3-axis DRO install. Knee, quill, or both?

[Senna]

I've been wanting to try the inexpensive Sinpo DRO's for a while now so I took the opportunity to order this one.

http://www.ebay.com/itm/221262889201?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

$480, glass scales, free shipping. Best deal I've seen yet.

Firstly I'd like to say how pleasant the experience was dealing with this seller. He was immediately responsive to my questions, offered advice which wasn't to his financial benefit but instead to my benefit, and he worked with me to get my order right.
I cannot say for certain but judging from this gentleman's writing of the English language I'd say he's a native English speaker which makes communication easier and less prone to having misunderstandings.

Anyway, on the advice of this gentleman I chose the shortest possible Full-Sized scales for the X, Y, and knee on my Gorton 8.5D.
I also ordered the shortest possible Slim scale (120mm) for my quill.
All scales are 5uM, again based upon the seller's recommendation.

Question, do I want to have my Z input to be off of my knee or off of my quill?
Why?
Here's an idea I've been kicking around. Since I'll have scales on both the knee and the quill would it be advisable to make/buy a two way splitter and a switch for the Z-axis input on the DRO to choose between which scale output is being fed into the DRO?
I'm thinking it'd work like this.
With switch set to the knee scale and the quill completely up zero out my work in Z and then switch to the quill scale and use the fine downfeed handwheel to make my Z moves.
On projects which exceed the 3.5" quill travel I could still make and monitor my Z moves if I used the knee scale.

Anyone done this?

- - - Updated - - -

I am getting an older 3 axis Acu-Rite MillVision DRO and scales from Don so I'll get a chance to compare the new Asian units against an older American made unit.
I'll reserve judgement until they are both put through their paces but up to now I've always recommended that people buy a used American, Japanese, or German DRO rather than a new Asian made one.
We'll see if my prejudice against the Sinpo units and for the established players was erroneous.

 

[darkzero]

Firstly I'd like to say how pleasant the experience was dealing with this seller. He was immediately responsive to my questions, offered advice which wasn't to his financial benefit but instead to my benefit, and he worked with me to get my order right.
I cannot say for certain but judging from this gentleman's writing of the English language I'd say he's a native English speaker which makes communication easier and less prone to having misunderstandings.

Yup, I agree. I got my Sino scales for my lathe from JJ & 2 years later a 1µm scale as well for my cross slide (I didn't get my display from him). My experience both times was exactly as yours, excellent communication & very helpful. I suspected that his english is not that great as there were times we had translation issues but if he is using a translator it is very good. I'm sure he's learned a lot more English by now if that is the case. I always recommend him when I can.

do I want to have my Z input to be off of my knee or off of my quill?
Why?
Here's an idea I've been kicking around. Since I'll have scales on both the knee and the quill would it be advisable to make/buy a two way splitter and a switch for the Z-axis input on the DRO to choose between which scale output is being fed into the DRO?
I'm thinking it'd work like this.
With switch set to the knee scale and the quill completely up zero out my work in Z and then switch to the quill scale and use the fine downfeed handwheel to make my Z moves.
On projects which exceed the 3.5" quill travel I could still make and monitor my Z moves if I used the knee scale.

Anyone done this?

I would say at the least, go with X, Y, & the quill. But if you can I would go for the 4 axis DRO, quill & knee. Why? Most 4 axis DRO displays can sum the two Z axes (quill & knee). It can be very useful but then again it may not matter to some. If your going to get the extra scale to have both the quill & knee, it shouldn't cost much more to get the 4 axis DRO display.

But if you would rather try the switching method....it's been a while since I looked at the pinouts for the scales, not sure how many pins are signal wires but those are the ones you would have to have switched by your switch. However you may have to have all the pins switched over with the switch cause you may have issues loosing read head position if the scales are powered off when switching & switching back.

Since the Sino scales are Sub-D 9 connectors which are the same as VGA connections, you might be able to use an analog VGA switch to make it easier, the old school kind that only switches the montior. Something like this. Not sure it would actually work, just a thought so please don't hold me responsible if you do try.

 

[keithmifflin]

My experience is that you should use your 3 axes DRO on the X, Y and Knee. Most of the time moving the knee is much more precise than the quill with more control. Now that said what I have done is to add a small digital scale to my quill as well so I do have the control that I may occasional want. This is cheaper. Once you get used to using the knee for most all Z movement you will naturally be more comfortable with it. The small digital scale I put on the quill is a nice option too, covers you on all fronts for not much money!

:hugethumbzup:

Keith