to make quarter-logs and then begin splitting out groups of blanks.
While the four blanks immediately surrounding the pith may be unusable because of knots and crooked grain formed early in the tree’s life, you should now see straight grain in the rest of the quartered billet. If you don’t, you may not want to waste further time on this billet.
Splitting out blanks and pins
Place the froe on the line nearest the center of each remaining piece and work outward to split out the four-pin blanks of the grid. Start in the middle of each piece because the split then is more likely to run straight down; if you start close to an edge, the split may want to travel the path of least resistance and drift outward. Point the cutting edge of the froe slightly away from the bark side since that is another path of least resistance. Once the split has started using the maul, set it down and torque the handle of the froe to complete the split. If necessary, steer the split by pulling on the top of the handle in the direction you want the split to go.
Take the square blanks and quarter them in turn (a smaller froe or an axe helps here) to make roughly square pins. These squares are larger in area than a corresponding-size round hole, such that when the corners are shaved down and tapered to size the pin should still fit snugly. A few ridges left with the drawknife are desirable to key the pin once it’s driven.
Froes and mallets
A word about froes: a good one for splitting out pins must have consistent taper for its entire depth; the cross- section of the blade should be a V. Some new ones available today are simply made from flat stock with a short bevel ground along one edge. After being driven to a certain depth, such would-be froes don’t continue to drive apart the workpiece properly, so they should be avoided. Antique froes have the long taper, as do new ones made by Ray Iles and Barr Quarton.
Two useful froes with forged full tapers and a less useful one, at right, with short ground bevel.
The mallet (or maul) takes considerable abuse from striking the froe. I have a 5-lb., cast-iron-head Garland mallet with replaceable rawhide faces that works well, but Dave Bowman, of Worthington, Massachusetts, the demonstrator in the photos, uses a beech maul that has lasted practically forever—reportedly 22 years and tens of thousands of pins. Dave’s explanation is that the maul is made from rootstock, which has very dense, interlocked grain.
To shape the squares into usable pins, take them to a shaving horse, to be worked into octagons with a drawknife (bevel down), or to a modified bench hook, to be worked with slick and handplane. The bench hook has lengthwise stopped and tapered V-grooves in its surface to elevate one end of the pin for convenient rotation.
Instead of working the square pins to octagons, some workers use a sort of die, a heavy steel plate drilled out with the desired pin size, or a short pipe of the desired inside diameter and with one end sharpened, to drive the squares through. The sharp edge of the hole shaves the square to round but doesn’t provide a taper. The pipe has the advantage of guiding the pin as it is shaved, the next square forcing the finished pin out the bottom.
There are two types of shaving horse: the English (or bodger’s bench), with a yoke to hold the work, and the Continental (or dumbhead), with a solid head open to the sides. The Continental horse is better for long pieces that can be inserted from the side. For shorter stock like pins, the English is preferable, since it holds better via the notch incised and centered in the yoke. (A notch might help under a dumbhead but would still be not centered.) Greenwoodworking.com/ShavingHorsePlans offers plans online, together with discussion of the two styles.
Drill holes in the bench seat or working surface to match the diameters of the pins to make. If the distance from the sloping work surface to the seat is about the same as the desired length of the taper, then this gauge will serve to check both diameter and length of the finished pin.
Start by squaring the pin if necessary (at this stage, the section might be a parallelogram), with the drawknife edge bevel down for best control. Evaluate the pin for any splitting taper; the narrower end obviously should be at the tip of the finished pin. Work the tip end first, finishing it before turning the pin around to work on the driven end. Place just enough of the driven end under the clamp of the shaving horse to hold, and carefully shave the faces square. Take only a few passes and at the same time introduce a slight taper (⅛ in. or so) over the entire accessible length. Then rotate the pin successively and take off the corners, first passes starting up near the clamp head and second passes starting about halfway down the pin. That should be all it takes. Don’t shave off too much: the resulting flat surfaces should all be about the same width. In other words, approximate an octagon.
The 135-degree corners left on the pin are good for gripping the pin hole, and with a proper taper the flats will also wedge into the sides of the hole when driven home, so don’t overdo it trying to get the pin round. Keep trying it in the test hole: the pin should just go snug in the hole as the tip nears the seat of the horse below. In any test hole, the pin should go snug at about the point along its length where the tenon would ultimately be in the assembled joint.
The next step is to make a heavy square taper on the last 1½ in. of the tip end, reducing the tip to a blunt end about ¼- to ⅜-in. square so that it can get started easily in the offset drawbore hole. Ideally this short taper should be slightly concave to help guide the tip through the offset of the drawbore, so turn the drawknife edge bevel up to shave it (Fig. 17). Once the pin is driven, the short taper will extend beyond the far face of the timber and the cross-section of the pin will appear to fill the pin hole.
Finally, flip the pin around and dress up the driven end, which has been marred by the clamp.
The thick end of the pin shouldn’t be able to enter the test hole, but rather just cover it, with a bit of the hole showing at the flats. When finished it should be slightly smaller than the pin hole when measured from flat to opposite flat and slightly greater than the hole when measured across the corners.
Having a slightly undersized pin is better than having one over-sized, since the latter could split the timber, and it’s the drawbore that holds the joint together more than the snug fit of the pin. A good pin will show fair lines, reasonable consistency in the flats and not too great a reduction in section where it will emerge from the joint after being driven tight.
The operation of riving and shaving tapered pins takes some practice. After a few dozen or so, however, consistent results are likely. Twenty pins an hour, including splitting out the blanks, is a good goal. A sharp drawknife is essential, of course. The quality of the blank is key to saving wasted effort. Reject blanks that have knots, splits or twisted grain. Rejected pins can be used to keep your dogs occupied so they don’t get to your good ones. And all those curly shavings make great fire starter.