Scribing with verniers

[Dr_GMJNParticipant @dr_gmjn]

All, I suppose I can predict the response to this, but I've got some nice Mitutoyo digital verniers, and sometimes use the points to scribe lines on permanent marker on cast iron, steel, brass etc. Assuming the faces and points are hardened, and I'm only using very light pressure, does it really matter for occasional use on materials like these? I know it's kind of wrong, but…

I suppose I could use my old set of verniers for this, but then again it seems to partly defeat the object of getting the new ones. Transferring a reading to other calipers or dividers would seem to introduce an error, so…what's the best method of scribing accurate lines offset from a face for model engineering?

I'm looking at getting a digital height gauge (fairly cheap one), and I notice their pointers seem to be specifically for scribing – I think I saw some described as scribing pointers? Presumably they are similar material to verniers?

Thanks.

[Dr_GMJNParticipant @dr_gmjn]

[SteviegtrParticipant @steviegtr]

Yes they are carbide tipped. I have 2 mitutoyo versions. They both have a carbide tip. Here is a pic. That said i & plenty of others use the calipers to scratch with.

Steve.

[Tony Pratt 1Participant @tonypratt1]

Nothing wrong in using calipers as a light scribing aid if you are careful, I though mainly used the end of a steel rule held in a combination set square head, just set the rule to say 10mm butt the head against the work surface & scribe a line, not at all accurate but gives you a rough guide to start with, I never actually worked just to lines but setting out a job saves scrappage, well usually. Back in the day most height gauge scribers were hardened tool steel but invariably are now carbide.

Tony

[JasonBModerator @jasonb]

If scratching with callipers it's best to use a dedicate one with modified ends, grind the fixed one shorter and flatter so the scale remains parallel to the surface as tilting them so one leg is resting against the edge reduces the length being scribed.

Or you can pay for someone to do it for you 

Though I prefer the height gauge to odd legs or the occasional digital calliper.

Edited By JasonB on 31/08/2021 16:16:37

[Dr_GMJNParticipant @dr_gmjn]

Thanks all.

I've ordered a 12" digital height gauge just now (an M-Sure one) at about £130. I've thought too often that one would be useful, so I can use that for most of the scribing work I think.

[Anonymous]

Wow, scribing lines? That really is old school.

I very rarely mark out now; mainly for sheet metal that will be filed/drilled by hand, and for the odd reference point to aid setting up a casting. I use a secondhand mechanical vernier height gauge and surface plate and very rarely odd legs; never used my vernier calipers. But then again I rarely use my calipers as I prefer micrometers.

Andrew

[Dr_GMJNParticipant @dr_gmjn]

Posted by Andrew Johnston on 31/08/2021 16:45:12:

Wow, scribing lines? That really is old school.

I very rarely mark out now; mainly for sheet metal that will be filed/drilled by hand, and for the odd reference point to aid setting up a casting. I use a secondhand mechanical vernier height gauge and surface plate and very rarely odd legs; never used my vernier calipers. But then again I rarely use my calipers as I prefer micrometers.

Andrew

It’s mainly to mark out castings as a sanity check for where things are going to be machined to with the DROs, like hole centres offset from edges, or heights above a datum. Also for marking around the circumference for turning things to length, or parting off, at least non-critical lengths.

I don’t do it routinely to machine to, but it’s sometimes useful.

[Mike PooleParticipant @mikepoole82104]

There are plenty of youtubers who are not shy about abusing their caliper, of course I would never dream of abusing a precision measuring tool for marking out but there is a bloke who looks remarkably like me who abuses my calipers. So far the points have not developed any obvious wear and I think it would be an easy job to stone any wear away, I am sure the frame and slide are not designed for this use either but if any problems do occur I shall drop this practice, buy a new one and put it down to experience. Many of our tools have useful alternative functions that often don’t do any real harm, scribers are excellent picks for some jobs and a quick touch up will soon restore the point. I would definitely not abuse someone else’s tools and I hope they won’t abuse mine.

Mike

[Mick B1Participant @mickb1]

I don't scribe with digital or vernier caliper tips simply because I don't know how I can keep from tilting or angling them.

I use the ground flat front edge next to the moving inside nib as a register to get the shaft of the caliper square to whatever datum I'm working from, as per step measurement guidance in most instruction sheets, set the distance, then scribe as near as I can to the ground front of the fixed outside jaw.

Then I work out the theoretical position of the same feature from the opposite face of the workpiece, if there is one suitable, and scribe similarly – and then, because errors if any are likely to be similar, aim between the two lines.

So far, this method has generally worked well enough when I've needed to use it. But it's better to edge-find and dial off your dimensions if you can, or use DROs if you have 'em.

