# Cleaning a Heidenhain DRO glass scale



## Holt (Feb 23, 2012)

Last week one of our EDM machines had a faulty glass scale and the technician decided to change it for a new one, i scored the old one, and will try to clean it.
Both ends of the scale can be removed, both ends are held in place with 2 philips screws and some silicone







The technician pointed out how dirty the reading head was, by braking the PCB off the head.
Fortunately i could glue it back on with epoxy after cleaning the lens and reader with 99% isopropylalcohol






I dropped a string through the scale and tied a piece of cloth from the optician at the end of the string, and pored some isopropylalcohol on the cloth, and dragged it trough the scale taking care to keep it at one side of the glass, so i knew that side was clean.






Then i did the same on the other side of the glass, i put a piece of foam inside the cloth to compensate for the larger space on that side of the glass.






The cloth reveals that it was about time to clean the scale






The reading head can only fit in one direction, and it's easy to see how.
Now the ends shall have some acid free silicone and the 2 screws, and the scale works like new (i tested it at work, on a lathe DRO)


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## HS93 (Feb 23, 2012)

Thank you for that, very useful to know.

Peter


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## AussieJimG (Feb 24, 2012)

Good one Holt and great photos.Thanks

Jim


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## Blue_Rock (Feb 24, 2012)

Interesting post. I've been trying to find a picture of the mechanism inside a glass scale. Thanks


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## d-m (Feb 24, 2012)

Holt 
I checked out your link On the Mini engine build VARY NICE STUFF!!!!! Hopefully here is a pic of my 62 Austin 28thousand original miles 
Dave


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## Blogwitch (Feb 24, 2012)

Simon,

Be careful, they are not all the same on the inside.

My Sino ones are totally different, on those, you can slide the glass scale completely out, and the head is supported by fine wires with ballraces on the end of each wire, a sort of shock absorber.


John


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## Blue_Rock (Feb 25, 2012)

Hi John

I've got the Sino scales too. Thanks for the heads up.


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## coopertje (Feb 25, 2012)

Hi Holt,

Nice job on the Heidenhain scale! Treasure it, you can use it in future on your new lathe. If it is too long you can make them shorter, I have done this when a scale on my Thiel broke down. I carefully cut away the aluminum housing by sawing and milling






Then took the dremel tool with a diamond cutting disk for glass and ceramic and cut of the glass scale. Finished up the side of the housing:






After cleaning the internal of the housing as you did, assembled and mounted on the milling machine. It works with out any hick-up for more then 2 years already!

Regards Jeroen


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## Holt (Feb 25, 2012)

coopertje  said:
			
		

> Hi Holt,
> 
> Nice job on the Heidenhain scale! Treasure it, you can use it in future on your new lathe. If it is too long you can make them shorter



It was the idea, that it should be used on the colchester. I knew about shortening it, i don't know if it's necessary yet, i just got it in the workshop tonight, been busy cleaning it up with a lot of help from my oldest son.

John, just changed the headliner to say "cleaning Heidenhain DRO scale"

Holt


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## coopertje (Feb 27, 2012)

Good to see that your lathe has arrived home, hope to see some pictures soon!

Have fun with your new toy, regards Jeroen


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## Swede (Feb 28, 2012)

This is good stuff. To many of us, the innards of a glass scale is a mystery, the whole thing being a sealed black box kind of thing. It's good to know they can be serviced if needed.


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## Blogwitch (Feb 28, 2012)

Holt,



> John, just changed the headliner to say "cleaning Heidenhain DRO scale"



I wasn't complaining at all, in fact it is very informative and we could do with people showing more obscure tips like this.

It was because that someone could in fact drop a bit of wire through and pull on it and cause some damage because it wasn't the same type of head, but now you have changed the topic name, that problem shouldn't arise.

Thanks


John


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## Holt (Feb 29, 2012)

John - you were quite right to point out the different types of glass scales, and that they should be serviced in different ways, i would also add that no one should clean their scales unless they don't work, there is always a risk involved, don't blame me if you can't get it working again.


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## NEEL (Feb 28, 2013)

I have a Heidenhain glass scale where in the LED light source is bad. Can some one suggest what type of LED to be replaced with as there is no type number printed on it


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