Quality of Engineer’s squares

[Geoff ManshipParticipant @geoffmanship78814]

Some time ago I brought two engineer’s squares. On checking the squareness of each, I found that one was appalling and the other just not very good. I now want to buy a 4” and 6” square of reasonable quality for use in the workshop. I don’t think I need inspection standard, just reasonable accuracy and quality.

I did intend buying Moore & Wright 400 series squares, but on the Tool Fast website I noticed their Fisher range.

 

http://www.toolfastdirect.co.uk/acatalog/Moore_and_Wright_Engineers_Square.html

 

According to the spec, accuracy appears to be comparable with the Moore & Wright equivalents but the cost is significantly lower.

 

If anyone has had experience of Fisher squares I would be glad of their comments.

 

Regards

Geoff

[Geoff ManshipParticipant @geoffmanship78814]

[chris stephensParticipant @chrisstephens63393]

Hi Geoff,

Cannot comment on Fisher, but M&W seem to have gone downhill in recent decades.

Have you considered one of these;

http://www.warco.co.uk/squares/318-knife-edge-square.html

Made from that wonderful stuff, if you have a damp old shed to work in, Stainless Steel. They are also of a one piece construction, so there is no risk of the blade coming loose as might happen on a cheapo piece of Tat.

chriStephens

[WALLACEParticipant @wallace]

Hi all.

 

Just a thought – I brought a nice, new Cromwell square of eBay – can’t complain about the qualitiy and squareness (not that I’ve measured it !) – BUT – it’s a bit of a silly design as the cut away that allows a scriber to go right to the edge goes to the top of the square if that makes sense.

 

So it’s easy to have the square not sitting quite square . . . .

 

The ‘notch’ scribber cut away (like the old beaten up M&W one I have) doesn’t suffer from this and is certainly the type I’d recomend.

 

WALLACE.

[Jim GreetheadParticipant @jimgreethead]

Interesting. I don’t recall seeing specifications before like those in the reference URL but if they refer to the accuracy at the end of the blade then they agree with measurements I took the other day of the squares in my workshop.

 

At the time, I thought the squares were of low quality, expecting better then plus/minus 0.02mm but it appears that they are suitable for purpose.

 

Jim

 

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

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Edited By MICHAEL WILLIAMS on 05/01/2012 20:19:08

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

If you have squares which are not very good as bought or have become worn it is quite an easy task to rework them back to perfect accuracy . A little work with slip stone and oil is often all that is nescessary .

 

You’ll need a master square to check your progress . The easiest master squares to make by DIY methods are the cylindrical square and the less well known 3-4-5 toolmakers button square .

 

MW

[Martin Walsh 1Participant @martinwalsh1]

Posted by chris stephens on 05/01/2012 17:24:14:

Hi Geoff,

Cannot comment on Fisher, but M&W seem to have gone downhill in recent decades.

 

yes I agree most M&W tools now seem to be made in china

 

Best Wishes Martin

[TerrydParticipant @terryd72465]

Hi Geoff,

 

The easiest way to check a square is to set it on a reference edge (side of surface plate etc) and scribe a line against the blade. Flip it over 180 and scribe another line against your first. If not accurate draw file and stone the blade until it is. – A very good exercise in benchwork which we all had to do in our apprenticeships. You never accept that things will be accurate enough and you need to know how to remedy faults as engineers did in the past, not simply use a chequebook as the answer.

 

Regards

 

Terry

 

p.s. have a look at the article in MEW number 1 or perhaps 2 regarding French try squares.

T

Edited By Terryd on 05/01/2012 21:51:11

[Jim GreetheadParticipant @jimgreethead]

Michael, Terry,

 

With my hand skills, I would have a very thin square at the end of that exercise. But I guess it would not hurt to practice on an old square that is already stuffed.

 

Might give it a go.

 

Jim

 

[mgjParticipant @mgj]

I have a mild disagreement – the turnaround method described by Terry is very good, but the most accurate way to check a square is to use the lathe bed (or other suitable) as a reference, and put it up against one of Michaels cylindrical squares, which are so easy to make. Some kind of light behind is best.

