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

Frame squares have all four sides finished perpendicular to each other. They are very versatile for doing alignment work.

But what do you call perpendicular? There is no spec for the accuracy of the sides so at that sort of price I would not expect them to be any better than a £40 Grade B square, maybe less.

The OP has said he does not want to buy squares that don't state the spec so why buy that?

Edited By JasonB on 02/12/2018 13:55:48

Thats a damn good set of readings for a new machine that has not had any adjustments to the head, got to be happy with that.

That's a small machine with a heavy head. The weight of the head will cause the column to bend by a different amount when the head is high compared to when it is low. Is this going to cause a headache when trying for accuracy? My solution for working with a round column machine will solve the problem for this machine, use a 16mm parallel shank ER collet holder in a 16mm R8 collet. You can slide it down for short tools and either use it all the way up for longer tools or take it out and use R8 collets alone. No head raising or lowering required.

Martin C

I wasn't referring to the particular one in the ARC link just that frame squares in general are made perpendicular on all sides close enough that they come fitted with an insulator for handling them lest you heat the top edge and push them out of square with heat from your hand.

Now that the class of machine has become apparent I guess it's all immaterial since it's not a very rigid design anyway.

I can't promise that! But in a batch of four I would expect at least one to be good enough to tram a mill.

I am concerned that although the OP's mill clearly needs aligning properly, expectations may be a little high.

An alternative to use with even a wonky square is to look at the readings with the square on the left, then on the right and adjust until the change is the same on both sides when the head is moved up and down. The column should now be vertical.

Now possible to set the head perpendicular by tramming, but I think the problem faced is that the head.can only be adjusted off the mill.

This is why I suggested the 'shim with paper' methodology. This must be more or less how they are set in the factory, however, they have the advantage of doing this before they are painted. When I discovered the head of my mill was out, it was evidenced by a crack in the paint where the two parts join.

Obviously using paper, a flat surface and painted castings isn't ideal, but I can honestly say it worked OK for me.

I described the process for the old-style X2 in this article from MEW 201:

www.arceurotrade.co.uk/reviews/MEW201_p52_58_X2_Mill.pdf

Page 5 describes what I did and there's a photo on page 7.

I strongly suggest trying this, followed by conventional tramming (as in Dave's photo) before investing in any additional equipment.

Neil

Yes, front-back is what I meant by north-south. Sorry about the confusion - I wasn't being consistent in my terminology.

The set-square is just to make sure the DTI is positioned close to 180 degrees around from its start position, ie exactly opposite.

See also Neil's post at 14:44 - I'd assumed any front-back shimming could done without taking the head off.

Dave

In Part 1 of my article in MEW 199 I described how I did the front-back tram by scraping. Despite my crappy scraping, the much increased contact area helped rigidity, but not as much as a bracing plate.

Problem is the fixing screws are nearly in a straight line:

Adding a bracing plate locks the column solid, front to back:

Allowing you to do stupid things which the original mill wouldn't have had a chance of doing:

.

That's a very impressive specification for the price, Pete

... well spotted

MichaelG.

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

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..

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...

.

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.

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

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.

.

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.

Mark,

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

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

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 .