Homemade tram tool

[Rustrp]

If I understand your question?

Yes you're correct but my question of "Why?" was more rhetorical. Tramming the mill or dialing in the centers between the chuck and tailstock only becomes difficult if a person doesn't understand the goal. I'm a **read the instructions first** kind of person which seems to make projects easier, IMO. Trammig the mill was one of my first mill projects, and knowing when it's accurate enough works well in many career fields. If I'm off a couple of thousandts and I'm milling a slot in a piece of flat stock that's good. If I'm milling a surface I want more accuracy. In both cases I begin with a square and place a light on the back side that gets me close, quickly.

With that said, and after all the keystrokes, I think making the tramming device causes one to think about the areas where we lose the accuracy we were trying to achieve or how to correct it.

 

[Uglydog]

My go to is a Starrett 650 back plunger.
I've never used a "tram" tool.
Merely wondered if a three point made any sense.

Daryl
MN

 

[tweinke]

I made one and like it, set zero off a gauge block from one point and go quick and easy

 

[RJSakowski]

Okay, that's the part I am missing. How do you zero the two indicators to be true normal to the spindle? What is the initial plane of reference?

You don't have to be normal to the spindle axis. All that has to happen is the indicators are zeroed at the same height. If you think about it, it's no different than tramming the traditional way with a single indicator except you now have two indicators set 180º apart on the spindle axis.

If you are out of perpendicular to the spindle axis with the tramming tool, you won't hit the same reference spot exactly but it would have to be a serious misalignment to cause a measurable error.

 

[woodchucker]

You are not missing anything! You have pointed out the BIG FLAW in that contraption! Why some people love that thing is beyond me! It needs to be calibrated every time you set it up! I’m very happy with using just one indicator. Marketing just loves to try and sell us new toys for our shop. A few are good ideas, but most are just a waste of money IMO.

So that might be true for a regular BP type of unit. One with a screw to adjust both tram and nod.
At least I might agree.

But I just rebuilt a Clausing 8520. It's a round support, no screw. So to tram you tap it with your hammer back and forth. When tightening the bolts it often changes.
With 2 indicators it would be easier, you would know if you went too far or not enough. And while tightening, you would get an idea of how much your are moving it and be able to tap it back as you tighten in stages.

 

[RandyWilson]

That is exactly the question I am asking; HOW do you get the indicators exactly even to the plane 90 degrees to the spindle? If your zero point on the two indicators are not exactly on the 90 degree plane, then you will not be normal to the spindle.

As I read the other reply, you keep spinning the spindle and adjusting until you get both indicators reading the same at a single test point. Then it's a matter of trusting the rig to hold calibration. Guess it depends on how often you tram the head.

 

[woodchucker]

So zero one, flip it around 180, then set the other to zero at the same spot.
Now they are both good to read.

You don't spin it again, you position in front of you and your good to read.
When you move your indicator back and forth (single indicator) you are trusting the rig to hold right?
Now you have zerod both on the same point when you have 2.

 

[Rustrp]

So zero one, flip it around 180, then set the other to zero at the same spot.
Now they are both good to read.

You don't spin it again, you position in front of you and your good to read.
When you move your indicator back and forth (single indicator) you are trusting the rig to hold right?
Now you have zerod both on the same point when you have 2.

True, but with the tramming tool (rig), I must trust that the rod through the cross bar is accurate, plus both indicators are accurate. With the single indicator swung from left to right and arriving at "0" on both sides, (after splitting the difference) I will be accurate without question. Even if the indicator reads accurate to .oo5", when it's .000" Lt. and .000" Rt. the questionable reading is eliminated. Of course I would do this with an indicator that rotates only one direction.

 

[woodchucker]

If the bar were 30 degrees off, and you zerod it , it would still be accurate. Because they were both reading zero at the same spot. Spin it around to face you and they should still be reading zero if in tram.
Now if it leaned, but then both would lean.
Probably more true than swinging back and forth. So I probably think this for some would be better. In my case for the 8520, yes. If I had a BP, it would be a luxury. Wish I had a worm gear to tram I would not want or need that luxury. without the worm gear you can tap too far in a heart beat. There's no way to control where you are, and how far you tap. Light taps often don't move it, then bammmmm it moves..
This looks better than trying to cobble a collar for a gear and add a screw...

 

[T Bredehoft]

Some of us have installed (on our PM25 type mills) a pair of captive screws, one on either side of the head. When snug they hold it in position, when one is loosened the other can be tightened and adjust the tram of the head.