Author Topic: BIG digital caliper  (Read 613 times)

Offline Joules

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BIG digital caliper
« on: April 27, 2017, 12:20:08 PM »
I've seen a lot of guys fitting digital calipers to lathes and mills, thanks for the inspiration.  I needed to measure a large item accurately, my height gauge is the largest digital measuring device I have at 300mm. OK I could use it over the side of the bench, but the lathe has DRO.



Meet my new 650mm digital caliper.  The DTI ensures you always have the same pressure on the part so you don't distort it.  Zero off the block (anvil) in the chuck.  It's a new way of measuring for me, so that lathe or mill DRO can also double duty as a massive caliper.  It's sure a lot more stable than my 150mm hand held version.
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline awemawson

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Re: BIG digital caliper
« Reply #1 on: April 27, 2017, 12:27:14 PM »
A nice bit of lateral thinking Joules  :bow: :bow:

(How critical IS this bicycle rim  :lol: )
Andrew Mawson
East Sussex

Offline Joules

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Re: BIG digital caliper
« Reply #2 on: April 27, 2017, 12:30:13 PM »
The cycle rim came to a sudden stop.  I had a go at making it round again, but failed.   :scratch:   Should have bid on your power hammer.
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline Joules

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Re: BIG digital caliper
« Reply #3 on: April 27, 2017, 02:41:31 PM »
Taking this a little further.  The DRO is switchable between lathe and mill, this means I can switch to mill and use the DRO for setting out work, bolt patterns, scribed lines etc. A cross drilled bar can be held in the tool post and scribe point lowered to the work surface for marking.   I wasn't expecting to make any use of the DRO's mill features....   BONUS 
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline jim

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Re: BIG digital caliper
« Reply #4 on: April 28, 2017, 09:24:02 AM »
Excellent use of the DRO :nrocks:
if i'd thought it through, i'd have never tried it

Offline DMIOM

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Re: BIG digital caliper
« Reply #5 on: April 28, 2017, 12:59:45 PM »
Joules,

I've done something similar on the manual mill, but totally non-contact (sorry no pics kept though).

I have previously probed items with a basic Renishaw probe, but several years ago I bought a (relatively) cheap USB microscope, which obviously had a very limited field of view - but it did have a cross-hairs option (it also claimed to have a calibrated graticule but I didn't trust/use that).  What I did was secure the USB microscope to the quill of my DRO-equipped mill, and then drove the mill bed around until features were under the cross-hairs, noted down the DRO readings, then moved on to the next feature etc.  - all total non-contact. I didn't take time to try and actually centre the USB device in the quill, what I did though was to secure the camera to the bottom of the quill but locked so it couldn't rotate. The USB microscope had limited depth of field, but on a workpiece of varying height I could move the quill up&down to maintain the focussing without touching the camera at all.

I have even used that rig for something similar to what you're doing: I had a nominally circular centre-less ring item to check, so not easy to spin on an arbor without fitting a web which might have distorted it. Firstly I found the centre by picking-up a point on one side under the cross-hairs, zero the DRO, pick up the other side and the use the DRO 1/2 to set centre on that axis, then repeat on the other axis; and to spot check if it was circular I used the DRO's PCD function to get to a number of radial positions.

Dave