"Projects" at georgesbasement.com

7. Replacement LRRCW Assemblies
Millers Falls No.2 drills have often lost their roller assemblies (LRRCW's in my Millers Falls No.2 Type Study) and so I'm occasionally asked for replacements.  As I have no leftover LRRCW's or their associated parts, I've had to reply negatively.  I decided to make some replacement assemblies, but I also decided not to make counterfeits.  Here's my solution: I am making redesigned LRRCW assemblies that do not require a screwdriver for adjustment.  I'm making the rollers themselves from scrap bronze (i.e., broken tensile test specimens) which is a nice way of recycling as well as a way of making use of the work hardened condition of the material, which cannot be heat treated to increase its wear resistance.  Rather than just making the offset cams with a screwdriver slot, I'm adding a projection to facilitate grasping the cam in order to adjust it.  The normally standard No. 6-32 screw that clamps the assembly will now have a crank shape so that it can be tightened with one's fingers.  Rather than trying to develop a heat-treating process for the cams, which are lightly loaded, I'm using drill rod as the raw material, as the carbides in the annealed microstructure will provide some wear resistance.  All you need do is remember to oil the assembly every few years !
Redesigned LRRCW assembly
Redesigned LRRCW assembly
Redesigned LRRCW assembly
Wrong hole placement for LRRCW eccentric cam
These three views show the LRRCW assembly.
Normal LRRCW shape, but in bronze.
Properly adjusted LRRCW assembly.
Another drill had its cam hole placed wrong.
The eccentric cam requires some precise machining.  I made a holding tool for the blanks by offsetting a piece of 3/8 inch round barstock in the four-jaw chuck so that its axis was 0.048 inch off the center of rotation of the lathe spindle and then drilling and reaming a 0.250 inch through hole.  The 0.152 inch diameter part of the eccentric cam has to be tangent to one side of the 0.250 inch body of the cam to maximize the range of adjustment of the LRRCW and yet still allow putting together the main gear and LRRCW assembly.  I got it right on the first try !
Offset sleeve
Offset sleeve clamping the drill rod
Eccentric cam machined
Reshaped LRRCW to accommodate the incorrect eccentric cam hole placement
Saw cut was made with a piece of bar inside.
Rod faced off & ready to machine eccentric.
Another eccentric cam ready to be cut off.
LRRCW reshaped to allow LRRCW adjusting.
One drill had its 0.250 inch eccentric cam hole drilled in the wrong place, so I had to enlarge the replacement LRRCW so that it could be adjusted properly; this drill probably was a factory second and did not have a LRRCW when I obtained it.  The far-right-hand images in the two rows above show the problem and its solution.  More to come: making the LRRCW itself.
Histogram of LRRCW diameter distribution
Histogram of LRRCW diameter distribution
Histogram of LRRCW diameter distribution
After the above debacle over the center distance and diameter of the LRRCW, I made some measurements of the drills in my Millers Falls No.2 Type Study.  I found that the center distance between the main shaft and the hole for the eccentric cam was usually about 0.81 inch, with all the measurements falling between 0.75 and 0.83 inch, but the LRRCW varied in diameter significantly, as shown at left.
Types K through H have LRRCW's that usually measure around 0.31 inch (5/16th inch), but the later Types G through D have smaller LRRCW's, about 0.28 inch (9/32nd inch).  Oddballs include a couple of 1/4 inch LRRCW's in the earliest Type K drills, which may have been either worn or replaced.  There is one large LRRCW in a Group  III, Type G drill that was probably commandeered from an earlier type.  Nearly all of these drills were made while the company was still located in Millers Falls, Massachusetts.  The histograms were made with PSI-Plot.
Making the cam holder
Miling the cam
Replacement cams
Clamp levers
Above: Some of the clamp levers that I made; note that I started with screws that had both a slot and Phillips recess, so I could support the outboard end with a live center. Original at right.
Above: Making the holders for milling the adjusting tab on the cams.
Above: End milling the tab on a cam, held in the cam holders.
Above: Eight of twelve LRRCW-GB cams that I made recently.
Above: The clamp levers are made from modern screws by machining in the lathe & bending.
Finished LRRCW-GB
Finished Product !

The No.2 Millers Falls drill at left with my LRRCW-GB installed.  This drill came to me with just a 1/4 inch slug of steel in the hole that was meant to hold the LRRCW cam.  It did serve a portion of the original purpose, as the slug had a small flat spot worn into it from rubbbing against the larger gear wheel.

I'm all set to make a bunch of bronze LRRCW's.  However, I'm slowing down a little and doing them one at a time for the half dozen or so No.2 drills that I have that are missing the LRRCW assembly or just the LRRCW itself.  The statistics are in favor of making the LRRCW's all one size (see the analysis I did above) but I'm still going to work my way through this group and see how they turn out.

I'll make replacement LRRCW-GB assemblies for your drills if you wish - Price $20, plus shipping in a First Class padded envelope.

These LRRCW-GB assemblies adjust easily to keep the gears meshing on their pitch lines, and without any need to resort to tools - the clamp lever holds the cam securely and won't unscrew and get lost unless you move the main gear wheel out of the way.  After unclamping the cam, the tab lets you adjust the position of the bronze LRRCW with your fingers, with visual feedback to simplify the task.

Orders to: