Mill tramming device

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Mr Ron
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Mill tramming device

Post by Mr Ron » Wed Jan 02, 2019 7:26 pm

After looking at mill tramming devices, I didn't like the prices, so I thought about making one. It wouldn't be hard to make, using 2 DI's, one at each end of a bar. say 12" long. My question is: how would I go about setting the 2 DI's the same distance from the bar and perfectly perpendicular to the spindle that would be held in a collet in a vertical mill. I know the spindle has to be perfectly perpendicular to the bar, but how would I determine that since I can't use the actual mill to be trammed to bore the hole for the spindle. I've tried using one DI at the end of a rod and turning the mill spindle 180° back and forth. That gets tiresome after a while and can't read the DI easily once rotated. It looks like a pretty simple device, but precision must be the key here in it's manufacture.

When I mill a surface, say 9" long, the thickness deviates from one end to the other by about .002"; not good.
Mr.Ron from South Mississippi

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BadDog
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Re: Mill tramming device

Post by BadDog » Wed Jan 02, 2019 8:18 pm

That's not a head alignment issue. That's a way or table alignment issue.

I've seen those fancy devices, but I just don't see the need. And indicol type holder makes it easy to add or remove from the spindle. and orient the DTI with face pointed at the ceiling and it's really not that hard to align the head to the table surface. Certainly not anything worth spending what those things cost, or going to the trouble of making one, and that doesn't even begin to consider the additional problems that could result from using such a device in a less than perfect world.
Russ
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John Hasler
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Re: Mill tramming device

Post by John Hasler » Wed Jan 02, 2019 8:41 pm

The bar needn't be perfectly perpendicular to the spindle axis. You just need to zero both indicators at the same point.

You'll lose accuracy with two indicators, though.

pete
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Re: Mill tramming device

Post by pete » Wed Jan 02, 2019 9:13 pm

Many on the PM forums think exactly the same as BadDog. I have to agree as well. I've got spare indicators and the aluminum plate to easily build one but I've just not bothered. Using a dti is almost as fast, much more accurate and can be extended for much farther distances on the X axis. There ARE a couple of tricks I've figured out while tramming that help a bit. Snug up the head and knuckel bolts to maybe 5 - 10 ft. lbs when you get very close to a zero tram, then use the worm to get your final zero setting, I gently tap on the end of the wrench that's adjusting the worm to get the very small movements needed.Eyeball the indicator depending on which axis your doing as you do the final torque to make sure the heads not moving as the bolts go tight. A light touch is needed though if doing it that way. Too much torque while trying to move the head with the worms and you can break expensive parts. After the heads been final torqued you then back each worm off to a neutral position so the worm isn't preloading the head in either direction. When done correctly you should be able to move those worms back and forth just using your fingers over it's backlash range. With any preload on the worm cutting pressures and the standard vibrations from cutting can and will help to move the head out of tram enough to matter. Since I started doing it that way my head seems to stay in tram much better and for longer unless I do something really stupid. :-) Over torquing the head bolts is almost worse than under torquing them though. Add too much and you can and will distort the head. I've read permanent damage can be done by hammer mechanic types. Mine might be a little in the high range but I usually use about 35 ft. lbs and that seems to work ok.

At around $100 those dual indicator tramming devices are way over priced for a bit of fancy cnc pocketing and anodizing since the indicators are just cheap off shore dial indicators. Calling em "Pro" Trams is just advertising hogwash. One would probably be ok for use on a drill press, but I'll stick with a dti for the mill. You still need some type of single indicator for vise tramming so that dti will do both jobs.

johnfreese
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Re: Mill tramming device

Post by johnfreese » Thu Jan 03, 2019 12:06 am

I use a back-plunger indicator for tramming. It sat on the shelf unused until one day I realized the dial would always face up.

