Homemade tram tool

One of the hiccups in the process leans heavy on accuracy, whereas what is probably more appropriate would be to define the calibration process of the two indicators as precise.

Exactly! When I was contemplating whether or not I was going to make it, I just couldn't wrap my head around the calibration process and was concerned on how super accurate the spindle had to be in relation to the bar. After watching the videos a few times, it clicked. Hard to put into words, but the best way I can explain it would be that you are eliminating the differential of 2 indicators that were referenced at the same spot.


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I drilled the first one on the drill press because I had not yet received my r8 integral shank drill chuck. I have one now so I have entered a new more accurate world
 
I built one out of scrap material and I already had the two indicators so it cost me nothing. I'm a novice machinist so I like the fact that you see both indicators and just split the difference. That way I don't have to remember any numbers.
 
Not to threadjack, but I've been wondering why people use 2 (or 3) indicators? As I see it, a single indicator on a sturdy offset arm should be sufficient.

That's all I use


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I drilled the first one on the drill press because I had not yet received my r8 integral shank drill chuck. I have one now so I have entered a new more accurate world

I read your OP and my question was based on putting the drill bit into the collet, the same one you have the spindle level mounted in.
 
There seems to be a basic misunderstanding with some members as to how the tramming tool works and how to properly calibrate it.

Part of this stems from SPI and Starrett making the instrument convenient by providing the base of the square as reference surface. That surface is "pre-calibrated" to be perpendicular to the shank of the square and the indicators are "calibrated: when they read zero when the tips are in the same plane as the base. Well and good..... as long as you don't disturb the alignment by bumping or dropping and as long as there is no angular runout in in the spindle mounting scheme. If either or both of these conditions exist, the calibration is useless.

Enter the Edge Technology spindle square and others like it. It is actually calibrated in the machine prior to use. The square is calibrated by zeroing the indicator on a fixed vertical reference surface.

In the following illustration, the square is mounted in the spindle and the first indicator is zeroed when its tip contacts the reference point "B" on the table. the square can be rotated and the circle the zeroed indicator tip describes is concentric with the true spindle axis and is contained in a plane which perpendicular to the spindle axis. Now rotate the second indicator to reference point "B" and zero it. If the square is rotated, it also sweeps a circle which is concentric with the true spindle axis and in a plane which is perpendicular to the spindle axis.

Since both planes are perpendicular to the spindle axis and both planes pass through the calibration reference point "B". The planes have to be coincident. To put it another way, if point "A" is on the true spindle axis, distances AC and AD have to be equal and the only way that can occur is if the line CD is perpendicular to the spindle axis.

Note that there are no assumptions made about the indicator mounting bar or the shank of the square being straight or there being zero angular runout. The bar and shank of the square simply are a means to rigidly position the indicators.

But what if there is runout due to a bent shank or angular runout in the mounting system? All the happens is the swept circles of the two indicators have slightly different diameters. As long as their contact point with the reference "B" is at the same z height relative to the spindle, the calibration is still good. If reference "B" is actually a small cylinder, the calibration will be good. Say that the spindle is out of square by .010" in 5" or .002"/". If the reference surface "B" is .25" in diameter, the error will be at most .0005". With any reasonable care in manufacturing the square, this error should be much less.

As to the issues with possible errors arising with using a cheap indicator, as long as the indicator will repeatedly return to a reading, there should be no problem. Whether a division is reading .001 or .0015 makes no difference. You really don't even need a scale on the indicator to use it. You can just adjust until both indicators read the same as your calibration point.
Tram Calibration Geometry.JPG
 
I've never seen a three point tram tool.
But, I am wondering if the use of a disc or plate instead of a bar with three holes and three gages would allow for simultaneously tramming of nod and tilt.

Daryl
MN
Might work, but why be shy, go for a 4 way tool.

The term tram for a mill is new to me, never heard it before joining this forum. maybe I was away that day we learned about it in trade school, but I don't think I've ever heard it used outside this forum. So what does it really mean and how did the term originate. I understand it is setting up a mill so that the table is square to head. and I realise the importance of that, just curious about the origin of the name.

Here in downunder a tram is an electric public transport vehicle running on rails, like a light rail. I think you call it a streetcar.
 
Hello,
If you own a verticle mill the best investment is a centering indicator, they speed things up in an order that is silly. I use mine on the lathe as well.
With a resolution of 0.01mm,(0.000394"), that is well within anything we will approuch manually. I am attaching an article I downloaded from Gadgetbuilder.com and another from Model Engineers Workshop.
Substitute a center finder for the DTI in the Homier article and once you've checked X & Y axies via Paul Murry's system I would look at a vernier replacement for the zero mark. Fretts.com also has a great quick 'N' ready method of getting close.
Invest in a center finder, one tool, only one dial and a bit of perspex makes life easy and encourages use of the tilting head if you have one.
Cheers,
- Barry.
 

Attachments

  • Alingning a mill head.zip
    1.5 MB · Views: 26
Hey bobshobby,
Those folks down there are a long way from Brisbane aye?
Tram in these terms means to track true & level. Maybe something only understood this side of the ditch?
And down there.
 
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