VMC Mill alignment

I have a Warco VMC mill it's not had too much use from new but have noticed an alignment problem.

Have looked at previous posts on how to align this is what I have.

Winding the table up and down the dial indicator shows no deflection on the vertical face of the machine vice.

When I wind the head down even with it being tightened to allow for any slop in it the DTI shows o.oo2" over about 2" vertical vice jaw.

It seems the head has a sag towards me everything is bolted tight

Any easy way to sort this

Just to be clear do you mean lowering the quill and are you doing this with the lever or the hand Wheel?

As a point of interest I was taught never to use the quill when milling but always to raise the table. Are you putting on a cut by moving the quill and if so has this shown up any errors in your work?

To be clear you will spend many happy hours on this quest but you will need to understand the theory of what is occurring.

To get you started you will need a truly square machined block not the vice jaw, your current readings are telling you something but what?

I would suggest you spend some time reading up on machine tool alignment. Good luck!

Tony

Your description, assuming you're measuring technique is reliable, suggests that the top of the table is square with the body of the machine and the head is where the error is. It can either be at the join where the head swings left and right (yaw), or the join that allows the head to roll not being square, or all the above is fine and the quill itself is not bored squarely with the rest of the machine. I had a similar problem but since I don't use the roll or yaw, I put a thin piece of shim brass (maybe only one and a half thou) in the lower part of the join that allows the head to roll. The shim is quite wide so I get a solid triangulated joint when bolted up. It's been like this for at least five years without issue and beautifully square machining.

Edited By Chris Trice on 16/03/2019 21:32:58

Have lowered quill both ways and still an error there has been a slight error on some work.

In future will just raise the table thank you.

It’s not uncommon for errant paint to cause a problem like this. In the first instance it may be worth removing the head assembly from the column and checking that all mating surfaces are clean and flat. It’s a job that’s easily done with an engine hoist!

I would think the critical point is that the quill is square to the table, tramming the spindle to the table should be informative, indicating the quill against the machined ways of the column should not have any error. The vice is adding an unknown into the checks as even if it is known to be true in itself it could still be sitting on a burr or dirt on the table. Taking measurements of machine accuracy is fraught with the problem of exactly what you are measuring and testing for. It’s worth having a good think before pointing a finger at an inaccuracy.

Mike

I think you’re right Mike, I certainly wouldn’t be confident about checking my machines for accuracy without the proper training and equipment. About the only thing I do from time to time is clock the head of my mill after moving it.

A half decent CAD program able to rotate things and set small angles can be a great help in figuring out what is going on.

Do a sufficiently representational drawing and rotate things, using suitably scaled up angles, to match equally scaled up lines drawn to plot out the DTI readings. Probably X10 or X100 will work depending on how the CAD program zoom control behaves.

I find it a good way to get a feel for how much error at the mating surfaces corresponds to the measured deviations when moving things. Great help when shimming.

Important to be really methodical. Write down the error, what you think caused it, what you tried to fix it and what the results were. If you start off on the wrong foot its really easy to wind into an endless loop introducing more errors to compensate other errors. Don't be afraid to go back to where you started from and try again from the beginning.

Clive.

Winding the Knee up and down I would expect the same reading.

What you do not say is whether you "Locked" the Knee for your "Quill Test"?

If the knee was not locked, then I would suspect play in the Knee Gib and this is allowing the Knee to drop forward.

However there is the assumption that the vice jaw is vertical, it may well not be.

To perform an alignment check of this nature you really need a "Cylinder Square". Using an ordinary "Bench square" will introduce errors as each square has a small inbuilt error from the manufacturing allowance. This however should be better than the vice jaw.

Homemade cylinder square shown below with the plastic knob, all it needs is careful turning.

Regards

Gray,