[Bob StevensonParticipant @bobstevenson13909]

……..Ooh er!….I think I must be the only bloke still marking out 'properly'…..

What does get me started is members of my clock club who use the vernier on work in the lathe and don't see a need to turn the lathe off first!

I did once see a vernia sticking out of someones thigh, although not from this to be fair……

[Nigel McBurney 1Participant @nigelmcburney1]

I started in the 1950s and am definitely old school and I dont see anyting wrong with that ,and why not most of the models we build are based on engines ,machinery etc which may have been made donkeys years ago and the castings and materials are nearly all similar, I would for a start never never use a vernier with pointed jaws for marking out, a scribed line needs some depth so that it can be felt bythe point of a prick punch (smaller than a centre punch) where the punch touches the point where two lines meet thats when you hit the punch or if you doing a very precise job check the position of the punch point with an eye glass. marking out machined parts and surfaces can be carried out with a surface gauge ,a more precise method is to use a vernier height gauge with a wide chisel like edge more modern ones have carbide scribing edge, marking out castings to establish datum lines and machining allowances use a surface gauge, to set the height make sure the rule is held vertical or use the square and rule from a combination set..like Andrew I prefer to measure accurate dims with a micrometer rather than a vernier, and still prefer non digital vernier and height gauge ,more reliable in the long term than digital.

[not done it yetParticipant @notdoneityet]

I know it's kind of wrong, but…

Says it all, really. Do you use your micrometers as ‘G’ clamps? Cheap digi or vernier maybe, but not a proper Mitutoyo!

The scribed line can only be most precise with zero overlap on the casting edge, so might just as well use odd leg calipers to do the job (if a rough line) or a proper scribe.

[SteviegtrParticipant @steviegtr]

Posted by not done it yet on 31/08/2021 22:11:40:

I know it's kind of wrong, but…

Says it all, really. Do you use your micrometers as ‘G’ clamps? Cheap digi or vernier maybe, but not a proper Mitutoyo!

The scribed line can only be most precise with zero overlap on the casting edge, so might just as well use odd leg calipers to do the job (if a rough line) or a proper scribe.

I only have moore & wright micrometer, but you have given me a great idea.

Steve.

[Pete.Participant @pete-2]

You can buy verniers designed for scribing, I own some, they are made of stainless steel, have a roller on the movable jaw, and a replaceable scribe point the fixed end, I'm not allowed to put a link, but you can buy them for under £7 delivered.

[SteviegtrParticipant @steviegtr]

Why is there always a strange smell in the room. Of course it is ok to use the calipers to mark out. the only reason you get comments is because there are those that have nothing better to do. Buy a TV license & watch some telly. Or just take the meds the doc prescribed.

Great forum. Love it.

Steve.

[Ron LadenParticipant @ronladen17547]

Ti's up to you if you choose to use your Mitutoyo for scribing lines but for me I would use your old caliper and save your Mitutoyo and keep it pristine as much as possible.

I have a Mitu and a cheapie caliper but I don't tend to scribe with them. For marking out to get a feel for general positioning etc I just use a quality steel rule a small square and a sharp scriber. Where I need accuracy I use a height gauge (non digital) and angle plate, I know some say they hardly ever use theirs but I use mine a lot.

[JasonBModerator @jasonb]

Not really a bad smell just pointing out that it may not do what the Doc wants.

" Transferring a reading to other calipers or dividers would seem to introduce an error, so"

This would seem to suggest he wants a fair level of accuracy as even the cheap callipers compare quite well with name brand ones in the accuracy of their measurements. As a couple of members including myself have pointed out unless the calliper is modified to have the fixed leg shorter you won't get your scribed line positioned from the edge by the amount shown on the calliper so may as well use an oddleg or Jenny set from a rule.

Look at this sketch, 20mm wide bit of metal and wanting to mark a line down the middle, if you set the calliper to 10.000mm it won't mark down the middle, it needs to be set to 10.050 assuming moving leg 1mm lower than surface. It's basic schoolboy geometry.

Certainly more error than you are likely to get between two callipers so won't suit the Doc but often good enough for a bit or roughing out.

What you actually do with your tools is upto the individual but if you think you are getting a line the distance in that is shown on the screen then think again or modify a cheap Aldi/Lidl pair.

[JasonBModerator @jasonb]

I suppose this is what can happen if you use them to scribe too much or take live measurements off rotating work, my Dad must have bought these 70 odd years ago but I don't know if they were new then or seconhand/surplus.

While on the subject of marking out I have had a dig into the back of a draw and this is how my equipment has evolved over the years, on the left a homemade scribing block from "unimat lathe projects" then an import one and finally an import height gauge.

