Homemade Concentricity Gauge

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FatSebastian
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Re: Homemade Concentricity Gauge

Post by FatSebastian » Tue Mar 06, 2012 11:51 pm

sporty wrote:I do see different readings if I do not use a pin gage matching the size of the bore.
I quickly investigated the potential errors of using an undersized pin by building two concentricity gauges. Gauge A was the inverted one using 3/32" drill bit and a 0.001" precision dial indicator. Gauge B was a "new and improved gauge" employing a #41 drill bit and a 0.0005" precision dial indicator. A #41 drill bit is advertised to be 0.096" in diameter (the shank measured 0.0955" with our micrometer). If pin size matters, then Gauge B should give different (more accurate) readings than Gauge A; otherwise, they should provide nearly identical readings.

I took runout measurements from some handy Revell wheels having a bore diameter of 0.0960" (as measured using pin gauges), which matched the pin size of Gauge B. The runout of these wheels was rather large (a subject for another topic), but the readings between Gauge A and Gauge B always matched to 0.0005" (which was the precision of Gauge B). After doing this eight different times on different wheels, it seemed that a pin undersized by ~0.002" was not going to be a significant source of error with this device... 8)

I then took some comparative readings with an old, pre-2009 BSA wheel (also having large runout). Its bore size was ~0.0975", this being the largest diameter bore we've ever encountered out of the box. I found with Gauge A (with the smaller 3/32" pin) that I could get differences of several thousandths in the run out measurements compared to Gauge B (with the larger #41 pin). These seemingly erroneous runout readings on Gauge A also tended to read smaller, or "better", as Sporty noted. So it seemed that a pin undersized by ~0.004" could be a significant source of error with this device. :doh:

Just how closely pins and bores need to be matched for a contraption like this may still be an open question, but based on these tentative results it seems reasonable to employ a #41 bit instead of the 3/32" bit to help maintain accuracy with "large"-bore wheels. (I'll also add that I mic'd the pin for the Pro-Wheel Shaver and it was ~0.095", which appears to provide external confirmation of that dimension being a useful choice.) Something like a pin gauge would seem even better, but a #41 drill bit is a regular hardware-store item and one would still need the drill bit to make a hole for a pin gauge anyway! Because of the tighter tolerances, it might be advisable to polish the shank of a #41 bit (with the caveat that polishing can remove the zinc-oxide coating or other protective plating).

I might also recommend drilling a second hole in the wooden chassis to hold a 3/32" bit for use with "small" bores, just in case you are lucky enough stumble across a wheel with a bore so small that it could get messed up if forced onto the larger #41 bit. One could swap out the different bits into their respective holes if / whenever this happens.
sporty wrote:...make one or get one. In the long run, its going to make sure you get what you pay for...
I might add that some vendors ream their wheel bores, sometimes out to 0.098", increasing the chance of run-out measurement error without a sufficiently matched drill bit or pin gauge; might a #40 (0.098") drill bit help in that case? :idk:



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Re: Homemade Concentricity Gauge

Post by cubmasterbob » Thu Mar 08, 2012 7:40 pm

whodathunkit wrote:I have a concentricity gauge by derbytek tools that I got off of Maximum Velocity a while back. It didn't occur to me until I saw this post that I might have been getting false readings due to the pin and different size wheel bores. Thank you for starting this topic and showing us what you made.

Whoda
For a day job, I make rivets{24yrs now}...we use TIR guages to check for ID or OD runout{rivet head or holes}. We have a triple roller head{2 fixed/1 movable}. When changing any part we zero out the gauge on one spot of the item to be checked and look for [junk] and neg specs when reading while rotating..our gauge has a thimble to readjust our zero point so you can get all [junk] or neg reads, but using one of the rotating analog dial face gauges you can do the same thing. A digi readout gauge would need to be rezero'd at a high or low spot to get a full [junk] or neg read rather than having a combo of, say, plus .002 and minus .003{total of .005}. Harbor freight has some reasonable gauges in digital or analog...there's other places too.
I'd find a pin that's fairly tight, but still turns alittle...your wanting to see how out of round the sections of the wheel are from "a" center point, meaning how lopsided it is. If a pin is too snug and the ID is anything but dead straight you'll get false reads...letting the wheel float a tiny it will show you at any spot on that wheel where it is thicker or thinner from center. Making a set of threaded cones and a thru rod that was smaller than the wheel ID would allow for offsized IDS and still retain center each time..a prop balancer for model aircraft would be a good example - but needs to be smaller for pine wheels.



