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Dial Test Indicator Pointers
A probably really stupid question about dial test indicators.
I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas |
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#2
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Dial Test Indicator Pointers
Gunner:
If your talking about the dial pointer length in my opinion length shouldn't really make a difference. If you draw a strtaight line up the center of the pointer to the scale on the dial it should give you the same reading no matter how long or short the pointer is. I've only had one beer so I might change my mind later Jimbo "Gunner" wrote in message ... A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas |
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#3
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Dial Test Indicator Pointers
Any length works just fine! (Been here) The dial doesn't read in inches,
it reads in some undefined units that fit into some limits. Any angle on the point, other than 0 or 90 deg will not read in linear units but some progression depending on travel depending on secant height. So, unless you're using a plunger indicator, you can call these units: "Miligunners" or how about "Gunnerdoos" or, my favorite "Gunnerinos" "Gunner" wrote in message ... A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas |
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#4
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Dial Test Indicator Pointers
On Sat, 14 Feb 2004 17:32:47 -0500, "Jimbo" .
wrote: Gunner: If your talking about the dial pointer length in my opinion length shouldn't really make a difference. If you draw a strtaight line up the center of the pointer to the scale on the dial it should give you the same reading no matter how long or short the pointer is. I've only had one beer so I might change my mind later Jimbo Sorry Jimbo..I communicate poorly sometimes. The lever pointer..the little ball nosed gizmo that actually contacts the work piece Gunner "Gunner" wrote in message .. . A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas |
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Dial Test Indicator Pointers
On Sat, 14 Feb 2004 22:37:29 GMT, "Tom Gardner"
wrote: Any length works just fine! (Been here) The dial doesn't read in inches, it reads in some undefined units that fit into some limits. Any angle on the point, other than 0 or 90 deg will not read in linear units but some progression depending on travel depending on secant height. So, unless you're using a plunger indicator, you can call these units: "Miligunners" or how about "Gunnerdoos" or, my favorite "Gunnerinos" OOOH! I like that...Gunnerinos! Chuckle..I need to use a DTI for measuring TIR of rotating collet closer bodies. How do I actually measure .0005 runout with a DTI? Actual tenths..not Gunnerinos. G This is why I asked the question about pointer/lever length Gunner "Gunner" wrote in message .. . A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas |
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Dial Test Indicator Pointers
In article , Gunner says...
How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? If this is a plunger type, where the point travels in a straight line and actuates a rack inside the instrument, then the length of the pointer (which screws into the plunger, using an unusual fine thread like 4-48 or something) then the length does not count. If it is a type similar to a last word, where the pointer swings in an arc, then the dial reading will indeed depend on the length of the pointer from pivot to tip. The longer the pointer, the more sensitive it will be, ie, for a given tip deflection, you will see a bigger dial reading. If this is the type, and you want to check that the one you have is more or less correct, then simply put the indicator in a lathe toolpost and use your crossfeed dial to wind in a given amount of travel. The only important issue is that the angle between the infeed and the length of the pointer's axis should be nearly 90 degrees. In those kinds of pivot pointer indicators the error between the actual travel and the indicated travel goes pretty much like the cosine of the error angle you need to get it really misaligned by a lot before you begin to see much discrepancy. But as mentioned, these devices work best as a null indicator, where one is trying to zero out some error. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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#7
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Dial Test Indicator Pointers
Calibrate to a known with the point at 0 or 90 deg. The secant error will
be minimal especially with small movements. At some point, it just doesn't matter when the gravity pull from Uranus will skew your readings. "Gunner" wrote in message ... On Sat, 14 Feb 2004 22:37:29 GMT, "Tom Gardner" wrote: Any length works just fine! (Been here) The dial doesn't read in inches, it reads in some undefined units that fit into some limits. Any angle on the point, other than 0 or 90 deg will not read in linear units but some progression depending on travel depending on secant height. So, unless you're using a plunger indicator, you can call these units: "Miligunners" or how about "Gunnerdoos" or, my favorite "Gunnerinos" OOOH! I like that...Gunnerinos! Chuckle..I need to use a DTI for measuring TIR of rotating collet closer bodies. How do I actually measure .0005 runout with a DTI? Actual tenths..not Gunnerinos. G This is why I asked the question about pointer/lever length Gunner "Gunner" wrote in message .. . A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas |
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#8