And for marking along an edge this one again from the Unimat book which is similar to a carpenters marking gauge

I certainly used the Unimat items and even that old vernier calliper to build my 10V as schoolboy pocket money was limited and that will run simply by blowing into it. Most of the Stuart Beam would also have used them and I think they were superseeded during the Minnie build

[Mike PooleParticipant @mikepoole82104]

Being guilty of abusing digital calipers I find the instant setup very useful compared to setting odd legs to a dimension. As I use a caliper for jobs where I would probably use odd legs the I would expect the accuracy to not be an issue. Although I don’t own a digital height gauge I think it would be very useful to be able to establish a datum at any height. My trusty old school height gauge is stuck with the surface plate being the zero datum so you need to set the job up to minimise awkward calculations.

Mike

[SillyOldDufferModerator @sillyoldduffer]

There's a hint of bad fish whenever an expensive tool is misused without good reason! Adapting and overworking tools is OK after engaging brain for deliberate benefit, but spoiling tools due to laziness, ignorance or bad internet opinion is surely to be avoided.

Presumably people cough up serious money for Mitutoyo verniers because they need the tool's extra features. To me, it's odd to spend big dosh and then risk damaging an expensive tool when a decent digital vernier suitable for scribing and other rough work can be had for under a tenner. Unlike a Mitotoyo, inexpensive verniers are disposable – replace when damaged. It's what I do.

I mark out much less often than I used to. Getting more confident in myself, the DRO and the dials seems to have reduced the need for sanity check marking, though I still do it when accuracy is critical. I mostly use a scribe and spring calipers plus a cheapo vernier for marking out. I don't expect the same vernier to measure accurately and scratch steel.

Dave

[Dr_GMJNParticipant @dr_gmjn]

Thanks all. The comments have prompted me to use the Mitutoyo ones only for measuring, I'll use the cheap ones for marking from now on.

Here's an example of what I'm using them for: I want to mark the centre of the brass extrusion to drill a hole. What I'd do is colour the surface with permanent marker, get the verniers, measure the minor dimension, set the verniers to half the value and scribe (or at least remove the ink) in a line from each side. Repeat with the major dimension, and that would give me an accurate enough point in the middle I could centre pop ready for drilling. I can then use that hole for setting up in the 4-jaw for further machining.

Same with the port face on the casting: I marked the oval port face from the upper valve face to get a line where on which the three holes needed drilling. I used the DRO to get the 'real' positions for drilling, but the line gave me a double-check.

[Martin KyteParticipant @martinkyte99762]

I have to ask the question. Does it actually harm the calipers? The extreme end of the jaws is not actually involved in measurement and unless scribing actually creates a burr rather than rounding the corners I don't really understand how it can reduce accuracy. I don't tend to use my calipers as a scribe but purely because it feels wrong to use a tool for other than it's intended purpose and I have a vernier hight guage anyway.

Answers on a postcard please.

regards Martin

[Howard LewisParticipant @howardlewis46836]

As an Apprentice Engineer, I was taught to use tools for the purpose for which they are intended.

A tool that is abused will eventually cease to of use for the original purpose.

Callipers are for measuring. Scribers are for scribing.

Carbide tips on tools are there to minimise wear, but will chip.

If you want to scribe on a workpiece, use a scriber, or a Height Gauge fitted with a scriber blade, on a surface plate, or failing that, a machine bed.

As someone once said to a Foreman at Rolls-Royce "There are two ways of doing this" and got the reply "I only know one way; the right way"

As NDIY says, you don't use a micrometer instead of a G cramp, or a Toolmakers Clamp, if you want it stay accurate. No doubt you could use a mic instead of a hammer, but I wouldn't trust it afterwards!

Howard.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Martin Kyte on 01/09/2021 11:33:55:

I have to ask the question. Does it actually harm the calipers? The extreme end of the jaws is not actually involved in measurement and unless scribing actually creates a burr rather than rounding the corners I don't really understand how it can reduce accuracy. I don't tend to use my calipers as a scribe but purely because it feels wrong to use a tool for other than it's intended purpose and I have a vernier hight guage anyway.

Answers on a postcard please.

regards Martin

That's really the question: does it harm them?

I can see that if the ends got deformed inwards, then the jaws wouldn't fully close, and then the zero point would be out. But with hardened jaws, it this really going to happen?

If it's just wear, then as you say, so what? I don't measure using the end 0.5 mm of the jaws anyway.

If it's not harming their effectiveness for their primary use, I can't see any problem with using a tool – any tool – for a purpose other than what it was designed for, if it makes things more convenient.

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