Milling Table “fault”

[Roger Williams 2Participant @rogerwilliams2]

Hello all, on my milling machine, an Emco F1P, I have found which I presume is not right, nearly 0.010 inches discrepancy over 5 inches of travel on the Y axis. The parallel I am using is perfect, there is no lift in the table and is fine on the X axis travel. Not knowing a great deal about mills, I am guessing that the top surface of the table isnt parallel with the bottom across ways so to speak . Oh, and the top surface of the table is unmarked.

I would be grateful for anyones help. Many thanks.

[Roger Williams 2Participant @rogerwilliams2]

[Neil WyattModerator @neilwyatt]

I'm always suspicious with indicators mounted on long arms like that,. can you mount it directly (or more nearly directly) in the spindle. Also reverse the parallel and try again, just in case.

Neil

[Pete RimmerParticipant @peterimmer30576]

It's far more likely to be the column that's out of perpendicular to the y-axis ways. Does the column bolt to the base?

[Roger Williams 2Participant @rogerwilliams2]

Neil and Pete, yes I will try out your suggestions. I have thought about the column being out ( it is bolted ), but cant see how it would make any difference, however, I will definitely try it . Hope Im proved wrong !!. Many thanks.

[Tony Pratt 1Participant @tonypratt1]

If you are traversing the y axis under an indicator the column being 'out' or not will make no difference.

Tony

[SillyOldDufferModerator @sillyoldduffer]

I've noticed quite a few reports of mills and pillar drills having a slight forward nod. Is it possible on the lighter machines that it's deliberate in that the column is designed to straighten out when cutting pressure is applied? My cheap pillar drill has a distinct forward lean, but it still drills vertical holes. Sticking a DTI on it shows it straightens up when pressure is applied to the drill.

Making a machine completely rigid is hard. Compensating for bending in use might be a clever way of keeping costs down. Obviously the result will be inferior to a truly stiff construction, but perhaps it's acceptable considering the reduced cost.

Dave

[Pete RimmerParticipant @peterimmer30576]

Posted by Tony Pratt 1 on 03/08/2018 17:57:33:

If you are traversing the y axis under an indicator the column being 'out' or not will make no difference.

Tony

Tony you're quite right, I had a senior moment there. I'll blame it on the heat, or the hard day at work etc.

[Gas_mantle.Participant @gas_mantle]

Do you get a similar reading across the table when measuring at each end ?

[Roger Williams 2Participant @rogerwilliams2]

Gas mantle, yes I do. The parallel itself is accurate to a couple of tenths over its length and the Noga DTI set up is rigid. Ive had the mill for about 10 years , this being the first time Ive noticed this error. The reason Im checking now is because a milling vice (5 inch width ) I machined 2 years ago, checks perfectly along its length, but 10 thou out across its width, the length clamped to the table on the X axis during the job.

Im beginning to think that the mill was sold because of this fault.Im convinced just about , that the table will need regrinding. Oh bother !.

Edited By Roger Williams 2 on 03/08/2018 22:43:28

[duncan webster 1Participant @duncanwebster1]

Can you masure the thickness of the table from top to bottom sliding surface front and back. If the 2 measurements are the same then I think the fault must lie elsewhere

[Paul LousickParticipant @paullousick59116]

Hi Roger,

"I've noticed quite a few reports of mills and pillar drills having a slight forward nod. Is it possible on the lighter machines that it's deliberate in that the column is designed to straighten out when cutting pressure is applied?"

To check if this is the case, machine a test piece and check to see if it is thicker at one end. If the column is bolted to the base, you can shim one side to make it vertical. Also do a Google search about fixing your mill problem. Lots of examples on the net.

Paul.

 

Edited By Paul Lousick on 03/08/2018 23:11:43

[I.M. OUTAHEREParticipant @i-m-outahere]

Do you have the X axis locks applied ! If not try it and if the problem dissapears or lessens your table may be bowed on one side .

The next step is to determine where the problem lies , is it the table and / or the X axis slideway out of kilter or is the Y axis slideway the issue ?

If the table is just a bad grind – thicker on one side than the other you could get it re ground at a reasonable cost .

I have heard of some machinist doing a fix themselves by using a face mill to re machine the top of the table .

[Roger Williams 2Participant @rogerwilliams2]

Duncan, Paul and XD351 ; as you are all saying, Ive got to measure the thickness of the mill table for a start and then the table underneath too if necessary. Im getting the same error all the way along the mill table. Im going to remove the table and put the parallel on the table below it and measure that, the Y axis, if that makes sense. It seems that one of them needs regrinding. So much for Austrian quality control. Thanks toi all.

[SillyOldDufferModerator @sillyoldduffer]

Before tearing the machine apart Richard, have you confirmed that the lean causes a problem in practice? Although you're probably right, it's remarkably easy to be led astray by when testing machines, and also easy to misdiagnose causes. If it ain't broke, don't fix it.

Also, if you haven't already done so, check everything. For example, does the DTI in your test set-up register any movement when you push the column?