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Dial Test Indicator Pointers
"Gunner" wrote in message ... A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas Yes, it matters if you have to measure in specific units. If all you want to check is straightness or concentricity, any needle of the right thread size should work, but if it has to be an accurate number, it needs to be the correct length stem for the indicator. -- Later, Charlie fix the e-mail address and it will get to me |
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#9
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Dial Test Indicator Pointers
Gunner,
It makes a big difference what the length of the lever arm was if you want "true" accuracy. "True" accuracy meaning where the deflection (in tenths) of the lever agrees with the indication of the dial. The pivot on the indicator actually measures angular displacement of the lever, so the lever arm length counts. Suppose you had an indicator with a 1 inch lever, and you measured a 0.010 inch deflection. Put on a 1/2 inch lever and you would measure 0.020. For concentricity purposes, such as centering a piece of work in a 4 jaw chuck, lever length doesn't matter much, as you are trying to eliminate TIR of the part. My 2 cents. Mike Eberlein Gunner wrote: On Sat, 14 Feb 2004 22:37:29 GMT, "Tom Gardner" wrote: Any length works just fine! (Been here) The dial doesn't read in inches, it reads in some undefined units that fit into some limits. Any angle on the point, other than 0 or 90 deg will not read in linear units but some progression depending on travel depending on secant height. So, unless you're using a plunger indicator, you can call these units: "Miligunners" or how about "Gunnerdoos" or, my favorite "Gunnerinos" OOOH! I like that...Gunnerinos! Chuckle..I need to use a DTI for measuring TIR of rotating collet closer bodies. How do I actually measure .0005 runout with a DTI? Actual tenths..not Gunnerinos. G This is why I asked the question about pointer/lever length Gunner "Gunner" wrote in message .. . A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas |
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#10
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Dial Test Indicator Pointers
Jim,
I don't agree. The longer the lever, the less of a reading you will see for the same deflection. The indicator is actually calibrated for angular displacement. A shorter lever will give a larger angular diplacement for the same tip deflection. Mike Eberlein jim rozen wrote: In article , Gunner says... How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? If this is a plunger type, where the point travels in a straight line and actuates a rack inside the instrument, then the length of the pointer (which screws into the plunger, using an unusual fine thread like 4-48 or something) then the length does not count. If it is a type similar to a last word, where the pointer swings in an arc, then the dial reading will indeed depend on the length of the pointer from pivot to tip. The longer the pointer, the more sensitive it will be, ie, for a given tip deflection, you will see a bigger dial reading. If this is the type, and you want to check that the one you have is more or less correct, then simply put the indicator in a lathe toolpost and use your crossfeed dial to wind in a given amount of travel. The only important issue is that the angle between the infeed and the length of the pointer's axis should be nearly 90 degrees. In those kinds of pivot pointer indicators the error between the actual travel and the indicated travel goes pretty much like the cosine of the error angle you need to get it really misaligned by a lot before you begin to see much discrepancy. But as mentioned, these devices work best as a null indicator, where one is trying to zero out some error. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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#11
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Dial Test Indicator Pointers
On Sat, 14 Feb 2004 22:04:12 GMT, Gunner
wrote: A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas Gunner the contact point length is important.. the higher the resolution of the indicator the more important the contact point length and the angle at which the contact point touching the surface to be measured is.. Other then Lufkin docs.. take your contact point.. make sure the contact point is does not have flats.. should be a perfect sphere...just test the movement on a height check.. a good test is plus of minus .0005.. in .0001increments.. with the contract point horizontal to the height check surface....and see how close it is.. should be perfect at .0005 and start to differ around .008 or so.. repeatability is always much better on test indicators then accuracy in travel , depending on the range quality, etc.. Lufkins are a little stiff so don't be discouraged if you can't see a ..0001 movement very well... and it could be dirty, etec.. later, Mike |
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#13
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Dial Test Indicator Pointers
My interapid came with 2 contact points. One is .75 long & the other is 1.5
long. With the 1.5 long point in, my dial reading is cut in half. |
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Dial Test Indicator Pointers
In article , Jim Kovar says...
I don't think so. Just the opposite. Indeed you are correct. My mind was a bit fogged after spending saturday at work. The simple rules of levers says that the shorter pointer makes the dial move more. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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Dial Test Indicator Pointers
In article , mikee says...