 

Put a bit of (true) bar of sensible size into a 4 jaw, and clock up true. Face the end, and then turn a recess. How deep doesn’t matter, but about 1/8 is fine – to relieve the base is all that is needed. Just make sure that the edge of the recess is as thin as is sane – say 1/16″. Dismount from the chuck and wrap carefully, because it will be square to within pretty much nothing. If one thinks of geometries of generated circles its easy to see why.

 

That was in ME years ago, when it still did tooling and printed in hot metal/B&W!

 

I accept that the thing can only be truly accurate if the edge is infinitely thin, such that it represents 2 points, but we don’t need to worry about that, especially as we can’t achieve it, but it will be the rightest angle one has in the workshop, or is ever likely to posses.

 

A 3/4/5 triangle is also absolutely a right angle, but there is the possibiltity of introduced errors if ones drilling and measuring are not spot on. Still, made properly such a triangle should be very accurate.

[John McNamaraParticipant @johnmcnamara74883]

 

Hi all

“Put a bit of (true) bar of sensible size into a 4 jaw, and clock up true” ? in the post above.

 

An interesting proposition. If the point to be measured on the bar is adjusted to be to be spot on the axis of the lathe spindle the indicator will “clock” perfectly; all good.

 

But what if at the same time the bar is actually off axis as it passes through the chuck jaws? the indicator will read a regular rise and fall as it travels the path of the ellipse generated, however the rise and fall will be very small, and maybe not noticed.

 

The small error however will be multiplied by the length of the square. it may well be significant.

 

A possible solution particularly for a longer cylindrical square is to finish face the ends using the fixed steady well oiled and fitted carefully with no play at one end. and only gripped by the last few mm in the chuck jaws at the other end (perfectly clocked true at that point near the jaws)

 

As only a small finishing cut is required a light grip will be sufficient.

 

This method effectively assures that the axis of rotation (of the bar) is correct at 90 degrees to the cut. while facing the ends.

 

The fixed steady is another source of possible errors, if off axis it stresses the chuck jaws, if it is not correctly aligned with the chuck, so this setup should be done carefully. However if the fixed steady is slightly off axis the most likely outcome is the bar will slightly flex the chuck jaws in and out (it is constrained in the fixed steady at 3 points). however the work will still rotate on its own axis.

 

A good analogy of this setup is the drive shaft of the car. The shaft rotates on its own axis while it can move up and down.

 

The setup of the fixed steady should ideally be centered on the lathe axis of rotation within .001 inches or less that way the errors generated by the less than perfect connection at the chuck will be minimised.

 

Cheers

John

Edited By John McNamara on 06/01/2012 00:00:17

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

To make a 3-4-5 toolmakers button square :

 

Make 9 identical rollers say 1inch diameter drilled big clearance for cap screws about 6 mm dia .

 

On a sutably shaped steel plate mark out and drill holes at 1 inch pitch in the 3-4-5 configuration . Do the marking and drilling as accurately as possible but final accuracy of the square does not depend on exact accuracy of spacings . Tap each hole 6mm .

 

Position 5 rollers on the edge with the 5 holes and arrange them to touch each other and touch a straight edge . Obtain best accuracy and lock down screws . By trial and error position the remaining rollers in the remaining holes so that they touch each other , the end rollers of the 5 row and a straight edge tested along each side . Lock down all remainining screws .

 

With all rollers along each side touching and also touching the straight edge(s) an almost exact 3-4-5 triangle is formed and the 90 deg angle is accurate to typically 0.0002 inch in 10 inches .

 

Sounds difficult but with the basic parts made beforehand takes about 20 minutes to assemble .

 

A developed version of the same basic idea can be used to set out other angles and make master dividing plates .

 

MW

 

[Chris TriceParticipant @christrice43267]

You don’t need to clock the bar at all. Just take a light skim off the surface and providing your lathe turns parallel (easily checked by measuring each end of the bar), once you’ve faced the end as described, it must be square. If you centre drill the end of the bar, you can use a rotating centre in the tailstock for support providing it’s set centrally, again easily checked by measuring each end of the cylinder for parallelism

Edited By Chris Trice on 06/01/2012 00:20:33

[John McNamaraParticipant @johnmcnamara74883]

Hi Chris

 

True if you have a near new lathe and you are happy with a turned finish.

