As peg reamers in Australia are approx. $130 each and peg shapers $225 each
I decided to experiment in making them. The required taper is 1:30 so I
first drew this full size and tried to estimate the angle of degree with a
protractor, but this is virtually impossible to do accurately as my first
prototype had too little taper and I also turned down the diameter to much.
The simplest way is to calculate mathematically the distance from the central axis at predetermined points and these are:
1'' - 25.4mm = 0.4233mm 7"- 177.8mm = 2.963mm 30" - 762mm = 12.7mm
2" - 50.8mm = 0.8467mm 8" - 203.2mm = 3.3867mm
3" - 76.2mm = 1.27mm 9" - 228.6mm = 3.81mm
4' - 101.6mm = 1.6933mm 10" - 254mm = 4.2334mm
5" - 127mm' = 2.116mm 11" - 279.4mm = 4.6567mm
6" - 152.4mm = 2.54mm 12" - 304.8mm = 5.08mm
Which confirms the increase in radius of .4233'mm (diam. 0.8466'mm) for each inch in length.
In this instance I used a nominal 3/8" cup head bolt with an effective diam. of 8mm and a thread free length of 7 1/4" (185mm). This was set up in a lathe with the cup head line drilled to take the spindle point and the threaded end of the bolt held in a standard 3 jaw chuck. it was then lightly skimmed to to get an exterior face parallel to the axis.
The correct degree of taper was then easily set by having the tool tip just touching the bolt at the chuck end and 2.54mm away from the bolt, at a distance of 152.4mm - 6" towards the spindle end. *It's of benefit to to have the taper reducing towards the chuck end as a tapered hole hole can then be turned into a wood or metal block held in the chuck with the same taper setting on the lathe, to expedite the making of a peg shaper.
As an aid to quickly resetting the correct taper angle for future use, I drilled three small 2mm holes in the turntable at equal distances to enable the correct taper angle to be quickly reset by inserting three drill bit ends into those holes and then securing the turntable at that point.
The reamers then have the threaded ends cut off at the narrowest point, the cup head sides are either sawn off or ground down to extend the square, with the removable handle simply made from a nut large enough to slip over the square, a hole drilled through it to suit a 1/4" thread, and then threaded, and two bolts or rods cut to length and threaded to suit and tightened onto the square with pliers or multi grips.
The reamers work fine, albeit slowly, simply by wrapping a medium grit sandpaper around them and rotating them in the peg holes. The next step (time permitting is to talk to a fitter and turner friend to see if there is a simple way to roughen them enough to make them file like.
One way I tried is to simply run a very coarse round file along their length to score cutting edges, which does work but not as quickly or easily as using sandpaper around them.
I guess the next step is to make a peg shaper to go with them.
This page was last updated on 07 April 2004