3 Axis Mini DRO for Mini

7/29/2019 3 Axis Mini DRO for Mini

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3 axis Mini DRO for Mini-Mill for ~$125

By jjsmn

Hi Guys,

Well, this project has taken several months longer than it was supposed to - not because of the difficulty of

the installation, but because of the installer - me.

Let's get at it:

Here is what I used:

Two 12" remote reading scales from Grizzly for the x and z axes: http://www.grizzly.com/products/12-Digital-

Scale-with-Remote-Readout-Inch-Metric-Fraction/T23012

One 6" remote scale for the Y axis. http://www.grizzly.com/products/0-6-Digital-Fractional-Horizontal-

Vertical-Remote-Scale/T21577

1 1/4" and 1 1/2" aluminum angle for the brackets.

#6 - 32 screws, washers and nuts.

Metric M6 x 1.0 x 16 bolt for x-axis bracket ( more on this later).

My goals were: 1. Have an affordable DRO. 2. Protect the scales as much as possible. 3. Have the readoutvisible. 4. Make as few modifications to the mill as possible.


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Let's start with the X-axis:

The X-axis scale is mounted so it hangs underneath a piece of aluminum angle attached to the front of the milltable. The mobile part of the scale is attached to the carriage by using the pre-existing holes for the X-axis table

lock bolt and the bolt for the little pointer for the ruler/scale on the front of the table.

Here is the step by step:

1. Remove the Y-axis handle/wheel from the mill and set it aside.

2. Remove the X-axis locking bolt and the little pointer and its bolt.

3. There is a ruler/scale on the front of the table. Pop out the little blind rivets that hold it on and peel it off thetable.

4. Drill and tap those holes for the screws that will mount the aluminum angle mounting bracket to the table. I

made mine 6-32.

5. Cut a piece of aluminum angle to the length of the digital scale and place it against the front of the table.

You will see that the gib bolts interfere with the angle and keep it from sitting flush with the table top. Trim thebottom edge so it misses the bolts.

6. Round the corners of the angle that stick out from the front of the table to prevent nasty surprises.

7. Drill holes in the angle to match the holes in the front of the table and attach the angle to the front of the

table making sure the top side of the angle is flush or a bit below the table top.


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8. The scale is mounted under the ledge of aluminum angle that is sticking out fom the table. You may need to

play with the mounting brackets on the scale to get the mobile portion of the scale facing the correct way so itdoes not hang up on the mill anywhere. I counter sunk the screws I used to attach the scale to the underside of

the bracket to make a smooth top surface

9. Drill holes in the angle to mount the ends of the scale.

10. The scale comes with a few mounting brackets. I used the angle bracket. If you attach it to the mobile partof the scale you find that it lines up nearly perfectly with the two holes you see in the carriage where youremoved the locking bolt and the pointer. Enlarge the holes in the small angle bracket so the bolts will pass

through it into the carriage.

11. The braket stands off from the carriage a bit, so I made a bushing out of brass tubing to fit between the

bracket and the carriage.

12. I put a M6 x 1.0 bolt through the center hole of the bracket and snugged it up to hold the angle bracket

firmly.

13. The X-axis locking bolt now threads into the other hole in the carriage. I chose not to try to replace the sliphandle. I just use a socket to tighten it now.

14. Replace the Y-axis wheel.

15. The X-axis is done!!


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The Y-Axis.

Here, the aluminum angle mounting bracket is attached to the mounting bolts that hold the mill to the table

on the left side. I ran the bolts up through the table and put on the nuts, and then slid the angle over the first

nuts and put another set on top of them. This eliminates dealing with the angled side of the base of the mill.

The aluminum angle sits with its vertical side facing away from the mill. The 6" Scale is attached to this

vertical leg, and the mobile portion of the scale is attached via a "z" bracket to the side of the carriage via a hole

drilled and taped there.

The step by step:

1. Cut a piece of angle the approximate length from the front of the table when it is extended forward and back

to the column. This my be too long, but you can always cut some off.

2. Attach the "Z" bracket included with the scale to the mobile part of the scale, and then clamp the scale to

the aluminum angle and push it up against the side of the carriage. This will tell you where to drill your holes inthe angle that the mill mounting bolts go through. Make sure you have enough length on your aluminum angle

to the front so that the scale can travel all the way forward when the table is brought that direction.

3. Make sure the mobile part of the scale doesn't get hung up on the "accordion" rubber chip guard between the

back of the table and the column. My scale is mounted so that the mobile part of the scale sits just below themetal strip that holds the accordion to the table.

4. Drill your holes in the aluminum angle and set it on the existing nuts and screw down a second set of nuts ontop of it.


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5. Attach the scale to the aluminum angle (Again I used 6-32 screws.) and then center punch where the "Z"

bracket rests against the carriage. Drill and tap for a 6-32 screw.

6. I am going to make a rubber flap and attach it to the end of the mill table using the existing screws that will

hang over the scale and protect it from chips. I am also thinking of installing a fitting and hose to carry

coolant/lubricant out of the table grooves and away from the scales.

Holy Crap! The Y- axis is done. Why did this take me 5 months???


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The Z- axis!

The Z-axis 12" scale uses the column mounting holes for the small metal angle iron that the vertical Z scale that

came with the mill. The mobile part of the scale is attached to the mill head by - you guessed it - the studthat the little pointer for the original Z-scale is attached to.

The step by step:

1. Remove the 4 Phillips screws that hold the metal angle and Z-scale ruler to the mill column. These weretotal pain to remove on my mill despite much Kroil and cursing. I ended up wrecking a couple of them.

They are M3 size screws if you find you need replacements.

2. Take a piece of 1 1/2 x 1 1/2 aluminum angle and lay the original Z-scale on top of it. Mark the screw holes

and draw the semi-circular cut out for the torsion spring for the mill head. By laying the original scale outsideand on top of the aluminum angle for marking, it moves the column mounting holes a bit forward on the

aluminum and this makes the aluminum angle sit back a touch. This gives clearance for the scale so it does not

get hit by the torsion arm as the mill head moves.

3. Screw the aluminum angle to the mill column.

4. Clamp the scale to the aluminum bracket. It's a bit tricky to thread the scale between the torsion spring armand the aluminum angle. Make sure you have clearance and that the torsion arm doesn't hit the scale when it

moves up and down.

5. You will need to make an "L" bracket from sheet metal to join the mobile part of the scale to the "Pointer

Stud" sticking out of the mill head. Remove the pointer and nut.

6. Attach the mobile part of the scale to the "Pointer Stud" with the original nut.

7. Drill your attachment holes in the Aluminum angle for the ends of the scale. Did I ever say I used 6-32

screws?

The Z is done!!


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Final thoughts:

This is NOT a replacement for a 0.0005" DRO. This one will read to 0.001". This should be good for me at

the controls of my mini mill as I will always be the limiting factor.

I used velcro tape to attach the readouts to a piece of scrap laminate flooring I screwed to the wall. There are

magnets and screw holes on the back of the readouts also.

I have not had a chance to test it much yet. However, the digital scales seem to correlate pretty well with thedials on the axis wheels. How will the mill motion affect it - I need to test more.

I have done my best to protect the scales. We'll see how it holds up.

Hope this helps someone.

JJS

3 Axis Mini DRO for Mini

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