Mill Quill DRO: Installing the Magnetic Scale and Configuring it to Sum 

Just added a quill scale and external summing box to my bridgeport DRO and was trying to decide which way the signs on the Z-axis should be, as you raise the table (work moving towards the cutter) on all manual milling machines I have used the handwheel scale is increasing - ie +ve - and as you move the quill down (tool towards the work) the mechanical scale is also increasing - ie also +ve - so it seems that to match the accepted Cartesian system on the DRO the scales on the machine controls will move 'backwards'? Not that it matters as you won't be reading them, that's why you fitted a DRO after all!

@@adriannicol8529 Yes, the hand crank for the knee typically is counting up as you raise the knee but that is because its easier for the human brain to perceive and comprehend increasing numbers when you need to increase depth. For example, if you set the top of the work surface to zero and you need to take say a .025" DOC, if the numbers on the hand wheel were to count down as you raise the table .025", you would have to start backwards from .100" and go back to .075" (assuming a .100" per rev like most). This could get confusing so it makes more sense to have raise count up so that way 0 is just that, zero and to tank a .025 DOC, you are just counting up to .025 on the dial. Remember, going negative from zero is still "counting UP", just it has a negative sign preceding it. *_"so it seems that to match the accepted Cartesian system on the DRO the scales on the machine controls will move 'backwards'?"_* As for the scale, a linear scale has no "Forward" or "Backwards" its simply a quadrature encoder (i.e., two channels that are either at 0v or 5v and are 90° out of phase from each). The DRO itself is what determines which way counts up and which way counts down. Most quality DRO's have a reverse function so that the user can set the direction based on how they mounted the scale. The scale itself is really just acting as a switch turning on and off the two channels in sequential order. The DRO is just looking for which channel changes state (switch on or off depending on its current state) to determine which direction the scale read head is moving and then based on its coding (The DRO's coding), this will either decrement or increment the counter. The Scale itself just creates a Binary code basically that has 4 possible outputs. Ch = Value A = 0 (off) B = 0 (off) --------- A = 1 (on) B = 0 (off) --------- A = 1 (on) B = 1 (on) -------- A = 0 (off) B = 1 (on) and starts back over with both = 0 (off) As you can see, there is a sequence and depending on which way read head moves determines which way the sequence goes and the DRO simply looks for the change in state on to off or off to on to determine which way the read head moved. For example, lets say that the current condition was state 3 (both on) and then A changed to off, that would mean that it moved to to state 4 but if B was the first one to change to off, then that means that it changed to state 2 (i.e., moved the other direction). In simplest terms, for any current state (1, 2, 3, or 4), the change can only go to the next or the previous, it cant skip. So if it was in say state 2, then it could only change to state 3 or state 1 and depend on which state it changed to, then the DRO knows whether to increment or decrement the counters depending on what its coded (programmed) to do. All in all, DRO's and linear scales are very simple devices. For that matter, with some pretty simple coding and a cheap micro controller like an Arduino, one could have dual scale "summing" on any DRO. I did it several years ago for the quill and knee on a Mill that I have before ultimately converting it to CNC.

@@CJ-ty8sv Hi, thanks very much for the detailed reply, yes I'm familiar with the principles of quadrature decoding - used to build my own crude optical rotary ones back in the '60s before such things were available at affordable (to me!) prices - my dithering was just over the semantics of the the sign for a given direction of travel on manual vs CNC vertical mill which I think you answered for me! I'm also debating whether or not to convert my Bridgeport to CNC and to that end am just putting the finishing touches to an X,Y,Z test bed with mag strip scales to explore closed-loop servoing using LinuxCNC - gives me something to play with in my declining years! Thanks again for the reply

😊😊

I thought the same, the stop is still handy at some times.

Oh, that's right! In glad I read the comments today!

@@Clough42Thanks! I was almost sure you knew about grey code 😄 Hope that blue tape cable management is not too permanent 😂

Hi James Another great video as always 👍 Just what I need to do as an upgrade on my mill, Who’s DRO do PM supply ? Keep up the good work !

@Dave Fieldsend I don't know. This one is from DRO Pros. (edit: spelling)

@@davefieldsend1909 They are MagExact, which looks like re-branded Electronica for their magnetic DROs.

That's a good idea.

I didn't. But it seems to work okay. :)

I prefer to set them slightly below the surface, so tightening the screw pulls the plastic parts into full bearing against one another.

