How to tram a mill

[John CoatesParticipant @johncoates48577]

Having got through my “crash and burn” learning phase I now seem to be able to approach jobs logically and machine them in a decent sequence to minimise wastage and produce a respectable finished article. Collecting back issues of MEW and reading them is probably helpiong the most

 

But I think I need to tram the head on my Chester Champion mill/drill. I have just started to make a small workpiece holding plate for my bandsaw. It had cut the plate to size and I was end milling the edges to tidy them up. I tried two different approaches. Firstly I clamped the raised plate flat and milled with the side of a large endmill. Next time I held the plate vertically and used the endmill like a facemill. On this, the way I had clamped it meant the mill could not track fully to clear the end of the cut and it resulted in a strange finish to the piece.

 

The leading edge of the cut left a very smooth finish but the trailing edge behind the path of the endmill was very rough. I am trying to figure out why this might be but am a bit confused because the mill was travelling along the Y axis which is a plane where the mill cannot be anything but square to the table. The Chester is a round column mill with rotatable head in the X plane. So the endmill could be not true in the X plane but I thought this would lead to different finishes left and right so to speak, not front and back as is the case.

 

Anyway I need to check the alignment of the milling head and have heard about tramming. Searching Youtube brought up Bogs’ tramming device but that will require the purchase of two matched DTI’s and some metal for the body. There’s no point buying stuff which will get trashed if the cutter is not square to the milling table. I did rotate the mill head to get the 12 degree angle to make a tangetial tool holder so I could have not put it back square (although the fiducial marks are lined up to the best my eyes can establish)

 

I have an unbranded Screwfix DTI and some 12mm stainless steel from which to make rods to enable me to make some kind of adjustable means of fitting it in a drill chuck to carry out the tramming but thought I would ask on here for any advice before I start in the hope of preventing any cock up I might be able to muster.

 

respectfully

 

John

[John CoatesParticipant @johncoates48577]

… without an expensive device!

[Gray62Participant @gray62]

Hi John,

 

Firstly, I wouldn’t use a drill chuck, they are generally not accurate enough A collet directly in the quill, or a collet chuck would be preferable.

take a look at this there is some useful info here on tramming a mill.

 

cheers

 

Graeme

[Steve GarnettParticipant @stevegarnett62550]

Posted by John Coates on 16/09/2011 12:44:49:

Anyway I need to check the alignment of the milling head and have heard about tramming. Searching Youtube brought up Bogs’ tramming device but that will require the purchase of two matched DTI’s and some metal for the body. There’s no point buying stuff which will get trashed if the cutter is not square to the milling table. I did rotate the mill head to get the 12 degree angle to make a tangetial tool holder so I could have not put it back square (although the fiducial marks are lined up to the best my eyes can establish)

 

I have an unbranded Screwfix DTI and some 12mm stainless steel from which to make rods to enable me to make some kind of adjustable means of fitting it in a drill chuck to carry out the tramming but thought I would ask on here for any advice before I start in the hope of preventing any cock up I might be able to muster.

 

 

You can’t tram mills by eye, that’s for sure! Well, not by looking at fiducial marks, anyway. My impression of Bogs’ device is that to make it accurately, it’s rather more important that you have a lathe set up properly, and that the faceplate has had a skim. The joy of doing this by Bogs’ method is that the DTI’s don’t have to be matched; all you need is a flat surface and to know what the zero point on both dials is when they’re mounted. After that, the setup is determined entirely by how accurately you made the rest of it. Note carefully his comments on turning the bar once it’s mounted on the crosspiece; this is important and ultimately determines the accuracy when using it as described.

 

The good news, I suppose, is that you only need to get the bottom of the dial gauge mounting bar flat somehow – the rest doesn’t rely on the mill’s setup at all. Once you have a flat reference surface to mount on your faceplate, everything else can be done on the lathe, and depends entirely upon the accuracy with which it was assembled. Specifically what it’s relying on is that the cross slide is mounted accurately at a right-angle to the bed, and generally they are pretty accurate in this regard, as long as the gib isn’t loose.

 

The other thing I ought to mention is that with the single-DTI tramming aids, you have the considerable inconvenience of having to read them from the rear (or at least from each side of the mill), and personally, I find that to be rather annoying. 

 

The leading edge of the cut left a very smooth finish but the trailing edge behind the path of the endmill was very rough. I am trying to figure out why this might be but am a bit confused because the mill was travelling along the Y axis which is a plane where the mill cannot be anything but square to the table.

 

You might like to think that, but I can assure you that it isn’t necessarily true. Ask all the people who’ve had to shim the bottoms of their mill columns – they’ll tell you! But also, when the mill is out of tram, you tend to get ‘stepped’ passes, rather than roughness per se – which makes me wonder a bit about the state of the cutter you are using, whether the cut was lubricated, how fast it was, how much you were taking off, etc…

Edited By Steve Garnett on 16/09/2011 13:27:01

[John CoatesParticipant @johncoates48577]

Graeme – thanks for that I’ve saved it in my bookmarks and am busily reading

 

Steve – having read the article mentioned by Graeme I now realise that the mill can be out of tram in the Y axis. This is why I still post in the beginner’s section !!

[Ex contributorParticipant @mgnbuk]

Firstly, I wouldn’t use a drill chuck, they are generally not
accurate enough A collet directly in the quill, or a collet chuck would
be preferable.

 

Why ?

 

Whatever method of holding the DTI on an offset rod arrangement in the spindle to measure the misaligment of the spindle axis to the table will not affect the result – the attachment arm is clamped in the spindle regardless.

