Hornady Concentricity Gauge

[autoxforfun]

I found an insert that may do the job.....it is on the way.  But if it doesn't a double sided chamfer with a small flat top would work too.  Thanks for all the ideas!!

[bikemutt]

I'm posting this only to alert others to shop around, buying direct from a retailer may not get you the best price.

I can purchase the Starrett anvil tip I posted about earlier directly from MSC Industrial, price is $19.11, sales tax $2.79, shipping $12.99, total $34.89.

Or, I can purchase the same item from MSC Industrial on their eBay store for $19.11, sales tax $1.66, shipping $0, total $20.77.

So, it would cost me $14.12 more to buy it directly from MSC  . I realize that's not even Big Mac money these days but hey, now that I'm retired, every dime counts. What I find astonishing is they ship items for free when sold on eBay where they have to incur seller transaction fees, I wonder how long they can sustain that business model?

[hdmunger]

At that price, for that little thing...probably indefinitely

[bikemutt]

I received and checked out the spherical spindle tip today; well worth $20 IMO.

My first impression was not good; the tip is not a tight fit on the spindle, that's when I connected the dots, it's not supposed to be a tight fit. The important thing is that the captured, precision ball bearing is allowed to rest on the flat face of the spindle on one end, while contacting the measured surface on the other end. Furthermore, a ratchet spindle is designed to apply just enough force to positively contact the measured surface without deforming said surface, the radial force of a tight fit may interfere with this delicate balance.

That said, the fitment area is split, presumably to accommodated small differences in spindle diameter. Here's a picture.



The piece of brass in the following pictures was outside mandrel turned on a lathe to 12.5 thou, the spindle tip adds 0.200 to the indicated dimension; it is right on. This micrometer tip allows me to examine thickness in the middle, towards the mouth and closer to the shoulder junction. It's not a donut hunter.







Noteworthy IMO, is the tilt in the piece of brass as it's being measured in the middle where it's plumb, tilted slightly counterclockwise as the shoulder is approached, and slightly clockwise as the mouth is approached. I think that's just center of gravity, not spindle-anvil alignment issues, I would've tried to keep them plumb but, I ran out of arms, lol. That's the beauty of spherical tips, they offer a degree of freedom  from perfect axial alignment.
 

[autoxforfun]

I received the radius inserts yesterday which allows me to put a nice 'ball' profile on the pilot of the gauge.  I also put a step on the other end to hold the base of the brass.  It is just slightly larger than the base so that it will rotate smoothly.  So far, this is working well.  It is now very simple to measure both the neck thickness and rotate the brass to see how consistent it is.  Also added a digital dial indicator.

[bikemutt]

That looks real good Bob, I may reclaim that Hornady gage I donated which no one uses 

[autoxforfun]

That looks real good Bob, I may reclaim that Hornady gage I donated which no one uses 

After having this tool collect dust for several years, it is nice that it can provide a useful function.  

[bikemutt]

Never willing to leave well enough alone, I made a Franken-Mic 


Mitutoyo offers standard outside mics with flat anvils and flat spindles, tube mics with flat spindles and spherical post anvils, and inside mics with spherical spindles and anvils. The problem is the last variant is not offered with a spherical post anvil; the offered anvils will not fit inside a case neck.

So, what to do? The spherical tipped mics are more rare, and more expensive, I found a nice used one on eBay. My thought was to play a TV doctor and transplant the spherical spindle onto my tube mic which has the spherical post anvil. What could possibly go wrong?

Here's a post-surgery picture of the mic:



Tell you what, there's a lot going on inside a Mitutoyo mic but, I got it done after watching 3 YouTube vids.
   

[autoxforfun]

Tell you what, there's a lot going on inside a Mitutoyo mic but, I got it done after watching 3 YouTube vids.

Did you post a YouTube Video of the operation?

[bikemutt]

Did you post a YouTube Video of the operation?

I have not, never tried posting to YouTube, don't even have an account, I probably should signup and try it one of these days.

Here's a close up of the parts and pieces:



The first part to address is the Spindle Gap Truing Grubscrew, upper left side. This tiny screw is designed to take up any gap between the spindle and body of the micrometer, a lucky person would have two spindles of the exact same diameter to work with, I was not lucky. The grubscrew must be adjusted to ensure a tight radial fit while allowing the spindle full axial travel; it's tiny, Mr. Magoo readers required  .

The digit counter drive wheel grubscrew locks the wheel to the shaft somehow so that it spins the counter when the spindle is turned while allowing for the spindle's axial movement. This part is a bit of a mystery to me, my understanding of it is anecdotal at this point.

The real trick, if having the vernier read zero when the mic is fully closed is desirable, is to separate the ratchet assembly from the thimble. These two assemblies are taper fit; after removing the ratchet screw a light tap with a rubber mallet frees the tapered parts. From there, it's simply a matter of closing the spindle to zero, rotate the thimble to zero, then reseat the tapered parts and secure the ratchet screw.

Setting the digit counter to zero is easy, especially if the person mad enough to attempt this is blessed with 3 hands  . Remove the two faceplate screws, loosen the counter screws, let it drop down so the digit wheel may be manually turned to bring the 4 digits to zero, push the counter back to engage the spindle wheel with the counter wheel, tighten the counter screws. Do this 10 or so times until the correct pair of amazingly small teeth are engaged, extreme patience and advanced anger management required, lol.

[jvw2008]

I think you are a lot happier when you are on the beach.