Mill Tramming Complications - Debugging Help Required

Not too long ago I set my Warco Super Major's head to 45 degrees for some 'V' milling.

[Project 3] Dickson T1 Tool Holder

Afterwards the head retrammed the head to within 0.015mm over a swing of 480mm.

Jason told me I could/should do better, so I had another go yesterday.

The good news is I managed to get to a point where there was no visible variance over ~300mm using a 0.01mm DTI.

[VIDEO] Head Tramming

Also tested from the back to the front of the table where I obtained a result of 0.01mm over ~300mm.

Probably not worth shimming for this:

[VIDEO] Head Tramming (Back to Front)

However, I decided to go further and read some odd results.

Firstly I indicated the vice to 0.01mm over ~75mm.

Not great I thought, but could be a ding in the table or a chip in/under the vice:

[VIDEO] Indicating Vice

So I decided to indicate the table. Similar results as the vice (despite potential cosine error):

[VIDEO] Indicating Table

Much more alarming however are the larger numbers obtained when indicating the Z:

[VIDEO] Indicating Z (left to right)

[VIDEO] Indicating Z (front to back)

My understanding of what's going on is that the table is "on the wonk".

Sloping down from right to left.

Some input some of you guys with vastly more experience/knowledge would be gratefully received.

Lee, firstly how square is your square & it needs to be clamped to the table to eliminate the vice adding errors. Clamp the square to the table & take your readings, then rotate the square 180 degrees & take the same set of readings of the same square face, the readings should be the same if the square is spot on, if not get a better square. On first viewing it seems that the spindle axis is not in line with the Z axis so it can be trammed spot on but you then switch to getting a Z axis travel error.

Tony

Lee,

You probably need to check your vice for jaw lift and your table has quite a few chips on it in the later video.

Is the fixed jaw on the vice the same?

Lee and Tony

I have watched a number on U tube videos by David Wilks---he makes large diameter trepanning tools to bore holes up to 12 inches diameter or more and straight over 5 feet or so in difficult materials.

He makes these tools on a Bridgeport milling machine and trams it square after angling by the simple means of butting the spindle nose down to the table and gently locking the holding bolts on the ram while keeping it in contact. He does nothing more and it takes minutes to do and then carries on with the job.

An alternative which I have used myself is to fit a lathe faceplate to the nose and bring that down flat on the table, holding it there while the bolts are tightened. Again, just a few minute's work.

0.015 mm is only 0.0006 inches [6 tenths] barely an error and surely good enough.

Regards Brian

Edited By Brian Wood on 06/12/2020 11:19:03

Brian, I agree the tram error on Lee's mill is nothing to worry about so I didn't mention it, I was just trying to address his question about the Z axis error.

Tony

I watch David Wilkes too, the method Brian described should be good enough, out of interest, what DIN rating is the square you're using?

It looks like you are moving the whole head up and down in the last test with the square and DTI. This indicates the vertical column is not square to the base and the table. Its a common problem on cheap Chinese mills when they arrive new.

Cure is to scrape or shim the base of the vertical column where it mounts on the base until you get a good reading on your square (and +1 on Tony's suggestion to clamp square down and check it from two directions to verify squareness. )

Once you have the column square to both X and Y axes, you can then go ahead and set your tramming on the spindle. Note Brian's good advice on striving for unnecessary perfection below about 0.025mm over 300mm.

Be careful too of taking readings off those cheap "hobby grade" Chinese 123 blocks in your vice there. They have been known to be manufactured out of parallel and out of square by a fair bit. Take your DTI readings directly off the vice base where the job sits and fixed jaw vertical face. (And check your 123 blocks carefully with a square and micrometer to make sure they are square and parallel.)

Edited By Hopper on 06/12/2020 11:55:19

The square is DIN875, and was weighted down (rather than clamped) directly to the bed.

I just checked again with the square 180 degrees (both directions) the reading was exactly opposite.

So yes, it's looking like the column is not square to the table. I guess I'll have to shim it *sigh*.

I checked the 123 blocks with a tenths indicator on a surface plate before using them. Not even a flicker.

Excellent work. (Clamping the square would be better though.) Now you have a little project fettling your new mill. I'm sure there must be threads on this or other forums or YouTube videos on setting up the column, it's such a common problem on the cheap Chinese mills.

Sometimes you can get lucky and its just some paint or burrs etc between the two mating surfaces but most often they seem to need shimming. Can be quite a test of patience as a very thin shim on one side of the base translates to quite some movement at the very top of the column. Bit of work with a tape measure and your DTI and you could probably calculate what shim you need on a right-angle triangle ratio calculation. To a ball park figure anyway. Final super fine adjustment can even get down to just how hard you tighten down the base bolts on one side vs the other.

Edited By Hopper on 06/12/2020 13:09:15

How does this look, from a back of a fag packet perspective?

For what my advice is worth, take measurements with as few items involved as possible. Every extra part includes a possible error. So, no vice, or 123 blocks.

The most extra that I would do for tramming would be to have a piece of gauge plate, or a known (Measured ) parallel to bridge the Tee slots. If in doubt, measure it so that you know what, if any errors / out of flatness , is involved.

The table is unlikely "To be on the wonk", but as Hopper says, the column may well be not be vertical. It could be out in, one or both, X and Y axes.

