Cosine Error Demonstrated and Challenged !
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- čas přidán 16. 01. 2018
- 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.
- Věda a technologie
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!
Thanks for the subscription. Every one means a lot to me.
Yeah Ole Joe Pie straight to the point no nonsense. Half the others bang on too long about nada. 😂
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.
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
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!!!
I'm with you, never knew this was a problem to some
Yeah, I literally thought he was going to show some weird tool I've never used and when he went to the shop to show us....I immediately thought wtf, who the hell is saying it doesnt work this way??!!
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
Richard, I had to throw my 2 cents in. The whole straight indicator BS was just too much to digest.
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.
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.
Go see NYNCNC video on that. Tell John that Joe Pie sent you.
I don't know who or what got you pissed off, but that was a good demo and explanation. It has long been a subject of discussion in my shop. That was the way I learned in 1976 as an apprentice. Nice job Joe P.
Thanks. I am not sure who fired me up, but I had to let the steam out.
I hope you keep putting these type of videos on CZcams 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.
thanks. That would be an awesome accomplishment if I could contribute that way. Be sure to pass it on someday.
Cosine error has been used to take tenths off on a lathe for many years... Set the compound to ~9° off parallel to centerline and each thou of dial movement will buy you a tenth of perpendicular to part movement. Very useful when grinding to super precise dimensions.. This may be a topic you could cover on precision turning in a future video.
jim richey - actually at 9 degrees offset the compound movement of .001” will move the Tool tip 0.00015”. If you set the compound at 5.739 degrees (call it 6 degrees for all practical purposes) you will move the Tool tip .0001” for every .001” compound dial movement.
Steven Haskell Dyslexic in my statement.. Thanks for correcting me on that. I'm still sure that it would make a great topic for Joe to cover though...
you have demonstrated Cunningham's Law. It states "the best way to get the right answer on the internet is not to ask a question; it's to post the wrong answer."
An older guy at the shop I work in told me the same now I can show him this video 👍
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.
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!
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.
Never had a problem understanding this. I had a compac extended range test indicator (.120 - 0 - .120) with a 26mm long point and a 2mm ball. The little pamphlet inside expanded it just how you did in the last clip on the white board. The extra range (and longer point) on the indicator made it so you could really see the error and explain it to others. I remember educating or quality manager in this one. Good video.
I find it hard to believe people would argue with any of this. seems like common sense stuff to me....
Me too.
I had no idea until today that anyone thought otherwise. Still trying to wrap my brain as to what mental disconnect must be happening here.
Always enjoy people thinking outside the box. Been a fan since the threading video. Keep up the great instructional videos.
Thx Joe for the video. My takeaway is that the ball ended lever indicators don't suffer from cosine error within their usable range. As you said in the beginning, that type of indicator mechanism is actually an angle indicator. The angular to distance conversion is done by the length of the lever itself. So, with that said, the ball, on the end of the lever, and angle measuring system acts like a sine bar. The angle of the sine bar is determined by the height difference between the rounded parts and the length of the bar which results in a particular angle. Analogously the lever indicator operates the same way.
Thx again, for showing us all, how avoid cosine error by choosing the right measuring instrument in this case a lever indicator.
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.
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!!
One note is that the error can be used to your advantage if you are wanting to get a part to run as true as possible. If the needle has to move 2 ticks to 1 tick of run out, it is easier to see the run out if you don't need a number.
That is very true. Just be aware if you are relying on the reading to finish a cut, you may not have as much material remaining as the indicator says you do.
If folks would read some instructions for indicators from the manufactuer's they explain the exact point you made about the test indicator, check out Interapids instruction sheet.
I have found that many view instructions as reference material for when things go bad. I know I have been guilty of that, but on things that seem so self explanatory, I understand why they get tossed aside.
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!
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.
Everything you showed is one of the first things you learn as a machinist.It's really comman sense.I can't believe people would argue that..I really enjoy your videos I've been machining for 28 years and still learning.
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!
Joe, you are absolutely correct. Awhile back, close to when I started at the company I now work for, I walked into a situation where all the guys were having a conflict over a long flat part that they were indicating with a lever style indicator. It took me a few minutes to show them how to properly use that style of indicator. The thing to know, is the indicator does not measure a linear movement, it measures only the relative rotation of the stylus to the body, and it it only exactly true when the stylus is at exactly flat to given surface. the further from that center, the wronger it gets. Their .035 in out of flat was only really out by .007 in. Naturally they had the stylus kicked up by 30 degrees or so from the perpendicular of the part. Took me a few, but now most of them understand that style of indicator is really no good for measuring, only good for comparing one position to the next. It is only somewhat accurate even in its proper use. Forget trying to explain the term cosine error, (the term "cosine" immediately toasts their brains then they run) simply teach them how to use the indicator correctly. It's easier... toolmaker, teacher 45 years.
