Dro scale lengths and shortening

[GraemeVW]

Thinking about maybe putting a dro on my lathe, at the learning stage.
How do you determine length? I assume it doesn't matter if it's longer and has unused length?
For example if it extends under the headstock along the back of the bed.

I'm assuming length is just a matter of 'can you mount it' and does it have enough working length.

Secondly, shortening, but specifically shortening Newell spherosyn.
I understand it's a stainless tube with balls inside. I've read it's not possible, and I've read about someone doing it and succeeding.

Site says the ball tension is set in a controlled environment, but could it just be calibrated by trial and error?
Traversing set distances and adjusting untill the scale agrees?

I appreciate I'm going from knowing very little about dro's to cutting up a complicated top of the range system, but sometimes diving into the deep end is the most fun.

Looking at the mounting brackets for the Newall scales, it looks like I can move the mounts to be the right distance and let the scales hang out the end if need be. As long as it's not crazy length. Is this right?

Thanks

 

[addjunkie]

My understanding is you can cut but it wont measure correctly……buy far eastern set……cheap, quick and it works……machine Dro do kits to suit specific lathes….

 

[Brad93]

Don't touch a newall scale, they're flipping hundreds if you muck it up.

Buy magnetic scales which you can cut down.

 

[GraemeVW]

Don't touch a newall scale, they're flipping hundreds if you muck it up.

Buy magnetic scales which you can cut down.

They aren't cheap are they!

I have 2 options, new Chinese, or second hand Newall with the risks involved in cutting them down (both are too long).

Sensible option is new Chinese, but the one article I read on someone cutting Newall down made it look pretty simple. I'm sure it wasnt though.

Both options are the same price.
Unless I ruin the newall. Then I've thrown £200 down the drain.

 

[Jelly_Sheffield]

You can cut the cheap chinese glass scales down, but you need to cut them long as the last half inch or so of the scale will be damaged in the process.

The accuracy of the undamaged portions of the scale remains fine so long as you avoid contamination during cutting (pack it with tissue around the cut first).

Magnetic strip scales can be cut pretty much with impunity.


Newall Spherosyn/Microsyn type tubular scales can theoretically be cut down, but require you to get the cut length to be a perfect multiple of the internal spheres to an extremely high accuracy to avoid introducing errors, they are also extremely expensive to start with and need an expensive counter (readout) unit .

 

[GraemeVW]

You can cut the cheap chinese glass scales down, but you need to cut them long as the last half inch or so of the scale will be damaged in the process.

The accuracy of the undamaged portions of the scale remains fine so long as you avoid contamination during cutting (pack it with tissue around the cut first).

Magnetic strip scales can be cut pretty much with impunity.


Newall Spherosyn/Microsyn type tubular scales can theoretically be cut down, but require you to get the cut length to be a perfect multiple of the internal spheres to an extremely high accuracy to avoid introducing errors, they are also extremely expensive to start with and need an expensive counter (readout) unit .

I know the balls are 1/2". I appreciate the tubes need to be multiples of this, but as the balls won't compress, I assume the end adjustment is to remove all loosenes between the balls.

No way of be thinking about it if I was paying full price, but a complete 2 axis set up, with slides that are too long, for the same price as new Chinese is tempting.

 

[Pete.]

Thinking about maybe putting a dro on my lathe, at the learning stage.
How do you determine length? I assume it doesn't matter if it's longer and has unused length?
For example if it extends under the headstock along the back of the bed.

I'm assuming length is just a matter of 'can you mount it' and does it have enough working length.

Secondly, shortening, but specifically shortening Newell spherosyn.
I understand it's a stainless tube with balls inside. I've read it's not possible, and I've read about someone doing it and succeeding.

Site says the ball tension is set in a controlled environment, but could it just be calibrated by trial and error?
Traversing set distances and adjusting untill the scale agrees?

I appreciate I'm going from knowing very little about dro's to cutting up a complicated top of the range system, but sometimes diving into the deep end is the most fun.

Looking at the mounting brackets for the Newall scales, it looks like I can move the mounts to be the right distance and let the scales hang out the end if need be. As long as it's not crazy length. Is this right?

Thanks

If you look at the ads for glass scales they usually have the overall length and the working length.

