DRO advice.

Discussion on all milling machines vertical & horizontal, including but not limited to Bridgeports, Hardinge, South Bend, Clausing, Van Norman, including imports.

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Lewayne
Posts: 75
Joined: Sun Feb 03, 2019 4:02 pm

DRO advice.

Post by Lewayne » Thu Mar 04, 2021 12:34 pm

Hi guys,I'm looking for an inexpensive DRO for my equally inexpensive Chinese round column mill.The hand dials are way off, due to backlash inherent in the machine. Since it has no knee ,I'm thinking I don't want the third (Z axes) scale. They seem to come in sets. I'd want just the X and Y axes two piece set, and a front mount Z axes quill scale. I am thinking right aren't I ? do they have those that would pug into the screen?

pete
Posts: 2147
Joined: Tue Feb 10, 2009 6:04 am

Re: DRO advice.

Post by pete » Thu Mar 04, 2021 2:19 pm

The bar type dro scales with an integrated display that are similar to digital calipers don't seem to last too well as far as there durability when exposed to chips and cutting oil. Plus the actual accuracy isn't that great compared to a more standard dro with glass or magnetic scales and reader heads with a separate X,Y display. And to me having at least the built in bolt pitch circle option is well worth stepping up to a more standard dro. Maybe with your mill the feed screw nuts aren't adjustable, but if they are and your back lash is excessive it's time to do some adjusting. If you do buy the more conventional type of dro just remember your scale lengths have to be longer than your table travels to allow for the length of the reader heads while there measuring along the full length of the scales.

armscor 1
Posts: 242
Joined: Sun Jun 12, 2016 3:12 am
Location: Philippines

Re: DRO advice.

Post by armscor 1 » Thu Mar 04, 2021 4:33 pm

My round column mill has adjustable feed screw nuts.
I have a 2 axis DRO and a bar type digital readout on the quill, so far no problems.
My X axis scale was too long so I cut it to length.

Lewayne
Posts: 75
Joined: Sun Feb 03, 2019 4:02 pm

Re: DRO advice.

Post by Lewayne » Thu Mar 04, 2021 6:47 pm

I'm not saying the backlash is excessive (for the machine), just that its there.
How long do I need the scales to be, or how much "longer" than travel? (4 inches, say) ?
My table is 28" by 9 1/2" not really relevant, except to compare to yours.
x travel is 20", Y is 7", Z is 6" on mine.
I expect yours is the same or very close.
Also the dials on the hand wheels have the little finger turn areas but not one of them turns
Do those lock somehow or do I have rust build up behind them and they're frozen?
I have no manual for operation.
you couldn't post photos of your scales in place could you? that may be asking a lot.

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NP317
Posts: 2952
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Location: Northern Oregon

Re: DRO advice.

Post by NP317 » Thu Mar 04, 2021 7:51 pm

Lewayne:
It would help us answer your questions if we knew what mill make and model you have, including posting some pictures.
And you can do a search here for previous postings on milling machine DROs, as there are several. Possibly many.
RussN

pete
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Joined: Tue Feb 10, 2009 6:04 am

Re: DRO advice.

Post by pete » Thu Mar 04, 2021 8:11 pm

The extra length needed is a factor of how long the reader head is and exactly where the sensor pick up is in the head. A reputable dealer should be able to advise how much longer the scales need to be verses the table travels you have.

armscor 1
Posts: 242
Joined: Sun Jun 12, 2016 3:12 am
Location: Philippines

Re: DRO advice.

Post by armscor 1 » Thu Mar 04, 2021 8:17 pm

Hope this helps?
Attachments
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Lewayne
Posts: 75
Joined: Sun Feb 03, 2019 4:02 pm

Re: DRO advice.

Post by Lewayne » Thu Mar 04, 2021 9:35 pm

Mill 7.jpg
this is my machine
in your last picture of the hand crank do those scales turn freely to 0 them? Mine looks just like yours but only turns with the hand crank.
And yes that did help , thanks a lot.
Attachments
mill room build 5.jpg

Lewayne
Posts: 75
Joined: Sun Feb 03, 2019 4:02 pm

Re: DRO advice.

Post by Lewayne » Thu Mar 04, 2021 9:38 pm

I see you put yours on the front. Dont you miss the stops? Or does that stuff on the front just not matter much?

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NP317
Posts: 2952
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Location: Northern Oregon

Re: DRO advice.

Post by NP317 » Thu Mar 04, 2021 10:40 pm

Thanks for the photos. Very helpful.

I had a similar mill except for a step-pully speed adjust drive on top and the "nod" arm.
The dials at the hand cranks could be loosened and zeroed with an allen hex wrench to turn the setscrews. They were hidden in very small holes in the dials.
And I never used the front stops in all the years I had that mill. I DID practice the "Harold" method of using the dials for all motions.

And I managed to do some careful, slow, serious machining, despite the lack of rigidity. I machined the stainless steel drive rods and valve gear for my Mikado.
Pics attached.

Rather than install a DRO on that mill, I finally was able to replace it with a larger machine more suitable for installing the DRO.
Not possible for everyone.
RussN
MillRods4.jpg
MillRods1 sml.jpg
Rods1.jpg
Valve Gear Rods.jpg

armscor 1
Posts: 242
Joined: Sun Jun 12, 2016 3:12 am
Location: Philippines

Re: DRO advice.

Post by armscor 1 » Thu Mar 04, 2021 11:40 pm

Mounting X scale on rear robs you about 1 inch of movement on the Y, not an option in my case.
Yes I miss the stops even though rarely used, never used the power feed switch so no great loss.
My dials turn fairly freely but hopefully never need them again, progressed from the dark ages to a DRO!

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