So you could find an acceptable variation in,say, the X axis, but still be way out in the Y axis.

Once you have shimmed the column to give acceptable errors in X and Y axes, then you can start checking the vice for the base being truly parallel to the Table. The fixed jaw will need to be clocked, and the vice body gently tapped to and fro until a Zero reading is obtained at both ends of the jaw.

To avoid having to spend time winding then table to and fro and adjusting, every time that the vice is fitted, it may be possible to fit tenons, or dowels to the underside to ensure correct alignment. If this is not possible, you can make up a "Goalpost" type fixture to align the vice before clamping it down. This is the method that I use.

The fixture involves little precision machining, (Just the base of the two pillars ) followed by a skim along each side of the top bar.

Once the Mill has been trammed to your satisfaction (Remember that this is a lightweight hobby machine, NOT a Tool Room Jig Borer ) you can start checking your 123 blocks and whatever else you fit to the machine IF that is what you want to do..

You have to make some assumptions. The first being that your measuring equipment is accurate and consistently repeatable.

If it is not, you are on a hiding to nowhere, and replacements, in which you are confident, have to be found.

Howard.

Once you have sorted tram and column you also need to look at the quill travel. Expect to have to make a compromise between head movement and quill movement, I opt to get head movement as good as possible as that is what I tend to do any milling or boring with.

It's not easy to get a perfect setting as to allow the head and quill to move they need to be unlocked, as soon as you lock them up the slight clearances that there must be to allow things to move will be taken up but the locking action and throw your reading out..

I think this is an important topic for us beginners, or really anyone who is using old/word machine tools and/or machine tools at the budget end of the range.

I mentioned this in one of the many ML7 setup threads I seem to have started: It would be great to have a resource that shows how to set up things to the best compromise. As you say, you can set something up perfectly in one position, unlock it and re-position it and it’s out.

Short of setting up every time (which is fine for critical work), what are the important settings? What tolerances are acceptable for say, tramming a mini mill, or setting a worn tailstock? What sequence of adjustment is optimum? I’ve spent hours chasing perfect settings which in hindsight are impossible, and I suppose often unnecessary in the first place.

From bitter experience I agree with Jason's second paragraph. The difficulty I have with setting a Z reading on my mill and having the same reading after I have locked the quill is so frustrating and maddening. It also means that any work I do must not involve moving the quill very small movements and then locking it, another means must be found where the quill remains locked and the movements are in X and Y axis!

Chris

It's out by 0.5mm over 180mm????

Holy leaning tower of Pizza, Batman. That's bad, even for Chinese junk. One heck of a shim you need there at over 0.75mm.

You might want to double check everything and make sure. Then try to determine if it's the column or the machine base thats been machined wrong and think about getting it remachined by someone who knows how to use a square.

If your machine is still under warranty now is the time to contact the seller. If they swap you for another machine, check it to as these things tend to be done in batches all the same and it's not unheard of for the replacement to suffer the same problems as the original. 

Edited By Hopper on 06/12/2020 23:33:54

Yes, do need to watch those decimal points, in the other post you said 0.1mm over 480mm not 0.015mm which I probably would not have worried about.

Your current 0.01mm over 300 is no different to 0.015mm over 480 give or take a micron.

Edited By JasonB on 07/12/2020 08:33:28

Don't mess about with converting to degrees and back again. Use ratios. 0.5mm over 150mm is the same as 1mm over 300mm. For your example the shim required would be 0.5 x 260/180 = 0.722mm

Also read up on soft foot. This occurs if the mating faces between base and column are not plane surfaces. Basically if loosening and tightening one bolt at a time causes the column to move you probably have a case of soft foot.

If you start moving the bolts holding the column to the base a torque wrench is often recommended to get repeatable results.Also tighten the bolts in the same order each time may be a good habit.

The machinists in the toolroom where I worked always used a fine flat stone on their machines and tooling to remove any dings or burrs before use. A light touch and figure of eight motion was all they did, they judged by feel if there was a problem with the surface so did not do more than one or two light passes. They were of course using very large rotary tables or dividing heads that were positioned by cranes and could easily ding the tables.

Martin C

Just remembered that if you tram in a pattern that matches the bolt holes then the shim value is as read on your dial indicator. So for 260mm given above measure over 260mm if possible or 130 to make a simple multiplication to work out the shim required.

Edited By Martin Connelly on 07/12/2020 08:48:33

The 0.1mm result was using the long janky brass set-up:

After receiving the collet held indicator holder from Arc, I dialled it in a lot better.

This time I have it to probably <0.002mm.

I converted to degrees to obtain the shim stock thickness required. Not sure how to do that with ratios.

It's not currently possible to move the bolts at all with the tools I have. I've since ordered a large 12mm hex key.

I'm also waiting on the arrival of a Norton India Stone funnily enough!

I'll try the tramming trick too to double check my initial results.

Thanks all!

Unfortunately, I bought it in July last year.

Not sure what else to check.  These are the test videos:

[VIDEO] Z Test (indicator facing right)

[VIDEO] Z Test (indicator facing left)

Edited By Lee Jones 6 on 07/12/2020 09:19:24

The formula is in the post above for shim stock thickness.

error x distance across shimmed distance / distance error was measured over = required shim thickness

0.5 x 260 / 180 = 0.722

Martin C