Cost effective way of measuring 90degrees very accurately on Milling machine

[JasonBModerator @jasonb]

It only gives the spec of the bubble graduations, would be interesting to know how "square" the four sides are ground and how true the bubble has been set to the base.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 02/12/2018 16:19:34:

It only gives the spec of the bubble graduations, would be interesting to know how "square" the four sides are ground and how true the bubble has been set to the base.

.

Agreed

[Men IfrParticipant @menifr84251]

Neil seems like we have similar ideas this is the back of my 9512. On my mill the back of the column is not level with the bottom of the base. So I added a base plate to give the required protrusion and hopefullh add a bit of stability.

Base plate

I've added these blocks and screws near the top of the additional plate to accurately tilt the column left of right with a find threads they work really well to dial it in within 0.01mm over 100mm then the rear bolts are tightened to lock it in place.

You can also see I've started to look at the flatness of the table and does not look good so far… I'm trying to work out if I can improve it by grinding with a fine cup wheel from the spindle..

[Men IfrParticipant @menifr84251]

I can tilt forward/back by pushing the head up against the table with a clamp screw before tightening the rear bolts also. So I have the ability to adjust the column but need to measure it accurately first.

I have also thought about using a normal not reference Square and rotating 180degrees, make another measurement and if the 2 measurements agree then column is out, if both measurements show a taper then the square is out this is how I believe my squares are not square! But also added in there is some movement of the square and the table as above is also not flat…

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Men Ifr on 02/12/2018 18:56:07:

… is out this is how I believe my squares are not square!

.

In theory, it's very simple to check a square [practice, of course, can be much more difficult] … all you need is a perfectly straight edge on a plate, a perfect scriber, and the ability to detect deviation of two lines.

Scribe a line, flip the square, scribe another … If they coincide, it's 'square' … if they deviate, it's not.

MichaelG.

[JasonBModerator @jasonb]

I practice your scriber line is likely to be more than 0.01mm wide so hard to see if your square is good for 0.01mm over 100mm. Not forgetting you will need an accurate straight edge to check that what you have the stock against is indeed straight.

Then there is the fact that this method uses the inner edge of the stock, so you have to hope both faces of the stock are parallel when you stand your square on its back.

Also worth remembering that all this fussing around to get the table trammed true goes straight out the window when you plonk a heavy rotary table and chuck on one end of the table and wind it to its extreme, this applies to all mills to some extent not just hobby ones

[Mark RandParticipant @markrand96270]

Posted by Men Ifr on 02/12/2018 13:09:50:

By precision square I mean one of these type of things. I don't know your location but if you were near to me in Kent I could loan you mine.

Arceuro do one that is claimed to be 4 arc seconds, which is plenty good enough for what you need.

Thanks for the offer Pete but I'm in Warwick

I think the frame levellers are just that – I need to measure 90deg and their tolerance (I believe) refers to detecting and angle from 90deg horizontal.

I'm in Rugby and have an 8" cast iron square with 0.0002" in 10" level, a 10" granite square, plus four 3"x5.5" cast iron squares that I ground up for a job. I could lend you any of these that might be useful.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 02/12/2018 20:34:10:

I practice your scriber line is likely to be more than 0.01mm wide < etc. >

.

Quite so, Jason … that's why I emboldened the first two words, and then included a caveat.

The OP, however, seems to believe that his squares are significantly 'out' … and therefore it might be a reasonably simple matter to demonstrate that.

Confirming that a sqare is right would be much more difficult than demonstrating a square is wrong.

MichaelG.

[Men IfrParticipant @menifr84251]

Posted by Mark Rand on 02/12/2018 20:50:52:

I'm in Rugby and have an 8" cast iron square with 0.0002" in 10" level, a 10" granite square, plus four 3"x5.5" cast iron squares that I ground up for a job. I could lend you any of these that might be useful.

Mark,

I may well take you up on that offer I'll see if I can drop you a PM thanks

[duncan webster 1Participant @duncanwebster1]

You can check the square by clamping it to the table along the x axis, running the dti up it using the Z, then reverse the square, run the dti up the same edge. If you get the same answer the square is OK if it is mirror image the square is wrong. With copious supplies of cold towels to wrap round your head you can allow for inaccuracy of the square. or easier put a bit of shim/tinfoil whatever under one end of the square when you clamp it down

[Mark RandParticipant @markrand96270]

Ian turned up at about 17:45 today and picked up the 10" granite square. He was also subjected to a mind numbing tour of the bomb site that I call my shed .

[Niels AbildgaardParticipant @nielsabildgaard33719]

Posted by Niels Abildgaard on 01/12/2018 19:08:09:

A borrowed diesel piston pin with one end on mill table and my trusted MC3 testbar in spindle of milling machine and a light-source convinced me that my mill was OK.

Only problem is that test bar has no pull in thread so I was always prepared for drop down.

It did not.

some pictures

[Author]

Posts