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BadDog
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Re: Mill tramming device

Post by BadDog » Thu Jan 03, 2019 12:14 am

As does a properly oriented DTI, but with much lower cost and likely far greater sensitivity and resolution.
Russ
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Harold_V
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Re: Mill tramming device

Post by Harold_V » Thu Jan 03, 2019 2:27 am

What BadDog said. Why ANYONE would want one of the two indicator arms is a total mystery to me. What REAL purpose do they serve? Unless you spin it and read both indicators, they serve little purpose, and if you have to spin it, what's wrong with trusting just one? In all my years of working in the commercial shop (I started back in '57), I've NEVER seen one used by a machinist. That's not to say some don't use them, but they are a perfect example of how one can be separated from money with no true gain. I wouldn't use one if it was given to me.

I use one of my BesTest indicators. I set it such that the finger makes contact with the table by only a thou or two. That way it goes across T slots without issue. I can set the head on my Bridegport within less than a half thou and do it in short order. Truth is, you can set the head closer than the mill is capable of working. That might not be true if Bridgeport scraped their machines, but they don't.

One more thing. All too many think it's a good idea to use something between the indicator and table. I don't. I'm not interested in readings that may or may not represent the table surface. The slightest ding in the area upon which an object would be placed for the indicator to sweep would be raised.

Learn to dress your mill table by draw filing, and use the table surface when you dial in the head (I don't like the term "tram". We're not talking about steam engines, which do require tramming to set the valve properly. When I dial in the head of my mill, there is no valve involved).

H
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wlw-19958
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Re: Mill tramming device

Post by wlw-19958 » Thu Jan 03, 2019 3:47 am

Hi There,
Mr Ron wrote:When I mill a surface, say 9" long, the thickness deviates from one end to the other by about .002"; not good.
I have to agree that this issue isn't the result of the head
not being square with the table. Tramming is important
but it won't fix this problem.

I would have to ask: "how are you holding the part when
this happens?" Is it clamped to the table? Is it held in a
vise? I ask because we're trying to track down the origin
of your error.

If the part is directly clamped to the table (with nothing
under the part), then the error exists in the table and its
ways. You can mount a DTI to the column of headstock
and position the button on the table between the Tee-
slots. Crank the table from one end (zero the indicator)
and then crank it to the other end and read the DTI.
This will give the error that exists in the table and its ways.

If the part is clamped in a vise, then the error could be
in either the vise or the table (or both). To the same test
as above so you can determine where the error lies.
Harold_V wrote:One more thing. All too many think it's a good idea to use something between the indicator and table. I don't.
I have to agree wholeheartedly. Putting anything between
the table and indicator tip is another point for error to
exist.

Good Luck!
-Blue Chips-
Webb

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SteveHGraham
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Re: Mill tramming device

Post by SteveHGraham » Thu Jan 03, 2019 9:42 am

I use a precision angle plate to tram my mill. Lower the quill all the way, put it down close to the table, and slide the block up against the quill. Put a flashlight behind it. If the mill is out of tram, you will see light coming through a gap. You can see even a tiny gap between the quill and plate.

You just crank the head until the gap goes away. If it's not accurate enough for you, you can continue afterward with an Indicol holder.

The angle plate is very, very fast. It made me unafraid to take proper advantage of my mill's movable head, because I knew I could tram it in a hurry. A movable head is useless if you're terrified of rotating it. I think we forget that the rotation feature is there for cutting, not just tramming. They don't make these things rotate hundreds of degrees just so you can tram your mill.

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John Hasler
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Re: Mill tramming device

Post by John Hasler » Thu Jan 03, 2019 11:31 am

That trams the quill, not the spindle.

John Hasler
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Re: Mill tramming device

Post by John Hasler » Thu Jan 03, 2019 11:47 am

Harold_V wrote:
One more thing. All too many think it's a good idea to use something between the indicator and table. I don't.

I do. I've draw-filed and stoned out the dings in my table (Chinesium from Grizzly) but I know it isn't flat. I know that the disk-drive platter that I use to dial it in is. I want the spindle axis perpendicular to the average table surface.

Mr Ron
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Re: Mill tramming device

Post by Mr Ron » Thu Jan 03, 2019 12:52 pm

I want to tram in respect to the vise, as that is what I use the most. The few times I use the table alone, I can shim the work to be perpendicular to the spindle.
Mr.Ron from South Mississippi

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