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Repairing a Verdict Dial Test Indicator

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Martin Dilly 230/04/2018 21:07:56
18 forum posts
3 photos

I've been given an elderly Verdict DTI (lever arm type) which appears to have a fault. The needle fails to return to zero with no load and on opening it I'm unclear how it is supposed to. The hair spring engages with the internal arm, but it's not clear whether the small knob-ended lever does what it should do; it biases the needle one way or the other but there seems to be no other centring action to do this.

I can take a picture but not sure if I can post it here.

Any help would be welcome; seems a shame just to bin it.

Mick B130/04/2018 21:45:13
1126 forum posts
62 photos

This bloke does a disassembly of one:-

http://ericweinhoffer.com/blog/2016/5/12/dial-test-indicator-teardown

You might get more from it than I did - to me it doesn't seem to go much deeper than "aren't all these fascinating little bits clever!" frown

I've got one that was given to me with a broken reversing lever - the thing that decides which way the finger is sprung - and I repaired it with a sort of Anderton clip from (I think) an old record turntable, and a piece of what might be spring steel wire, or maybe just part of a paper clip. But it still works 30 years on - only in one direction, but that's never bothered me even slightly.

I'll post a pic of the fix tomorrow - it seems possible your gauge might have similar damage, as it seemed a vulnerable feature to me.

Edited By Mick B1 on 30/04/2018 21:50:22

DMR01/05/2018 00:45:01
102 forum posts
9 photos

You seem to be misunderstanding the action that is supposed to happen. Non Verdict DTI's sit (sort of) in mid range and will work either way, not necessarily returning to a zero on the dial unless you rotate the bezel to read zero. Some of mine go a bit over a full turn each way but one does one and a half turns each way.


Your Verdict should have a little external knob under the dial which biases the action one way or the other. It is not meant to go plus-minus of some reading and the full needle rotation is only just over one turn. That is to say that the needle is biased to one end, or the other, of its one turn by the external lever under the dial. On some the little lever was plastic and broke off but you can replace it with a bit of sheet springy steel correctly bent. I seem to recall I repaired one once. If you have a missing lever and nothing to go on to make a suitable replacement (another Verdict) then you will struggle. It has a washer and a pin externally too. The shaft for the lever should exist with its cross hole for the pin.
Hope that makes sense. Could try and take some pictures for you, but it's all tiny. PM me if you wish.


Dennis

Clive Hartland01/05/2018 08:18:49
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2456 forum posts
40 photos

The verdict type D/indicator is only used in the mid range mode so it registers + or - readings on say centering a piece in the chuck on the lathe. I would say it is not accurate when the probe is sitting at zero, Zero is set at half the needle rotation so it registers both ways.

Clive

Roderick Jenkins01/05/2018 08:52:39
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1757 forum posts
445 photos

I've got a couple of these little Verdict gauges. The plastic direction change levers gave up years ago and I replaced them with a bit of bent brass sheet:

verdict.jpg

Rod

Mick B101/05/2018 09:42:56
1126 forum posts
62 photos

I think Roderick's fix is probably better than mine, but that I'd find it more difficult to do:-

dialgaugefix1.jpg

dialgaugefix2.jpg

Basically the wire just retains the direction switch in the clockwise position so that the DTI reads upward movement of the finger. I can't remember why I used the spring clips instead of making a washer, but I'd be unwilling to disturb it now.

smiley

Edited By Mick B1 on 01/05/2018 10:04:36

Clive Foster01/05/2018 09:43:06
1776 forum posts
57 photos

Further to what DMR says you set the direction of indication then adjust the position of the indicator so that the probe moves to apply the desired bias. Usually that will be with the needle central in the travel range but sometimes its easier to set the workpiece or whatever offset in a known direction and apply minimal bias to the indicator leaving plenty of travel to record the adjustment. Sometimes its a lot easier to (hopefully) do all the adjustment in one direction.

It should be obvious that a bidirectional movement indicator, where the rest position at is centre zero, of this style is potentially iffy device as zero bi-directional backlash is essential. Hard to achieve zero. Verdict style bias one way or the other ensures that any backlash or other internal setting errors are spring loaded out.

The innards are very simple, almost crude, but they are remarkably accurate. Most especially so close to the centre of travel. That pear shape geometry correcting end used on the Verdict stylus is not techno puff. It does do what it says on the tin and the error reduction effect as compared to a plain ball stylus is measurable. Why one would bother is perhaps a moot point as no one in their right mind would use a Vertical for proper measurements despite its accuracy. When you are simply shooting for nearest to zero deflection details of non linearity are of little importance.

Clive

Mick B101/05/2018 10:00:33
1126 forum posts
62 photos
Posted by Clive Foster on 01/05/2018 09:43:06:

...

Why one would bother is perhaps a moot point as no one in their right mind would use a Vertical for proper measurements despite its accuracy. When you are simply shooting for nearest to zero deflection details of non linearity are of little importance.

Clive

I see your point but there are overlapping cases. I can remember an instrument shop I worked in in the 70s, where the QA inspector would check milled steps with a similar clock on the end of a Vernier height gauge - a good one with a magnifier for viewing the scale. He'd set the required offset on the height gauge and read the deviation on the component from the clock. Nobody challenged this, 'cos IIRC it wasn't easy to see a more reliable way to do it.

DMR01/05/2018 14:01:53
102 forum posts
9 photos

Just for Martin's sake (and if we have diagnosed his problem correctly) I have put some pictures in an album of what the lever under the dial should look like. The washer is chamfered on the outside and creates friction with the lever to hold the lever in place. Have a go Martin. Don't sling it.

