The Roberts gauge does the work of both a "bore gauge" and a "tuning fork wall thickness gauge" but only to the depth limited by its size. I compared to both. I also compared to the Galazan (and others') apparatus which has "poles" affixed upright in a base and a gauge mounted to measure wall thickness. This latter device is the one with which we concluded familiarity helped reduce inconsistent readings. I suppose the same is true with the tuning fork set up although the people using it had pretty much overcome its deficiencies for their purposes. (That is, more of the people playing around with the tools had used the tuning forks wall thickness gauges and regular bore gauges more than they had used the table top wall thickness gauge. One fellow had a gauge that looked something like a pencil compass.) Hope this clarifies.
