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tramming mill with brake rotor (practical machinist advertising)

Yes and front to back.
Start with a gauge block or something in the vise. Twist,shim whatever to make somewhat flat.
Put on the indicol out a ways to the side with the DTI. Put the machine spindle in neutral.
Move left or right and zero on the block. Make a dot on the block with a sharpie where you made zero.
Move the table to the other side and swing the spindle over the mark. Do not use the arm of the indicol to turn it or you will upset it.
Twist the head to get both to match. Take out half the error and go back to the other side. Rinse and repeat.
Now move the table in or out. Pick up the same point on the block at 6 or 12 o'clock. Move the other direction and pick up.
Adjust the nod to get zero difference as you did with the side to side.
Go back and check the tilt and nod at 12, 3, 6, 9 o'clock moving the table axis to the dot on your gauge block turning the spindle to each position.
Now you are aligned square to the X/Y table motion. Shim and or twist the vise so that it now runs true.
Yes this is a lot of work but eliminates table top or vise errors.
To get really picky now Z. Using the indicol indicate a pin or better a tooling ball at a marked height.
Move the knee say 6 inches. Indicate it again. This is Z on the knee not straight. You can make a correction table to comp for this when you move the knee.
Bob
(confusing, maybe I should learn how to make a video)

ok, thanks for the clarification, thats what i thought you were describing, this is the exact procedure i use to correct tram on bridgemills, our specification on a new machine is less than 10micron per 500mm. just for a bridgeport because you have easy adjustment and often work will often fit in a vise, i only concern myself with dealing with an 8" swing. imo anymore is deep into diminishing returns, if you barely push on the head you can see an indicator move a couple thou. what you are looking at on the z is not straightness, you are looking at parallelism error between the quill travel and the knee travel. this is also part of my geometry correction on a bridgemill because our machines also have 2 axis of vertical motion, i will correct parallelism in 2 planes between the z (spindle ram) and w (bridge motion) in relation to x, and also in relation to y. if you have a linear error in your travel, its straight, its just not parallel
 
In my, limited, view there is one major reason for tramming the head on a turret mill like a bilgeport. That's to ensure that the cutter axis is normal to the table. If it isn't then you get steps in the surface when face milling and vertical faces that aren't at right angles to the horizontal ones. This does assume that your milling vice beds are parallel to the bases and the jaws are normal to the beds (If not, they can/should be fixed or scrapped).

Having said that, tramming, using a parallel ring resting on the bed is the correct way to proceed. I do use a 10" commercial (ventilated) brake rotor for this purpose and I did check it before use. It blues up well on my surface table and the two faces are parallel to a tenth of a thou according to my best indicator (Mahr Extramess 2001).

Tramming by using the knee travel and indicating off the quill will achieve pretty much the same result, but it's a far less direct and less efficient way to do it.
 
terrible approach to advertise without plenty disclaimers. the way the post came off is that you could just throw on any rotor and use it to tram, without knowing if the 2 faces are parallel to each other and flat. i've bought and changed plenty of rotors in my life, and none of them looked like they were ground. so i wouldnt trust that shit as far as i can throw a rock.
I understand your resistance to using a brake rotor as you don't trust it being flat or parallel. Now as for all rotors being ground, no. But I have seen ones that are.

Upon questioning this method the first time I saw a brake rotor being used to tram a mill, they stated it had been checked on a calibrated granite surface plate and was parallel and flat to .0002"

Are all rotors this good? Who knows.

And no I don't use this method to tram my mill as I have other tools to do it and am too cheap to buy a brake rotor.
 
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Brake rotors out of even most of China will be true to tenths.
Have a lot of experience here as a tooling supplier to the makers.
A thou out is not accepted by any that I know of now. This a world of tenths and microns otherwise brake pulsation.
The trick is how to mount that brake rotor on your mill.
Again trust my table top to be zero.
I guess it comes down to making .005 parts or under .0005 parts on a B-port.
What is your 6-sigma and CPK on a B-port? Is that a stupid person crazy question?:willy_nilly:
With one micron readouts on mine I am hard pressed to stay inside a 6 sigma .001 with a reasonable band.
Maybe you do better.
Bob
(all that annoying 6 sigma and CPK shit, why would people care or check... I make good parts)
 
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who doesnt check their tools before they use them for the first time? at the precision most of us are working at, you have to assume its shit until it has a calibration sticker on it and or you have validated it yourself. i just got myself a precision tilting level and until i have a chance to check its calibration im super weary about using it at different distances, but i do know at the same distance it will transit the same reference height.
you and i take that for granted that its a given. but out on social media? it gives off the false assumption that its just good as is.
 
You know, any one of us could probably do some episodes for the channel (including you). I'm not being a smart ass. Others have done video content for PM and there isn't a reason in the world you couldn't do a shop tour, or a lesson on how you like to tram heads or what you do when making soft jaws or whatever.
fair point. just need to find someone decent at video. because god knows i'm a lot better at machining than filming... lol
 
The latest video to drop. Interesting that it's only hours old and already has 1,300 views. This thread only has a thousand total views since it started. Somehow the videos are reaching people that the forum isn't.

 
The latest video to drop. Interesting that it's only hours old and already has 1,300 views. This thread only has a thousand total views since it started. Somehow the videos are reaching people that the forum isn't.


And this is surprising? Lots of people like to watch TV/videos. Not so many actually like to read. I'll stick with my guys that like to read, personally. :D
 
it simply depends on what you are doing. lets face it, for most jobs a rotor is god enough. even a used one, btw. you just want to get the head you moved back into position. i suspect on most machines you even dont have to tram, they will have some fixture like a pin for "zero".

for pecision work (that should not be done on a knee mill anyway) there is half a dozen of possibilities to tram to. you have to choose the right one.

to tram to table (if needed for some reason): large piece of preferably thick float glas on a thin piece of compressible foam. this will average out the irregularites over the area you desire.
 
'sigh'.......I feel like all the table-sweepers are the same guys who show up to look at buying a 45 year old 24" swing lathe with a .0001" dial indicator in hand.

Indicating a mill is a lot like using a degree wheel...the larger the diameter, the better. A brake rotor that was 48" diameter would do a really good job, if it would fit in the mill.

So I'll say it again....many, many jobs on a mill don't care at all, or hardly, about what the table does when it's at one extreme or the other. That's because you won't be approaching those limits. Tramming the table? Might as well spend that valuable time masturbating.

The brake rotor method - assuming the rotor is parallel - is plenty good for most jobs. And, it's got to be the fastest or close to it.
 
'sigh'.......I feel like all the table-sweepers are the same guys who show up to look at buying a 45 year old 24" swing lathe with a .0001" dial indicator in hand.

Indicating a mill is a lot like using a degree wheel...the larger the diameter, the better. A brake rotor that was 48" diameter would do a really good job, if it would fit in the mill.

So I'll say it again....many, many jobs on a mill don't care at all, or hardly, about what the table does when it's at one extreme or the other. That's because you won't be approaching those limits. Tramming the table? Might as well spend that valuable time masturbating.

The brake rotor method - assuming the rotor is parallel - is plenty good for most jobs. And, it's got to be the fastest or close to it.

why not both at once?
 
The brake rotor method - assuming the rotor is parallel - is plenty good for most jobs. And, it's got to be the fastest or close to it.
So, adding another degree of uncertainty is faster? How about simply using an indicator of appropriate sensitivity without an additional interface.
 








 
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