Tramming my mill... simple question.

[BaronJ]

Hi Pcmaker,

Yes you do need to calibrate your device !

The technique is to put a parallel flat on the table and adjust one indicator so that it reads zero when the stylus is placed on it. You do this by rotating the scale. Then rotate the device 180 degrees so that the other indicator is in the same place and zero it the same way. You may need to use a mirror to see the other indicator since it will be facing away from you.
At this point the device is ready to use.

I've found it very interesting to put the device across the mill table and wind the table from end to end !

 

[bhigdog]

Bend a piece of 1/4" metal rod to 90 deg. Put in collett. Attach indicator. Swing same on table. I swing over a 12" square piece of plate glass. Nice and smooth and it's as close or closer than me or my machine are capable of..........Bob

 

[RJSakowski]

Its mostly a marketing ploy. the (2) indicators will never be in the same plane, and will introduce some error.

You calibrate the tool by touching off and setting zero on the same point. There should be no error other than the resolution of the indicator. It does the same as a single indicator but allows you the convenience of being able to see both sides at once and not having to swing the indicator.

 

[Technical Ted]

My question would be , why does anyone need 2 indicators and fancy tool to tram a mill ? What ever happened to using 1 indicator in an adjustable bar ? Am I missing something ? That thing looks like it turns a simple task into a nightmare . JMO

I made my own using two extra indicators I had on hand that weren't being used. Thought it looked like a good idea. To tell you the truth, I haven't used it since shortly after making it...

Yup, I just use one in the spindle now.

Ted

 

[bhigdog]

You calibrate the tool by touching off and setting zero on the same point. There should be no error other than the resolution of the indicator. It does the same as a single indicator but allows you the convenience of being able to see both sides at once and not having to swing the indicator.

Of course thats assuming the tool is perfectly aligned in the collet which is perfectly aligned with the spindle and the indicators are perfectly at 90 degrees and square to the spindle.
Good luck with all of that.......Bob

 

[ConValSam]

Stefan Gotteswinter posted this excellent method for tramming a small mill regardless of what measuring method one uses.

I can't remember where I saw it, but someone else posted a method using jack screws to tram a mini mill using 3 points of contact.

When my purchased my Sieg X2D, I went crazy for a few sessions trying to tram it dead nuts and failing miserably: then I read an OCD releasing post here (I think) informing me that the column flex on a mini mill likely exceeded my tramming accuracy anyway.

 

[RJSakowski]

Of course thats assuming the tool is perfectly aligned in the collet which is perfectly aligned with the spindle and the indicators are perfectly at 90 degrees and square to the spindle.
Good luck with all of that.......Bob

That doesn't matter. The calibration process accounts for that. Set a boss on the table and zero the first indicator. Swing the tool 180º and set the second indicator. The second indicator now duplicates the reading on the first. You can now directly compare the readings as you adjust the tram. No need to swing the indicator back and forth. No need to use a mirror or contort your body to read the indicator when it is swung around and the dial is facing the rear of the machine.

Now if the setup had a great deal of runout so the effective radii traced by the indicator points were different, that could have an effect but that would have to be extreme and if you had that much runout in the mill, you would have more serious issues to deal with.

Note that this calibration procedure must be done every time the tram indicator is installed as it compensates for any runout at the time. This isn't a big issue as the calibration takes only a few seconds. Note also the there have been You Tube videos showing an improper calibration procedure,

The Edge Technology video show how to correctly calibrate the tramming tool. http://store-1wa94vq6.mybigcommerce.com/product_images/product_manual/pro_tram/pro_tram_manual.html

Here are examples of how not to calibrate a tramming tool. They don't account for any spindle runout. http://www.starrett.com/docs/defaul...649-spindle-square-user-manual---form-954.pdf