Cosine Error Demonstrated and Challenged !

This video puts some mechanics to the term "Cosine Error" and offers up a different point of view vs the popular belief of indicator to tip positioning for accuracy. It will certainly give you something to think about. Take a look.

[bobgodburn]

Joe, good video. I’d never heard of that “keep the indicator tip in line with the body” argument. However, here’s the point I found helpful in my training: I was always told, “you can’t measure with a (test) indicator”. Truly, such an indicator is really to be used as a COMPARATOR. Unless your setup is perfect, there will be a theoretical error. Such an indicator is to be used with gage blocks or a Cadillac gage ideally, although we all use the numbers on the indicator face to tell us where we are. The point that the old guys who taught me were making was that you need to be aware of the limitations inherent in your equipment, if only for those occasions where you are truly measuring in microns or microinches. Nice explanations! Always something practical to learn with your channel.

[johnswilley]

Mr. Pieczynski, I've been watching your videos for some time, I'm a highly critical person for numerous reasons. I've watched many channels over the last few years, BUT yours Sir is the first of any to which I've subscribed. I greatly appreciate your didactic and pragmatic style with which you convey your subject matter. Your efforts are greatly appreciated. Many thanks Sir!

[istvanmeissler]

I hope you keep putting these type of videos on YouTube because you are an excellent teacher and your hard earned knowledge could be making many men better machinists for many many years to come. We all thank you very much.

[samrodian]

Thanks Joe cosine error explained in a language and visual that I CAN understand. And I'm definitely taking that one to the bank! You are by far the best shop teacher on you tube! So please keep them coming lol

[terrycannon]

I always stay with you Joe. Sometimes I have to rewind and re watch because of my thick skull but you are always very informative and worthwhile to watch. Thanks for taking the time to explain in detail and then prove your points at the machine or the bench.

[richardedwards]

I am a bit amazed that this video was even necessary, but excellent as always.
Two points, firstly you did not mention the use of involute tips on some dti's and secondly some manufacturers actually state that their dti is to be used at an angle of 10 or 12 degrees for a zero cosine error. It is always worth checking the manufacturers instructions. Thanks for your videos they make my day.
Best Regards Richard

[wesbiglin]

Joe, You are totally correct. I was in business with family in a job shop my father started. When we got large enough to have to hire a full time inspector and meet QC for a number of companies we worked for, I had this argument with the inspector. We had several boring mills, we were making large radar antenna structures and counter boring large bearing diameters, , I had a mueller gage big enough to do 20" and larger diameters, I set the gage with crow blocks with the gage on precision parellels when we set the indicator. The inspector did not understand cosine error, and did not always use ground same size parallels to set the gage on when he checked the bearing diameters. now for most things there was not enough error to worry about. But when trying to hold .001-.002 on large diameters, it matters. I am long since retired in Texas. great videos.

[nevetslleksah]

Great demonstration and great job explaining the mechanics of using and setting up dial & test indicators. Thanks for taking the time to make the video.

[nickfox]

Thanks again Joe, another fantastic tutorial. Your a real champ for taking the time to put these videos together and explaining them so well. Thanks again.

[justinrowe]

Joe I have to say as an aspiring machinist between you and abom I have learned a lot of how to safely set up, machine, and test parts. Where I'm cursed as a perfectionist your videos and setups make me happy because they are so precise, I will add this tid bit to my mind for when I'm checking parts, just keep up the good work!

[chaoticlogic]

Awesome video. As another visual learner, greatly appreciate your approach. Do wish you had demonstrated cosine error with an improper indicator setup, just to be complete.

[horacerumpole]

Absolutely correct, very well presented! The angular measurement occurs from the tip to it's pivot, it is then converted to precise linear travel up the body of the indicator and then is expressed in linear distance on the dial through the precise rack and pinion mechanism. One lever controlling another longer lever in turn contolling a pivot. Great job Joe!! Best machining stuff on youtube!!

[sonicdewd]

I'm not even a metalhead - I just come here to watch for things I have never even considered. Keeps me grounded, interested, and at times, amazed.

[marcellemay]

You are absolutely correct. What matters is the angle of the arm relative to the swing, on a test indicator. The body can really be at any angle relative to the swing arm, provided that it allows for enough swing of arm. The 10 degree rule of thumb for the swing arm is all that matters. I knew this, but I'm glad you made a video about it. Good one Joe!

[fj]

It seems like when i bought mine the directions that came with the indicator said to use it the way you just explained Joe. That's why the lever is movable. Good job, it's a no brainer.

[brianp]

Always enjoy people thinking outside the box. Been a fan since the threading video. Keep up the great instructional videos.

[ellieprice]

Thanks Joe. I've had both types of indicators for many years but never considered the point relationship to the work. Now I understand thanks to your great teaching and illustrations. Now it's "in my head."

[drumlover]

Joe, your absolutely spot on your reasoning, and explanation of cosine error. I have had to do like anyone else, indication like this many times because of tight confines and having to position the body of the indicator at the same angles you demonstrated. And as you absolutely just proved, the parallelism of the contact point to the indication surface is indeed what matters. Thanks for another great video Joe!

[ctpctp]

I'm trying to figure out why anyone would have ever questioned this, other than someone who never used a test indicator before. I mean THIS is how and WHY we use this style of indicator!!!

[anthonycash]

1- Everything you said made perfect sense to me.
2- Every time I watch one of your videos I learn something.
3- Never challenge someone who is a professional at there trade.
4-As long as you keep making videos, I will keep learning more about machining.
Thanks for the videos Joe.