It may be you have a wrongly ground table from new, but that seems unlikely. It could be due to wear, but the table top being clean suggests otherwise. Unless, that is, the top was reground badly in the past by a dodgy salesman to make it look good! Most likely, I feel, is that the column/head has moved in transit and you may be able to fix it by shimming.

I think it's worth spending some time checking work made by the mill, and also taking more measurements to pin down the cause. Apologies for wasting your time if you've already done all that!

Dave

[anthony smith 4Participant @anthonysmith4]

HI ROGER LOOKING AT YOUR PHOTO OF MILL THE HEAD IS TILTING TO FRONT OF THE MACHINE I WOULD SHIM THE FRONT OF THE COLUMN WITH A FOUR THOU SHIM MOUNT THE DTI IN THE CHUCK

AND CHECK AGAIN THIS WILL TELL YOU IF YOU HAVE TO INCREASE THE SHIM OR SHIM THE REAR OF THE COLUMN CASTING

[Paul LousickParticipant @paullousick59116]

Roger,

If the discrepancy is similar for the whole length of the table, it is probable that the column is not perpendicular to the base. Either the mounting pad or the base of the column has not been machined square. It is easily fixed by smimming one side of the column base to make it vertical. This will require a bit of trtial and error to achieve the correct thickness of shim material. If you do not have the exact thickness of shim for packing one side only, you may have to pack both sides with differen thicknesses to achieve the desired thickness between front and back.

This is not an uncommon problem with lots of examples published on the internet.

Paul.

[HopperParticipant @hopper]

Could it be a bit of swarf, packing gunk, paint, burr or the like on the dovetail slides under the table, or under the X axis slideways?

Is this a new machine? Has it been used at all? Did it machine square if so?

[Nick HughesParticipant @nickhughes97026]

If the OP was holding the DTI in the spindle and then rotating the spindle by hand, then the error would be the column, but as he is not and just moving the Y Axis then the error is in the table.

0.010" is nothing to worry about IF you're happy producing wedge, or parallelogram shaped parts. However if you want to produce accurate, square work then it needs correcting (and THEN also check the Column alignment, shimming if needed)

Nick.

[Mike PooleParticipant @mikepoole82104]

Providing the column and indicator are rigid and you are seeing the error when you wind the table in and out then I would strip the X and Y axis and check there is no foreign bodies or dirt or damage to the slides. After a good clean and inspection reassemble the first layer and check that the table guides are true, if they are ok the refit the table and check all the gib strips are in the right way as they can lift a slide if they are the wrong way up. While it is all apart and clean it should be easy to take some measurements to establish that the parts are machined correctly. I would find it surprising if the parts are badly machined and you are probably going to find a foreign body or an assembly error.

Mike

[EmgeeParticipant @emgee]

Hi Roger

I'm surprised that if using the mill for 10 years you haven't noticed thickness differences back to front on parts made during that period, it does seem that either the Y axis base slideway is not ground on the correct plane or the table surface is not parallel to the slldeway, either way for accurate parts you need to rectify the problem.

Emgee

[Nick HulmeParticipant @nickhulme30114]

Posted by anthony smith 4 on 04/08/2018 09:53:35:

HI ROGER LOOKING AT YOUR PHOTO OF MILL THE HEAD IS TILTING TO FRONT OF THE MACHINE I WOULD SHIM THE FRONT OF THE COLUMN WITH A FOUR THOU SHIM MOUNT THE DTI IN THE CHUCK

AND CHECK AGAIN THIS WILL TELL YOU IF YOU HAVE TO INCREASE THE SHIM OR SHIM THE REAR OF THE COLUMN CASTING

Unless the head lifts as the Y traverses this will make

NO DIFFERENCE AT ALL!

😀

[Roger Williams 2Participant @rogerwilliams2]

Hello all, Im taking it to pieces tomorrow. The reason Ive come across this error now is because Ive always assumed every thing tobe correct, until I measured a piece I had machined for accuracy and was shocked. The DTI base is clamped under the head, rigidly too. Ive reasoned that if the column, which is bolted up solid, were at 45 degrees to the vertical, it wouldnt make any difference. Unlikely I know !.

The mill is in supeb condition, and not really over used. I did most of my machining using a Jones and Shipman vice (stupidly sold!!!) which is probably why I havent noticed anything . All the later work ona vice machined from castings by me, which is out on it sliding surface by this 10 thou .

Anyway , everybodys advice is much appreciated. Thanks.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Nick Hulme on 04/08/2018 17:22:35:

Posted by anthony smith 4 on 04/08/2018 09:53:35:

…

Unless the head lifts as the Y traverses this will make

NO DIFFERENCE AT ALL!

…

Nice one Nick, I've been educated.

My earlier point was about the risk of misunderstanding measurements. How ironic that it was me who was confused. (Again)

Dave

[Ian HewsonParticipant @ianhewson99641]

Reground the surface of my magnetic table by mounting the head of my quorn in the spindle of the mill and taking small cuts, came out ok.

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