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Tenson
25-05-2012, 09:21 PM
All my tape measures are crap; the hook at the start is not fixed and has about 0.5mm play, so it is impossible to accurately measure things like lengths of steel for my CNC machine frame.

Can you guys recommend an accurate tape measure where the hook is fixed precisely, or another way to go about measuring longer items?

C_Bubba
25-05-2012, 09:28 PM
The movement of the hook is to have an accurate measurement of both ID and OD or length measurements. The movement is about the thickness of the hook.

Tenson
25-05-2012, 11:38 PM
The movement of the hook is to have an accurate measurement of both ID and OD or length measurements. The movement is about the thickness of the hook.

Ahh I see, but still can anyone recommend an accurate item, rather than one where the movement is only about right?

John S
26-05-2012, 12:01 AM
How accurate ? How wide is your stick of chalk ? :friendly_wink:

C_Bubba
26-05-2012, 01:07 AM
I agree with John on this one. A "tap measure" is not a real accurate measuring device.
I would not even agree that the markings are real accurate! (precision)

Jonathan
26-05-2012, 01:18 AM
i always measure from the 100mm mk.

Same.. it's the obvious solution.

Surely for a frame what's more important is to get repeatability since it's unlikely to make much difference if you measure 600mm and get 600.5mm as with the error you describe every piece will be 600.5mm. The frame will still be square etc, just negligibly off the size you wanted.

JAZZCNC
26-05-2012, 02:10 AM
Tapes are for wood and rough material sizing, precision engineers rule is the minimum I would recommend and even then I'd double check every time.!

Tenson
26-05-2012, 04:31 AM
How would you accurately measure 1800mm, Jazz?

John S
26-05-2012, 08:40 AM
put two one metre rules end to end.

Web Goblin
26-05-2012, 08:56 AM
Tapes arent that accurate anyway and I think are only reasonable good at 20 degrees C. Since most tapes get wear and tear at the ends the best way as the others say is to measure from 100mm mark remembering to adjust for it at the other end. We used to get 15mtr tapes sent for calibration at one point, total waste of time in my opinion.

i2i
26-05-2012, 09:59 AM
have a search on ebay, i'm sure they used to sell a digital vernier tape. :lemo::friendly_wink:

i2i
26-05-2012, 11:00 AM
i think this was his username..

ihaventgotacluebutidontcare101

JAZZCNC
26-05-2012, 11:01 AM
How would you accurately measure 1800mm, Jazz?

Me personaly I would use my Rabone Chesterman No64R 1.5m rule and a 3.2.1 block as accurate marker then go again. Or. . . has john said use 2 rules, probably a 310mm engineers rule in this case.? I do have 1 mtr rule but don't class it has accurate enough to be called precision.! Still leaps ahead of a tape thou.

To give some idea of the quality and accurecy of a precision rule stamped on the Rabone is the warning "Only standard at 20c" and originally came with a certificate of calibration. I've had it for many many years and one of the nice things about living close to Sheffield is you drop across some high quality tools. :toot:
( If that border jumping gringo Bandit John S don't snaffel em first.!!!)

JAZZCNC
26-05-2012, 11:07 AM
i think this was his username..

ihaventgotacluebutidontcare101

Hey.??? . . . . You been out in the sun too long i2i. .!!

i2i
26-05-2012, 11:18 AM
Hey.??? . . . . You been out in the sun too long i2i. .!!without a doubt..:peaceful:

Robin Hewitt
26-05-2012, 05:05 PM
My Stanley FatMax is accurate at 20 degC, it's written on it.

Here compared with my Mitutoyo caliper over 150mm using digi microscope.

I can't see any error because Stanley chuck any blades that fail their test :whistle:

Jonathan
26-05-2012, 05:14 PM
Here compared with my Mitutoyo caliper over 150mm using digi microscope


I just checked one from the pound shop vs my 600mm digital caliper using mark one eyeball and it looks spot on. As expected, pointless exercise.

Tenson
26-05-2012, 05:27 PM
How about if you include the hook, is it still spot on?

Jonathan
26-05-2012, 05:36 PM
How about if you include the hook, is it still spot on?

Yes is it still correct

Robin Hewitt
26-05-2012, 05:41 PM
I just checked one from the pound shop vs my 600mm digital caliper using mark one eyeball and it looks spot on. As expected, pointless exercise.

Putting your scratch slightly off the mark is only human when all's said and done.

Blaming your tape measure is even more human :hysterical: