the other night I saw a post by Chris Schwarz about some weirdo wooden pins securing joints… (many will have seen it, but here it is just in case http://blog.woodworking-magazine.com/blog/An+Unusual+Shape+For+Wooden+Nails.aspx and immediately recognized what was happening there. Turns out to be a long-time favorite topic of Jennie Alexander’s – the use of spoon-type bits, variously called “peircer bits” “table bits” “shell bits” etc., for boring the peg/pin holes in mortise-and-tenon joinery.
Alexander taught me a lot about these bits, we have used them for years in the joinery work we do. They make a very distictive hole, with torn grain resulting when the bit comes around from the “long” grain to the end grain of the stock. Here’s one from a 17th century joined chest front that was attached to board sides with square wooden pins. Alexander calls the torn grain disturbance “sprucks” – a case of onomatopeia says Jennie…the bit makes that sound. I haven’t heard it myself, but I see it all the time.
So I wrote to Chris and told him there was no mystery tool to fashion those weirdo-shaped pins; it’s the bit that makes a funny hole, then the pin is shaped by the bit. Mike Seimsen clocked it as well, but he uses gimlets according to Chris’ note: http://blog.woodworking-magazine.com/blog/Weird+Wooden+Nail+Its+The+Bit.aspx
The bits are often found in two different configurations; one of which might result from sharpening the other over time….
One way to think of it, says Alexander, is that the one in the top of this view will hold water, the bottom one will not. But over time, the top one evolves into the bottom type here…sort of.
Like any tool, you can hear a lot of different ways to sharpen these. inside, outside, files, stones. I say inside only, I have worked them with burnishers, files and stones. these days I mostly do it with a burnisher. Mark Atchison, the blacksmith I work with, has a nice method of getting these things really sharp. He takes a worn-0ut round file, and grinds the end of it square and uses it as a burnisher run down the inside of the piercer. Needs various sized burnishers to fit different sized piercer bits.
To get back to Schwarz’ original post, I tried to replicate the exaggerated shape of the sprucks and pins in his example, I took a quick swipe at it – note that the example Chris had was in softwood, I assume some European Pine; so I used white pine in my shop. (Sorry for the garish light, Thanksgiving season is no time in my shop for experiments & photos)
Here is one in oak, a photo Alexander shot years ago. Note that these disturbances (sprucks) happen more dramatically in the tangential plane of oak, as here in this 17th-century joined stool.
(that’s a photo of a photo, sorry for the glare)
In the black & white shot above, it appears that the boring was counterclockwise, based on the direction of the torn fibers. For many years I thought that, but now I think it’s an exit hole. that photo is of a rabbet joint, fixed with wooden pins. I have found the easiest way to eyeball the placement of pin holes in rabbet joints is to bore them from the inside.
Someone asked over on Chris’ blog, where do you get these bits – they aren’t terribly old, I assume, but not made these days. Typically nowadays I get them in box lots in auctions, it’s a grab-bag but not too pricey. Otherwise, digging thru antique dealers’ odds & ends…