question about tape measure

[Artonelia]

Yesterday I needed to cut some 1 1/2 x 25 x 3/4 stiles. I pulled out my Stanley 16 ft tape measure and measured 25 inches and marked the wood from one end. Since I was going to be making a lot of these I wanted to be very sure that they were cut accurately so I checked it against two metal rulers and found that although both metal rulers (one an old carpenter's square and the other a new machinist's square) and found that although both agreed that 25 inches was 25 inches, neither agreed with the Stanley tape measure. The steel rules were consistently about 1/6 more than the tape measure. I then picked up another steel ruler, this one only 18 inches long and measured 18 inches plus 7 inches. This resulted in the same mark as the other metal rules.

Am I wrong in expect less than 1/16 accuracy over 25 inches of the Stanley tape measure? FWIW, I checked it with a 25 ft Stanley tape measure and it measured the same as the 16 ft tape measure.

I ended up using the mark from the metal rule and then cut all 16 of these stiles to the same length using a stop-block. It was more important that they all be the same than that they be exactly 25 inches. Yet, 1/16 in 25 inches means a lot when you are trying to join multiple pieces together squarely.

Any thoughts by other woodworkers? Is it just Stanley or was I expecting too much from a tape measure?

 

[Doug71]

You get Class 1 and Class 2 tape measures depending on their accuracy. Think Stanley only do class 2, I always use Fisco Big T tapes that are Class 1.

Explained here

https://www.thetapestore.co.uk/tapes-ru ... e-accuracy

 

[Phil Pascoe]

The error is probably in the hook. If you wish accuracy, use a rule rather than a tape and then use the the first piece after you've double checked it to mark off the rest.

 

[MikeG.]

It actually doesn't matter what you use, so long as it is the only thing you use. The problem comes when you start using 2 or 3 different things for measuring. It actually doesn't much matter if your measuring device is inaccurate when measured against the universal standard. What matters is that it is internally consistent, so to speak (ie the 100mm from 200 to 300 on the scale is the same as the 100mm from, say, 150 to 250). Also, as has been said, never rely on the hook on a tape measure. Move the tape along a set amount (100mm, 200mm, or say, 6" or 1') and use it as a rule (not forgetting to then add/subtract the amount you moved it along). And then there are rods........

 

[sunnybob]

as per Phil, but with more detail;
The hook MUST be square to the tape when its laid flat along a board. 1/16" is easily lost on a bent hook.
The hook MUST be loose. If you have got fed up with the hook flapping and have sealed it somehow, There is your problem.

I have known people glue and even tack weld the hook because they thought they were "improving" the tape. It has to move, to be accurate in both internal and external masuring.

 

[Trainee neophyte]

I recently bought a cheap yellow square, china-mall style. It has a ruler printed on both sides, up to 45 cm. One side measures 5mm more than the other - I think the makers mark is "Sum Ting Wong".

I only use it when I'm feeling lucky.

 

[rafezetter]

While I understand people like the accuracy of class 1 & 2 tape measures - the reality is it's all relative.

If you are working to anothers given dimensions, unless you have specified they use a class 1 or 2 tape, then one of you will have a margin of error no matter what you do.

If you're measuring something up yourself, such as an alcove for shelving, then as long as you use the SAME TAPE MEASURE for all the measuring AND the sizing of shelves it really doesn't matter whether it's 1mm "out" or 50, use the same numbers and you're golden.

This is one of the reasons why when accuracy is absolutely paramount, many craftsmen don't even use a tape measure, preferring story sticks or a mark transfer from an adjacent item - there's no actual measurements to get hung up on, a mark, is a mark, is a mark.

Edit - ahh MikeG beat me to it.

