Dial Test Indicator

I would appreciate some help as I am having problems looking for a Dial Test Indicator that has a high level of measurement, all I can find is instruments with a maximum range 0f 40 thou, my dial indicator has a range of 1" but cannot be used horizontally to measure the inside of a hole, the only option I can think of is has anybody built or designed a jig that can use a dial indicator in a vertical position to measure the offset in the inside of a hole, I need to know as I had a job and the hole was not regular and I had problems using my own dial Test Indicator as it could have been damaged due to its small range.

Is this the your general idea ?

**LINK**

https://www.starrett.com/metrology/product-detail/671

… seems awful pricey for what it is, but those nice Starrett people have done the design work for you.

MichaelG.

Depends on the setup but the co-axial indicators have quite a wide range if movement. They only indicate movement not distance but a quick bit of testing and maths would give you the actual movement for whatever level length is being used.

I'm mot sure if Michaels link would work with a 1" range of movement as the arc the lever moves in would have it come off the end of the indicator.

What sort of size hole are we talking?

.

Most unlikely

But it’s a big improvement over the aforementioned 40 thou

MichaelG.

This is an attachment for my Mercer dial indicator. I have longer fingers which screw into the attachment to give longer depth.

David

The longer flat area against the end of the indicator would work better but it's like the co-axial one in that it shows a deviation or movement of th eneedle not a measurement and would need to be worked out for each length of finger and maybe a bit of trig thrown in as things are moving in an arc.

Does depend on the part and what is available, if the part could be mounted on say a mill table then you only need set one hole true and zero the dial/dro and then set the offset hole true which will give you how much it is offset by simply reading the dial or DRO in this case 40thou would be ample.

Edited By JasonB on 22/10/2022 08:59:34

Edited By Michael Gilligan on 22/10/2022 09:18:55

If you need to measure a movement or offset of 1", a dial indicator is probably not the best way of doing it. But your description of what you are trying to do is very vague and incomplete. I am totally unsure what you mean by "measure offset inside a hole" or by mounting a dial indicator horizontally vs vertically. You can mount them upside down if you want to. A pic or more thorough description of what you are actually trying to do, and whether it's in a mill or on a lathe etc etc might bring you more helpful suggestions.

Further to the above attachments for a dial indicator, Harold Hall did some articles in MEW years ago about making your own. Details and drawings are still available on his website here LINK It's a neat little project. I have been meaning to make a set for years, but have never really had a need for them so never got around to it, yet.

Bell crank devices are primarily for changing the direction of measurement. They are inherently prone to cosine error so for accurate results the base setting needs to be with the arm perpendicular to the indicator plunger and movement restricted to ± 2.5° to 3° before cosine error sets in.

Making the measurement side arm longer increases the physical range but reduces sensitivity commensurately.

Had a slightly similar situation where I needed to get down inside a bore to verify the various errors to ensure that I had enough room to re-machine a podged up taper. I setup the seesaw probe out of a Starrett Last Word indicator kit and an indicator on my lathe cross slide using a magnetic post mount.

Something off a KTM enduro bike I think. I was very lucky that the Pratt Bernard precision 3 jaw held it accurately enough to dispense with for jaw games.

The Starrett kit uses a back plunger indicator **LINK**

https://www.starrett.com/metrology/product-detail/196A5Z

so the mounting stalk gets in the way on a set up like this.

Using the cross slide feed effectively extend the range considerably. A DRO set up would be most accurate but my cross slide screw and nut are good enough to use as is for better than ± 0.5 thou overall.

I see no reason why the measurement arm could not be made rather longer to increase the operating range but the set up is likely to get very twitchy if you go too far. 10 to 1 at 1 thou per division accuracy is theoretically possible using a tenths thou indicator but the chances of it being stable enough to actually use are slim. 2 to 1 is probably OK.

The Starrett see saw has small spherical contacts at each end and the plunger indicator has a dome end contact. This increases the angular movement range before cosine error sets in. Calculating the effects is possible but not as easy as it might seem. Size matters! In practice anything significantly more than ± 10° or so has the see saw end running off centre round the plunger end so things start to mis-behave and it all gets a bit fraught.

Bottom line is it all worked but I din't want to do it in the first place and, frankly my dears, I'd rather not do it again!

Clive

Edited By Clive Foster on 22/10/2022 11:07:24

Oh dear, maybe it is just me, but I have just tried the link to Harold halls website and it keeps dropping the connection. I will try later today and hopefully it will work again. Has anyone else had a problem?

Martyn

.

Just tried … No joy

also tried one level up, and that doesn’t connect either

MichaelG.

.

https://www.homews.co.uk/page619a.html

https://www.homews.co.uk/

https://www.homews.co.uk

Edited By Michael Gilligan on 22/10/2022 11:26:04

Harold Hall's dti accessories will be found in:

MEW14 (Dec 1992) (or MEW 151/152 (Jun/Jul 2009) for a later version).

Also WSP 39, Ch.12.

HTH,

Peter G. Shaw

I have a long stylus Girod indicator with the small dial. It can get in about 30mm or so just on the stylus. On things with a 40mm hole it can get in as far as you can read the indicator. For getting into very long holes around 250mm deep, I made a pivoting gizmo and use the low press finger indicator with it. It is close to 1:1 ratio. I use this for indicating the bottom of a drilled hole , to align the hole and make the outer true to this hole. I will try and post an image of one of the setups. This is an early one that used a brass tube to keep the weight down and only used the indicator stand end for the pivot. It shows testing at the front of the part checking it's error reading on an area that is known. My latest one uses a piece that has 2 ball bearings in it to reduce pivot drag. In hindsight I probably should have used the type of pivot used in indicator stylus ends.

I made a homespun version of the Starrett lever & stylus. I have both 180 and 90 deg levers. There was a design in one of the very early MEW's. Not difficult though - a scrap of ally plate, afew small screws and a some steel rod plus an afternoon's work.

Martin

Harold’s site worked for me a minute ago with Michael’s links, iPhone and Safari .

Ian

And fine for me from a desktop; it's also a lot faster than when I previously visited, so maybe a server upgrade.

Bill

Page opens “in the blink of an eye” now

Well done Harold [whatever you did]

MichaelG.

Thank you Gentlemen, I can now work out what to do as it all looks very good.

Richard Marks

Great, thanks everyone, now got Harold Halls site working very well.

Martyn

But, as I said before, if you are trying to measure 1" of runout in a hole with a dial indicator, there are probably better or easier ways of doing it. Depend on what you are trying to do as to exactly which alternative would suit your needs.

That's why nobody uses the Harold Hall type attachments anymore since lever-type DTI's became commonly available. (They used to be an exotic luxury item until recent times.)

One problem with the Harold Hall and Starrett type attachments is the ball on the end of the lever moves in an arc while the dial inidcator plunger moves in a straight line. So it will struggle mightily to read correctly over a 1" range due to the ball on the end of the lever misaligning with the plunger at each end of the 1" of travel. It was really intended to do the same thing as today's lever DTIs and measure runout of maybe 100 thou or less.

Edited By Hopper on 23/10/2022 13:24:14