.

Eric,

I would not trust a [typical "hobbyist"] digital angle gauge for this job

… The accuracy and repeatability are simply not good enough.

Of course: That might be how they assemble them wrong in the first place

MichaelG.

Eric,

The normal digital angle gauge (Wixy type) has a claimed accuracy of 0.1 degrees, which translates to an error of almost 0.007" in 4". That's nowhere near good enough for a mill.

With regard to the MEW article, what's wrong with holding the pillar in the lathe chuck and taking very small cuts from the bar? Yes, I know its an intermittent cut but that shouldn't present any problems.

The suggestion in the original article was to mount the bar on a faceplate and trim the pillar, so it obviously must be possible to swing the bar.

The longer the bar the more accurate is the trammelling.

Sorry Neil,

I must have missed something – who's Ken?

Anyway, yes, you can do it with one clock but, as you clearly stated, it creates problems. The only objection to the 2 clock method is that it requires 2 clocks. They don't have to be identical, just accurate enough, Second hand ones will do.

For those with plenty of the folding stuff I've seen adverts for a dual dial gauge to set up the mill trammel from Chronos £80 or £90 from memory

Lionel

I use one of those Edge technology units and it works well, they supply a small magnet that is placed on the table and you zero the gauges off the top of it then lower the spindle until one [ or hopefully both] gauges read zero. if they don't then adjust the tram until they do . The only thing that irritates me is that the magnet will pick up any chips or fine iron dust and getting it off the damned magnet is near impossible !

I found also because of the crud sticking to the magnet it was best to slide the magnet into position to ensure any junk caught under it will get wiped off then wipe the top surface as well , I then sweep the indicator nib across the top of the magnet to make sure nothing is caught between the two before setting zero , I also sweep the indicator nibs around on the table surface when I lower the unit down to take a reading – sounds like a hassle but once you have done it a few times it becomes second nature and the readings will be consistent .
Now I just need to get the fine metal dust off that magnet and I will be happy , may try compressed air .

Ian

I use a Verdict dial indicator using one of the attachments gripped in a collet. It sweeps about a 6 inch circle. To avoid the problem of the tip catching in the tee slots, I place a plate of 6 mm float glass (my first surface plate) on the top of the table for the indicator to sweep. Float glass is dead flat and parallel, as you can check by spinning the plate whilst keeping the indicator still, the needle doesn't move. It seems pointless to me to spend money, or time making, a gadget that you can equally well improvise and only use occasionally.

Why use a magnet on the mill when a disc of non magnetic metal would work just as well. If it was a vertical surface I could see the point, but otherwise magnets just make life more of a hassle.

Doug

Jason, why go the trouble when float glass is is so chap, flat, and self checking?

Bother, JasonB beat me to it. The Pilkington spec on thickness isn't that good either, ±0.13mm I think for 10mm sheet. I rarely tram my mill; when I do a check I use a DTI and four parallels. And before anyone asks the parallels were made by the late father of a friend of mine, who was a tool maker. I can't detect any variation in thickness across all four, using a micrometer. So probably within a tenth or so.

Andrew

You don't even need a DTI. I was taught to use a "z" bar and two fag papers to check the mill head for vertical, but that's another story.