Mill Alignment

[PeeWee]

Hi All,

i have what i think is a silly question, but i have to ask so feel free to take the mick 

I borrowed and engineers level etc to level and true up the mill at the weekend, however i am alarmed that i require 7mm of lifting at the back to level the front/back axis (level on the table). on a Warco WM18 this leaves a lot of weight on the smallish shimming areas. 

My question is, would i be better to leave the bottom casting fully in contact with the bench and simply ensure the column is true to the table in all axes according to Bogs article http://www.homemodelenginemachinist.com/index.php?topic=2641.0 second section ref the table and vice settings?   I know this is far from best/ideal practice but i am concerned by the weight being concentrated in a too small an area.

regards

[Jasonb]

I'd use jacking screws in the four mounting holes to set the table level and then just adjust the column the small amount if any to get it to tram true to the table.

Jason

PS how level is your bench, is the 7mm due the the base of the casting not being true to the table or the table sitting on a sloping bench?

[PeeWee]

i'll check the bench out, it was level when i built it but then the floor is uneven and i could have moved it onto either a lump or dip.

[Bogstandard]

Ian,

It is more important that your lathe is level and without twist rather than the mill.

The most important part, as Jason stated is the tram between column and table.

The main reason for levelling the mill is to reduce moving strain, and thus, expected wear on the bedways. As I have a very heavy table on mine, that is why I went to such lengths, but even now it isn't perfectly level, now it has settled, somewhere around 0.003" over the 36" table length. To me, it isn't far enough out to justify me going to the effort to get it spot on. Quintuple that figure, and I personally, would start to worry about levelling it up again.

If I was you, I would concentrate more on getting the level only near enough (one or two marks out on the bubble), but still making sure that the base is rock solid, then concentrate on getting your column perfectly in tram with the table, both front to back and side to side, then your vice jaws completely parallel to the table and square to the quill in all directions.

If you get those bits done, you should find you will be able to machine to very good standards.


John

[PeeWee]

Thank you all for your comments. I checked the bench out this morning and believe it or not the back leg is indeed in a dip.

I shall put some plating under the back legs to reomve most if not all of the drop and then remove the shimms and start again.

[latheman]

Hi,

I'd like to, er, sort of hijack this thread a little bit.

Now, I know about setting up the lathe BED to turn parallel and that is easy enough especially when the feet are as far apart as they are and one can turn something to check it. But, how do you check that the mill BED is, or isn't set up correctly. As I see it, tramming and what is it, nodding ?, are all to do with the table to head relationship, yet I could see that if the base was twisted, this could throw things out before we even think about tramming etc. As much as anything, I'm thinking of the back to front movement (Y axis?) causing the X axis to possible tilt as the table is moved in the Y direction.

In my case, I bolted the thing down with 4 bolts through about 3" of wood and steel so heaven alone knows how level it is. I must admit, I assumed that any twist in such a small area would be negligible. It's an X2 clone by the way.

Regards,

Peter G. Shaw