Chris Schwarz's Blog

Eccentric? Not so Eccentric?

The historically correct shape of the drawbore pin shown in our Autumn 2005 issue has come into question this week. Joel Moskowitz, a tool historian (correction: and a user) and the owner of Tools for Working Wood, reports that his pins are not a straight taper but are eccentric in cross-section instead (“eccentric” is my word; he calls it an “oblique cone” in his comment below). So one side has no taper. This, he reports, causes the joint to tighten up with the twisting action required as the steel pin is inserted. Interesting!

The drawbore pins I’ve made over the years have used machinist drift pins from Sears. These have straight tapers , no eccentricity. Intrigued, I went out and examined closely the antique smallish English set in my toolbox (shown above). They have a straight taper. In truth, one of them is bent so you couldn’t call it a “straight” taper really. A “crooked” taper perhaps? Also, they are not oval-shaped in any way. I put my dial caliper on them in several locations and found them to be of a consistent diameter as they tapered , cone shaped, really.

When I researched this article I bought four other sets of English pins (really, honey, it’s all in the name of journalism). I haven’t been able to check these yet as they are loaned out to people in far-off places. But I’m putting out the word today for them to examine them.

Also today, I consulted Paul N. Hasluck’s “The Handyman’s Book,” which has several drawings related to drawboring on page 204. The large drawing of a pin looks like a straight taper to me , of course, you cannot see it in cross-section, which would have been helpful, Paul. One of the drawings, Fig. 634, shows the pin being inserted, and it could be eccentric.

A drawbore pin from Joseph Smith’s “Key to Sheffield Manufacturers”

If you own a set of these pins, could you check them out and send me some information on the shape of the steel pin on your set? I’ll be happy to post the results here. Also, from a user’s point of view, I’ve been drawboring since 1999 or so with straight tapered pins, and they work great. And John Alexander also recommends drift pins on his site. So my instructions on making your own pins stand, unchanged. I wouldn’t give up my shop-made pins for anything.

Christopher Schwarz

3 thoughts on “Eccentric? Not so Eccentric?

  1. Michael Hahn

    Hi Chris
    You recently sparked my interest in making a pair of drawbore pins and was looking for the ‘drift pins’ (or Starter Drift Punches as they seem to be know in Australia). I also picked up on Joel’s ‘eccentric’ design with the Ray Iles pins he sells and thought initially drift pins were also of such a design. Perhaps they are a descendant of "Podging spanners" or "Podger bars" which I have seen scaffold and steel beam construction using. This looks like a 1-foot long Prybar at one end and an off-alignment cone at the other. This alignment is such that one side of the pin looks straight while the other acts as a Cam- a gradually increasing radius as you twist. I imagine you would get a huge amount of leaverage off this design. Where does the name ‘podger’ come from? No idea- perhaps a long lost trade position.
    Cheers
    Michael

  2. dave brown

    Joel,

    Is there any way for you to manufacture eccentric drawbore pins? Maybe the same manufacturer that is building your new hold fasts could crank some out? =)

    Dave

  3. joel

    Chris,
    I’m not says that my (and other) drawbore pins are eccentric in section. They are round in section but the entire shape isn’t a dowel or a cone. More like a (I think it’s called) an oblique cone.

    Incidentlyly it’s accurate that as you say I’m "a tool collector and the owner of Tools for Working Wood" but, and I know this is hard to believe, I do occasioanlly use the tools – I’m not just a collector and my use of drawbore pins isn’t just theory. I was once using mine, never noticing the offset and I just absent mindeledly turned them in the joint – which immediiately tighted up tremendousely. THen I turned them again and they loosened up. COOL I said. then on checking historic records, and other people I knew It turned out mine were not an isolated case (note: pam’s pins are like mine). What I don’t know is if all drawbore pins that were actually marketed under drawbore pins had the feature and the symetric drawings we sometimes see in catalogs are just errors by the engraver, or if it took time to develope the form and if other styles didn’t have the feature.

    I posted a picture on woodnet along with the following test – don’t know how to send you a picture with this form. THe marples 1909 catalog shows them and the offset is pretty easy to see if you use a ruler for reference. the section of the steel is round, but it leans over like the tower of pisa.

    I do have a question on your antique drawbore pins – how do you know that’s what they originally were sold as? There is also the possiblity that there were different styles (which there most definitely were) with different advantages that are now lost – I’m not arguing that they don’t work – they obviously do – but being able to get almost clamping pressure with mine seems to be an advantage and not having to force them in is really nice too. But unless of course we compare them in side by side use it’s pointless to speculate.

    I’m also not sure why mine are so long. all the ones I have seen are much longer than yours. I think the length might help in getting leverage in a really hard to explain way but I don’t really know.

    THe shortest drawbore pins listed in the marples catalog were 3/8" round by 8" long . mine are 10" long by 1/2" diamter.( not including tang and bolster)

Comments are closed.