# DRO for knee mill



## DanP (Jul 1, 2012)

Hi all. I am looking for a dro for my mill and wondered if any of you know about the ones Grizzly sells.

http://www.grizzly.com/products/8-x...bsp;

This is the particular one I am looking at for my mill. H7848 - Digital readout 8x20x16 ¾ 3 axis - $765.00

I think this is the one I need for my mill. I am just a hobbyist, no production work.

My mill is a Rockwell #21-100. Working surface is 6.5" x 24". X axis is 16", Y axis is 6.75" and Z axis is 16.5"

Your opinions are wanted please.

Dan


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## ksouers (Jul 1, 2012)

Hi Dan,
Welcome to HMEM.

Sorry, I have no experience with the Grizzly product you mention. 

But I did get one of these 3-axis DRO from Shars in Chicago a few years ago:

http://www.shars.com/product_categories/view/40602/Digital_Readouts

It's made in China but it is one of the very few quality products they produce. It has glass scales on all axes with very fine resolution, .0001 inch. Also has many built in calculations (bolt circle, arc, angle, etc.) I think it even has step milling a curve, if I recall.

Anyway, welcome to HMEM. Please feel free to post an introduction when you get a chance.


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## gbritnell (Jul 1, 2012)

Hi Dan,
Take a look here. I bought a set for my knee mill and am quite happy with the product and service.
gbritnell
http://www.dropros.com/


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## steamer (Jul 1, 2012)

Welcome Dan!

Dave


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## DanP (Jul 2, 2012)

DRO Pros mentions a 4 axis DRO. What would the 4th axis be? I am a real beginner so any help is needed.
Thank you all for the welcome, I think I am going to like this form.
Dan


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## Blogwitch (Jul 2, 2012)

Dan,

I would suspect the 4th axis would be the quill feed down/up measurement.

For my 3 axis unit, I use the normal X & Y plus Z1, which is table up/down, and for my quill, fourth axis, Z2, I use a normal Chinese scale driving a display head of it's own. Much cheaper than buying a 4 axis display head and glass scale to fit the quill. Because the cheapo scale is well above the swarf/coolant firing range of the table, it has never caused one bit of trouble in over 3 years.


John


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## DanP (May 15, 2013)

Hi all.  OK, I picked up the Grizzly DRO and am now in the process of installing it.  I have not found anyone locally to help me so it has been a bit challenging, the instructions are mostly useless, still, I am enjoying the challenge.  The X axis is on and works great.  I am now working on the Z axis.  The only way I can see installing it is to have the "reader" on the knee moving up and down the spar.  That's OK but it will have the open part of the spar facing the table so lots of chips will spray toward it. I can see no way to protect it.  My question is, will this be a problem?  The opening is covered by a slit weather strip type closure.  I&#8217;m not sure how do describe this.


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## Davo J (May 16, 2013)

Hi,
I have fitted a few DRO's, the normal way to mount the knee one is to face the opening backward and fab up a bracket from the knee to the reader head that goes around/past the scale.

Dave

PS
Just did a search and found these for you
http://www.ebay.com/itm/Acu-Rite-Li...-Knee-PN-689404-03-/251264879317#ht_212wt_679

http://bedair.org/Mill/6760mill9.html

http://knifedogs.com/showthread.php?25509-DRO-install-WIP

The DRO PROS should have details of installing it as well.


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## Davo J (May 16, 2013)

I mounted my scale on the front of the table, I hope you can see the install in the link if your not a member.

http://www.chaski.org/homemachinist/viewtopic.php?f=43&t=84767

Dave


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## DanP (May 16, 2013)

Dave, you are a Godsend, these pictures and information will make the whole project come together sooner while having a cleaner, more professional look to it. I must remember to ask more questions on this site.


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## Davo J (May 16, 2013)

No problem and I am glad it helped.

Just a tip,
If you go to Google and type in "milling machine DRO knee scale" or "milling machine DRO install"
Then select images you will get a lot of pictures.

If I am searching something I always go that way first. Please don't get me wrong I don't mind answering any question, it's just a tip.

Dave


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## Mike N (May 16, 2013)

I bought mine from:
http://cdcotools.com/

I have these on my Bridgeport milling machine & lathe.


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## DanP (May 21, 2013)

OK, I have my DRO installed and working like it should.  I just wanted to thank everyone for the help and support.  I am very new at metal work; I have always been involved in wood work.  I must say it gave me great pleasure making the few small pieces I needed to make for mounting the scales and readers.  I could really get into machining; again thank you for the help.

First of all, I have many parts I need to make for my Gauge 1 projects then I hope to make a 1&#8221; scale Heisler so get ready for more questions. :>)


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## johnny1320 (May 22, 2013)

gbritnell said:


> Hi Dan,
> Take a look here. I bought a set for my knee mill and am quite happy with the product and service.
> gbritnell
> http://www.dropros.com/


 

Which system do you have? the glass scale or magnetic, I was looking to put a dropros on my lathe.


