Mill tramming device

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BadDog
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Re: Mill tramming device

Post by BadDog » Thu Jan 03, 2019 1:01 pm

Again, shimming on the table is not going to correct for head alignment to a different reference. If you are feeding along X with the head is tipped to the side, you'll get troughs for each path because one side of the cutter is lower than the other. If the head is nodded, then you'll get taper in the Y axis and steps between each path. Variations of that (along with related hole issues for drilling, squareness of wall sides, etc) are what make aligning the head normal to the table top is all about.

The head isn't moving, the table is. So all you can do is align the head so that the tool cuts at the same distance from the reference surface all the way around. Generally by sweeping the table top with a DTI. If you are getting taper in pieces, then your piece is not referenced to the plane normal to the axis of rotation, or the piece isn't moving along that plane. The first is an issue with the reference surface (table top, vise, parallel) being out of plane, and the second is an issue with the ways being out of plane.
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SteveHGraham
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Re: Mill tramming device

Post by SteveHGraham » Thu Jan 03, 2019 1:25 pm

John Hasler wrote:
Thu Jan 03, 2019 11:31 am
That trams the quill, not the spindle.
Sounds clever, but isn't true. If it were true, the results would show it. Perhaps there are mills out there that have quills that aren't aligned well with their spindles, but mine is not one of them.
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BadDog
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Re: Mill tramming device

Post by BadDog » Thu Jan 03, 2019 1:32 pm

I suppose it's all in what you need/expect from the results. You approach may always be great for your needs. I most often work within relatively lax requirements and take liberties where I judge them acceptable. But there are reasons that precision spindle bearings have alignment dots on them to account for tenths, and why spindles are best ground in-situ to account for any tiny run out. When or if those things matter, you'll find your approach is no longer good enough.
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SteveHGraham
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Re: Mill tramming device

Post by SteveHGraham » Thu Jan 03, 2019 1:46 pm

Which is why I said you can finish up with an indicator if you need to. In the meantime, the angle plate will save you time getting into the ballpark--a very small one--after tilting your head 45 degrees.

How many people here would be brave enough to tilt a mill's head three or four times in one day? It doesn't intimidate me at all. That's a real bonus.
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BadDog
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Re: Mill tramming device

Post by BadDog » Thu Jan 03, 2019 1:56 pm

Agreed, which is why I also said that I take liberties where I deem acceptable.

As long as you never expect to walk in your shop and start to work without concern for the mill alignment, then it works. For many, they prefer to leave it accurately aligned because they don't need to tilt that often, and they want to just get down to work without always wondering if the head is actually true, or just looks really close. I read/heard somewhere advice to never leave a mill head "close" to true. That way if it looks true, it is. But if it's not, always leave it far enough out that you know it's out. But obviously that's for someone who wants to be able to walk up (or change shifts) and find the mill in a state they expect and can trust day to day.

Each to their own and all that.

And for what it's worth, I don't worry much about tilting mine, it's actually not that hard to get back right for most my needs using a 0.001 indicator and indicol. Which means "pretty close". When it really matters, like when I use a large fly cutter, I always dial it just to be sure anyway.
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RSG
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Re: Mill tramming device

Post by RSG » Fri Jan 04, 2019 11:16 am

If I can add my two cents to the topic, I recently had to tram my new mill and I started with a cylinder square against the quill to get it close, then put a tenths DTI on an indicator holder that fits in the spindle. I was able to achieve success in a short time and quite accurately I might add.

One thing that caught my eye was a post from Pete regarding Torque on the head bolts. I'm going to capture his remark and post it in it's own thread so this topic can be discussed more in-depth as it is of interest to me.
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SteveHGraham
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Re: Mill tramming device

Post by SteveHGraham » Fri Jan 04, 2019 11:48 am

That's exactly the method I'm talking about. I found it on a DVD, and it made my life considerably easier.
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johnfreese
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Re: Mill tramming device

Post by johnfreese » Fri Jan 04, 2019 7:10 pm

Mr Ron,
that only works for drilling or boring, or squaring the end of a part. If the spindle is not square with the table facing cuts made with an endmill, face mill, or fly cutter will not be flat. Each pass will result in a shallow scallop. Tramming the head isn't hard. You would need to do it once. If you are shimming the part you need to deal with shims every time you put a part on the mill.

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Re: Mill tramming device

Post by spro » Fri Jan 04, 2019 8:24 pm

Perhaps you have newer machines which haven't yet displayed saddle and table way wear. It will happen and I think Mr. Ron is onto something more than tramming or centering. We do like older machinery and that is the way it is. It is a big job to have everything planed and scraped. I think it is a question of balance when the heavy vice courses the middle of the knee. A heavy table drive or index head at one end, is liable to effect the table traverse as it moves upward on fresher surfaces. I'm not suggesting that he has ancient machine but I do.
These are heavy tables so they get saddle backed in the middle work platform. Lost my train of thought :)

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Re: Mill tramming device

Post by Mr Ron » Fri Jan 04, 2019 9:10 pm

spro wrote:
Fri Jan 04, 2019 8:24 pm
Perhaps you have newer machines which haven't yet displayed saddle and table way wear. It will happen and I think Mr. Ron is onto something more than tramming or centering. We do like older machinery and that is the way it is. It is a big job to have everything planed and scraped. I think it is a question of balance when the heavy vice courses the middle of the knee. A heavy table drive or index head at one end, is liable to effect the table traverse as it moves upward on fresher surfaces. I'm not suggesting that he has ancient machine but I do.
These are heavy tables so they get saddle backed in the middle work platform. Lost my train of thought :)
I have a 6x26 vertical knee mill, made in Taiwan in 1976. The ways are hand scraped. It's not a bad little mill. It cost me $1300 back then. A similar mill new today costs about $2500 and is made in China.
Mr.Ron from South Mississippi

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BadDog
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Re: Mill tramming device

Post by BadDog » Fri Jan 04, 2019 10:30 pm

At that price, I would be floored if it were hand scraped. Mills costing several times that are not scrapped. But a lot of them have "flaking" on them, which looks somewhat like scraping, but is for way oil management rather than precision alignment and flatness.

That said, scraping isn't really relevant to this discussion. But that has established that it's a privately owned machine rather than an old machine that gave much of its life to production, so wear shouldn't be much of a consideration.
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Re: Mill tramming device

Post by Harold_V » Sat Jan 05, 2019 2:59 am

Mr Ron wrote:
Fri Jan 04, 2019 9:10 pm
I have a 6x26 vertical knee mill, made in Taiwan in 1976. The ways are hand scraped.
I would be shocked if such a machine had scraped ways. They typically do not.
Easy enough to determine. Look at the ways. Do you see repetitive lines that parallel one another, often in a circular pattern? They're real obvious on a Bridgeport, even those with chrome ways. You also see what most folks think is scraping---which, in a sense----it is. It's flaking (some folks call it frosting, a term I don't care for), which is intended to do two things. One of them is to mislead you to think the mill is scraped, and the other one is to provide minute cavities in which a film of oil can reside.

True scraping will display a mottled surface, that has been flaked.

H
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