Searching for a good quality, metric-only, 300mm steel ruler

[Donald MacDonald 1Participant @donaldmacdonald1]

OK… we have a WINNER.

And the winner is…. [drum-roll please]

"Kinex Flexible Metric Steel Rule 300mm"

Reasons:
– Super-simple ==> Looks pretty easy to read, even upside down
– No 0.5mm markings! ==> easy to read off the mms
– Thin (0.5mm thick) ==> very little parallax ==> easy to be accurate
– Being made from stainless steel, it makes a good cutting edge, with no risk of accidental damage from scalpel blades
– Low cost

Weaknesses:
– Overall build quality looks cheap
– Surface is bare metal with a rather directional reflection of light ==> harder to read
– One reviews claimed that it is quite easy to bend permanently out of shape
– the reverse surface is blank (I think) ==> (so no possibility of right-to-left help on the reverse side)
– It doesn't even have a non-slip rubber or cork rear
– Worse, at c.20g it may be rather hard to keep in place
– Cutting will need to be done very carefully because the blade is so thin & narrow

But… It's cheap and I needed to make a decision!

IF it does get bent out of shape, and/or I find that it is too dangerous to use with a scalpel… then I shall buy my runner-up which is…

[drum-roll, please]

"SHINWA Steel Rule Pick-Up 300mm" 

Reasons:
– No 0.5mm markings
– Very nice finish
– Easy to read markings
– Red lettering will stand out in my tool collection ==> easy to find!
– Red lettering jumps out at you so that:
a) you don't get confused about which 'decade' you are in (unlike the Kinex)
b) makes it easy to read when upside down
– Being thicker and wider than the Kinex this will make cutting slightly safer.
– "Easy pickup" gimmick might even be useful
…} Looks like a very nice piece of kit!

Weaknesses:
– Only one side is useful (so no possibility of right-to-left help on the reverse side)
– No non-slip grip (but being a bit heavier [c.60g] than the Kinex [c.20g] it may not need it)
– Cutting with a scalpel will still need to be done pretty carefully
– Being 1mm thick ==> slight parallax risk (?)

Well, that's my reasoning.

I'll try and pop back in due course to let you know how I get on. 

J

 

 

Edited By Donald MacDonald 1 on 24/03/2022 00:33:05

[HopperParticipant @hopper]

Well you certainly analiysed that issue within a millimeter of its life, literally. Well done. You will be able to measure things and cut things all with the one guiding tool. It may be an advantage that it does not have markings on the reverse side. This way you can be sure to cut a dead straight line without massive notches in it from the graduations jagging on the scalpel blade. Just be sure to angle the scalpel blade ever so slightly away from the top edge of the rule/r so it gildes along the lower edge unimpeded.

If holding the scalpel blade at 89.75 degrees to the surface being cut instead of 90.000 degrees is a problem, you might have to look at using one rule/r to measure and another ungraduated precision ground straight edge to cut with. Unless you get a guided cutter where the cutting edge runs back and forth along a linear rail in a holder on ball bearings.

Of course then you can run into problems because ball bearings always have a small amount of clearance in them that could affect accuracy by a small amount if you are doing precision work.

Sticking with the rule/r in hand, I would not be too worried about the error of parallex at 1mm thick. Develop the skill of looking straight down on the graduations to minimise the error of parallex to a few microns or so.

The wider one might be a more stable guide for dealing with the considerable sideways forces of cutting, but I think the red numbers at the 10, 20 and 3o marks would be really offputting and could result in an injury while distracted. So I concur with your first choice as the correct one.

The other factor you may need to take into account is that the edge of the scalpel blade is in effect a bevel, so even though the flat side of the blade may follow the straight edge faithfully, the actual cutting edge is at the other end of that bevel and so will be that small amount over from the straight edge. This could add another sort of error of parallex that perhaps could be accommodated by placing the straight edge that small amount to one side of where actual edge of the cut part is desired to be.

Please do let us know how you get on with it all. It is an intriguing conundrum.

 

Edited By Hopper on 24/03/2022 04:35:11

[Pete.Participant @pete-2]

Posted by Bill Phinn on 23/03/2022 11:46:56:

Posted by Neil Wyatt on 23/03/2022 10:49:46:

Posted by Pete. on 22/03/2022 00:28:44:

You're unlikely to find a rule with a non slip back, maybe a straight edge, because these are used more for scoring lines, not saying they don't exist, just might be easier to buy a straight edge, and a rule separately.