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Re: Homemade Concentricity Gauge

Post by cubmasterbob » Thu Mar 08, 2012 8:02 pm

Ok, just a thought here....do you want OD out of round, out of round from from inner ID hole or out of round from a centered ID?
OD o/o/r could be done with two rollers for the wheel to lay against instead of the center pin idea...you'd lose the ID centered reference but more easily gain your OD spes via the fixed rollers.
To gain true ID centered to OD runout you'd have to enlist sized drill rod{a few different sizes at that} to fit the pin to any ID you may encounter, but then you run into having to change pins per different IDs and then attaching said pins...maybe a dremel 3 jaw drill chuck head in back of your wooden block - make a pin to mount the chuck to{snug fitting pin but some rotation would be ok so long as it isn't sloppy}, installed parallel, then you'd have unlimited pin size capability.
To simply get inner ID to OD runout any decently close pin could work but you wouldn't get true centered ID then...as it's my understanding, when we the racers turn down our axles they fit a tiny bit more sloppily in the wheel ID anyway so if your runout gauge works in the same manner via a loose pin, your only concern would be wheels with little to no out of round...am I correct? By loose I'd mean with an .089 wheel hole while checking using an .080 pin...or .085 if one didn't have a pin set and that was as close as you could easily get.
I'm trying to help, thouhg it may not seem like it....



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Re: Homemade Concentricity Gauge

Post by macd » Mon Apr 02, 2012 5:59 pm

The dial indicator is on sale at H.F. now for $11.99. They usually let you stack a 20% off coupon if you can find one on the web.
Time to go shopping. :-)



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Curse You Red Baron!
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Re: Homemade Concentricity Gauge

Post by Curse You Red Baron! » Mon Jan 07, 2013 11:39 am

:bigups: This is fantastic, F.S, thanks for posting! We built your updated version of the gauge and my scout loved using it! We used the #41 drill bit and tested about 50 wheels (30 purchased this year in an 18 wheeler truck package plus 3 car blocks from our troop, about 15 from prior years, and the Revells mentioned below). We found 2 with variance under .001, 6 between .001 and .002 and 2 between .002 and .003. Most were about .005, with some approaching .01! I thought I'd mention the rough distribution so other folks can have an idea what their results might be, or, if the distribution seems odd, that discussion can happen. Our Gauge point is just mildly off-center, so that may have impacted our results a bit also... but we're just happy to have at least 8 wheels that are under .002 and to have discarded the dogs.

We also have one set of Revells (scout licensed) we tested with a bore too small for the #41. The #41 went about half way in from the inside of the wheel, but would not go through the outside. Since this indicated some real variation in hub diameter from one side of the wheel to the other (and these 4 wheels were China made while most of ours were USA versions & we wanted to be consistent in our source, assuming the wheels would in general be more alike if we did so) we decided to end our testing of the Revells there. We have a pretty tight build window, and needed to stay on schedule...



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Re: Homemade Concentricity Gauge

Post by macd » Mon Jan 07, 2013 11:58 am

I'll share our results too.
My son ran out of steam after testing just 18 from a big rig kit. We got a good set of four, and still have extra wheels to measure for next year.

Of our 18, five had smaller bores (.0965), while the rest were .0970). Interestingly, the small bores were all #11 and #6 mold numbers.

Of our 18, six had run out measurements of 0.001 to 0.002. The best happened to be mold numbers #8 and #15.

The #11 wheels with the small bore had the worst run out (0.007).

For us, on this small sample set, the mold numbers would have been a good proxy.



