Fig. 2264.
[Fig. 2263] represents a reamer in which the distance between the cutting edges a b, [Fig. 2264], is greater than between b c, and so on, the spacing decreasing from tooth a to tooth a. The spacing of a, b, &c. to f on the other side is also irregular, so that if the reamer be given half a revolution no two teeth will have arrived at similar positions except a and a, the former arriving at the position occupied by the latter.
Now suppose that a hole to be reamed has a hollow or spongy seam along it, and if the reamer be regularly spaced, there will at this point occur a lateral movement of the reamer that will impair the roundness of the hole, and this lateral movement the irregular spacing tends to prevent.
If a solid reamer is made to standard gauge diameter when new, and the bolts or pins turned to standard diameter, then by reason of the wear of the reamer the work will become gradually a tighter fit and finally will not go together, hence the reamer must be restored to standard diameter, which may be done by upsetting the teeth with a set chisel. Furthermore the workman’s measuring gauges are themselves subject to wear, those for measuring the pins wearing larger and those for the holes wearing smaller, and this again is in a direction to prevent the work from fitting together. It is preferable, therefore, to employ adjustable reamers.
Fig. 2265.
Thus [Fig. 2265] represents an adjustable reamer in which the teeth fit tightly into dovetail grooves, that are deeper at the entering than at the shank end of the reamer, so that by forcing the teeth up the grooves towards the shank the diameter is increased.