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Cutting down a linear glass DRO encoder

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Robin Graham26/04/2020 23:33:42
709 forum posts
167 photos

In another thread I asked about electronic compatibility between the linear glass scale encoders from ARC currently being sold at clearance prices and a Sino readout which I have. Thanks to advice on that thread that is sorted out.

I would like to shorten the 500mm encoder I bought. I've had a look around and although there are some who say that it can't be done, there are some videos on YouTube showing successful methods. I also came across a 2010 discussion on HMEM in which someone reported success just cutting through the whole thing, casing and glass together, with a bandsaw. That seems too scary for me!

My current plan is to hold the whole unit (casing and scale)  in the 4-jaw on the lathe and have at it with a diamond disc mounted on a toolpost spindle, using the cross slide to advance the cut.

This is just a trawl for any more info, either from direct experience or links to internet sources, before I take the plunge.

Robin.

 

Edited By Robin Graham on 26/04/2020 23:34:56

Edited By Robin Graham on 26/04/2020 23:36:53

mgnbuk27/04/2020 07:46:20
766 forum posts
60 photos

Will a diamond disc cut the aluminium extrusion without clogging ?

I am of the "it can't be done" persuasion, but I guess it depends on how lucky you feel ? Might work , but you might also end up with an unusable scale & a spare read head.

Good luck.

Nigel B.

John MC27/04/2020 07:52:09
avatar
279 forum posts
38 photos

I've done it with an angle grinder with a very thin cutting disc graded for Aluminium. Worked fine. The scale I shortened had plenty of length so I was able to make a "practice" cut. I also left the scale as long as possible so if there was any damage to it it wasn't in the measuring length .

John

Robert Atkinson 227/04/2020 08:39:20
avatar
645 forum posts
16 photos

An abrasive / diamond disk should cut the glass scale without issues. Make sure that if it has an index mark that you don't cut that end off.

Robert G8RPI.

Dave Halford27/04/2020 09:50:38
750 forum posts
6 photos

I would cut the end off without the label. If you hacksaw a slot in the aluminium side to get access to the scale, then diamond disc cut that followed by cutting the remaining alloy with the hacksaw.

Ordinary Dremel steel cutting discs will not cut glass.

Edited By Dave Halford on 27/04/2020 09:51:26

Paul Rhodes27/04/2020 10:09:33
15 forum posts

I held the glass flat against an MDF board . Using a very thin sheet of foam such as used under wood effect flooring as a backing to ensure no grit stress risers, the supported glass was then easily cut with a Dremel and a diamond coated cutting disc.

Robin Graham28/04/2020 22:10:05
709 forum posts
167 photos

Thanks - reassuring for the most part! I realised after posting that the nay-sayers I'd come across in my searches were either vendors, who obviously can't recommend this sort of thing, or folk who hadn't actually tried it but had heard from 'someone' that the glass is tempered and would shatter to smithereens at the first touch of a cutter. Which seems to be a myth.

The scale in the encoder I have looks like it's glued to the ali extrusion along its whole length:

glassscale.jpg

so I can't get it out and cut on the bench. I have spare length, so shall make practice cuts with discs I have - I think I need to go through metal and glass with one setup to get a square end to refit the end cap. Squareness won't happen with a hacksaw in my hands!

Robin

Paul Rhodes29/04/2020 11:44:23
15 forum posts

Robin, IIRC my glass was held in with 1/2inch long 1/16th rubber strips which came out with a small pick.Take a picture before removing as I think there was an offset against the reading head. The ends had a dab of glue holding them in the end caps.Of course the wiper seals pull out permitting better access.

I would not be confident of the glass remaining intact if the glass were to be cut in situ. I have seen it done on YT but....

Robin Graham01/05/2020 21:53:08
709 forum posts
167 photos

Thanks Paul, but after taking the read head off and removing the wipers it's clear that the scale is glued along its whole length, so no chance of getting it out.