 

[GraemeVW]

Have you ever shortened a Newall scale @Brad? It’s not rocket science. Probably a lot safer than trying to cut a glass scale and just as easy as shortening a magnetic scale. It’s comments like yours that make people think there are complex nuclear reactions going on inside a Newall scale.. it’s a load of balls. As long as they go back in with no,side to side play, they work perfectly. Take that from somebody who has successfully shortened two Newall scales, not someone who knew someone who once met someone on the internet who said he heard it was difficult to do….

Now this is very encouraging.

They say on their website that they are assembled in a temperature co drilled environment, but I smell a bit of marketing there. What if your working environment is a different temperature?

 

[Jelly_Sheffield]

I know the balls are 1/2". I appreciate the tubes need to be multiples of this, but as the balls won't compress, I assume the end adjustment is to remove all loosenes between the balls.

No way of be thinking about it if I was paying full price, but a complete 2 axis set up, with slides that are too long, for the same price as new Chinese is tempting.

If you have adjustable end caps (the scales I've used in the past did not, possibly modified or an early model), then it will take a lot of the difficulty out of it, just ensure you get the ends cut dead perpendicular to the axis to give them the best opportunity to seat the balls correctly.

Also, the carbon fibre Microsyn tubes are much more liable to crack, so if you have those then you want your cutting tool to be as sharp and fine toothed as practical.

The Newall system is about as good as it gets for scales, albeit incompatible with everything else, I would certainly be happy using it if available.

 

[Jelly_Sheffield]

How do you determine length? I assume it doesn't matter if it's longer and has unused length?

Longer is fine as long as it doesn't get in the way, if you can find a way to keep them long, it will work fine and give scope to move to a larger machine in the future should you so desire.

 

[GraemeVW]

Longer is fine as long as it doesn't get in the way, if you can find a way to keep them long, it will work fine and give scope to move to a larger machine in the future should you so desire.

Just plonked the saddle and cross slide on, and I think getting a dro on that is going to be a struggle. Its going to have to be quite dainty.

The newall one probably won't work as the reader looks too big.

It's going to have to go headstock side too.

 

[GraemeVW]

What's the smallest type, in overall dimensions?
I think I'll have to mount the reader to the saddle and the strip to the cross slide, but unless the reader is small, it's going to restrict travel alot.

 

[Brad93]

Have you ever shortened a Newall scale @Brad? It’s not rocket science. Probably a lot safer than trying to cut a glass scale and just as easy as shortening a magnetic scale. It’s comments like yours that make people think there are complex nuclear reactions going on inside a Newall scale.. it’s a load of balls. As long as they go back in with no,side to side play, they work perfectly. Take that from somebody who has successfully shortened two Newall scales, not someone who knew someone who once met someone on the internet who said he heard it was difficult to do….

No but why risk it. Just buy a scale that can be cut down with no risk.

I do love your comments johnny.

 

[pressbrake1]

Newall are surprisingly robust, essentially like the old way of setting jig bores with rods and gauge balls
On a small machine I’d rather use compact magnetic strips

 

[GraemeVW]

Newall are surprisingly robust, essentially like the old way of setting jig bores with rods and gauge balls
On a small machine I’d rather use compact magnetic strips

This is it, it's quite cramped.
It's smaller than a colchester but still has 6.5" center height so the saddle is quite small, but with a reasonable amount of travel.
It seems most people mount them on the tail stock side, but the gib strip is that side and the adjusters and locking screws are somewhat in the way.
Plenty of room headstock side, just more in the firing line for cutting fluid/swarf.

 

[pressbrake1]

This is it, it's quite cramped.
It's smaller than a colchester but still has 6.5" center height so the saddle is quite small, but with a reasonable amount of travel.
It seems most people mount them on the tail stock side, but the gib strip is that side and the adjusters and locking screws are somewhat in the way.
Plenty of room headstock side, just more in the firing line for cutting fluid/swarf.

I mount them away from the cross slide if there’s room behind the machine

 

[GraemeVW]

I mount them away from the cross slide if there’s room behind the machine

When you say mount them, do you mean the reader? Or the whole lot?
Got a pic to show what you mean?
I may well be able to do that, in which case the extra length of the one I'm considering may come in handy.

The newall ones, at shorter lengths, only need supporting at one end too, or so ive read.

I could mount both readers on the read of the saddle, but at 90° to each other, one above the other.
Moi t the rod at one end only and let it run out the back into free air.