Author Topic: Digital caliper mounted on lathe  (Read 2839 times)

Offline PekkaNF

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Digital caliper mounted on lathe
« on: October 05, 2016, 02:28:43 PM »
I'm pretty sure more people have build these. I have seen some applications of test dial indicator or tyre thread gauge used on cross slide. On my wish list possibility to set diameter display to known (measured diameter would be high on my list. I haven't been able to come up meaningfull solution that would be much better than test dial indicator (or tire thread gauge!).

I figured that much easier application would be to use digital caliper to measure carriage travel lengthvise. Dial gauge travel is often short, caliper is short too, but often enough.

Hardest part was to drill hole on jaw, three drlls later I took solid carbide drill and pu oversize hole. Most important was to have caliper body parallel to lathe ways.

Pekka

Offline krv3000

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Re: Digital caliper mounted on lathe
« Reply #1 on: October 05, 2016, 05:08:18 PM »
a good job well dun

Offline ddmckee54

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Re: Digital caliper mounted on lathe
« Reply #2 on: October 06, 2016, 11:03:01 AM »
Pekka:

I've seen other applications where a caliper is used like this, but most used a clamp to hold the caliper in some type of a pocket.  Probably just to avoid having to drill through the caliper.

Don
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Offline Manxmodder

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Re: Digital caliper mounted on lathe
« Reply #3 on: October 06, 2016, 11:58:56 AM »
Good move,Pekka. I have seen similar ones mounted on the tailstock to register the quill movement....OZ
Helixes aren't always downward spirals,sometimes they're screwed up

Offline seadog

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Re: Digital caliper mounted on lathe
« Reply #4 on: October 06, 2016, 01:10:52 PM »
Like this.

Offline Manxmodder

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Re: Digital caliper mounted on lathe
« Reply #5 on: October 06, 2016, 01:54:24 PM »
Exactly like that  :thumbup: ....OZ
Helixes aren't always downward spirals,sometimes they're screwed up

Offline seadog

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Re: Digital caliper mounted on lathe
« Reply #6 on: October 06, 2016, 02:28:35 PM »
I must remember to resize images in future  :doh:

Offline awemawson

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Re: Digital caliper mounted on lathe
« Reply #7 on: October 06, 2016, 02:33:33 PM »
I must remember to resize images in future  :doh:

... I never said a word .... :lol:


But 640 x 480 is so much more universally seeable  :thumbup:
Andrew Mawson
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Offline seadog

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Re: Digital caliper mounted on lathe
« Reply #8 on: October 06, 2016, 02:56:36 PM »
But I knew it was coming Andrew  :wack:

Offline PekkaNF

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Re: Digital caliper mounted on lathe
« Reply #9 on: October 07, 2016, 03:35:21 AM »
Thank you all.

Hardest part was to design the general shape that could be build out of 14*22 mm standard key stock (pretty free cutting material), would have display angled for easy viewing and could be easily taken out and put back. Should also clear tail stock.

It worked out pretty well.

Things to learn:
* Often stuff comes a little oversize and wobbly, this come out pretty tight, maybe few file stokes would help?
* I paid attention to ease of dismounting, therefore locking bolt must be come undone. Should not have been a smart ass and cram it that close to scale plastic cover - it's used to make bolt captive...works too well.
* I choose magnet to the other end (tapped hole for bolt would have come uncomfortably close lathe carriage lock). This would also break free if moved too far out. Success.
* The locking plate under the scale has a load bearing face on 45 degree angle - the other end has a 6 mm silver steel rod to take that load. Made it pretty tight fit. If it gets a little loose then it's perfect, now it is uncomfortably tight to turn sideways and to take off the slack, but locks up tight as a carriage stop. Amusing, but probably not the best solution here.
* Found out that the whole system has to very straight, there is very little play on the system, minor tilt would cause side load, measured it and got it right, but had to make one "special" thickness plastic washer that provided enough adjustment when squashed with a scale on the lathe carriage end. Found sweet spot easy and now it looks like very accurate.
* The lathe carriage end is a little overkill, but I was not sure if I could get away without bolt. I got better idea, I might try on MK II model if I ever need to build one.

Like this.

Did you had any trouble drilling trough the scale? Mine caliper from Lidl was hard and work hardening, needed a solid carbide drill to drill the hole.

Pekka

Offline seadog

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Re: Digital caliper mounted on lathe
« Reply #10 on: October 07, 2016, 04:31:31 AM »
Yes I did Pekka. I bought mine from eBay but no doubt they are both from the same source. I tried using a sharp standard drill first off, no chance. I then bought a cheap carbide drill, that didn't last too long either  :doh: In the end had to pay out for a better quality carbide drill and finally managed to drill the hole  :clap: I wasn't interested in absolute accuracy since it's only on the tail stock so used three neodymium magnets to hold the body of the caliper to the casting which, conveniently, has a sloping face that presents the scale at a nice readable angle. There's a small amount of twist in the barrel, despite making a longer guide pin, but the magnets allow for a slight sideways movement so this isn't a problem.

