Mini mill Y-axis DRO question

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dml66

H-M Supporter - Gold Member
H-M Supporter Gold Member
I'm starting DRO installation on the mill, X and Z axis mounting looks to be pretty straightforward, Y-axis mounting raises a question.

The picture was taken from the operator position. The DRO scales I've used all require that the head and the scale must be in the same axial plane, the mill's base where either the scale or the head is mounted is angled with respect to the Y-axis carriage where either the scale or head is mounted.

Wondering how others have rigged their Y-axis scales?

20260706_073803.jpg
 
I used the front-left mounting ear to install a short length of aluminum "L" extrusion on my DRO setup. The DRO was mounted on the vertical section. It seems to be good enough. Your DROs are a different style but I don't think different enough to preclude this approach.

The brass sheet that drives the sensor is flexible enough to accommodate a small angular misalignment. Planning for some misalignment can avoid some "aw shucks" moments. The sheet is plenty-stiff on the long axis to move the sensor w/o any noticeable backlash.


Y Axis DRO.JPG
 
dml66 said:
I'm starting DRO installation on the mill, X and Z axis mounting looks to be pretty straightforward, Y-axis mounting raises a question.

The picture was taken from the operator position. The DRO scales I've used all require that the head and the scale must be in the same axial plane, the mill's base where either the scale or the head is mounted is angled with respect to the Y-axis carriage where either the scale or head is mounted.

Wondering how others have rigged their Y-axis scales?

View attachment 578618
Click to expand...
On my LMS 3990 HiTorque Mini-Mill I mounted a spacer block to the saddle using the existing tapped holes (visible in your photo), cantilevered a steel angle from the block and attached the scale to the angle. The read head is mounted on a bent steel plate attached to the base (read head is fixed & scale moves). Details are in my article in The Home Shop Machinist July-August 2022. Joint copyright won’t allow posting the details (photos, drawings and description) but a digital copy can be purchased here:

 
For now I'm planning to use a 5µm magnetic read head for the X-axis, I already own it and have plenty of magnetic tape, waiting for a piece of tape support to complete that axis.

For the Y and Z axes I'm starting with 5µm glass scales; 170mm and 270mm. These are cheap enough I can always replace them if and when the magnetic read heads come back down to earth price. In any event, the 170mm glass scale was DOA, that's being replaced, the 270mm worked fine.

I planned to mount the mill on a 1-1/2" thick, 12"x12" or so wood block so I can move it around on the bench as needed, I could top the block with a 12"x12" piece of A36 hot-rolled 1/4" steel plate, that provides a flat, square surface to mount the scale. $20 for the steel plate.

20260706_170120.jpg

A short piece of 1" tall by 2" wide aluminum angle would be attached to the Y-axis base on the 1" side, the 2" side would project enough to cover the read head, and be secured to it. The scale would shimmed as needed off the steel base to properly align it with the read head. The power feed adapter is close but, I can trim as much as another 1/2" off the bottom to clear the angle bracket without exposing the bottom of the motor, if needed.

I'd probably also mount a full length piece of thin aluminum angle between the read head and bracket to keep the swarf out of the scale, like this one that came with the scale:

1783386934686.png
 
Your DRO has a larger footprint than the DRO I used so your approach looks better suited. I like the swarf cover, too.
 
ChazzC said:
I'd recommend a Steel angle as it will flex less than Aluminum.
Click to expand...
If I attach the read head to the angle bracket, it's almost as long as the bracket itself, about 3-1/2" or so, I think I'd be OK with 1/8" thick aluminum. The disadvantages to that approach are the the head with it's armored cable becomes the moving part, and it exposes the scale's rubber seal which in turn requires additional swarf-defense efforts.

If I attach the scale to the angle bracket then I'd definitely want to use steel for the bracket. The disadvantage to that approach is I'd have to add a 9" long piece of bar stock to the bracket; the scale can only be secured at it's ends. I could probably avoid swarf-defense since the scale's rubber seal points downwards.

I'm inclined to go with the latter method above but I need to see if I have enough height clearance for the bracket and the additional 9" long bar stock.
 
Anyone know what these two tapped holes are intended for?

And more importantly, has anyone accurately measured distance apart, distance from base etc?

20260707_153348.jpg

The holes were plugged with M4 setscrews, they are bored all the way through to the dovetail. I measured with a a digital caliper and my finest Mr. Magoo shop spectacles.
 
I'd recommend mounting the read head so it's stationary since it keeps the cable from flexing. Make a read head mounting block for the base that's angled so it's aligned with the scale. Mount the scale on the moving part. The "L" channel will act as swarf protection.

Here's a photo of mine. It's a different mill, but it might give you some ideas:
mill y axis (2).JPG

I bought a really small profile scale; it's fully enclosed in that little checker pattern square you can see on the right. The read head is mounted on the base with some "L" channel.
 
dml66 said:
Anyone know what these two tapped holes are intended for?

And more importantly, has anyone accurately measured distance apart, distance from base etc?

View attachment 578759

The holes were plugged with M4 setscrews, they are bored all the way through to the dovetail. I measured with a a digital caliper and my finest Mr. Magoo shop spectacles.
Click to expand...
The most obvious is that they're for a DRO. I have never seen them used for anything else, but that's all been hobbyist-style upgrades rather than a commercial product.

When I take measurements of pieces or holes in my lathe and mill, I assume that the target dimensions probably are "nice" metric numbers. So in your case I'd assume the actual distance is supposed to be 53 mm. Once you throw in some additional clearance for thru-holes that would be "close enough" for most requirements.
 
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