I have one, just not sure where I got it, and it's metric/imperial.

Yes, I have one too. I seldom use it, though, because the non-slip backing prevents you from sliding the rule/ruler smoothly into position; instead you often have to perform a series of tedious lifting and repositioning operations to get it where you want it. The same would apply if it was a steel straight edge.

I have a suspicion non-slip backings on rules and straight edges are there mostly for novice users who haven't yet learned to push primarily downwards with the pen or knife, rather than downwards and (more than very lightly) sideways at the same time.

Edited By Bill Phinn on 23/03/2022 12:13:43

John stated he wanted double sided markings on the rule, and non slip back, I can't picture how that would work? I don't remember seeing anything like that but it might exist.

[JasonBModerator @jasonb]

The Shinwa rule is also available without the pickup end if you don't like that feature. I've bought quite a few handtools from Dictum over the years and all good quality, they do the flat Shinwa in 15mm wide flexi. or 25 mm wide which would be better to hold for cutting. Shop around if you want a UK supplier.

I'd suggest you consider two rules, one for marking out and another for cutting just stick something to the back of one that you like the markings of.

Kinex also so a right to left reading rule but you would have to buy that separately as I can't see one with both and probably more hassle to swap rules than read upside down.

Edited By JasonB on 24/03/2022 07:11:19

Edited By JasonB on 24/03/2022 07:48:07

[JasonBModerator @jasonb]

Posted by Pete. on 24/03/2022 04:52:00:

John stated he wanted double sided markings on the rule, and non slip back, I can't picture how that would work? I don't remember seeing anything like that but it might exist.

No he said Either double sides or non slip back. I've posted images of my cutting rule with NS back and there are many more options but when I used to work in the graphics/art trade this one outsold the others 10:1 as a cutting rule.

[Grindstone CowboyParticipant @grindstonecowboy]

Posted by Hopper on 24/03/2022 04:24:06:

The other factor you may need to take into account is that the edge of the scalpel blade is in effect a bevel

Excellent point, and one that probably has not been taken into account. I seem to recall left and right-handed ground marking knives for woodworkers – fire up the Google machine, we may be looking for those next

Rob

[Nick WheelerParticipant @nickwheeler]

Posted by Bill Phinn on 23/03/2022 11:46:56:

I have a suspicion non-slip backings on rules and straight edges are there mostly for novice users who haven't yet learned to push primarily downwards with the pen or knife, rather than downwards and (more than very lightly) sideways at the same time.

I suspect it's for use on delicate surfaces to avoid unacceptable scratches.

[Bill PhinnParticipant @billphinn90025]

Posted by Nicholas Wheeler 1 on 24/03/2022 09:00:55:

Posted by Bill Phinn on 23/03/2022 11:46:56:

I have a suspicion non-slip backings on rules and straight edges are there mostly for novice users who haven't yet learned to push primarily downwards with the pen or knife, rather than downwards and (more than very lightly) sideways at the same time.

I suspect it's for use on delicate surfaces to avoid unacceptable scratches.

I'd not considered that, Nicholas, but could you give some everyday examples of delicate surfaces you'd want to measure and cut that would be unacceptably scratched with a bare ruler?

[Nick WheelerParticipant @nickwheeler]

Posted by Bill Phinn on 24/03/2022 10:57:50:

Posted by Nicholas Wheeler 1 on 24/03/2022 09:00:55:

Posted by Bill Phinn on 23/03/2022 11:46:56:

I have a suspicion non-slip backings on rules and straight edges are there mostly for novice users who haven't yet learned to push primarily downwards with the pen or knife, rather than downwards and (more than very lightly) sideways at the same time.

I suspect it's for use on delicate surfaces to avoid unacceptable scratches.

I'd not considered that, Nicholas, but could you give some everyday examples of delicate surfaces you'd want to measure and cut that would be unacceptably scratched with a bare ruler?

Aluminium sheet used for decorative covers would be a good example. A stainless steel rule easily does that. I made a bulkhead cover for a friend's kitcar at the weekend that took as long to remove handling scratches as it did to do the final fitup.

[JasonBModerator @jasonb]

Maybe the specially textured ABS that the OP posted about earlier would mark easily, he even had a problem with fingerprints on it.

