you can find a separate dro for the quill its like a digital caliper turned sideways. mitutoyo has one but its costly I got mine for about 40 bucks made a quick mount and I just need to remember to turn it off or barrery replacement time they come in 5" and 6" lengths . they are cuttable with no damage. just make sure the cut is in the mount not used. I got mine at a local tool store. this store sold machinist tools. If I knew how to post pictures I would bill
After studying the options, I installed a Mitutoyo Quill DRO kit on my PM935 mill. I acquired it on sale at Zoro for a decent price. The kit is for a Bridgeport or clone.
The install went reasonably well but did require a few tweaks to get it “right and tight”. I am sharing some of the details with some photos in case it may help someone who decides to go this route.
While the kit comes with instructions and a very good parts list, Adam’s (ABOM79) YouTube on mounting a kit on a Bridgeport was very helpful to familiarize one with the kit and how it mounts.
The kit came with all the hardware needed with the exception of two mounting screws needed for my PM935 install.
Here is a list of the things I did to make it fit and make the install better for my particular mill. This list is not intended to be all inclusive and one should confirm that the dimensions of your mill would require everything I did or perhaps something different.
Tweaks and insights:
I had to chase the small M3 threads in the mounting frame – the powder coat had choked the threads.
I had to countersink the holes on the back of sending unit mounting plate to accommodate the included #5 gun screws. Screws were too short as supplied to get proper thread engagement. I could have ordered proper length screws from McMaster but decided to simply use what I had and milled a step for them to sit in.
I milled off .060”of mounting bar to move the assembly closer to mill and to maximize the insertion of the mounting tube into the stop ring on the mill.
I bought two new mounting screws to attach the mounting bar (M4 x 12), one had to be ground slightly shorter to not interfere with the power feed mechanism. I did not leave the depth scale on the machine as called for in the instructions. I found this to not be needed for spacing nor add any functionality since the scale was covered if left in place.
I shimmed the mounting tube to the mill’s stop ring joint to take up .010” of slack in the fit. This allowed the set screw to expand the mounting tube to a good firm fit and eliminate any wiggle in the joint. You can see the copper shim wrapped on the split tube in this photo. This shimming avoids the wiggle that ABOM79’s video shows. Thanks to Adam for making the YouTube since it catalyzed me shimming the tube/stop joint in the initial install and making it rock solid.
All in all a very good fit and function with just a little adapting and tuning. There's still plenty of room behind the Mitutoyo for the original depth stop function to be adjusted and work well. I can still put my depth stop clamp on the rod as well. Although many folks keep them removed anyway, the front fine feed crank/wheel also still fits without interference.
Hope this may help others if you decide to go this route. Here is the unit installed on my PM935TV.
Rich, thanks for posting Adam's YouTube. I had missed that one somehow. It was helpful and pushed me forward in buying the Mitutoyo kit. As I pointed out above, it also clued me in on the wiggle issue and to be prepared to address it.
I did not get the mounting screws for the Mitutoyo mounting bar short enough. The mounting bar uses the same holes as the factory depth scale for installation. The factory scale is mounted over the Auto Feed mechanism (see pg 14 of the PM manual). While I did not believe the bottom screw was interfering with the trip push rod that locks the "Quill Auto Feed Lever", turned out that it actually was interfering just enough to cause a problem.
While everything appeared to be fine, the screw was just long enough to bind the "Trip Push Rod" itself and the "Quill Auto Feed Lever" would not lock and hold position. Lesson learned - Make sure that screw is short enough that it will not infringe onto the trip push rod.
As always, Matt at QMT was ready and willing to help but it turns out that I had laid a trap for the both of us and I wasted Matt's time. Sorry Matt!
Trip Push Rod schematic:
Here's a photo of the mounting bar in place with the two screws in the original attachment points for the factory depth scale. Size the length of this screw to not interfere with the function of the Trip Push Rod (#5 in schematic above):
Apologies, I posted elsewhere on 935 quill DRO & then found this post specific to the Mitutoyo model 053906 (sometimes B on end?).
I'm relatively sold on the Mitutoyo, mostly because it happens to be on sale right now! But I've noticed I have not seen a picture of the DRO in conjunction with the down feed hand wheel. Is that because people just don't use the hand wheel much, or the DRO conflicts with it?
The Mitutoyo Quill kit is ok, it works, doesn't impinge on the downfeed crank-handle. That said, I prefer to make my own mounting brackets, which you've probably already seen ( LOL ): https://flic.kr/s/aHsmpXogeF
...which you've probably already seen...
David, with your integrated set screw micro-adjusters, does it lend itself to running a test indicator up the face & edge of Mitutoyo scale on quill movement, kind of like dialing in your XYZ DRO scales? Or is it mostly about dealing with casting variations & geometry in general? Any general words of wisdom re drilling & tapping cast iron for bracket items like this?
Peter, please realize that the primary reason I ditched the Mitutoyo supplied quill mounting bracket system is because I needed to integrate a proximity sensor into the quill DRO encoder mounting system. This proximity sensor triggers an auto-reverse when the sensor detects the quill stop, and is handy for threading operations. Thank you Mark Jacobs.
If I had not needed to add the proximity sensor, I might have used the Mitutoyo supplied bracket system, modified along the lines of what Alan H did.
If you do decide to make your own brackets, here are some tips. First, be very careful where and how deep you drill and tap the head casting for mounting screws. You're working in an area where the power downfeed trip mechanisms are buried inside the casting. See this for more info: https://flic.kr/s/aHsmq2F8fj
The other thing is that if the Mitutoyo scale is not precisely aligned and kept flat, the encoder part (which is attached to the traveling doughnut ring) will drag on the scale enough to add friction to the quill movement, defeating the auto-retract spring no matter how much you tension the retract spring. That was the purpose of the jacking set screws in my bracket design - to be able to tweak the angle and casting offset for each scale end.
There is no practical way to check the alignment of the scale part using an indicator or similar - it's a matter of fussy trial and error, and to get all the friction of the Mitutoyo DRO dialed out of the system, it took me a couple of hours tweaking things. Since I didn't install the Mitutoyo bracket, I have no idea if it's easy or fussy in this regard.
David your projects are always a joy to behold. Thanks for sharing your thoughtfully and well engineered ideas. Coupled with the magic of Mark Jacobs and its Wow! You both deserve a heartfelt thanks for sharing and enlightening the rest of us.
OK, here goes with my installation. I will preface this by saying - what a weird piece of kit! Kind of a puzzling assortment of hardware & bits of pieces with no clear instructions as to what they are for. Unlike the proverbial Ikea furniture build, I had hardware left over! Recognize there may be variations to '935' mills out there. Also I am no expert. I'll run it this way for a while & if I see things I don't like, I'll report back.
My stock rule scale was removed & exposed M4 screws & threaded holes in the casting. Similar to others, my screws did not have sufficient clearance in the slot so cleaned up the aluminum bar with 4mm end mill. Found center & took off about .007" on either side, just enough to give the shank clearance. It wasn't just anodizing buildup, the slot itself wasn't cut so great.
I measure how much the stock screws protruded into the casting & ended up using M4x10mm cap screws to give me the same penetration. Someone pointed out if the lower one goes in too deep, it can mess up the down feed mechanism. Thanks for that heads up!
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....?
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.
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
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.