Mill Tramming Tool (& Use on a Centec With Riser.)

[peak4Participant @peak4]

This is a topic which seems to come up regularly, so I though I’d add a specific thread, which may help people if they are able to search for it in the future.
I’ve written about this gauge previously, so some of the following is a copy and paste from previous threads, which are now outdated as my original forum photo album has been deleted.

Tramming my mill(s) became much less daunting after I’d made one of these gizmos.
It’s made roughly to a design by John Moore (Bogstandard), though mine has an MT2 arbor to suit both my Centec and Dore Westbury mills; his fitted directly into his milling chucks, so had a parallel arbor.

It’s slightly different to most of the commercial ones, in that it’s self calibrating.
To achieve that, it’s essential that the arbor is exactly perpendicular to the bottoms of the two little feet.

I ensured this both by careful boring and assembly, but also by spinning the final thing in the Myford’s gap bed space.
This limited the length, but it seems fine in use.
The arbor was fixed directly in the Myford’s spindle with a drawbar, and the feintest skim taken off the bottom of the feet.

Note that the final fitting of the clocks, has the tubular outer section all contained within the bottom alloy bar; it actually only goes about 2/3 of the way through.
This means that one can stand it on a known flat surface, before fitting to the mill’s spindle, and zero the clocks exactly. Effectively it self-calibrates, without needing to go through the normal rigmarole of turning the clock’s supporting arm by 180° and constantly re-checking.

I bought two cheapo metric DTIs off ebay, nothing special and something like £4.50 each, the alloy bar I had in stock and made a steel arbor to suit, pre tapped 3/8″ BSW.

To use, fit the tramming gauge to the mill spindle and raise the table (or lower the quill as appropriate) until the stylus on each clock touches the table.

Tilt the head to correct any error, which shows as the clocks will display different readings.
One can monitor for angular movement whilst nipping up the mill head fixings.

Spindle Square in its box.

Sitting on a flat surface for self calibration

Square in use before I found a long riser block for the Centec

Vertical Head now Trammed Left to Right

It can also be used with blocks to save raising the table all the way up

It was at this point that I realised I’d made a slight error in the design as the main bar was just too long to spin through a full 90° on the Centec, though it’s fine on the Dore Westbury.

See Part 2 to follow.
(Please don’t reply yet, to maintain the continuity.)

Bill

 

[peak4Participant @peak4]

Part 2;
Just after the 1st Covid lockdown I found someone selling a brand new Tony Griffiths riser block for the Centec; arranged to meet, brought it home and stared to fit it.
This means first removing the vertical head for obvious reasons.
What I hadn’t realised, was just how much strength I’d lost during my bout of Covid, so when I slid the head off forwards, I very nearly dropped it; previously I’d been able to remove it and swap for the horizontal arm without much issue.
Blocks of wood etc allowed me to install the riser block and re-fit the vertical head.
Recently I’ve been having issue with work not quite being square, and put it down to carelessness in not allowing for vice jaw lift.
More investigation followed, and I found that I could get a thin feeler gauge under one side of the  head, and under the other side of the riser block.
By coincidence, the two gaps matched each other, so when I check left right tram after fitting the riser, everything still matched.
It did however leave a forward nod.

There’s another thread on here posted after I’d completed the rectification, which also points out the cause of the issue.
Effectively, the sharp edges of the milled dovetails in the new riser block were fouling in the inner corners of the vertical head, and also the main body of the mill.
Filing these back a bit on the riser block allowed the mating surfaces to fit flush.

To remove the vertical head without injury I jury rigged as below.
Sorry these photos are poor, I was set up for the job, rather than photography

Wooden block clamped down to the table for support, with table fully backwards

As you can see from the above, I used an old bearing outer to provide support for the nose, as well as a second block to support the sleeper end.

Head now screwed down with some perforated galv strip, so I don’t lose it, and then the table raised and wound out.

The Riser can now be removed backwards and modified slightly; about 50 thou taken off the sharp edges, on top and one bottom, opposite the clamps.

Riser block removed, and everything still quite stable and safe(ish).

Left Right could now be trammed fine, which is much as before, but I still had a slight nod forwards.
Far too much to be acceptable at about 5 divisions on the metric clock.

Setup for initial rough tramming with 2 thou shims, above left hand clock

Note that Now, I can recess the riser block slightly and spin the spindle gauge through 90°

2 thou shims were just too thick, but after much experimentation, 3 layers of green cigarette papers proved to be about spot on.
In theory, that comes out as 3 thou, but the paper distorted into the machining marks on the riser block and works nicely.

It now trams quite well as regards front to back nod, with a more precision granite U block.

Left right can now be adjusted quite accurately, just by the conventional swivel locknuts

To mix my units a bit, over the 7¼” long bar between the clocks, I’ve gone from about 10 thou nod, to a bit less than 0.005mm, which will do OK for me
Similarly left right tram is also close to spot on as well.

I’d also made sure the table top was square to the column, just using an engineers 12″ square, to check as well as I was able.
I later fitted an MT2 test bar to the spindle which showed negligible runout and no real visible light between it and the square.

The original inspiration for the spindle gauge was from John “Bogstandard” on Model Engine Maker
I think the article is reprinted on this website somewhere, as part of a list of John’s projects, but I can’t currently find the link

Bill

[JasonBModerator @jasonb]

I put a lot of Bogs articles into a sticky at the top of “Workshop tools & tooling some years ago, the gauge is towards the bottom of the list.

[VicParticipant @vic]

I’ve no idea of the accuracy but the quickest and easiest device I’ve seen online was of a disc brake rotor with a permanently fixed shaft. The described technique was to secure the device in a collet in the quill and with the head unlocked raise the table as far as it will comfortably go then lock the head. I’m pretty sure this method would work for the stuff I do? Refitting my vice is pretty quick as well due to the collars I made for it to fit the T slots.

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