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Re: Homemade Concentricity Gauge

Post by Vitamin K » Sun Jan 18, 2015 7:42 am

After having the dial indicator sitting in the workshop for over a year, I finally got around to assembling this gauge. Would you believe that finding the #41 bit was the hardest part? My local hardware place was sold out, and I had to drive a bit to an Ace Hardware that had one. (Seriously, I grabbed the very last one on the rack).

I like that the HF dial indicator has a ball on the end, which, to me, seems like it would be gentler on the wheel face than anything else.

One question: The wheel can be placed on the 'pin' at differing heights (and held in place by the compression of the spring). Should I take the reading in the center of the tread? Or should I try to read it closer to the edge that will contact the track, if I'm going to be canting the axles?



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Re: Homemade Concentricity Gauge

Post by ngyoung » Sun Jan 18, 2015 10:05 am

I may be mistaken but I think using a pin that is close while allowing the wheel to turn is fine. The dial pin tension will hold the ID hole against the axle pin. This will still indicate any varience of the OD to the ID. Using an axle pin too small can possibly introduce some slop when you're turning the wheel so minimizing slop will still help. It is not as important to get a perfectly matched pin to measure from the center of the bore as it is to measure the bore edge to the tread edge. In a race that is how the wheel will be running on the axle.



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Re: Homemade Concentricity Gauge

Post by Stan Pope » Sun Jan 18, 2015 3:57 pm

Vitamin K wrote:One question: The wheel can be placed on the 'pin' at differing heights (and held in place by the compression of the spring). Should I take the reading in the center of the tread? Or should I try to read it closer to the edge that will contact the track, if I'm going to be canting the axles?
Since the run-out may differ across the tread, it makes sense to measure what the wheel will actually experience when running! I'd go so far as to say, if the axle is angled at 3 degrees, so should the indicator! It is a small difference, but could be important if the inner edge of the tread is irregular!


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Re: Homemade Concentricity Gauge

Post by Gtdhw » Mon Jan 18, 2016 1:27 pm

Almost 4 years later, and this post is still helping derby Dads & boys alike.

I made mine from an extra car block for extra size/sturdiness (in little hands), and set the #41 pin @ .040, and then made another hole & set the #42 pin @ .060. I will be ordering the flat end for the gauge as well.

From the 10 or so wheels that I have on hand, the Chinese wheels seem to by far have the least runout, averaging .002-.004. The USA wheels that I have, are horrible, lol, ranging from a best .004 to two coming in @ .012! Will be going to the Scout store tomorrow, to pick up another 20 USA wheels, and hope I find some better!

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Re: Homemade Concentricity Gauge

Post by Vitamin K » Mon Jan 18, 2016 4:09 pm

Gtdhw wrote:Almost 4 years later, and this post is still helping derby Dads & boys alike.

I made mine from an extra car block for extra size/sturdiness (in little hands), and set the #41 pin @ .040, and then made another hole & set the #42 pin @ .060. I will be ordering the flat end for the gauge as well.
Nice! I like the extra solid block and the dual-size pins!

Where do you order the flat tip for the dial indicator from?



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Re: Homemade Concentricity Gauge

Post by Gtdhw » Mon Jan 18, 2016 4:25 pm

Thanks!

Hoping Derby Evolution. They offer one as a $10 option for their gauge, so hoping they sell it on it's own. Did't get a chance to call today, but will tomorrow.


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Re: Homemade Concentricity Gauge

Post by Derby addict » Sat Mar 23, 2019 4:51 pm

So I know this is an old tread but this was my daughter's first year in cub scouts and it was a blast. With watching a couple YouTube videos we won her pack but were middle of the pack at districts. So I caught the fever and I've been reading websites like this one for months now. I have also been "acquiring" tools and supplies at a feverish pace. Much to my wife's chagrin. When I came across this tread I thought I could use my newly "acquired" bandsaw and drill press to make this gauge. So I built on today and dang if it didn't work like as advertised. It amazing how different one wheel is to the next. But I do find molds to be fairly consistent. Thanks for sharing this tool build.



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