You are correct. The body angle is irrelevant, only the angle of the tip to the work matters. Anyone who thinks the tip has to be in line with the body was never taught the proper use of a dial indicator.
Technically, an indicator is just that. It demonstrates differences in geometry or size. It should only be used to measure if correctly setup.
You're absolutely right of course. Anyone that would argue that the angle between indicator body and the tip is the critical factor, simply doesn't understand how the Test Indicator work (or dial/digital indicator for that matter). Nice video.
Great videos Joe. The info in this particular video I've been aware of, but you post a lot of videos that I've learned a lot in. I've been a toolmaker for 17 years now and continue to learn everyday. I think you are probably the sharpest guy on CZcams when it comes to machining. I especially like your video about turning super small impossible diameters by just going for it!
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."
As a person trying to learn and understand machining, once again, you have made it really easy to understand... thanks!!
Joe, Thanks for the video. Best explanation that I've ever seen. Keep'm coming!
I used to have this argument with a guy for hours. He had no comprehension of how a lever indicator worked and would get irate when I would move the nib to indicate what I needed.
As an amateur that's pretty good info to know. I have always tried to be perpendicular or straight on. The surprise to me was the angle movement on the in line dial indicator. Mathematically and mechanically is makes perfect sense when visualized and demonstrated. Thanks for sharing your knowledge and experience. Best Wishes n Blessings. Keith Noneya, Slidell, La. USA
best wishes back at ya neighbor. Thanks for the comment.
Super useful as in addition to proving the points you were making it also gave me practical information on how to test if one is measuring what one thinks. So clear to under set by 10 thou, then put a 10 thou feeler gauge in to see if the dial gauge goes to zero. I am always fighting myself & having ways to see if what I am doing is right gives me great confidence or forces me to do it better, both being highly valuable to me. Thank you for sharing!
I've never heard of the 'needle having to align with body' thing before lol. That's a good one! 😂.
Anyways glad you feel better. Super clear video to anyone with a brain stem an an ounce of common sense and for once im already up to speed.
Nice and I totally agree with what you showed. The body of the DTI doesn't matter at all. What matters with a DTI is the angle of the tip relative to the surface being measured. You can easily calculate the error for the drop indicator by taking the measured size and multiplying by the cosine of the indicator angle (I guessed 20 degrees) so 0.6375 * cos(20) = 0.59905 so the angle must have been close to the guess of 20 degrees. If you reverse the calculation, you can find that the angle had to be invcos(0.6/0.6375) = 19.7499 degrees. This is similar to how you would measure a taper. It's more complicated with a DTI since it has features to try to reduce the error.
I've battled the same argument since the 80's. You are 100% correct, It's the needle to the part that matters.
Recently stumbled on your videos and I've probably watched half of them already. You always provide such a clear and concise VISUAL explanation and demonstration of the things you talk about and I have learned so much in such a short time thanks to these videos! Thank you!
Thanks for the comment. I am glad you find the material helpful.
Excellent explanation, Joe! Thank you providing the “why” behind the error.
Yes sir. In my limited knowledge, your explanation clears it up for me. We sometimes go down a rabbit hole. Great video.
I wish I could give this a thousand likes. I'm new at this, and a hobbyist, but this seemed obvious to me when using a lever-style indicator, and I'd felt something wrong in my guts whenever "more knowledgeable" folks had said otherwise. Thanks for setting my mind at ease!
Good video Joe. Your are spot on and this is nothing more than common sense if you understand how these instruments work..
Keep up the good work.. I enjoy all your videos..
Excellent demo on cosign error . Love your videos Joe, you do some of the best.
Good video- It is amazing it needs to be said really. I was taught on the first day we were shown such tools, way back when, that a "plunge indicator"( as we called them) and a DTI ( or lever style as you call them) were generally really two separate pieces of equipment and as you say,the first , when set up properly is for measurement and the second for comparison thought there is of course overlap in their use.Thanks again for sharing your knowledge!
Great illustration, Joe!
As always, thanks for sharing your knowledge and experience
Great explanation. I think that the confusion started when people who don't understand trigonometry got confused about the different types of indicators. I've seen more than a few people talk about "cosine error" and then say that it's too complicated to explain. It's not actually too complicated to explain. You've proven that. Thanks!
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.
Thanks for watching.
Well stated! The indicator reading is a function of the operator's or the user's setup. Thank you, Joe.
