Electronic vernier accuracy

[Steve Maskery]

I posted recently about a Little Accident I had when using a 1/4" cutter in my router table. It chattered, came loose and ruined my workpiece. When I measured it, my digital vernier said it was 6.2mm, well under the 6.35mm that is 1/4".

Lurker came today and we had a look. Sure, it didn't look good as a cut, but we measured a few other cutters, and they were ALL coming in at about the same! Different manufacturers, different ages.

So I got out a second vernier, Jim found a battery in his car, and we measured them with that. 6.32 or thereabouts. So two different tools were giving two different readings of the same shank.

Go figure, as the Americans might say.

 

[Brandlin]

No sure why you are surprised.

Any device used to measure will give you a different reading to another measuring device.

Precision is the ability to take consistent readings
Accuracy is the ability to take a reading which is close to the actual measure

Sounds like your calipers were pretty precise but not very accurate

 

[Phil Pascoe]

Try them with a micrometer?

 

[Brandlin]

Try them with a micrometer?

Micrometers vary too.

Admittedly micrometers TEND to be more accurate and precise than vernier calipers simply because of the method of construction and the manner in which a measurement is taken. But you get good and bad levels of accuracy depending on the quality of the tool.

 

[MusicMan]

Get a calibrated set of slip gauges. Doesn't cost the earth and saves the hassle.

Keith

 

[Eric The Viking]

I have three digital callipers, only one of which I trust. And I've misplaced that one - grrr!

So I do relative readings mostly (and have a good one on the shopping list).

 

[memzey]

I posted recently about a Little Accident I had when using a 1/4" cutter in my router table. It chattered, came loose and ruined my workpiece. When I measured it, my digital vernier said it was 6.2mm, well under the 6.35mm that is 1/4".

Lurker came today and we had a look. Sure, it didn't look good as a cut, but we measured a few other cutters, and they were ALL coming in at about the same! Different manufacturers, different ages.

So I got out a second vernier, Jim found a battery in his car, and we measured them with that. 6.32 or thereabouts. So two different tools were giving two different readings of the same shank.

Go figure, as the Americans might say.

Slight attack of pedantry oncoming but aren’t they either digital callipers or vernier callipers?

 

[Jacob]

Try them with a micrometer?

Micrometers vary too.

Admittedly micrometers TEND to be more accurate and precise than vernier calipers simply because of the method of construction and the manner in which a measurement is taken. But you get good and bad levels of accuracy depending on the quality of the tool.

Micrometers will be more precise but not necessarily more accurate. Accuracy and precision are not the same thing.
Personally I stick to the same cheapo Draper vernier calliper which I've had for many years. It's precise enough for all woodwork purposes and easy to use and read. It's probably not very accurate - it doesn't zero at zero, but that's OK once you get used to it.
Basically the more precise the instrument, the more varieties of instrument you try, the more discrepancies and errors you will discover and the more confused you will get!

 

[Steve Maskery]

Slight attack of pedantry oncoming but aren’t they either digital callipers or vernier callipers?

Ooh, I've been out-pedanted. That doesn't happen very often

 

[Rorschach]

Who did the measuring in each case?

When I watch friends use a caliper I find that most of them don't know how to take an accurate measurement with them.

 

[Duncan A]

Digital calipers are often cheap rubbish and slip in use so will give inconsistent results. Good quality vernier calipers are often to be found at sensible prices and never suffer from flat batteries!
As stated by others, a micrometer is more accurate than calipers and multiple measurements are best all taken by the same person.
Don't forget to measure in two axis and at several points along the shaft - there's no guarantee that it will be circular in shape or that it won't be tapered!
Duncan

 

[Jacob]

Digital calipers are often cheap rubbish and slip in use so will give inconsistent results. Good quality vernier calipers are often to be found at sensible prices and never suffer from flat batteries!

Actually poor quality ones aren't so bad either

As stated by others, a micrometer is more accurate than calipers and multiple measurements are best all taken by the same person.

More precise, not necessarily more accurate.

 

[Racers]

I have just checked my Mitutoyo micrometer aganst my silver and black workzone digital calipers using a ball bearing.

Mic 16.000mm stopping turning as soon as I felt resistance 15.998 with the clutch.
Black calipers 16.00mm.
Silver calipers 15.98mm.

So not a lot in it, I don’t think 0.02mm will matter for woodworking.

Pete

 

[Steve Maskery]

I did the readings in both cases.
I have two digital calipers. They are different, but they are both cheapo Lidaldi ones. They take different batteries. I'd be happy to use a trad vernier if the scale were easy to read.
I'm coming to the conclusion that it is the Xtreme Xtension reducing sleeve that is the problem. They do wear. The last replacement I bought was when Roger Phoebe owned the franchise, so that tells you how old it is. I must drop Peter Sefton a line. The sleeves are not listed on his website, but that doesn't mean he can't supply them. They must be available as a spare part.

 

[Eric The Viking]

I have a similar problem with my little Bosch POF 500/600 routers They do seem to get through collets fast, and their collets are expensive! The design isn't as good as the ones for my T10/11* - the clamping only really happens at the end and relies on a narrow ring at the other end (deeper into the router shaft) to maintain concentricity. The bigger router's collets clamp over more of the cutter shaft.

E.

I use a proper 1/4" collet in my T11 - no reducing sleeves from 1/2" - and have very little problem with that at all. I also got a second nut for it to reduce the swap-over time, so only need to un-clip the actual collet occasionally for "deep cleaning".

 

[user22161]

I'm not surprised 2 different makes of verniers showed different measurements, same applies to tape measures, I had two which showed 1/8" discrepancy over around 8 ft.

 

[Racers]

You can’t compare a printed tape to a digital caliper they are totally different things.

Pete

 

[Peter Sefton]

You can’t compare a printed tape to a digital caliper they are totally different things.

Pete

and difficult to use when 8 foot long

 

[Peter Sefton]

I did the readings in both cases.
I have two digital calipers. They are different, but they are both cheapo Lidaldi ones. They take different batteries. I'd be happy to use a trad vernier if the scale were easy to read.
I'm coming to the conclusion that it is the Xtreme Xtension reducing sleeve that is the problem. They do wear. The last replacement I bought was when Roger Phoebe owned the franchise, so that tells you how old it is. I must drop Peter Sefton a line. The sleeves are not listed on his website, but that doesn't mean he can't supply them. They must be available as a spare part.

Give us a shout on Monday Steve, we have Whiteside and Muscle chuck reducers in stock.

Cheers Peter

 

[user22161]

You can’t compare a printed tape to a digital caliper they are totally different things.

Pete

I'm well aware what verniers are, I have a digital and an ordinary one. I was commenting about not being surprised they vary. Some makes obviously better than others.