I too have watched YT videos - at least one person has got away with just chopping through the ali extrusion and glass scale in one go with a standard metal cutting bandsaw. I reckon the blade must have chipped the glass which then broke in the right place. The blade cannot possibly have actually cut the glass. He got lucky I think!

Being a scaredy-cat I've been making experiments on mock-ups and have come to the conclusion that it's probably best done by hand, so I've ordered up some carbide tipped hacksaw blades.

What can possibly go wrong? Watch this space and you'll probably find out....

Robin

Paul Rhodes02/05/2020 22:30:06
15 forum posts

Good luck....I will listen for the scream!

Les Jones 104/05/2020 13:08:28
2130 forum posts
146 photos

Hi Robin,
After reading this thread I have bought one of these scales from Arc Euro.(500mm) I notice from your other thread on the subject that you made an adapter cable. I thought at first that the connector on the scales was a 7 pin DIN but on checking I found the pin layout was different. I assume that you must have found a source for a 7 pin socket to match the scale. Could you please tell me what it is called and where you managed to obtain it. I think I can fit mine to my Seig X3 without having to shorten it.

Les.

Robin Graham04/05/2020 23:39:01
709 forum posts
167 photos

Some measure of success. First attempt wasn't good - this is the test cut-off piece:

glassscalecut1.jpg

I cut the case as near to the glass as I could with a junior hacksaw, then tried to open the kerf with a carbide hacksaw blade (the red bit) with the intention of working round to get the blade flat on the glass and at least make a score line. The grit on the blade was far too coarse and it all broke apart before the blade got to the glass.

On the plus side, (a) if that had been the final cut it wouldn't really have mattered because the read head doesn't get that close to the end, and (b) the glass didn't shatter. On the minus side - well, it's not nice.

Attempt two - this time I cut as before, but went went into the kerf with a diamond wheel on a Dremel type tool , nicked the glass, and with my heart in my mouth and my bowels in my trousers I snapped the end off:

glassscalecut2.jpg

Result!

Robin

Robin Graham05/05/2020 00:13:30
709 forum posts
167 photos
Posted by Les Jones 1 on 04/05/2020 13:08:28:

Hi Robin,
After reading this thread I have bought one of these scales from Arc Euro.(500mm) I notice from your other thread on the subject that you made an adapter cable. I thought at first that the connector on the scales was a 7 pin DIN but on checking I found the pin layout was different. I assume that you must have found a source for a 7 pin socket to match the scale. Could you please tell me what it is called and where you managed to obtain it. I think I can fit mine to my Seig X3 without having to shorten it.

Les.

Les- my adapter cable was a lash-up. I found a 7-pin female DIN socket in my bit-box which fitted the plug on the ARC scale and wired it to a 9-pin D plug to fit my readout following the pinouts Dave gave in my other thread. I wanted be sure it would work before doing any mods. I can confirm that the pinouts and wire colours given in Dave's post are correct for the ARC scales . I ended up cutting the cable and soldering directly to the new plug, but if you want to make a proper adaptor cable it looks like this should mate with the plug on the ARC scales.

Robin

Edited By Robin Graham on 05/05/2020 00:29:26

Edited By Robin Graham on 05/05/2020 00:31:52

Edited By Robin Graham on 05/05/2020 00:41:53

Les Jones 105/05/2020 12:35:53
2130 forum posts
146 photos

Hi Robin,
Thanks for the reply. I am now wondering if the connector on your scale is different to mine as the pin layout is different to a DIN connector.

Here are pictures of my plug.

2005051134561859126.jpg

2005051137362019370.jpg

Looking an the Farnell website I think I have identified the connector as a Binder 680 series connector.
This is the Farnell web page for the sockets.

**LINK**
I have also found a chasis mounting socket on ebay eBay item number: 362709678935

They are quite expensive so I think I wil try to make some kind of connector to test the scale. When I know it is OK I will fit a different connector to the scale.

Les.

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