Setting up mill

Hi I spent this afternoon trying to get a better set up / understanding of my mill.

First I checked x axis witch is fine, I the wanted to check y, I put a new brake disc down , the checked y found it to be out by 0.02mm really happy. Then things started to happen.

when I zeroed my DTI buy lowering the head, started to turn the spindle it dropped by 0.3mm, this did not happen when I raised the head.

I started to look and can get 0.3mm free play in the spindle, so thinking I should tighten the spindle using the clamp at the head, great it stopped the movement, but now I have 0.08mm over 150mm swing on the y axis.

is there something else I could try and get rid of the 0.3mm on the spindle.

couple of photos to show

Do not accept that the brake disc is perfect. I have measured new ones and they can be several thou' out. I would suggest you tram the table 1st using either the table itself or a known good large parrallel.

Try to use an indicator in a collett in the spindle. IMHO The holder you are using is not the best way as they are not as rigid as they seem.

regards

Definitely take off the fancy looking green disc, is the .3mm free play with the spindle locked?? Tram off the table itself with the spindle locked, using an nicely ground object to bridge the tee slots.

Tony

Hi when the spindle is locked there is no movement, I can check off the table, but why a difference when I lock or unlock using the same disc and not moving it?

I would guess the quill is loose in the mill head & tightening the clamp pulls it to one side? As I said check the tram with the quill locked as this is the way you mill.

Tony

Edited By Tony Pratt 1 on 04/02/2021 17:26:31

I will set up a system tomorrow to check from a collet in the spindle, and have it locked, just thinking what I can do to bridge the tee slots

Vee block, parallel, gauge block, something like that. Even the top of that angle plate.

Tony

Edited By Tony Pratt 1 on 04/02/2021 17:28:32

Thanks Tony, if the quill is loose can this be fixed adjusted?

I always have some drag on the spindle to take up as much slack as possible but too much will cause backlash. Is the spindle sprung to lift when released or to lower when released? The normal situation for a drill press is sprung to lift when released. Due to the forces on a milling cutter it is often recommended to have a mill set so that it drops down onto the spindle raise/lower gearing so that it is held against the pull down forces, the spring just reduces the effort needed to raise it. A mill drill causes issues because it is used for both roles.

The worst situation is probably a balanced setup where the spindle is not pushed either up or down by the spring and the spindle can float between the limits of any backlash.

Martin C

6mm float glass plate.

Not really, if the quill is moving about in the bore because of excessive clearance there isn't much you can do about the situation, when you are machining [milling] the quill should be locked anyway that's why I said tram it in the locked condition. Obviously the quill is unlocked when drilling.

Tony

okay could not wait until tomorrow, this is the set up and this is what I have found.

spindle locked. Zero as shown, when turned 180degrees it shows 0.1mm out,.

spindle unlocked zero as shown, 180 degrees 0.09mm so not much difference. But movement on the spindle 0.3mm

is 0.1mm over the width of the table acceptable?

Also noticed if I pull or push the head I also get 0.1mm of movement

Ok, just a small point but have your DTI stylus nearly horizontal not nearly vertical as you have it now. I would not be happy with .1mm over the table width but that is me, if you want it better then you will need to shim the base which holds the round column, there are multiple threads on this subject. Your mill is not a heavy weight job so you are able to flex it by push/pulling the head.

Tony

Hi thanks very much for your comments Tony, think the best thing out of all this is to understand the limits of your equipment, shimming the column is a possibility, think I could look at how the bolts have been torque down.

if I can’t get it better what about shimming the vice when I put it on? Also if I can’t get better least I know the error and possible manage the limitations.

regarding the mill itself nothing I can do, again know the limitations of the machine.

agian thanks for help, I am just trying to get better, more accurate least to max out limitations of my machines

Check the column to base bolts are torqued properly.

It's possible to adjust tram on a 'non adjustable' mill by changing torque values (if that doesn't work you may also have to shim different quadrants of base)

I got my mill drill with an 'inspection chart' that was pretty worthless but eventually got it near perfect by thinking about which bolts to tighten and loosen. The various sections of cast iron will distort tiny amounts but can be set pretty accurate (less than0.01mm over 8" swing)

Sorry to be swapping imperial / metric but I was brought up on imperial measurments and trained as metric was being introduced so have little trouble switching between the two(I'm sure there are plenty of us 'old duffer's' who do the same?)

Just noticed the post directly above mentions the samwe thing about column  bolts but didn't see it while I was typing (and running around doing 'other stuff)

Edited By Peter Jones 20 on 04/02/2021 20:05:45

Hi Dullnote, shimming the vice to suit the head will not cure your problem but it will create another one in that the vice working surface will not be parallel with the table movement so you will end up with tapered work. Machine geometry isn't always easy to understand but it is all interconnected to each other.

Try the machine out on some metal & see how you get on then report back.

Tony

As Tony said the DTI probe needs to be close to horizontal if you are you get anything near accurate height measurements. The cosine error with the probe as close to vertical (as seen in your picture) must be significant!

A plunger type indicator is possibly a more suitable device if you want to measure absolute distances, lever types are good for comparative readings but since you are using a block under the probe that will allow the probe on your DTI to be set parallel to the table surface so the height readings should be quite accurate.

I usually indicate directly of the table surface, sicne we are only looking for height changes in tenths of a mm I have never found the 'T' slots gaps a problem as the probe ball tip will cope with half a mm easily.

Ian P

Update, been working on the mill today, after shimming and torque the bolts I have the y axis at 0.02mm over 150mm, which I think is a great improvement from yesterday, worked in the x axis and over 500mm I have 0.06mm. Change my DTI to plunge type held vertical to give better results

this is with the quill clamped, so I think the will be better than my machining capabilities. Theses measurements were taken with the quill and head in low position to the table, out of interest I raised the head and extended the quill to full amount, no great deal of difference possible 0.01 added to both readings.

no doubt next time I use the mill it will shake itself out of calibration, learned a lot today, Thanks a lot for all the help and advise. I think I will use the mill and try blocking out some material for another job, see how that goes and if need revisit.

brake discs has a runout so are not truely flat, this is push the brake pads back into the calliper slightly when you are not applying the brake,