[Donald MacDonald 1Participant @donaldmacdonald1]

Posted by Grindstone Cowboy on 24/03/2022 08:49:11:

Posted by Hopper on 24/03/2022 04:24:06:

The other factor you may need to take into account is that the edge of the scalpel blade is in effect a bevel

Excellent point, and one that probably has not been taken into account. I seem to recall left and right-handed ground marking knives for woodworkers – fire up the Google machine, we may be looking for those next

Rob

Since you ask….

Yes it's a slightly interesting question. Obviously to get the bevel error one measures the blade width then one divides by 2. Depending on what I'm doing, in general, for me anything less than 0.25mm error I tend to ignore.

Of my blades, for heavier cuts… yes I do start to think about it:
– Snap-off blade (carbide): <0.5mm ==> 0.25mm error
– Stanley Blade: < 0.6mm ==> 0.3mm error

However for these I simply ignore the error completely:
– Logan Matt Knife: 0.3mm ==> 0.15mm error
– Rotary Cutter: 0.3mm ==> 0.15mm error
– Scalpel blade (S-M): 0.4mm ==> 0.20mm error

 

Well… you did ask

TBH, I tend to avoid the Stanley blade except for rare brute-force situations.

IME, the other thing that CAN happen – e.g. when cutting greyboard or 'millboard' – is that particularly if you don't have the thinner blades correctly aligned… either the blade itself can bend, or it can stretch the material being cut. And on longer cuts this can create massive errors (> 1.0mm).

For straight line cuts on thing/softer materials the rotary cutter is a game-changer. For shorter cuts that need to stop at a precise point, you can't beat a nice, new scalpel blade.

Talking of which, personally I don't find Swann-Morton last very well, and I find I can damage import work quite easily with a blunt S-M blade. But at least they are cheap, so I now tend to replace blades at the start of EVERY important new cutting session.

If anyone knows of better quality /(carbide?) blade scalpel blades, please let me know.

J

 

Edited By Donald MacDonald 1 on 24/03/2022 12:20:11

[Bill PhinnParticipant @billphinn90025]

Thanks, Nicholas and Jason.

In circumstances where I needed to avoid marking a surface, I think I would probably still use a plain rule (and probably wood or plastic, if applicable), and just stick something (e.g. clean paper) to the back of it temporarily, as Jason suggested earlier, rather than use a rule with a permanent cork or rubber backing; those backings tend to get undetectably embedded with minute abrasive particles that will scratch your vulnerable surface anyway, where a strip of clean paper will not.

The permanent backings are certainly a help in discouraging the rule from moving during a cut or when marking a line, but when you're cutting many sheets or strips of paper in succession and you need to slide the ruler up to divider marks each time, the non-slip backing becomes literally a drag that slows the work down considerably.

[JasonBModerator @jasonb]

You can get single bevel blades for the Logan cutters then no need to worry about lining up to half blade offset. Also if I remember rightly we used to sell a holder for them that was like a knife handle so you could use them against other straight edge snot just their guide rails.

Strip of masking tape stuck to the rule can help stop it slipping about but don't leave it stuck to the rule for longer than needed as glue can go off.

[Donald MacDonald 1Participant @donaldmacdonald1]

Posted by JasonB on 24/03/2022 12:30:02:

You can get single bevel blades for the Logan cutters then no need to worry about lining up to half blade offset. Also if I remember rightly we used to sell a holder for them that was like a knife handle so you could use them against other straight edge snot just their guide rails.

Strip of masking tape stuck to the rule can help stop it slipping about but don't leave it stuck to the rule for longer than needed as glue can go off.

The theory is good, however in my experience single-bevel blades tend to cut in curves.

Fwiw, when working in a nice clean studio, I have been known to use a "dual tack" double-sided sticky tape on the back of my ruler. This allows you to give your ruler a nice, repeatable/re-positionable/"Post-it" level of adhesion.

I found that it can work brilliantly. i.e. You get the ruler to exactly where you want it and then squish it down! This not only minimises accidental errors, but it also helps to prevent softer materials from moving under a scalpel blade. A real game-changer! And of course when the tack wears out you can simply replace the tape.

This is what I used:

VERY sadly I think Letraset gave up making the stuff several years ago. And now I have very nearly run out.

Last time I looked I couldn't find a 3M /"Post-it" type tape that is dual tack.

J

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