Author Topic: Dial Gauge Mill Tramming Tool  (Read 33185 times)

Offline Jo

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Re: Dial Gauge Mill Tramming Tool
« Reply #30 on: February 23, 2015, 05:38:27 PM »
You lost me a bit with there Michael  :headscratch:


The only critical element here is to make sure that the indicator mounting holes are are equidistant and parallel to the central shaft. The rest is non-critical at all.

To calibrate the device, you zero both indicators at the same spot. Zero the first one, then rotate the device 180 degree so that the second indicator is at the same spot and zero it. That's all. Now proceed with tramming.

That makes it so much easier for me to understand  ;).

Jo
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Offline BaronJ

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Re: Dial Gauge Mill Tramming Tool
« Reply #31 on: February 23, 2015, 09:23:55 PM »
Hi All,

I thought you might like to see mine.  Its one that I made based on Boggs thread.  At this point it is uncalibrated.  You will notice that, though the two dial gauges are 0.001, they are two different ones.  The supplier swapped one for me so that I had a pair that were the same.  When I made mine I bored the centre hole on the lathe and made the 12 mm shaft a press fit.  The 8 mm holes at the ends were drilled on the mill.
Best Regards:  Baron.

I don’t regret the things I’ve done, I regret the things I didn’t do when I had the chance.

Offline Courierdog

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Re: Dial Gauge Mill Tramming Tool
« Reply #32 on: January 28, 2021, 01:55:15 AM »
Michael:
I want to clarify your statement
"The only critical element here is to make sure that the indicator mounting holes are are equidistant and parallel to the central shaft. The rest is non-critical at all. The aluminum body can be machined or not, be crooked and not perpendicular to the shaft, etc. It doesn't affect the performance of the device."
IF I am to understand correctly, My take away is,
the Key is the three holes must be absolutely Parallel to the central shaft.
IF I am to read correctly the squareness nor the absolute dimension of the bar is non-critical.
BUT
The Absolute Equidistant and Absolute Parallel placement of the outside holes to hold the Dial indicators are the key elements.
The calibration of one dial indicator to the relative ZERO Must then be repeated or be copied on the exact same spot by the opposite Dial indicator.
The surface of the indicator pin side or the Dial Indicator Meter side is immaterial.
The original Bogstandard approach of having the respective face of the bar is not essential to the measurement nor its accuracy, The facing is only a convenience to setting up and calibration as outlined in Bogstandard's original proposal/concept
My first thought as I read the article and others like it, the face of the Didicator Meter Side and the actual Pin of the measurement probe of the Dial indicator had to be perfectly level.
How the initial setup was done and as others read it the bar was set on a surface Plate forsimplicity.
This would allow much more leeway for a prank set up.
I was initially thinking of using if possible an R8 Arbor like the FMB-22 while this may allow for simplistic storage of the Bar only it does not comply to the original Bogstandard article.
I assume you have other thoughts and I would appreciate hearing them.
Thanks
Dave C

Offline peakfour

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Re: Dial Gauge Mill Tramming Tool
« Reply #33 on: February 14, 2021, 04:17:16 PM »
I actually only joined this forum to see how John "Blogwitch" ex "Bogstandard" was getting on; I see he's not logged on since last October.

There seems to be a few folk who have missed the basic principal behind the way John designed the tool/gauge.
The most important aspect is that the arbor is perfectly parallel to the two separate feet at the ends.
That being the case, if you stand the gauge on a flat surface, the arbor is exactly perpendicular to that surface.
The idea is that you fit the two gauges, sufficiently high in their respective holes, that the plungers can fully retract when when the gauge is stood on its feet.
Next job is to set them at the same height, lock the allen screws, and zero the clocks.
That's all you need to do in order to calibrate the gauge.

Essentially, if the gauge is fitted to the arbor and the table is perpendicular, the two feet will be equidistant from the table; the clocks are only there to indicate the difference between the two ends.
You have previously zero'd the clocks with the feet on a flat surface, so they now show the two distances, one at each end.
This indicates which way, if any, that the table is out of square with the arbor/spindle.

The main difference between John's design and mine is that his used a parallel arbor, whereas I've used an MT2 taper, to suit both my milling machines; a Centec 2B and a Dore Westbury.
John went to great lengths to ensure perpendicularity; as did I, though I fitted the arbor into the spindle of my Myford (with a drawbar) and took the feintest skim off the two feet.

My tool/gauge in its box;
Mill Tramming Tool/Gauge by Bill Williams, on Flickr

Sitting on a flat surface to zero the clocks. Any flat surface will do; these appear to be slightly different, but that's parallax error from the central camera
Mill Tramming Tool/Gauge by Bill Williams, on Flickr

Now set up in the spindle and just touching the table with the two clock plungers.
As you can see, the left clock impacted first, by about 18 thou over 8"
Mill Tramming Tool/Gauge by Bill Williams, on Flickr

Centec head now trued up; again slight parallax error is a bit misleading
Mill Tramming Tool/Gauge by Bill Williams, on Flickr

Finally, if you don't want to wind the table all the way up, a couple of precision ground blocks will assist.
Mill Tramming Tool/Gauge by Bill Williams, on Flickr

If you want to spin the whole arrangement around to check the nod, either use a long enough precision parallel, or a brand new car brake disk.
The latter is likely precision ground out of the factory, and has the advantage that the clock plungers don't drop into the Tee slots as you rotate the spindle.

Also, once everything is set true, I then slackened off the arbor in the spindle, rotated the spindle 60°, nipped up the drawbar again and re-measured.
I did this for one full rotation of the Centec spindle, as that would show if there was anything bent, or bruised inside the taper, thus throwing the arbor out from the axis of rotation.

I'm hoping this clears up a few points in the absence of John being around to comment himself.
I did discuss my method of construction and use with him when I called in and bought some kit as part of his great workshop clearance.
All the best
Bill
« Last Edit: February 14, 2021, 04:21:16 PM by peakfour »

 

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