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## DanP (May 22, 2013)

I bought the Grizzly Model H7848 which has glass scales.  I am a hobbyist and did not think the added cost of magnetic scales was necessary.  This is a very nice piece of kit, armored wires, steel ends on the scales plus 1/5th of a thousands resolution.


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## Davo J (May 23, 2013)

DanP said:


> OK, I have my DRO installed and working like it should. I just wanted to thank everyone for the help and support. I am very new at metal work; I have always been involved in wood work. I must say it gave me great pleasure making the few small pieces I needed to make for mounting the scales and readers. I could really get into machining; again thank you for the help.
> 
> First of all, I have many parts I need to make for my Gauge 1 projects then I hope to make a 1 scale Heisler so get ready for more questions. :>)


 
We all like pictures, and it might help someone down the track.

I have high praise for the guy that sells Sino on ebay. I have also read about other guys having good experience with him.

It works out a lot cheaper buying through him, from memory the 3 axis is around $520 delivered and the 2 axis is around $420 delivered, which is really cheap. The Sino has a die cast housing which is a lot more heavier and robust than the plastic ones offered by other sellers.

Dave


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## DanP (May 23, 2013)

OK, I hope this works.  I just finished a little job so there are chips all over.  Tha's a piece of 1.25 x .25 cold rolled steel behind the Z axis.


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## Davo J (May 23, 2013)

You did a great job on the mounting brackets considering this is your first one, I bet it has taken your machining to another level.

Just a few tips, 
1 You need to turn the scale around on the knee so the cable exits toward the bottom.in the manual it should tell you how to reverse the scale direction.
2 The scales really need cover over them that come down to cover the gap between the scale and reader head to stop anything getting in. It also protects the scale from knocks as it's meant to be around 3mm (1/8) from the scale.
The X axis would be easy to add a cover and with the Y the picture below show an easy method. The Z being vertical could really do with something as it's the most exposed being vertical. It's not only chips that get in, dust can also.
3 The cables need to be tied up before something snags them and damages either the socket or the reader head.

Dave


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## DanP (May 26, 2013)

Yes, I knew the cables needed to be tied up/organized so they were not going to snag, I have done that now. I don't understand why you suggest the cable exit out of the bottom of the Z axis, the way it is there is less kink in the cable. Yes I can see that it will be easy to cover the X axis and your idea for the Y axis solves that problem. What to do with the Z axis well I'm not sure yet. On another note, what size should pictures be for posting on this site?


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## Davo J (May 26, 2013)

I think the forum resizes the pictures as they look fine.

With the knee cable, if it's toward the bottom it acts as a drip relief, where the way it is now any oil or coolant etc will run strait to the reader head.
The cable is usually looped at the bottom and then cable tied to the bracket, this way if you happen to drop anything it will pull on the cable tie and not the reader head.

The first one I installed I used steel angle everywhere to cover the scales. This included the knee scale and I made up a plate on top to cover the scale and reader head. It was a bit of an over kill with the thickness of steel I used, but the few times I dropped a spanner etc I was so glad I didn't have to worry about anything.

Dave


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## DanP (May 27, 2013)

OK, I understand why the knee cable should be changed.  And I thought I was finished setting this up.

"I bet it has taken your machining to another level."  I don't know if it's to another level but it sure has lowered my machining time for a given job.


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## Davo J (May 27, 2013)

Yeah and no more backlash to worry about with counting hand wheels.

I just thought I would mention those points to make your system last longer. I know with me things are are one off purchase and I cant afford to be buying them twice.
Talking about buying, I fitted a 5 axis readout to my mill last week and a 4 axis readout to the lathe. They have come down in price so much since buying my first one 6-7 years ago.

Dave


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## DanP (May 27, 2013)

I don't want to buy anything twice if I can help it.  5th axis on the mill, the angle?


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## Davo J (May 28, 2013)

The DRO has rotary capability on the 5th axis, but I am using it on the ram as it's a knee mill. This way I can throw the Y number into to the calculator and subtract or add the ram, then put that number back into the Y.

It would be good if they had summing of the Y and B (5th) and the Z and A (4th) but that will come.

I have had a few teething problems with them as they are new out, but the manufacturer is working with me to fix the few little problems. The price was unbelievable and is why I bought them. I only bought the readouts as I have about 13 scales from other sets and ones I have bought cheap on ebay.

I originally contacted them because my Meister XPOS3 lathe readout quit working and after contacting the Meister guys they wanted $390 for a new board. These guys would supply a new 3 axis for $82 and around $50 postage, just goes to show the rip off from Meister. I can buy a brand new XPOS3 direct from China for under $150, so not sure where there price came from, but they lost me as a customer for life.

Dave


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