DRO for surface grinder

skipd1 · Dec 17, 2020

I just recently installed a inexpensive imported DRO with glass scales for my mill. As it is suppose to be a 5u scale, would this be adequate for my Harig Surface grinder. I currently us a .0001 indicator and it works fine returning back to a project from a redress the DRO certainly would help.

skipd1

Glorifire · Dec 29, 2020

Why not test the one on your mill for accuracy using gage blocks? Use a mounted dti to register the zero, stack some blocks and zero on the end of the stack and seevif it matches the dro, that should show accuracy over range pretty well, then just test its repeatability, and check its accuracy over small intervals at several poistions using gage blocks that differ by tenths. I would think that would give you a general image of how reliable that particular DRO is for your purpose

Mike1974 · Jan 5, 2021

skipd1 said:
I just recently installed a inexpensive imported DRO with glass scales for my mill. As it is suppose to be a 5u scale, would this be adequate for my Harig Surface grinder. I currently us a .0001 indicator and it works fine returning back to a project from a redress the DRO certainly would help.

skipd1

Unless I mis-understand, dressing your wheel will change your Z by thousandths, not tenths. At that point, I would think .001/.0005 resolution would be fine.

eKretz · Jan 5, 2021

Which axis are we talking about? On a grinder, spindle height from the table is Y axis. Z axis is cross movement (table or wheel in and out) and table back and forth long ways is X axis.

Anyway, I've got a .0001" resolution readout on my grinder that came already fitted for Y (height of wheel from table), and have a Sony DRO that is yet to be fitted for X and Z. The Sony box and scales are 5 micron (.0002") resolution, and that should be fine as far as I'm concerned. I definitely prefer the .0001" on the Y though.

Mike1974 · Jan 5, 2021

eKretz said:
Which axis are we talking about? On a grinder, spindle height from the table is Y axis. Z axis is cross movement (table or wheel in and out) and table back and forth long ways is X axis.

Anyway, I've got a .0001" resolution readout on my grinder that came already fitted for Y (height of wheel from table), and have a Sony DRO that is yet to be fitted for X and Z. The Sony box and scales are 5 micron (.0002") resolution, and that should be fine as far as I'm concerned. I definitely prefer the .0001" on the Y though.

I didn't know they were different on a surface grinder? I guess I could see it both ways as a traditional (vmc,BP) Y axis would feed the wheel into the work, but lowering the head also feeds into the work... but I digress. If you want to control front to back, like grinding a shoulder, I can see a tenth resolution being very handy, and highly recommended as trying to split .001" with a scale on a wheel takes a lot of finesse (even with a vernier, but maybe it was just a sloppy grinder...)

Mark Rand · Jan 5, 2021

They aren't different. X is long axis and Z is spindle axis. Always.

CarbideBob · Jan 5, 2021

Many think Z as up/down on a SG.
I know this violates the machine tool rules of forever but glued to the earth it sort of makes some sense.
Surface grinders are not machining centers.
Z axis is up and down on my cnc grinders, all wrong for sure to the classic definition but easier for operators to understand and work with.
I have no problem breaking the rules if it makes things easier for my employees. KISS.
Bob

eKretz · Jan 5, 2021

Yes, it's very easy to remember, Z is always the axis of the spindle as if it were moving in/out of its bearings or the table axis that would make the same movement. This is so on every machine tool, and will be labeled as such when the machines come from the factory with readouts pre-installed.

Anyone is free to label any axis whatever they choose on their own machine, but will make it confusing for others by all the flip-flopping.

steve-l · Jan 5, 2021

Now, I'm confused. I always thought Z is up and down. Y is in and out and X is longitudinal left to right. Why would it be different on a SG? On the use of a DRO on a SG, I don't think they would be near accurate enough. There is a big difference between resolution and accuracy. I would never trust one to tenths.

CarbideBob · Jan 5, 2021

steve-l said:
Now, I'm confused. I always thought Z is up and down. Y is in and out and X is longitudinal left to right. Why would it be different on a SG? On the use of a DRO on a SG, I don't think they would be near accurate enough. There is a big difference between resolution and accuracy. I would never trust one to tenths.

No. Z is defined by the standard as the spindle axis so it is in/out on a SG.
A SG is more like a horizontal maching center. On a lathe Z is sideways movement.
There are rules but like you I like to ignore them on grinders.
Have had micron DROs or the ilk on SGs for many, many decades. They are a huge advantage.
Bob

eKretz · Jan 5, 2021

steve-l said:
Now, I'm confused. I always thought Z is up and down. Y is in and out and X is longitudinal left to right. Why would it be different on a SG? On the use of a DRO on a SG, I don't think they would be near accurate enough. There is a big difference between resolution and accuracy. I would never trust one to tenths.