Joe, You are so correct on this. I've had to prove this to many folks over the years in regards to the test indicator
FANTASTIC DEMONSTRATION LOVE IT THANK YOU
Zdravím Vás pane Joe!!! Vaše videa jsou naprosto perfektní! Spoustu věcí které jsem nevěděl tak jsem se od Vás naučil!! Děkuji vám!! Jarda - Česká republika
Zdravím tě Jarda. Před pár lety jsem měl možnost navštívit Českou republiku. Budova opery a hodiny v Praze byly docela krásné. Přál bych si, abych tam měl více času. Děkujeme za vaši podporu a za přihlášení.
Excellent explanation! Just remember, the keyboard "Rambos" will always find a reason to gripe/argue.
The way I see this, a drop indicator with the plunger "true" (perpendicular to the face of the part in both axes) will always give an accurate differential measurement to the extent of the system's capabilities. A lever-style indicator with the lever parallel to the face being measured will give an accurate differential measurement regardless of the orientation of the indicator body, as long as the the change in height on the part does not greatly affect the angle of the lever (leading to cosine error). The classic example is the change in height of a pendulum swinging from rest; at very small angles, the horizontal displacement can be apparent but with almost negligible displacement in height, but as the angle increases, the height increases more and more with less and less horizontal displacement.
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.
I never really thought about it until i picked up a compac dti off ebay and read the manual that came with it , it explained exactly what you are talking about but some indicators are not set up withe the stylus centre line parallel with the test piece some are meant to be at a certain angle to the workpiece regardless of where the body is lined up . Have to be careful of stylus length also as some people think they can fit a longer one and it won't change the accuracy .
Once again another high quality educational video for us to enjoy !
Thanks Joe .
That longer tip can be handy, but does change things.
You are correct, and well demonstrated, The measurements you get is an arc converted to a linear measure, no mater where the body is if the tip is perpendicular to the part the arc will always change the same.
Only the tip to registration plane relationship is important.
Beautiful execution of explanation! Thanks Joe!
Helping make common sense common...I'm glad someone is working that!
Thank You, Thank You, Thank You-At last an explanation I can follow. I enjoy all your posts and have learned a great deal from you. Hope you can make it to the Bash this year.
I really plan to make it this year.
Lol. Nice job explaining that through the frustration. I saw it building from the last vid. It's inspiring that you can deal with commentary as "challenges". I read a lot of them and lose my mind! Kudos.
Good explanation. I'm glad you feel better, and I'm sure you helped some people understand how to use those indicators better.
great video Joe . very informative and very well explained . I love your videos Joe , keep it up fella.
Good video, as always. Lever indicators were never designed to be height indicators. Their purpose is to check run-out and to indicate minor height variations, like squaring up a mill table. They are excellent for what they were designed for. "Drop" or plunger indicators will work for height as well as run-out. As always, use a tool for what it was designed for, otherwise suffer the consequences. As you stated, setup is the key. Old retired engineer and machinist.
Go Joe ! Nice demonstration - plain talk straight to the topic. Thanks for taking it on in language we can all follow. Trig was a long time ago.
_Dan_
Thanks ! I have always wondered about that. I was thinking. That as long as you did not change the angle of what you were measuring. That you would be OK. But NO. Everyone says you need to be at some magical angle for it to work. Glad you showed that it works !!
Great! Simple and clear explanation of the obvious which is sometimes not that obvious . I will watch out for that in the future. Thanks
Thank you for another excellent video.
Joe! you and I both will be able to sleep better now that we have examined and digested these details. I have unknowingly been doing this procedure correctly all along
Hi Joe,i knew this years ago an old timer showed me this when i was grinding a part. You should have shown the small indicator at 20 deg out. GREAT VID..
What you got fired up about and was demonstrating and teaching I was lucky to learn 20 some years ago when I used to work in Norton's Advanced Ceramics division. The man that taught me was Verbatim what you just put on your video. It's something I see guys with 40 and 50 years in the trade do and they think I'm wrong thank you Joe the joke's on them. 10 degrees or less on the lever who was taught that too. .004 spring pressure on a brown & Sharpe also
I really like your presentations. Most useful lessons artfully presented.
In this installment, you state the obvious, but let me augment a bit.
The plunger type is known as "Dial Indicator". It measures actual distances, with typical resolution of 0.001" (sometimes 0.0005") and range of 1" - 5" (or more)
The lever type is known as "Test Indicator", it measures relative motion, with dial resolution of 0.0001" or better and range of 0.004" - 0.010".
The Test Indicator uses a [friction] clutch which enables positioning of the lever anywhere in a range of some 180 degrees. It really measures the arch drawn by the ball tip, not any streight line.
I hope this makes the obvious stated even more obvious.
Finally show and tell with facts!! Great vid. Thanks
Just started a co-op in a shop at my school. I’m loving your videos.
