Glass scales vs. magnetic scales.

[NeoTech]

Im thinking of getting myself a DRO for my Aciera Milling machine.. But need to figure out what works. Lengths, tech, instrument..

2 cents anyone?

[awemawson]

Newall Spherosyn in my book are the best as they are extremely robust. I think the beams and pickups are guaranteed for life.

Got them on a lathe and also a surface grinder - excellent kit

Andrew

[vtsteam]

Beware of some Ebay seller's descriptions of the cheaper individual axis LCD magnetic DRO's if you have a specific length in mind.

I bought a so-called 24" LCD DRO, but it only gave measurements to 19.5".

True, the actual "scale" was 24" long, but the pickup and end brackets ate up 4.5" of that. This was not mentioned in the ad description. A simple "Measurement range -- 19.5" would have been sufficient to let me know what was up.

Since many 24" table mill drills and Bridgeports only need 19.5" of travel, this may work for most people buying the DRO despite the misleading ad title.

But I actually expected a 24" DRO was a 24" DRO. When I wrote the seller about the problem they point blank refusd to change their description. Wrote me 4 times about my negative feedback with nonsense about testing their scales and finding none defective. I told them I would change the feedback to neutral if they altered their description to include the measurement range. They wouldn't.

[NeoTech]

Ah well i wanna get a kit i can shorten to fit to the machine properly. Thats why, glass scales or magnetic scales. =)

awemawson, where do you buy the Newall dro kits? Cant find any price anywhere. :|

[awemawson]

I got mine a few years ago when they were doing an offer that included a chap coming to fit then ! eMail them for your local rep.

Andrew

[NeoTech]

hehe i tried to mail them through their contact form.. error.. and their mailed bounced.. i guess they are one of "those" companies.. *its a common issue* ;D

[krv3000]

hi this is just my bit i had a moor and right hight gage with a glass beem its was brill but in my damp and cold workshop condesashon wood seter on the scale and send the digetel reed out mad in a stabel inviroment it worked well so in my cace magnetic is the best for me as its not a fekted by damp

[Jonny]

Have a search in the other threads.

Since you want something built in that pretty much rules everything out except the magnetic which can cut to exact length needed plus reader. Takes up no  where near as much room either.

Due to repeatability I would only go for 1micron. 5 micron on cross slide causes havoc.

[tom osselton]

I have been drooling over the magnetic ones at dro pro's check out their video's on cutting them to length.
http://www.dropros.com/DRO_PROS_Digital_Readout_Videos.htm

[chipenter]

Glass scales require an extra 131mm over the travel distance .

Jeff

[NeoTech]

yeah i will go with magnetic scales much due to price and you get really slim ones. 5my will most likely be sufficient on my mill though.. and if i need to chase smaller increments than 1/100mm i will setup multiple dial indicators anyway.. its rarely i need to do that though.. 1/1000mm is horrible to achieve.. 1 thou of an inch is 0.025mm, and i can usually dial myself in to 0.01mm by hand, scales was just to make it.. faster.. and not that much of swearing and 

[Jonny]

Missing the point here Neo, disregard manufacturers info and stated tolerances. The down to earth reality with 5 micron will be at least double when rigid.
On cross slide lathe have seen repeatability error in excess of 0.1mm+ on diameter, so on mill that would be half at 0.05mm good enough. Causes havoc when threading fine threads needing to be cock on. Good day its circa 0.04mm repeatability.

Took me ages to figure, at first disbelieved the scale. Found out by using machine dial and dti.
Will buy another but in 1 micron and swap 5 micron current to one of the mills on spindle downfeed.

I don't have repeatability issues with the glass scales on both mills and X axis lathe, just need cleaning twice a year.

The point being overlooked by most not only is it that glass need an extra 131mm length, you are also limited to buying the next length available upwards which can be as much as an additional 5". Not good on a tailstock, no names them compare to mine with 1/4" overhang of casting.

[NeoTech]

Hmm i see.. Well i will not be fitting my lathe anytime soon.. not really worth spending cash on that hunk of junk - maybe if i swap it out.

But its interesting to know that scales isnt that precise as expected. One would think they should be spot on.

[Arbalist]

There are loads of glass scales out there aimed squarely at the hobbyist, and by all accounts some of them don't last very long. Putting anything less than Magnetic on something like an Aciera is sacrilege surely! 

[NeoTech]

yeah rest assured, glass wont be mounted.. I have ordered magnetic scales, and a cheap DRO, 5my sensors - cause im a cheapskate.. All in all 550£  which isnt that bad. No fancy functions though, just absolute, incremental and normal measuring modes.. no hole patterns and such but i figure i could do that either way by just squaring on the workpiece edges and measuring from the zero point to each hole..

[Jonny]

5 micron will be fine on X and Y axis, what you gone for 2 axis?

Let us know how you get on, do a good job no stunts and post some piccies.
Dare say theres room on X axis to hide the backing plate and reader under the bed ie to the side of the lead screw.

See Allendale have pulled their budget readouts, wonder why. 3 axis lathe don't hold memory when powered off, 3 axis mill starts counting up on its own at times but does hold powered off last position.

[NeoTech]

ah i went with 3 axis for my Aciera F3 mill..

I do have the old "scale" still on it, the old way of measureing travel so i will mount the scale ontop of that in the dovetail instead of under the table where it will be drenched in cutting fluid. =)

[Jonny]

Depends what backing you have for the magnetic strip, mines a two part and sealed with silicon then screwed together, no problems with direct force fed coolant in 3 years.

Just had an email for those interested, if you pre order and collect you could save up to 15%
Allendale will once again be attending the Midlands Model Engineering Exhibition (October 17-20th).
Think cheapest 3 axis readouts now £171

[Boxfordian]

Good thread, its helping me with which way to go with DRO too

Cheers fella's 

[NeoTech]

A picture of how i mounted the scales.. The sensors arent mounted everywhere yet though..