Quill DRO for a PM935?

[petertha]

Issue 1 was the block that holds the round stem & gets mounted to the DRO back. It took me a while to figure out what was going on - it just didnt fit nice to the DRO display unit. First I increased the depth of 90-deg countersink because the 2 flatheads protruded above & plate would not sit flush.

The plate itself is mounted with four 5-40 screws which is a WTF choice of bolt, at least for my inventory. Why not M3? Why not 4-40? The SR# label sticker raises the back a couple thou & yes this makes a difference of how the crazy thing wants to be mounted. If you over tighten, it can bind the sliding action. If you loosen it too much, well, you've lost some of your 2 threads of engagement. At some point I'm going to back & either blue locktite my current setup or 'ever so slightly' counter bore so the heads are slightly recessed like someone else did. Nope, I didn't want to re-tap the stainless DRO back! LOL. There are some strange stickers that come in the kit which I thought might be for shimming but I couldn't figure them out. I just experimented with tape until I had the right fit. This was some kapton I had laying around.

Nope the washers don't appear to be for standoff on the back face of DRO. And if you install them between bolt head & plate, the screws dont engage. Hmm....?

 

[petertha]

Trial fit #1. I installed the assembly the way it looked in instructions & I had about 0.1" gap. I suspect this might be normal, someone else milled the bar thickness down which is one option. The bigger issue is that the stem does not get much penetration into the donut looking depth collar. So I put the scale on the opposite side of the metal frame bar to net me the distance. Since it gets pre-assembled anyway, I didn't really see any downside.

I also replaced the supplied 10-40 set screw with a normal cap screw & that allowed me easy & positive tightening with ball end hex wrench. The set screw is a royal pita.

 

[petertha]

I used pop can aluminum to make kind of a round shim collar between the clamp pin OD & the donut ID. I think it was about 0.005" That made for a nice slip fit & the tightening was just a quarter turn & it was solid

 

[petertha]

To install I left all the fasteners just finger tight & got the DRO scale lined up close. Then I set up the mag base & indicated first on the front face ground edge, then on the side edge by extending & retracting the quill. After a few iterations its about 0.001" runout over travel & appears to be staying put nice & tight. Note you can bend the steel frame 'door handle' thing 10 thou just tugging on the cantilevered ends, so A) easy way to adjust the in/out B) try not to bump the frame or if you do, run the indicator over it again.

 

[petertha]

Here is my bass-akwards scale installation that actually seems to offer a few advantages over front mount.

 

[petertha]

Final install. Yes the down feed 'captains wheel' handle fits too.

 

[davidpbest]

Looks great.

 

[Firstgear]

If anyone needs countersunk Allen screws 5-40 thread, I bought 100 and will be glad to send you some...PM me and I will give you an address to send a self addressed stamped envelope to....The screws are 0.5” long so you will need to shorten them up.

 

[Firstgear]

This is what I bought... https://www.amazon.com/Socket-Screw...F8&qid=1545505997&sr=8-15&keywords=5-40+screw

 

[kb58]

This thread brings up something I hadn't thought of:
With a knee mill, how is a hole in the work bored? DRO sensors are typically on the knee, which implies that the knee controls the cutter feed. The thing is, most quills have a fine feed lever (much more fine than the knee handle), which seems to imply that's what's supposed to feed the cutter into the work. Which is it? My PM935 hasn't arrived yet, hence the question.