Outstanding. be careful and good luck.
VERY well put - thank you very much for explaining this.
Hi Joe, good demonstration. But it misses the true concern over cosine error. The Leaver type Indicator, has a pivot point. The tip of the stylus is what moves, and causes Rotation of the Pivot point.
If you were to use a different length Stylus, you now Introduce Cosine error in the Measurement. The More the Stylus tip moves, the greater the cosine error caused by the rotation around the pivot.
The Leaver type Indicator is best Used to check repeatability, to a known dimension.
Set up gauge blocks, and zero the indicator on that known dimension.
Now check the same dimension on your Part. A zero on the Indicator, means both Dimension are the same.
A non Zero indicator reading, means the part does not match the known dimension.
The amount of out of tolerance, needs to take into account the length of the stylus from the pivot point, to adjust for the cosine error.
.
As they say Joe, "The proof of the pudding is in the eating" and you certainly demonstrated that without a shadow of a doubt. Nice one! cheers from the UK
Another great video with theory and practice joe.
Ive learned from your knowledge and skills and practiced on my 12x36 lathe with great results thank you very much.
It makes my effort worthwhile if your work is easier. thanks.
Nice to see a good clear explanation of this. This is how I was taught and I have been doing this for years. Can't tell you how many times I have been given flack for "wasting time" trying to get the arm and the part as close to parallel with each other as possible while checking a dimension. They would always say, "just touch the part, it's all the same." Didn't seem right to me, good to know I was doing it right this whole time.
Same here. What we're talking about is THE difference between a 'skilled' engineer and just about anybody else.
Hey Joe, I'm an old guy.....real old! I'm retired and only have a small hobby machine, garage type shop. I would never buy a "new to me" lever style indicators because I didn't "get" how they worked. Like I told a friend, back when I went to school Persian Blue was high tech!! Now that I've seen this video, I am going to order a lever indicator from my supplier. Thanks Joe!
Best tool in the toolbox box. Way to go.
Prussian Blue
Thank's for the schooling Joe. As a home hobbyist machinist, was wondering what type of angle limits were involved with a last word indicator. This was a BIG HELP. Thank's again for sharing.
Clean, straight forward demonstration.
RESPEC! I love these videos!
I don't ever use those for distance anyway. I only use it to reference a single zero point for my DRO to determine distance. Then cosine error comes from my setup or machine.
Joe you did a nice job explaing that , I'm taking it to the bank !
Nice job on this vid. I've been a machinist for over 30 years and I knew about these two kinds of indicators and how to use them before my first year was up. Two different tools doing to different jobs. I never thought people did not know this? As you said, I had never hear of the term Cosine Error before now ether. Well anyway keep up the good work.
Thanks Joe, you're a wealth of knowledge.
Simple clear and as always with your video`s very understandeble!!!
Amazing demonstration ! Thanks !
Excellent demonstration.
Joe you are 100% correct. I am going to speculate that most people that make this type of error have never used a sine bar.
Verdict gauges company in the UK have a patented, non-spherical tip stylus for use with their DTIs (the lever type). It’s like an egg shape tapering down towards the tip. This is to compensate for cosine error generated when the tip cannot be near parallel with the surface. It is not meant to compensate for body angle relative to work, because, as some of us already know, and you have demonstrated, that doesn’t cause an error. Well done for a simple demo.
Interesting concept. I have never seen one.
Yay Joe! That makes me want to go out and buy a cosine just so I can have an error.
thanks Joe. ive been confused about test indicators and errors. i didnt think to experiment and see for myself, but I didnt think there was any error that way. great video. shared
Hi Joe,
I think this topic has been around since the invention of indicators. LOL Your explanation was excellent. I was taught many moons ago, indicators are only a reference and not a measuring device. This is why it really does not matter the position.
If we need to measure a .600 dimension, we set the indicator to "0" with the jo block and not move the indicator. Then test the part. Simple. I usually laugh when the term cosine error and parallax error come into the conversation. Keep the vids coming
Im an old dog and can always learn a new trick!!!!
Hi Joe. Long time subscriber. I still look back at a lot of these old video. I always love your "Just Pisses Me Off" video. I have learned a lot from them. You need to bring them back some day.
I knew my free subscription to you channel would pay off again.. : ), thanks again for the content always nice to see you pick stuff that is not out there already, and to the point, great stuff.
Thanks joe, for teaching me how to use an indicator.
This is at least the one thing I understand in the shop. Probably due to the fact that one of the first Gaging Insp. Fixtures I had to design (40) years ago (with a great deal of assistance from two very experienced Tool & Die Makers) had (8) indicators on it. (2) DTIs and (6) DIs. Excellent learning experience. Remember when Federal was stateside?