Proper use of a "dial test indicator" (DTI) vs. dial indicator (DI)?

[HMF]

A question for the group:

1. When using a *dial indicator* (plunger type) is there a right and wrong way to use this instrument when indicating on a lathe? Photos would be very helpful.

I.E., can a dial indicator be used in a vertical position, upside down position, horizontal position, or at an oblique angle? An example might be, but not limited to this example, indicating runout on the inside shoulder of a Bison 5-C collet chuck where the indicator may have to be turned at a strange, awkward angle for the bottom of the plunger to engage the articulating surface where the angle of the collet seats?

2. Is a *test indicator* designed to be more versatile?

I.E., can it be used on a mill as well as the lathe and in far more strange positions or is the test indicator’s use limited? Is there a difference between test indicators which are "vertical" or "horizontal"?


Thanks,


Nelson

 

[awander]

Re: Proper use of a "dial test indicator" (DTI) vs. dial indicator (DI)?

A dial indicator(DI) can be used at any angle if you are strictly testing concentricity. If you want to know that you are actually measuring the numbers on the dial, then you need to use it perpendicular to the surface being measured.

The difference between a DI and a DTI(Dial Test Indicator) is that the DI is designed to actually measure or indicate an actual distance distance(when used parallel to the motion), while a DTI is typically designed for use in the other way, where you donlt care about actual distance, just relative distance(centering an object in a 4-jaw chuck, for instance.

Many DTIs, due to their design which incorporates a lever that does the actual measurement, cannot be used to indicate actual distances at all. Many DTIs are also more sensitive, and may have less total range of motion-on teh order or 30-50 thousandths, while there are DIs that can measure 2 inches or more.

 

[Ulma Doctor]

Re: Proper use of a "dial test indicator" (DTI) vs. dial indicator (DI)?

another way of looking at this:
the dial indicator = iron sights, .001" accuracy for the norm 1" or better travel
the test indicator= sniper bullet, .0005" accuracy for the norm .030" (or so) travel

 

[Ray C]

Re: Proper use of a "dial test indicator" (DTI) vs. dial indicator (DI)?

Also, there are indicators that have 0.0001" graduations with just a +/- 0.005 total swing. These are what I use when I'm looking really close at a finished part and I use the 0.0005 with +/- 0.015 swing when I'm setting up parts. I have several each of the same brand and model and purchase ones with different color faces so I can always grab the right one. Travel indicators are good for ballpark situations like drilling to a specific distance.


Ray

another way of looking at this:
the dial indicator = iron sights, .001" accuracy for the norm 1" or better travel
the test indicator= sniper bullet, .0005" accuracy for the norm .030" (or so) travel

 

[Richard King]

Re: Proper use of a "dial test indicator" (DTI) vs. dial indicator (DI)?

I found this on You Tube and shows a plunger type Dial Indicator.
http://www.youtube.com/watch?v=qMgXGedDffw

I will add more later on the other types that should not be used as a plunger type I will explain later. Rich

This explains the use of gage blocks and at the end of the video you will see how to set up your indicator. I was taught as an apprentice to never have the stem more then 15 degrees from parallel to the part as he will show you. I will see if I can find more. I have some pictures I can add too. But please never mix up the plunger type indicator with this type of stem dial type. If you are caught in a shop using a stem type as a plunger type you will be teased.

http://www.youtube.com/watch?feature=fvwp&v=nG3yfeGxcWg&NR=1

 

[komatias]

Re: Proper use of a "dial test indicator" (DTI) vs. dial indicator (DI)?

I think this one has been answered pretty much, so I will only add my experiences on when to use what.

Setting up either measurement devices is at best arbitrary. You will never get the plungers vertical or normal or the little feelers perfectly horizontal. With that in mind, I use all my dial indicators as a means to compare. I also feel, so may be wrong, that the translation of actual arc described by the measuring point/ball on the finger to the dial reading may be prone to trigonometric errors whereby the actual angles you place the feeler at may affect your true position.

I personally do not feel confident to say that I have a try absolute measurement, only a comparison which is accurate to within so-and-so. This is where the gauge blocks or height masters come into play.

The only exception is if I have the plunger type chucked in a collet on the mill. I use this sometimes to calibrate my vertical axis readings on my hobby CNC machine.

There are many ways to use either instruments and you will have to figure this out on a application to application basis. Both can be used upside down but remember that the arms (most probably the joints) of the magnetic holder may flex under their weight if you are taking a measurement rightside up and then upside down. It is all about being consistent and minimizing errors.

The general rules of thumb I follow are dependent on the accuracy and resolution of comparison I want. If I am comparing in a range of 0.05mm then I use the dial test indicator (DTI) e.g. runout on a lathe, flatness of a scraped part on the granite table. If I am looking in the region of 0.1mm then the dial indicator (plunger) is my favoured option. Then you need to think about resolution, a larger dial will show more white between the lines and so would a smaller range DTI.

If you are interested in accuracy and working to tolerances, you will probably start accumulating various devices, just make sure that if you buy used, they return smoothly, are not stiff and definitely not sticky. The less sensitive devices are the magnetic holders.I would recommend anyone interested in metrology and working to tolerances have a look at Phil Kerner's videos on youtube and look up his blog. He calls himself the tool and die guy.

 

[Richard King]

Re: Proper use of a "dial test indicator" (DTI) vs. dial indicator (DI)?

Something I forgot to add is never flip the indicator over as the indicators are designed to read upright. Some are better then others and the distance you reach out will magnify the error. Barry up in Montana added the following post when we were discussing lathe alignment.
This is a test I learned from Forrest Addy several years ago when I was teaching a scraping class where he was the apprentice instructor. Try it it will blow your mind. Never indicate a tail-stock (TS) in off the head-stock (HS) unless you pre test your indicator sag. The Drake indicator was made to be used in the HS, but the dial mechanism stays up and the stem that is supported with an bearing turns, it's a different animal compaired to these dial indicators we are talking about.
Look at item # 1. Rich
http://www.hobby-machinist.com/show...-Tailstock-with-Headstock?p=106737#post106737

also found this: It's a bit hard to read and a bit boring, but shows how to.


http://www.mitutoyo.co.jp/eng/products/menu/QuickGuide_Dial-Indicators.pdf

 

[awander]

Re: Proper use of a "dial test indicator" (DTI) vs. dial indicator (DI)?

Hi Richard:

Is it possible that some of that sag is due to the test stock itself?

Just guessing at the magnitude,but a long bar like that will deflect as well.

 

[Richard King]

Re: Proper use of a "dial test indicator" (DTI) vs. dial indicator (DI)?

Hi Richard:

Is it possible that some of that sag is due to the test stock itself?

Just guessing at the magnitude,but a long bar like that will deflect as well.

Sure it can, but I have done this these tests on the flats of camel-back straight-edges that won't bend and get the came results. Go out and try it in your shop. The short the set up the less the sag. The longer and the size of the rod will change the results, but it will change the indicator reading I promise. Rich

 

[awander]

Re: Proper use of a "dial test indicator" (DTI) vs. dial indicator (DI)?

Sure it can, but I have done this these tests on the flats of camel-back straight-edges that won't bend and get the came results. Go out and try it in your shop. The short the set up the less the sag. The longer and the size of the rod will change the results, but it will change the indicator reading I promise. Rich

Oh, I don't doubt that it will change. I've always been amazed how just leaning on the lathe can change an indicator reading.