Right, as Bob noted, it's different because the spindle orientation is different. Machine tool axes follow the machine orientation, not spatial orientation. If you were to take your vertical mill and lay it down so the spindle were horizontal then the axes would match up.

As far as readouts... Again as Bob noted: They are absolutely a huge advantage. Readouts these days are pretty darn good, and you still measure even with the readouts.

Modelman · Jan 5, 2021

Mike1974 said:
Unless I mis-understand, dressing your wheel will change your Z by thousandths, not tenths. At that point, I would think .001/.0005 resolution would be fine.

Bad advice.A surface grinder is one tool that can easily work to tenths, but not if you don't know how far you've moved the down feed.Use of the DRO on the Y (down) axis of a grinder is always an excerize in incremental measurement; get close to finish size, dress the wheel, dust the part, measure it, then RE-ZERO the DRO and go from there.

Dennis

machinistrrt · Jan 5, 2021

eKretz said:
Yes, it's very easy to remember, Z is always the axis of the spindle as if it were moving in/out of its bearings or the table axis that would make the same movement. This is so on every machine tool, and will be labeled as such when the machines come from the factory with readouts pre-installed.

Anyone is free to label any axis whatever they choose on their own machine, but will make it confusing for others by all the flip-flopping.

Labeling axis on the machines always caused me headaches as I learned the mathematics coordinate plane, would try to find a way of looking at it that the machine plane would match, and it doesn't, necessarily.

dian · Jan 11, 2021

i think if you use the fingers on your right hand it helps.

michiganbuck · Jan 11, 2021

eKretz said:
Which axis are we talking about? On a grinder, spindle height from the table is Y axis. Z axis is cross movement (table or wheel in and out) and table back and forth long ways is X axis.

Anyway, I've got a .0001" resolution readout on my grinder that came already fitted for Y (height of wheel from table), and have a Sony DRO that is yet to be fitted for X and Z. The Sony box and scales are 5 micron (.0002") resolution, and that should be fine as far as I'm concerned. I definitely prefer the .0001" on the Y though.

It is good to stick with calling: Down - Cross -and Long travel for manual SGs

And for CNCs draw a sketch on the machine door so a new guy coming to the shop does not error.

I forget now what SG manufacturers say one way and the one or ones that say the other. But they do vary...

Fingers on your hand don't work because you are looking at the spindle from a different direction.

I guess if all your CNCs SGs are the same you might just make sure a new guy is told.

michiganbuck · Jan 11, 2021

I think DRO on down and cross can be handy ..but knowing the old tricks is good to use also.

Long stop is better with a drop-in and a box of shims on a manual. I'v never set a long part stop on a CNC, except for reversing the feed.

You can't beat using spotters and setting a diamond to height for making parts to size quickly.

Doozer · Jan 21, 2021

Z axis is always in line with the spindle.
If you thought otherwise, correct yourself
as you learned the proper information right
here on Practical Machinist. I can assure
you that Z being inline with the spindle
axis of any machine is correct. I have
machine tool design textbooks, masters
level college textbooks on the subject of
machine tool design, and for sure, and
without question, the Z axis is in line
with the machine tool spindle.

-Doozer

pb1 · Jan 22, 2021

Doozer said:
Z axis is always in line with the spindle.
If you thought otherwise, correct yourself
as you learned the proper information right
here on Practical Machinist. I can assure
you that Z being inline with the spindle
axis of any machine is correct. I have
machine tool design textbooks, masters
level college textbooks on the subject of
machine tool design, and for sure, and
without question, the Z axis is in line
with the machine tool spindle.

-Doozer

Except for those pesky machines that can rotate the head, right? If I rotate my B-Axis the spindle axis is not perpendicular to the X-Y plane, but the Z-Axis still is.

CarbideBob · Jan 22, 2021

Doozer said:
Z axis is always in line with the spindle.
If you thought otherwise, correct yourself
as you learned the proper information right
here on Practical Machinist. I can assure
you that Z being inline with the spindle
axis of any machine is correct. I have
machine tool design textbooks, masters
level college textbooks on the subject of
machine tool design, and for sure, and
without question, the Z axis is in line
with the machine tool spindle.

-Doozer

How did this rule come to be?

Mark Rand · Jan 22, 2021

pb1 said:
Except for those pesky machines that can rotate the head, right? If I rotate my B-Axis the spindle axis is not perpendicular to the X-Y plane, but the Z-Axis still is.

Ok pedant. Howsabout 'The Z axis is parallel to the spindle ways'?

Does that make sense?

DRO for surface grinder

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