It took me way too many seconds to realize you meant "isopropyl alcohol" and not "India Pale Ale". 😂

It's on my list. :) I'd actually like to put a float-lock and a tapping head on it.

It sure makes pretty parts.

Because the read head isn't adjustable, I chose to just align to the head with the shims. Side to side misalignment too small to see would not contribute enough error to matter in this case. For a grinder? Maybe. For a mill quill? Not really.

I usually work that way, too, but every once in a while I need to readjust something to reach and it will come in handy.

@@Clough42 Understand fully 😋! Thank you for the videos. There is some new thing to be learned allmost every time 👍🏼!

I started using threaded inserts precisely because I had a number of tapped threads in plastic fail. The brass inserts have been much stronger and more reliable.

@@Clough42 Like for like sure brass is stronger than plastic. However, a well formed thread that is say 2-3times as deep actually has a stronger pull out load. But I get the point about the durability and cross threading issue. Like anything, its about making the right choice for the right application.

I actually want it recessed slightly so the screw will pull the faces solidly together.

It's a single-phase mill with a variable speed belt drive.

@@Clough42 well drat, I guess replacing the motor or finding a single phase vfd is likely not worth the effort. I'm so used to 3ph system's I didn't even consider that

Yeah. I've cut many, and I thought about it after seeing the project done. :)

I wanted to try the laser process, and the plasma could never have cut the small holes. There's a plasma video coming next week. :)

That's about my speed.

In actually thinking about putting a tapping head and a float lock vise on my drill press to give it purpose.

I've been shopping, but I'm picky, and good industrial scanners are expensive.

That would be interesting to try. I would expect a little flex in the machine.

There's still plenty of opportunities for that.

Yeah, I had issues with the PM940. The one I received had some squareness problems in the saddle machining. PM took it back and gave me a good price on the upgrade.

Yes. I didn't mention it, but it's easy to reach. It would probably be better with a quick-release button nut.

It's easily accessible from the right side. A pushbutton quick stop would be a good addition.

You must live someplace with actual humidity. :)

@@Clough42 yeah, it's that tiny eu country below sea level.

Oh, it doesn't stick? I guess I haven't turned it off yet.

I read your comment and thought about it.

Everyone needs a 3D printer. Or two. Or five.

That's well within ISO 2768 mk.

@@Universal_Craftsman yes, a lot of errors are within standards, until they don’t match.

@@melgross I agree, but it seems that he didn't specify any fits and tolerances, so the supplier didn't know. Edit: clough42 called out M4 6H so tolerance is specified accordingly.

@@Universal_Craftsman ok. What I’ve found is that is that small holes aren’t reliable for accurate fits using this method. Larger ho,es are fine. The problem is that tolerances remain the same regardless of hole size. You can see the problem. 0.002” can be enough to break taps on small sizes, or give fits that are too loose. True that mostly it won’t be a problem, but I’ve found that it can. Tap type can determine this as well. The strongest tap is a three flute spiral tip. The weakest is a two flute spiral. There are a lot of variables.

@@melgross The standard calls out a minor diameter of 3.242 mm to 3.422 mm. 0.18 mm / 0.007" tolerance for M4. That means that the supplier is definitely off the hook.

Yeah I was going to recommend the same thing. It might not be accurate enough to be able to fit first try kind of thing but should at least get you most of the way there.

Right.

Yes, as @Silicon Alchemist stated, it should be negative (or decreasing) as the knee moves up. Z movements (whether its the knee or the quill) is always tool getting closer to work (so quill DOWN or knee UP) is Negative or decreasing value and tool getting further from work (i.e., quill UP or knee DOWN) is Positive or increasing value.... Basically, you always think in tool movement regardless of what is actually moving. This tends to trip up people on vertical mills a lot on all axis because of the fact of the work is whats moving most of the time, not the tool moving but you have to think in tool movement, not work movement.

He has a 4 axis DRO with 2 axes sharing the Z readout. He set them to calculate the differences between positions so yes. Remember, the readout is displaying the relationship of the tool to the part not neccesarily the position of the knee or the quill. So raising the knee has the same affect on the readout as lowering the quill in relationship of the tool to the work.

I've seen a few. I actually have a Dremel drill press that would make an excellent platform for such a tool.

@@Clough42 There ya go! Nice. If you modify it to the purpose, let me (and/or us all) know how it goes. :)

A warm feeling of accomplishment.

Because if I don't, I get never-ending comments asking what that tool was.

@@Clough42 that's fair, thanks for taking the time to reply