Poor Mans DRO

vendredi 29 mai 2015

I did say I would do a thread on the DRO installation on my mill. I thought I would get started with it. I have not had much time to spare, but I did steal a bit of time tonight. I have been doing lots of stuff including another improvement on my hay/lifting trailer. It has a 3000lb winch on it now and I was repositioning it for better leverage. I fitted a jockey wheel which is much easier than the stand it had. I also made a cap to cover the chimney for our kitchen range. This was made from steel, not Villaboard. Hopefully the stove won't get dripped on when it rains now. I did not destroy any files in making this.

I am about to start building a fence post driver to attach to the tractor. This will involve machining of the cable drum, but I wasn't planning on a build thread unless people want to see it going together. I was going to try and machine grooves in the cable drum to guide the cable, but decided to make a spring loaded fairlead that is controlled by the cable on the drum and will hopefully lay the cable neatly. This is important with these drivers unless you want to spend ages untangling the cable on the drum.

The DRO.

Scale Brackets and Readout.jpg

One of the scales with the readout mounted on an ali angle bracket along with the mounts for the other 2 readouts and brackets that came with the RDO's.

The top bracket actually came with the 24inch scale. This is the only one supplied. The other brackets were supplied with each unit. There are little plastic knobs on the readout mounts that fit inside keyhole slots on the back of the readout unit. They don't fit very securely and can and the readout can come off easily. The slot in the mounts is a dovetail accessed from the rear. I hammered some 3.2mm wire into a rough wedge shape gave it a bit of a curve to hold it in and pushed it into the dovetail slot. The readouts have magnets on the back that line up with the slot. This gives it more stability.

LED Worklight.jpg

While I was doing the DRO on the Z axis I fitted the LED Work Light. It works well although I am still intending to get a goose neck from Jaycar as mentioned in a thread on this subject. It is powered by a powerpack in the electrical enclosure and comes on with the mill power. This is a 10w light. I should make a new bracket to mount the light. I just drilled a hole in the existing one. It is a bit untidy. The black wire at the back is from the DRO.

Mill Head with DRO.jpg

I just posted re the lack of progress with the quill rotation problem. This is the way I have connected the Z axis scale head. Allthread, springs and nylock nuts. It works well. I need to do something with the block that holds the mill depth scale pointer. The threaded block that the pointer is attached to has about 6mm too much clearance at the back of the ali cover plate where the depth scales are printed. This meant that it could foul the read head of the DRO. I had to put some HDPE packing behind the cover plate. This is visible under the scale pointer. The block is also not properly aligned with the slot in the ali so it sits on an angle. I may just get rid of it. It is only useful for tapping now. The upper gear lever had to be rotated 180 deg. This was a problem as it was secured with a pin which was as per usual on these Chinese machines, way off centre and off square as well. When I removed it however, I found that the handle had a steel hub which was drilled and tapped for a grub screw already. Once I have decided on a position I will grind a small flat for the screw to engage and re-lable.

Readout Bracket.jpg

The readout bracket mounted on the side of the electrical enclosure. You can see the bashed bits of wire in the horizontal slots. The readouts do not turn off automatically. Maybe this is why they came with a spare set of batteries each. CR2032. I will connect them to another powerpack when I have finished the installation so they also turn on with the mill power.

Mill Table Rotated.jpg

Tonights effort involved working out how to attach the X axis scale and read head. I worked out that I had to undo the table rotation bolts in order to get the table off for rear access. I was not wanting to play with this, but I had no choice. When I undid the rotation clamp bolts, I found that the table could be rotated 360 deg, provided I moved the table to provide column clearance. This is the rear of the table in the picture. It will be a simple job now to attach the scale and read head. Putting the scale on the edge of the table will reduce the Y axis movement by a small amount. Less than 10mm I think. The longest scale is sitting on the table.

I bought these DRO's in a set of 3. 6 inch, 12 inch and 24 inch. They came from the US in case you haven't realised. All up they cost less than $A180 delivered. Considering the cost of a full DRO, I could not see enough benefit in spending several times this figure for a cheap hobby machine. I would rather buy more tooling.

Dean
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