Graham

Offline PekkaNF

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Re: Digital caliper mounted on lathe
« Reply #11 on: October 07, 2016, 05:38:36 AM »
So, it wasn't only me that had the hard one?

Next one is for cross feed. Maybe? This lathe is pretty far from ideal, but it is nevertheless very useful to have. I have decided to use some time to improve it's accuracy, fix some problems and make it easier to use. Sort of DRO is convenice, that I'm not prepared to buy real one, but some sort of would be nice.

I have used a dial gauge, it works on finishing steps, but it is always a bit of an add-on that gets fumbled.

I am thinking of using a digital caliper parts for cross slide. There are some problems that has to addressed:

1) Mounting.
* I don't want parts to stick out, as flat as possible. There is very little real estate on the either side of the cross slide.
* If caliper type scale is used just about tailstock side could be used, but needs a stop to prevent tail stock from crushing the scale
* Very easily separate scale would complicate maintenance and collect swarf
* There is a little space inside if the cross slide. Could mount the magnetic/capasitive tape + head there.

2) Reading ergometrics - most likely a separate display would be nice, Diameter set and diameter display would be rally nice.

2a) Cheap caliper scale with separate display
http://www.arceurotrade.co.uk/Catalogue/Measurement/Digital-Readouts-with-Dedicated-Remote-Display/Digital-Readout-Bars-with-Dedicated-Remote-Display
* Price is right, but the scale/read head looks sort of clumsy.
* Has no diameter set/display. I.E. functionality is no better than digital caliper

2b) I could try to mutilate one caliper and see if the scale tape can be persuated out of the caliper and see if the display can be moved few centimeters of flat cable to somewhere more comfortable.

2c) Magnetic tape + read head + display, this would come easily bit too expensive for this project. Fine if I had a nice lathe, then 280 EUR could be justified, but not for this one.
http://www.machine-dro.co.uk/m-dro-magnetic-scale-eh-3119.html
http://www.machine-dro.co.uk/mini-single-axis-display-console.html
This would provide best functionality, it would have diameter display and set. pretty much only thing missing from real DRO would be lack of tool offsets.

Anybody mutilated calipers and found out working way to put them together?

Pekka

Offline Manxmodder

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Re: Digital caliper mounted on lathe
« Reply #12 on: October 07, 2016, 06:40:06 AM »
Pekka, don't know if this is any help to you but Machine-DRO do a good number of replacement reading heads (left and right handed) very reasonable prices.

Link here: http://www.machine-dro.co.uk/spare-parts-and-consumables-battery-reading-head.html

Also available on fleabay : http://www.ebay.com/itm/Replacement-Reading-Head-For-150mm-300mm-Digital-Caliper-With-Hold-Function-/291409531737?hash=item43d95c9359:g:8agAAOSwWnFV~Bz2

......OZ.

Helixes aren't always downward spirals,sometimes they're screwed up

Offline PekkaNF

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Re: Digital caliper mounted on lathe
« Reply #13 on: October 07, 2016, 02:10:10 PM »
Thanks, that might come handy.

Inside is probably very much like this:
http://www.grant-trebbin.com/2014/04/digital-calliper-teardown-and-repair.html

Before taking one completely apart: How do wire a LCD display that is designed for zebra?

Much of the other stuff looks doable.

Pekka

Offline sparky961

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Re: Digital caliper mounted on lathe
« Reply #14 on: October 07, 2016, 05:15:51 PM »
Masonry drill bits are a cheap and readily-available solution for drilling the occasional hole in hard materials. Sharpen the tip similar to a standard bit on a silicon carbide or diamond wheel.

Offline PekkaNF

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Re: Digital caliper mounted on lathe
« Reply #15 on: October 09, 2016, 06:13:40 AM »
I had another identical lying around. Now I have a better caliper, I took it appart to se the innards.

Now: How to extend the zebra connection to LCD?

Pekka

Offline PekkaNF

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Re: Digital caliper mounted on lathe
« Reply #16 on: October 09, 2016, 10:17:54 AM »
It starts to look a little complicated....

I have been trying to find a commercial alternative, but magnetic tape models with displays seem to be over 200 EUR/GBP. Bit steep for a cheap lathe.

Pekka

Offline mechman48

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Re: Digital caliper mounted on lathe
« Reply #17 on: November 04, 2016, 02:45:10 PM »
I have used similar digi callipers on my machine... not cosmetically perfect, but  does the job... :thumbup:
George.


Always look on the bright side of life, & remember.. KISS..' Keep It Simple Stupid'