 

On the other hand if you have a nice piece of precision ground stock you want to turn into a square you will not want to damage the fine finish.

 

I doubt if there are many lathes used by members that can turn parallel over the entire length, say 300mm to within .001″. you can get the ends to match but what about the middle? and over longer lengths spring of the work starts to starts to cause errors

If the ground stock was not available it is not hard to hand lap a turned shaft to parallel

 

Turning on accurately located centres using the fixed steady as above (it is unlikely the bar will fit through the spindle 75 to 100mm is a good size) will work as an alternative to the method I proposed in the previous post. However if the stock is a tube quite often used as a square plugs will have to be made and centred then fitted in the tube.

 

My “best” square is a piece of precision ground drum 5mm thick rescued from a scrapped printing machine

100 mm diameter and 350mm long.

 

Cheers

John

[TerrydParticipant @terryd72465]

Posted by Jim Greethead on 05/01/2012 21:57:52:

Michael, Terry,

 

With my hand skills, I would have a very thin square at the end of that exercise. But I guess it would not hurt to practice on an old square that is already stuffed.

 

Might give it a go.

 

Jim

 

Hi Jim, if you have duff squares what’s to lose? it can be good experience and you may well end up surprising yourself with improved skills. File off the bulk of the error across blade with a fine 4 to 6 inch file, then carefully and deliberately file along to remove marks and flatten along the blade, then draw file and finish by draw filing with fine emery cloth held on file. Do it a bit at a time and keep checking. You may well surprise yourself, but think and analyse what is happening as you are working, it ain’t so hard.

 

Terry

[Geoff ManshipParticipant @geoffmanship78814]

Hi all,

 

I thought my question was too trivial to merit more than perhaps 1 or 2 replies.

Thank you to everyone for their answers and comments.

 

I think I shall try one of the Fisher squares and see what they are like. I’ll post here with my findings.

 

Thanks again for your replies.

 

Geoff.

[mgjParticipant @mgj]

I agree about the limitations of making cylindrical squares. Technically you don’t need to clock the thing at all. – as long as it holds parallel.

 

But reality intervenes.

Ideally one wants to clock the thing true and set it parallel in a fixed steady with a proper DTI – I did that with my Quorn spindle, and eventually got it true to .00002 in 4″., before machining the bearing seats. Madness approached.

 

So you have to accept a point where good enough is good enough, and one can make it as well as it need be.

Edited By mgj on 06/01/2012 18:20:54

[Jim GreetheadParticipant @jimgreethead]

Michael: Your method of making a 3-4-5 square sounds like a good use for a bit of ground bar salvaged from a printer or copier. And there are other sources of cylinders that are accurate in diameter over sufficient distance; some drawn pipes might serve. Sounds like a job for a time when everything else is going wrong and one needs a break.

 

Terry: Thanks for the encouragement; when I did a Tech course a couple of years ago, I was obliged to file the usual drill gauge etc. and surprised myself by being able to do it. Filing a square is another order of accuracy but using your advice, I think I might be able to do it.

 

I did think about clamping the worst of my squares to the milling machine and taking a light cut. But of course, that would only make it as accurate as my mill.

 

All the discussion about cylindrical squares set me thinking (oh no!): flat plates are made by testing three against one another. That should work for three squares shouldn’t it? Of course they would have to be set on a flat surface. The good news is that you would end up with three really accurate squares and could sell the other two.

 

Just a thought

 

Jim

 

[Sub MandrelParticipant @submandrel]

I have three small squares (1″, 2″, 3″) from Chronos, all spot on as far as I can tell.

 

I have another, much older square apparently of english make, patent design and high quality – it’s bent as a dog’s hind leg and IO can’t see how it could ever have been straight.

 

Two woodworking squares I have are close, but not good enough for metalwork.

 

Neil

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

The 3-4-5 method of making squares is an a example of an ‘absolute’ method – that is you don’t need to know the exact dimensions of the rollers – only that they are the same .

