by: German A. Salazar
There is no shortage of concentricity checking tools on the market today and it seems new ones keep coming to market so a quick survey of what we look for in a concentricity tool might be useful. I don't intend to cover every tool available, after all, this is all done on my own time and budget! However, I have three concentricity checking tools and a comparison of their features and ease of use might be useful for someone contemplating buying this type of tool. The three tools are: the old Sinclair, which is a traditional V-block and dial indicator tool; the Bruno's tool, a high quality unit which has some interesting features; and the NECO tool which is really a very adaptable case checking tool, not just concentricity although we will limit this article's coverage to concentricity.
This article does not address the question of the accuracy effect of greater or lesser concentricity, that's a topic for another day (if ever). We are simply concerned with the accuracy, ease of use, limitations and other features of the three tools covered. It's up to you to decide which one, if any, is worth your time, money and effort. I have all three and use them at different times for different projects; to me, all are worthwhile, but I'm a tool hoarder anyway. Let's have a look at them individually.
Sinclair (old model)
There are a couple of points to watch out for with the Sinclair tool. The first, which is common to all of these tools is to keep the V-block clean as it has a tendency to accumulate a bit of grunge and that can have a small effect on readings. The other is that the smoothness and perhaps accuracy of the tool can be affected by irregularities on the case base, including from the primer. I generally prefer to remove the primer with a decapping die prior to using the tool on fired but unsized brass. If the case has some nicks and gouges on the rim, such as a semi-auto's extractor might cause, it's best to dress these down before checking runout.
Visually the Bruno tool is a gem, the anodizing is bright, the polished pieces are well done and it uses a high quality lever-arm test indicator with 0.0005" gradations which allows for very precise readings. My first impression, however, was that it might be too small for some of the work I do, especially the .30-06. It really looks like it's scaled for the 6PPC, or maybe I thought that because it comes from Lester. Well, this was one of those ocassions when I was quite happy to be wrong, it easily handles the .30-06 and larger cases as you can see in the pictures.
Basic adjustment for case length is simple enough: loosen a lock screw on the tapered case mouth/bullet support and slide it to the desired location. The more challenging part is moving the indicator to the new location. The indicator is mounted on a tool post and while the holder is sufficiently adjustable, it is not easily adjustable. Frankly, it takes a bit of work to properly locate the indicator, but once that's done (a matter of a few minutes at most) it will hold its setting perfectly. The rear of the case is supported by two tapered posts. In the middle there is a central tower with an interesting case support: a vertical rod with a contoured case-riding piece that presses lightly down on the case to keep it from tipping upward from the finger pressure at the rear - quite clever and effective. The case mouth rides in a horizontal tapered post which also has a central hole in which the bullet tip rides when measuring runout on seated bullets.
Using the Bruno tool isn't very different from the Sinclair, you maintain a slight forward pressure as you rotate the case. However, the design of the Bruno with the end of the case hanging in the air makes it much easier to turn it consistently through a rotation. Bring the central case-rider to bear on the case tiny bit of downward pressure prior to starting; that keeps the case rotating smoothly but there is no need to press on the post while actually rotating. The 0.0005" indicator reads smoothly and really gives a better visual indication of runout than the 0.001" indicator that I have on the Sinclair. In part this is due to the smaller, more precise contact point of the lever arm indicator used on the Bruno tool. I should also mention that reading the Bruno is a lot easier since the indicator faces up, whereas on the Sinclair I have to crane my neck to look at the forward-facing indicator. The Sinclair is a good tool that has given me many years of good service, but the Bruno is a better setup for real precision.