 

Don’t run the DTI directly against the table top, but interpose a ground block between the two. This way the DTI doesn’t rattle over the Tee slots – position the DTI & carefully slide the ground block on the table top under the plunger (set the DTI to give around half a dial rotation only so the block slides in easily). I use a roller from a large roller bearing 1/18″ dia. x 1 1/8″ long – with nice radiused corners it slides in gently & doesn’t knock the DTI – but a slip gauge or ground parallel will do just as well. Take the reading, slide the block out, rotate the DTI & repeat. Always re-ckeck your intial position to make sure the DTI han’t been knocked. A small mirror makes taking the rearmost reading easier – but be wary of getting the sign wrong !

 

[Steve GarnettParticipant @stevegarnett62550]

That’s the other good thing about the 2-DTI solution – you can align directly to the mill bed without any difficulty. Which also removes a potential additional error in the form of the ground block. Not the block itself, just the fact that you’ve introduced another metal to metal interface in your measurement.

 

Oh, and a good accurate chuck like an Albrecht keyless is fine, I think. But anything cheap and cheerful that allows even the slightest movement of the rod in the chuck can introduce a potential axial error that may not be symmetrical. That said, with the single DTI method a symmetrical cyclic error should cancel itself out in terms of what you read on the dial when you change position, yes. Wouldn’t want that to happen with the 2-DTI method though, after you’d pre-aligned it on a surface table; you’d be relying on the chuck/collet fixing to be correctly aligned, otherwise it would get rather confusing.

[BogstandardParticipant @bogstandard]

There is a way around the rubber necking problem with a standard DTI. I was informed of this when my twin clock checker was shown on another site.

 

You can buy DTI’s with the clock sitting horizontal on the top, rather than vertical, or you could just use a normal dial indicator with the probe sticking out of the back.

 

But as mentioned, using a single clock does have drawbacks if you want to get a good reading. The main problem is getting it over the table slots, I used to use a bit of litho plate or 100 gram paper to slide it over. Lifting the quill is not an accurate method, in fact the quill should be locked while carrying out the tramming.

 

By raiding my scrap box, I made my double gauge tram for just over 20 squid, the cost of the two gauges.

 

People seem to think that tramming isn’t really necessary, or getting it near enough is fine. In fact, without having your mill in correct tram, you won’t be able to get a truly flat or even a square cut in some situations..

 

Even though I have a larger and more rigid machine than most, the first thing I do when starting a new job is to tram up and check my vice for squareness to the table, it only takes five minutes at most. It is amazing how easily things can be knocked out of wack if you are doing a bit of heavy cutting.

BTW, if you do have a go and make the one as I described, the final face plate work is the secret to getting the tool spot on.

 

John

[Nicholas FarrParticipant @nicholasfarr14254]

Hi John, I have a Chester Champion, and I agree with Steve’s statement about adjusting by eye with the fiducial, they are not likely to be accurate mine certainly isn’t, and as has been said the column had to be shimmed, (a bit of a lobourious task) but before that, I skimmed the mounting point of the base using the table to mount a small milling cobble up I made from a motor from an old Black and Decker lawn mower, just to get a reasonably flat surface for the column to stand on.

 

I trammed mine with a single lever type DTI held in a collet and onto the table in its mid position.

 

Regards Nick.

[Stewart HartParticipant @stewarthart90345]

I built one of those two dial trams following Bogs methods, worked out great.

 

The critical part is turning the bar up square to the base, best way is to face up a chunk of ally clamp the tram to this and gently turn the bar up with a sharp tool, don’t be tempted to use a running centre this will pull the bar off square, that way it must come out square.

 

On my first attempt I used a running centre and it didn’t come out square, Bogs told me where I went wrong, and my second attempt came out perect.

 

Its a great bit of kit to have arround you quick and simple to use.

[IMG]http://i431.photobucket.com/albums/qq32/sbwhart/Tram/100_1520.jpg[/IMG]

 

Stew

Edited By Stewart Hart on 17/09/2011 09:24:24

[John HaineParticipant @johnhaine32865]

I use a piece of 6 mm plate glass on the mill table and sweep the DTI over that so the plunger doesn’t drop in the tee slots. Float glass is extremely flat by virtue of the way it is made, but you can check your piece by setting up the DTI in the mill spindle as if to tram, lowering it to get a convenient reading on the dial, then rotating the glass rather than the spindle. My bet is that you won’t see any change in the dial reading as you do so. If not then go ahead and tram the head.

 

I have to say (now it can be said) that I found I had to tram the column on my (bought new) Myford VMB because I was getting a similar effect. When I loosened the bolts on the column foot I found that one was held in only by paint – the hole had obviously been drilled oversize before tapping and the thread stripped when they tried to tighten it. Of course the VMB was made in Taiwan and “fettled” in Beeston, but they obviously missed this one. Myford offered to fix it f.o.c. if I transported it back…..

 

So in the end I just fitted a longer bolt with a nut underneath (actually a spare Tee nut so it would engage the inside of the base casting so could be tightened without a spanner). But I had a strange feelinthat you shouldn’t have to do that sort of thing with a Myford.

[John HaineParticipant @johnhaine32865]

…and by the way, it’s much easier to use a “finger type” DTI rather than a “plunger Type” since you can mount it on a mandrel so the dial is horizontal facing up, and you don’t have to peer round the back of the mill to see it.

[blowlampParticipant @blowlamp]

Posted by John Haine on 17/09/2011 17:36:30:
…and by the way, it’s much easier to use a “finger type” DTI rather than a “plunger Type” since you can mount it on a mandrel so the dial is horizontal facing up, and you don’t have to peer round the back of the mill to see it.

 

 

+1 on this way of squaring the spindle and is the way I do it – very simple too, with no need for anything else in my opinion.

 

 

Martin.

[BogstandardParticipant @bogstandard]

Commercial dual gauge tramming tool

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