Internal Concentricity Comparator (Vern Juenke Machine) PART 1 

Just heard of this machine and was looking for what it actually was, how it worked and what it did. Very good presentation. Thank you, sir.

Interesting to see someone covering these in 2023. All of it was on point but some things need emphasising or expanding upon. The simplicity of the original circuit that Vern designed was quite frankly genius. There would be very few I expect in this day and age that could replicate it. Vern utilised aspects of the components of the time to make the circuit self oscillate at a suitable frequency to achieve some degree of depth of penetration. Depth of penetration is deeper for lower frequencies and less for higher frequencies. With modern components of the same designation (2n2222 transistor as an example) and same design specification don't work in the circuit because vern utilised aspects of the components that were outside of the design parameters for the components core functionality. For depth of penetration the optimum frequency is 100kHz and that's very close to what Vern achieved with his circuit. It's not so high that the penetration is blocked by skin effect (a type of signal push back) and it's not so low as to penetrate too deeply into the lead core where it's pointless to be measuring anyway. The lack of modern component equivalents is why there's no real "like for like" successes when it comes to remaking them them in the modern era and the only successful replacements available today utilise different techniques of forced fixed frequency rather than self oscillating to maintain the penetration and reduce skin effect. There are alternatives out there for those that search for them. There's my ones and there's another one that's made into a small toolbox that I cannot find a link to but it is out there.

Nice presentation. It is a useful technique in the inspection of balls for bearings down to 1/4" and up. On those machines, three concurrent measurements are run. Eddy Current, vibration, and optical surface laser. Sometimes, a part will pass for optical surface reflection quality and vibration, yet fail eddy current. When sectioned, the flaws are revealed. Looking forward to the next video.