Dial Gauge Mill Tramming Tool

[AussieJimG]

I built one and went crazy trying to get the calibration correct. After several attempts including boring the hole for the main bar on the faceplate, and substituting an aluminium bar for the steel one so the final skim would not cause deflection, I still had 0.02 error.

Then I realised: follow Bogs' directions and then simply lower the tool onto the table until one of the dial gauges reads zero, rotate the tool until the  other gauge is over the same spot and tweak it to read zero as well.

That got rid of the last 0.02 and the tool is ready for really accurate use.

In retrospect, I could have done that to remove the error prior to using the faceplate. But I am glad I tried Bogs' method even though I failed. I am sure it will come in handy in the future.

Thanks John

Jim

[AussieJimG]

Oh yes, I forgot to ask:

Is there a better way to tram the mill than by tapping the head with a lump of wood and a 4lb hammer while gradually tightening the three bolts holding the head?

Perhaps is does only take 5 minutes but it seems longer 

Jim

[Bearcar1]

Jim, a large rubber mallet is a good 'attitude adjuster' for tramming the mill. The one I have is about 3-1/2" in diameter and is made up of some sort of a hard-ish grey rubber/vinyl material that has just a touch of resiliency to it. I bought it at Sears a long time ago and it is the perfect tool for the job. It has enough -weight to it that it will nudge the mill head or the vise,l for hat matter, a few thousandths at a time with just a light tap without fear of damaging the machine's surface.

BC1
Jim

[sco]

I have a plan forming in my head to make one of these tools using an MT3 blank arbor fitted to a cross bar carrying the dti's.  The lathe headstock taper is MT3 same as the mill, so I'm thinking of fitting the arbor directly in the headstock, turning a suitable boss on the end of the arbor and then mounting the cross bar on this boss. 

Staying in the lathe I'm then thinking of facing the pads of the cross bar to get accurate reference surfaces relative to the MT3 taper - I know this will be an interrupted cut but any good reason why this method isn't as good as Bog's original method of mounting the cross bar on the faceplate and skimming the mandrel?

[Bogstandard]

That should work just fine.

John

[sco]

That should work just fine.

John

The Gold Seal of Approval - thanks very much 

Simon.

[Bogstandard]

No problems Simon, there are always more than one way to skin a feline.

John

[ScroungerLee]

Is it correct that the accuracy of the bottom pads really only comes in to play when installing the dial indicators and getting them to match readings?

If one were to set one indicator, swing the entire thing 180 degrees, and set the other indicator at the same place on the mill table wouldn't that ensure accurate setup?

Seeing an easier way almost surely means I am wrong, but I don't see why this wouldn't work.

Lee

[zeeprogrammer]

I'm not that experienced myself...

I used to do it that way. Very time consuming for me and prone to error.
Any flex in the arm holding the indicator will add error and you have to push the indicator up out of way to clear the table which can add error to the arm.

I've since gone the route describe below with the dual indicator.
(Except I cheated and bought one rather than make one.)

I like it and it's also easier to check in Y too.

[ScroungerLee]

To clarify, I meant initially mounting up the two indicators in the arm by referencing each to a single spot on the mill table, then using the two gauges as expected.

Not sure if that explained my question well.  It's not too important anyway, just me being curious .

Lee

[Don1966]

Lee I understand what you mean and don't see why it should not work. Seeing as you are just setting the dail indicator to the same as the other. The only thing I see is you have to have some accuracy in mounting the shaft and drilling the holes. should the holes be drilled at any angle other then 90 degrees to the shank the indicator would have a tilt and an error would surface.

Don

[Bogstandard]

Lee,

To put it as simply as possible for this unit to work.

There is only ONE critical item, the spindle MUST be perfectly square to the two datum faces, whether you do it my way or your way.

The setting up of the gauges can be almost anywhere, as long as when the datum faces are set onto a flat surface, without the tool being mounted into the spindle, both gauges are in fully operational mode and the zero setting finger is pointing to the gauge finger on each dial, to indicate a zero setting.

When the unit is then mounted into the spindle, and both gauges in operational mode, to get the quill perfectly square to the table, just swing the head until both needles are pointing to the two previously set outside zero pointers, but care must be taken that the tiny scales are working at the same sort of settings as when initially setting the two outside pointers.

I went to great lengths when setting my gauges and pointers up, setting them at the fully up position, with the same rotational setting on the two small clock faces. That way, even if I was half drunk, everything would be very easy to do.

I think people are looking at this tool and are expecting it to operate in a very complicated way, nothing could be further from the truth. Once the gauges, pointers and fingers have been set, they should never again need to be played about with at all. Just pop it in the spindle, and check or set the zero position of the head.
That should also work perfectly even if going from mill to mill, or lathe to mill or vice versa, as long as the spindle used is compatible with each fitting.

John

[ScroungerLee]

Thanks Bogs,

I didn't mean to disrail your fine thread .


You wrote "That way, even if I was half drunk, everything would be very easy to do.". -  I had noticed your DRO readout says ALE, I assume that is used as a reminder

Lee

[Bogstandard]

No problems Lee, if someone doesn't understand what I have written, then it is up to me to make things, hopefully, a little easier to understand.

With regards to the mention of alcohol consumption, for the first time in a very long time, last night I got bladdered, not normally touching it, and my head today says I won't be doing that again anytime in the foreseeable future.

John

[MichaelP]

I'd like to thank the OP for taking his time to take photos and write his posts. This is a nice project. It just doesn't need to be so complicated, IMHO.

I'm afraid that all the efforts to make everything square and precise were required only because of the suboptimal calibration routine.

The only critical element here is to make sure that the indicator mounting holes are are equidistant and parallel to the central shaft. The rest is non-critical at all. The aluminum body can be machined or not, be crooked and not perpendicular to the shaft, etc. It doesn't affect the performance of the device.

To calibrate the device, you zero both indicators at the same spot. Zero the first one, then rotate the device 180 degree so that the second indicator is at the same spot and zero it. That's all. Now proceed with tramming.