PM728VT quill DRO

[kmanuele]

I noticed an odd thing while using the quill DRO and fine spindle feed.

Whenever I changed direction and moved a few thousandths the DRO reading wouldn't change. The quill (and handle) was moving visually.

A dial indicator on the quill showed that the DRO was missing about 3 to 4 thou of movement.

Then I found that if pressed lightly on the DRO case, the reading would jump to the expected reading. Which is weird, since I don't think there is anything mechanical in there.

The effect is most noticeable when lowering the quill after raising it.

New-ish battery, DRO components firmly attached.

Anyone experience this, or similar?


Speaking of batteries: the DRO defaults to metric after power is lost, as in a battery change. I learned this the hard way in the middle of a milling operation :-(

K

 

[Sqidget]

I had this happening to mine. The slide is binding inside the housing. I found the lower mounting screws on the quill too tight and the play in the quill was causing binding. In fact, it was actually damping the free play. After loosening the screws I couldn't believe how much more play was in the quill. Unfortunately, I ruined a few parts before I noticed the binding. I was getting up to .010-.012 of movement after you set the depth of cut.
I junked it and installed a Mitutoyo 4" scale.

 

[kmanuele]

I had this happening to mine. The slide is binding inside the housing. I found the lower mounting screws on the quill too tight and the play in the quill was causing binding. In fact, it was actually damping the free play. After loosening the screws I couldn't believe how much more play was in the quill. Unfortunately, I ruined a few parts before I noticed the binding. I was getting up to .010-.012 of movement after you set the depth of cut.
I junked it and installed a Mitutoyo 4" scale.

I disassembled it, found that attachments to the head and the quill were out of plane, bending the lower end of the slide back toward the quill. A thick shim and a bit of bending on the mount realigned it.

Also found that the slide has adjustment for drag (much like on a dial indicator). These were very loose, allowing lateral motion. Tightened these.

Unfortunately, this didn't help much. Still off by .003 when moving the quill up by 0.010 and back to zero.

I'm going your route with after-market unit.

 

[Mr Mike]

I had this happening to mine. The slide is binding inside the housing. I found the lower mounting screws on the quill too tight and the play in the quill was causing binding. In fact, it was actually damping the free play. After loosening the screws I couldn't believe how much more play was in the quill. Unfortunately, I ruined a few parts before I noticed the binding. I was getting up to .010-.012 of movement after you set the depth of cut.
I junked it and installed a Mitutoyo 4" scale.

Hello I am considering the 728VT, If you don't mind me asking how come you guys didnt get another Quill DRO scale from PM, wont that render the buttons & LCD on the head useless...?

 

[kmanuele]

Hello I am considering the 728VT, If you don't mind me asking how come you guys didnt get another Quill DRO scale from PM, wont that render the buttons & LCD on the head useless...?

The 728VT is a great mill. Don't discount it just because of this discussion.

I would expect a replacement DRO from PM would have the same problems, and they don't seem to offer alternatives.

And yes, a different quill DRO would render the existing one useless, but any replacement would have their own display and controls.

Haven't replaced mine yet.

 

[Digger42]

Having similar problems with the quill dro. Wondering if anyone has replaced with one of the lower priced 4” dro and results.

 

[Mr Mike]

I had a long conversation about the Quill DRO issue with Mike @qualitymachinetools about this topic because I am on the fence about getting 728VT or the 727V, He said they haven't heard much about this problem, They know about it turning off and battery issue.. He said he would basically do as @Sqidget did and install an aftermarket one.

Personally I don't like the idea of having to replace the factory installed one and hope if enough people with this same issue let them know maybe they can find a fix for it.

 

[mksj]

I have had the same issue with a previous bench top mill (Optimum BF30) that had a similar digital scale on the quill, there was some degree of binding because of the alignment as well as the retention screws being loose at the reader and the bar. I shimmed the bar so it wouldn't bind and tightened the mounting screws, but still had a bit movement in either direction before the reading changed. Similar to what one does when measuring when using mechanical dials on a mill/lathe one needs to go back and then forward past that point to get an accurate reading, once loaded in the direction of travel (take up the play in the system) the reading should be consistent. Accuracy with these types of digital scales is typically +/- 0.001", maybe a bit less with cheaper units. The other disturbing issue with the quill on this mill was the mechanical knob for adjusting the quill had about a 1/4 turn of play before the quill would move, and the quill lock would dig into the ram and not release. I ultimately replaced the BF30 with a knee mill and installed a 4 axis DRO.

 

[qualitymachinetools]

I dont know why he would say to install an aftermarket DRO. Its not a commonly reported thing specific to the 728, no. We have shipped over 1000 of these mills in the past year, and I see maybe 2 comments about that DRO. If anyone is having a problem with that please report it so they know. Its not a .0001" DRO but it should be accurate within .001-002, Not .010

 

[Mr Mike]

I dont know why he would say to install an aftermarket DRO. Its not a commonly reported thing specific to the 728, no. We have shipped over 1000 of these mills in the past year, and I see maybe 2 comments about that DRO. If anyone is having a problem with that please report it so they know. Its not a .0001" DRO but it should be accurate within .001-002, Not .010

Just to clarify the context, Mike wasn't suggesting anyone currently having this issue with their PM-Mill run out and get an after-market replacement in lieu of contacting Precision Mathews about the issue.