Adjustable Y tram for Emco FB2 mill

The Emco FB2 is a good mill overall although it has it’s fair share of misalignment here and there. Most of them are very acceptable except for the tram along the Y axis which is 0.05 mm over 150 mm. With this amount I got steps on surfaces milled with tool ends ( facing heads or end mills ) . As I have got more spare time recently due to the lock down, I decided to do something about it.

Many has suggested scrapping but this is absolutely not an option for me because I lack the skill and the change is irreversible. It is highly likely that I will end up in destroying the machine instead of fixing it.

Grinding is another option but I have to get another machine to do it. Not possible for me.

Then I came up with the idea of using the machine to fix itself by making a wedge shim to be placed at the joint between the vertical slide block and the mill head. The only difficulty is that the shim has to be precisely made with one side exactly 0.037 mm thicker than the other side. After a bit more thinking, I realized that such precision is actually not necessary if the shim can be rotated hence the shimming angle can be adjusted in a stepless manner.

The shim is made from 2mm thick cold roll steel plate. It is held on an inclined 15 mm thick steel backing plate by super glue to allow machining to be done. It can be seperated from the backing plate simply by heating . The tap sticking out at the side allows the shim to be rotated and Y tram adjusted. It works extremely well. For the very first time, the X and Y tram of the machine is close to perfect.

Edited By Y C Lui on 19/03/2022 13:51:31

That's very ingenious. Keep us posted how it works when you make some test cuts or setup the tramming.

And very wise decision about not scraping it as a beginner. It is one thing to be able to make pretty surface patterns with a scraper. It is another to be able to make a machine tool more accurate by scraping it. Scraping used to be a four year apprenticeship in the old days. It's not something that can be learned in a weekend or three.

Scraping used to be a four year apprenticeship in the old days.

4 years was the "modern" reduced time apprenticeship - the "old hands" here did a seven year stint !

Neat, non-invasive solution to your alignment issue. Nice clean machine as well.

Nigel B.

Interesting concept.

However, unless I am misunderstanding the issue completely.... I trammed Y on my FB2 by shimming the column base mounting at the 4 attachment bolts that fasten the base to the XY axis base. Simply add shim stock to under the top bolts to tilt rearwards, or under bottom bolts to tilt forwards. Much easier, and keeps the head square on to it's tilting ring.

Joe

They are two seperate requirements that need be satisfied simultaneously.

1) The column has to be perpendicular to the XY plane or the XY position of the spindle relative to the workpiece will shift when the height of the mill head is changed for such purposes as accomodating a longer tool or measurement device. The column of my FB2 is slanted backward by 0.02 mm over 90 mm which is not too bad. Shimming the column base will fix this problem.

2) The spindle has to be perpendicular to the XY plane ( defined by the X and Y rails, not the table surface ) or steps will be created on milled horizontal surfaces.The shim is designed to fix this problem.

If I shim the column base only, the column will slant backward more. While this can eliminate the stepped surface problem, the Y position shift of the spindle due to change in Z will become more severe.    

Edited By Y C Lui on 19/03/2022 17:38:26

I understand - I did not have that problem on my FB2's - A test bar in the spindle morse taper run up and down with a dial gauge fitted to the column showed less than 0.008/0.01mm delta, so the head is nicely parallel to the column on my machines. Shimming the column perpendicular to XZ sorted my tramming issue.

Joe

After some adjustment of the shim, perfect Y tram is achieved at this position :

These are the test cut results. Material is 6061 aluminium. The surface is milled with a 63 mm diameter facing head. Two passes seperated by 60 mm are done, Then the flatness of the machined surface is checked by dyeing the surface of the mill table and rubbing the workpiece against it. There is no step. This is the very first time I saw such beautiful surface created by the machine.

This was before the adjustment : 

Other than the elimination of steps on machined surface, the improved perpendicularity of the spindle also brought substantial reduction in the XY position shift of the tool tip relative to the workpiece when the length of the tool is increased and the head need be moved up to accomodate the tool.  

Edited By Y C Lui on 21/03/2022 11:00:58

I am not that lucky unfortunately. My FB2 has compound misalignment ( slanted column + head droop ) as depicted below   

Edited By Y C Lui on 21/03/2022 10:49:04