 

When laying out patterns with rollers it is sometimes nescessary to cut parts of the rollers away so that they don’t interfere inunplanned places – other than that it is dead simple to do .

 

A non absolute but perfectly practical alternative way of doing the samething is to just use rollers at the corners and separate them with accurately made rectangular bars of calculated length .

 

The common sine bar uses essentially the same principle . 

 

Another absolute method is to make 3 ordinary squares but with hinged blades . By testing them all against each other on a straight edge and adjusting so that they all touch full length on the blades in any combination you end up with three perfect 90 deg squares .

 

Its a bit tricky to make three ordinary squares with narrow blades by scraping and testing against each other on a surface plate . More usually three angle plates are made with faces at least 20 mm wide .

 

Super precision cylindrical squares are made by turning and grinding the cylinder surface to best accuracy and then dividing the length into numerous zones and hand finishing each zone to be exactly the same diameter . Each zone is usually separated by a cylindrical V groove . Again this is an absolute method – you don’t need to know the exact diameter of the cylinder- only that all the zones are the same diameter . Hand finishing is usually done by lapping but for home workshop a fine slip stone would do perfectly well .

 

The base seating end of the cylinder is always finished at the same setting as the cylindrical surface and again is usually hand lapped for flatness .

 

The cylindrical square has a rarely seen but perfectly practical inverse – basically a faceplate with a smaller diameter true bar coming out from the centre of it . Can be turned from solid or made in two parts . Very easy to make in small sizes .

 

A type of precision toolmakers square is similar and uses a precision round bar inserted into a hole in a rectangular bar .

 

MW

Edited By MICHAEL WILLIAMS on 07/01/2012 00:09:35

[Jim GreetheadParticipant @jimgreethead]

“
Another absolute method is to make 3 ordinary squares but with hinged blades . By testing them all against each other on a straight edge and adjusting so that they all touch full length on the blades in any combination you end up with three perfect 90 deg squares .“

 

Thank you Michael, that is a great refinement on my thought about the three squares. Three steel rules – the ones with the holes in the end – for the blades, a bit of flat rectangular stock and some work with the slitting saw and Robert is your father’s brother.

 

And no filing (sorry Terry)

 

Sounds like a plan

 

Jim

 

[TerrydParticipant @terryd72465]

Hi Jim,

 

The filing method is simply good practice. I agree about the three squares method, but that only gives you a test square. An adjustable square is just that – adjustable, and if only using one hole to assemble, how will you prevent it moving?. One knock or drop and you have to go through the process again. If you try to drill an extra hole to lock blade how do you ensure no movement. You can’t silver solder, that can cause movement or distortion. Loctite may work but only if you’re quick in your three square testing.

 

After any attempt to make the blade fixed permanently you have to check the square and then make it accurate,- – by grinding on a precision machine – or hand file. Square one!

 

Good luck and share your experiments and results, we are all keen to learn new tricks.

 

Best regards

 

Terry

[Gordon WParticipant @gordonw]

We had to make a square in apprentice training ( here we go again ) made the actual square 6″ x 4″ x 1″ from gauge plate by filing, then riveted two flats for the handle bit. This is accurate and cannot move. I’m still using it almost every day.

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

(1) Squares with settable blades are quite common in inspection departments . The normal method of making the hinge is to use a fitted dowel pin as the pivot and a ring of usually three holes around with small locking screws . The stocks of these squares are often more chunky than than on workshop squares so that they can sit solid on a surface plate . The blade never works in a slot but seats against a half cutaway in the stock thus giving a solid against solid lock down .

 

Ultra posh ones in metrology laboratories have the blade sitting in a machined half round saddle which sits on a half round section on the stock and theses are locked down radially .

 

(2) There is a distinction to be made between the way primary reference squares and practical workshop squares are made and used .

 

(3) I think Terry and I agree that correcting normal squares by means of the turn around test on a straight edge and a little hand work will give tools that are as good as need be for general workshop use .

 

MW

 

Edited By MICHAEL WILLIAMS on 07/01/2012 10:38:35

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