Dennis

colin hawes01/05/2018 14:37:18
496 forum posts
18 photos

Can you buy replacement probes for these older Verdict lever indicators? I've got one with the ball broken off. Colin

Mick B101/05/2018 15:14:28
1126 forum posts
62 photos
Posted by colin hawes on 01/05/2018 14:37:18:

Can you buy replacement probes for these older Verdict lever indicators? I've got one with the ball broken off. Colin

Any trauma severe enough to break the ball off - you have to wonder what else it might've done...surprise

Mick B101/05/2018 15:24:19
1126 forum posts
62 photos
Posted by DMR on 01/05/2018 14:01:53:

Just for Martin's sake (and if we have diagnosed his problem correctly) I have put some pictures in an album of what the lever under the dial should look like. The washer is chamfered on the outside and creates friction with the lever to hold the lever in place. Have a go Martin. Don't sling it.

Dennis

Absolutely!

I think the lever on yours is a lot more robust than the one on mine when it was given me. It was just a tiny triangular plastic pointer with a couple of feeble lugs to rotate the shaft via its pin, and the pointer was already cracked through. It seemed to me that any similar gauge was at risk of similar breakage. Mine was of about 1987 production - is yours is of a later design?

Bob Youldon01/05/2018 15:44:17
183 forum posts
20 photos

Hi chaps,

Try www.mjallen.co.uk they make the Verdict DTI can overhaul yours and probably supply replacement parts for the reverse toggle.

Regards,

Bob

Martin Dilly 201/05/2018 19:24:16
18 forum posts
3 photos

Thanks for all the advice gents. I'll give it my full attention later.

Martin Dilly 202/05/2018 11:09:09
18 forum posts
3 photos

verdict 1.jpgverdict 001_edited.jpgI thought I'd attached three photos to yesterday's post but nothing seems to have happened. Let's try again.verdsict 2.jpg

Clive Foster02/05/2018 12:36:16
1776 forum posts
57 photos
Posted by Mick B1 on 01/05/2018 10:00:33:

I see your point but there are overlapping cases. I can remember an instrument shop I worked in in the 70s, where the QA inspector would check milled steps with a similar clock on the end of a Vernier height gauge - a good one with a magnifier for viewing the scale. He'd set the required offset on the height gauge and read the deviation on the component from the clock. Nobody challenged this, 'cos IIRC it wasn't easy to see a more reliable way to do it.

Mick

Been there, dunnit, got the teeshirt. Its an effective and common way to see if things are within calibration. Most good height gauges have the requisite fittings in the box.

But its not properly measurement, just seeing if things are within the right range. Strictly you should use one of those big "stack of disks in a casting with monster micrometer dial on top" setting devices to verify top and bottom limits. Mine is a Frenco, google comes up with some decent pictures. Done that way a blank dial and 3 adjustable indicators works just as well. Arguably more correct as there is no operator judgement involved. In practice the "measurement" error is pretty darn small so you might just as well set things up for zero at mid point, read the range off the dial and be done with it. Tolerance range for things that can be so measured is rarely uber critical and if you are regularly approaching the limits its time to take close look at your production processes.

Clive.

DMR02/05/2018 22:07:43
102 forum posts
9 photos

Martin,

To me, your verdict is not just elderly, it's very elderly/old and nothing like the pictures posted. Does it say Verdict on the dial or are you just referring to it as a Verdict type? Go back to my first post and consider that the dial pointer only travels just over one full turn. Move the lever under the dial to each extreme and you should find that the dial pointer reverses its action by one turn. The probe then works the dial in the other direction. It is not a centre-zero device. Rotate the dial's bezel to reset to read zero if required. If you do have a fault the spring wire (your "hair spring" description I think) on the inside end of the external lever looks bent in your top picture.

Mick,

I have no idea how old my Verdicts are; they came to me with a Myford years ago. I would assume that a plastic lever would represent a more recent 'improvement' as they say. I have three of them, all in their blue boxes with fittings but I only ever use one of them and there are multiple variations of the included fittings The two unused ones have one inch diam dials and 0.01mm and 0.001" ranges. The inches one sports an extended probe (by me) to the original, 20mm long instead of the original 10mm that I made when I needed longer reach, not considering the loss of sensitivity as a result. Just a means to a tricky end. Incidentally I have two spanners to fit the flats on the probes included in the boxes so some gauges probably came with multiple probes with different lengths and/or tips.

The DTI I do use has a 1.5" dial and 0.0005" scale which totally beats the other two, I normally use a dial gauge through choice and never measure with any of them.

Dennis

Martin Dilly 202/05/2018 22:32:12
18 forum posts
3 photos

Yes, it really is a Verdict (or so it says on the dial), but I suspect it's pretty elderly, as you suggest. I'll ponder some more. Maybe a trip to a Museum of Bygones...

DMR02/05/2018 22:50:47
102 forum posts
9 photos

So it is a Verdict.

Your "hair spring' in your top picture is bent such that it appears to be trying to move the main lever upwards but the lever has not moved upwards. Couple that with the external ball-end knob in your bottom picture being apparently centre biased then the spring should be quite straight and unseen under the main lever, unless things have changed between pictures.

Edited By DMR on 02/05/2018 22:52:48

Martin Dilly 204/05/2018 13:42:04
18 forum posts
3 photos

I just spotted a patent number on this, 468,243, and thought that might produce a drawing or some details. However, Googling it bought up several different Verdict guages with completely different mechanisms and no drawings. Another blind alley...

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