 

[Doug71]

Back in the day when life was simple and all windows were single glazed I used to cut quite a bit of glass. A customer phoned me with measurements for a piece of glass they wanted cutting which I cut and they collected. A bit later I got another call from them saying I had cut it the wrong size, I apologised and said I would cut another. They came over to collect the new piece and pulled out their tape measure to check it, this is where we discovered the problem. Their tape measure was a childrens sewing tape measure which they had got out of a Christmas cracker, it was about an inch out over 12 inches and even more if you pulled it because it stretched very easily =D> =D> =D>

As somebody already said make sure you are working off the same tape measure.

 

[Simon89]

My ‘favourite’ tape is now getting a little worn on the end and requires a +- 0.5mm correction depending on if you are measuring inside or outside. Like others have said you just need to know what your working with

 

[Phil Pascoe]

If it is properly designed and manufactured, the movement of the hook allows for the difference in inside/outside measurement.

 

[HappyHacker]

Out of interest I found and tried a range of my tape measures.

From seven tape retractable tape measures ranging from a free one (metric only) through a B&Q value, a old rusty Stanley through to a Stabila, once I had straightened a couple of bent metal tabs they were all giving inside/outside measurements accurate to less than 0.25mm or about the width of the line over 12 inches 300mm. Most appeared spot on.

I then tried a 50m Silverline fabric (fibre glass?) tape which was about 5mm out over 300mm but I know from experience when measuring long distances I can vary the reading by a couple of centimetres depending on how hard I pull. I then tried a 30m Imex steel tape which was spot on at 300mm.

I also tried a Bosch laser which was again spot on at 300mm.

The steel rules I tried all agreed with each other to the limits of my eyesight.

Given the abuse my tapes receive I was surprised. I am sure I have one where the metal tab moves far too much between inside/outside but I did not manage to find that one.

 

[Phil Pascoe]

As pointed out before, the accuracy is to a large extent irrelevant as long as you use the same ruler or tape all the time, and if possible use a comparative measurement. If you're measuring accurately things less than a few inches or a couple of hundred mil you shouldn't use a tape anyway.

 

[RobinBHM]

Ive used tape measures in a busy joinery shop for years without issues.

Its only on here have I seen the discussion about class 1 and class 2 tapes.

I think possibly that the key is the difference between the true measurement of a standard compared to accuracy of repeatable measurements.

For accurate measuring, its best to ignore the hook and measure off the 100mm ( and try not to cut things 100mm short)

My biggest frustration is that almost all tapes these days have crap hooks, no matter what I do, they always ping off the end.....Grrrr

Oh and the cheap stanley tapes from screwfix. They dont hook over well because the tape itself flexes too much and the 5m tapes dont extend to 5m -they break if you try (DAMHIK).

In joinery precision requirements vary so much, so its important to keep it relative. Tenon thicknesses and some grooves may need to be within 0.1mm, the rebate dims for a casement 0.5mm, overall size for a window 2mm.

Ive trained my joiners to do culmultive measurements -its so much more accurate. For example a large roof lantern 5metres long with 6 or 7 rafters, I work out every measurement and then the tape measure can be hooked over 1 end and all the marks pencilled along to the end.

 

[Doug71]

If anybody is frustrated with all the rubbish tape measures out there just get one of these. I have used many different tape measures over the years and these are best by far.

The hook is really solid, you can pull it out past 5m and it still goes back in and once you use the quick release belt/pocket clip you will never go back.

https://www.screwfix.com/p/fisco-bt5me- ... lsrc=aw.ds

 

[Inspector]

Years ago I took a weeklong timber framing class with Ted Benson. He had a problem with framers "burning and inch" when they marked a beam for cutting only to discover they were too short. To combat it he had Starrett make a batch of tapes with the first inch after the hook blank before the graduations began. His guys could start the layout on zero and never forget to add the inch to their measurements. It would be nice if some manufactures would offer the same on a production tape.

Pete

 

[YoelD]

Is the hook shift still accurate? Test is with a rule to make sure the hook is still moving the correct distance for internal and external measurements.
Although as someone said above, as long as you use the same measure for the work and it's consistent, there's little in it.
In all honesty though, I only use a tape measure for rough measuring allowing for waste.