Newall scale bent, advice needed

[marrt]

I have 3 mills but one doesn't have a DRO. I've had a Newall kit for a while and finally found time today to install the kit. This kit has a knee scale for Z (as opposed to the more typical quill scale). We were almost through with the installation and, unfortunately, let our guard down and started talking about my helper's family issues.

The knee scale is vertical of course and we'd temporarily tightened the bottom scale mount to keep the scale in place. My helper was running the knee up and down so I could align the reader head +/- 2 thou and I didn't notice the scale wasn't fully "floating". Long story shorter, the scale was binding during this process, and we bent the scale 3-4mm or more over its length. Also, the reader head “may” be damaged since they are fairly particular about alignment.

The model number on the scale is SS0418LS. However, I can’t find this number anywhere on the internet. It’s a 16” travel, 26” OAL, stainless steel scale…about ½” in diameter (not the micro-spherosyn). I need some help identifying the proper model numbers for this scale and reader. Newall’s website is useless in this regard. Any advice or thoughts appreciated. It’s also OK to “make fun of me” for such a stupid, novice mistake. I’m 58 and you’d think I would have learned, by now, the importance to stay focused to the absolute end of the job.

 

[alphonso]

Not the proper way, but we had a bent rod that we only clamped on one end. The float didn't seem to hurt the reader or the work.

 

[Milland]

Straighten what you have, as best you can. Don't overbend it. Install per instructions, including read head.

Recalibrate [Edit: Requalify] by using two gage blocks, 1" and 2" (or any combination that gets you a 1" spacing between the two).

Run the knee up and down over its range (but especially ~2" past the kink in both directions), and using a magnetic stand and indicator of some form on the vertical column, contact the high block, then shift the low block over and crank the Z up ten turns. Is the new reading at "0" on the indicator? [Edit: Scale display too, of course]

Repeat as needed, moving the indicator stand to work with the high block. If you get uniform readings along the test distance you're good to go. You may have some localized wear on the knee leadscrew, so factor that in if you get some "off" readings.

 

[Billtodd]

The scale is a thin walled stainless steel tube with precision balls inside . The bend, 4mm over 400mm, doesn't sound too bad as long as there are no kinks to cause binding. The readers are pretty robust, three coils around another tube, so if it works it'll be fine.

Fixing one end of the scale and allowing the other to float is one option, although it will wear.

Straightening, might be an option, as long as the balls inside stay under some tension, Does the scale have tension adjustment screw in the ends?

Accuracy will obviously be affected but maybe still acceptable over a typical Z range.

 

[Milland]

Straightening, might be an option, as long as the balls inside stay under some tension, Does the scale have tension adjustment screw in the ends?

Pedant mode: Compression, surely?

[Obligatory "Don't call me Shirley!"]

In fairness, if the tubing kinks in a way that allows a ball(s) to shift so they're not dead in line, then that likely does compromise the accuracy and display reading.

 

[Billtodd]

Pedant mode: Compression, surely?

[Obligatory "Don't call me Shirley!"]

In fairness, if the tubing kinks in a way that allows a ball(s) to shift so they're not dead in line, then that likely does compromise the accuracy and display reading.

Yes I thought about it later, as I was checking one of the scales I have here. Balls are under compression, tube is under tension . 8⁠-⁠)

Kinky- If it was that badly damaged then it'd be useless anyway .

 

[bob]

I have a new scale and/or reader head should you need it. I suspect yours will be ok as others have said

 

[marrt]

Thanks for the replies everyone. The scale is not kinked, it's a smooth arc. I will clamp the scale in a couple v-blocks and apply pressure to the peak of the arc use something cut to the same length as the read head. Then I'll proceed with the advice given to test and measure.

 

[Milland]

Thanks for the replies everyone. The scale is not kinked, it's a smooth arc. I will clamp the scale in a couple v-blocks and apply pressure to the peak of the arc use something cut to the same length as the read head. Then I'll proceed with the advice given to test and measure.

If you have some hardwood blocks, bore them the diameter of the tube and split them in a saw to make your support and press V-blocks. Soften the end edges, the stainless tube may be thin enough to dent under load otherwise.

 

[tomjelly]

It might be advisable to loosen the tension screw in the end of the scale before you try to bend it back, because you will need to overbend slightly to get it straight. I'd count the turns you unscrew then after it is straight return it to the original position/tension. You can then calibrate it.