Jim, I don't agree. The longer the lever, the less of a reading you will see for the same deflection. The indicator is actually calibrated for angular displacement. A shorter lever will give a larger angular diplacement for the same tip deflection. An additional oops here, to add to the other one I posted. Of course the rule of simple levers says you are correct. My only possible defence is that I was operating with a scrambled head from spending saturday at work.... Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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#16
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Dial Test Indicator Pointers
Gunner wrote:
A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. The pointer should be long enough to reach your target. It's similar as your leg length when you walk. If your legs are too long you stumble, if too short you float. Fortunately most persons have the right length legs. HTH. -- SATOR AREPO TENET OPERA ROTAS Have 5 nice days! John ****************************** --- ILN 000.000.001 --- |
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Dial Test Indicator Pointers
In article ,
jim rozen wrote: : :If it is a type similar to a last word, where the pointer :swings in an arc, then the dial reading will indeed depend  n the length of the pointer from pivot to tip. The longer the ointer, the more sensitive it will be, ie, for a given tip:deflection, you will see a bigger dial reading. You've got that bass-ackward. -- Bob Nichols AT interaccess.com I am "rnichols" |
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Dial Test Indicator Pointers
"Gunner" wrote in message ... SNIP How long are the pointers supposed to be? SNIP Most are 11/16" long, unless using an extended tip indicator. Don't believe the stories about milli units or whatever. With the pointer as close to parallel to the work surface as possible,(orientation of the body does not matter) the graduations on the indicator should be very accurate to the actual deflection when using the correct length tip. -- Steve Walker (remove wallet to reply) |
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Dial Test Indicator Pointers
On Sat, 14 Feb 2004 23:26:29 GMT, "Charlie Gary"
wrote: "Gunner" wrote in message .. . A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas Yes, it matters if you have to measure in specific units. If all you want to check is straightness or concentricity, any needle of the right thread size should work, but if it has to be an accurate number, it needs to be the correct length stem for the indicator. I do indeed have to measure in specific units, hence the original post. How do I determine the correct stem lenght? Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas |
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Dial Test Indicator Pointers
I do indeed have to measure in specific units, hence the original post. How do I determine the correct stem lenght? Gunner This is what jo blocks are for. |
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#23
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Dial Test Indicator Pointers
Probably the best way is by trial measurement on something and comparing the
reading with another indicator you know is accurate. Do it this way. Put any size lever on your Luftkin. Chuck up something round in a 4 jaw chuck on a lathe and deliberately dial it in so it has about 0.025 inch TIR with the known good indicator. Now measure with the Luftkin. Say you get 0.040 inch. The trial lever length is too short, as the indicated Luftkin reading is too big. By simple ratioing, the true length should be (0.040/0.025) x (trial lever length). If the Luftkin reading is less than the true TIR you need to lengthen the lever. Lets say you get 0.015 reading on the Luftkin. By ratioing, the true length should be (0.025/0.015) x (trial lever length). When doing the measurements, the more TIR on the test part the better as it will minimize reading erros, etc. Trying to make a new lever from scratch would be a real challange, I think. The threads are DINKY on those levers You might want to consider calling Luftkin and asking if they can supply the correct size. Good luck, Gunner. Mike Eberlein Gunner wrote: On Sat, 14 Feb 2004 23:26:29 GMT, "Charlie Gary" wrote: "Gunner" wrote in message .. . I do indeed have to measure in specific units, hence the original post. How do I determine the correct stem lenght? Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas |
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#24
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Dial Test Indicator Pointers
"Gunner" wrote in message ... On Sat, 14 Feb 2004 23:26:29 GMT, "Charlie Gary" wrote: "Gunner" wrote in message .. . A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas Yes, it matters if you have to measure in specific units. If all you want to check is straightness or concentricity, any needle of the right thread size should work, but if it has to be an accurate number, it needs to be the correct length stem for the indicator. I do indeed have to measure in specific units, hence the original post. How do I determine the correct stem lenght? Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas Have you tried a Lufkin catalog or web site? If it's anything like my B&S, the part number on the indicator (I hope there is one) should be specific to the length of stem it came with. Knowing that, you should be able to determine which one it needs. If I'm really lazy, I just dial 1-800-734-9099 and ask for Mike. I tell him what I've got, and he looks it up in his vast library of resources. Perhaps he can do the same for you. If he can find it, he can also probably get it for you, delivered right to your door. Visa and Mastercard gladly accepted. -- Later, Charlie fix the e-mail address and it will get to me |
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#25
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Charlie Gary wrote:
Have you tried a Lufkin catalog or web site? If it's anything like my B&S, the part number on the indicator (I hope there is one) should be specific to the length of stem it came with. Knowing that, you should be able to determine which one it needs. If I'm really lazy, I just dial 1-800-734-9099 and ask for Mike. I tell him what I've got, and he looks it up in his vast library of resources. Perhaps he can do the same for you. If he can find it, he can also probably get it for you, delivered right to your door. Visa and Mastercard gladly accepted. -- Later, Charlie fix the e-mail address and it will get to me Charlie, Lufkin has been out of business for a long time. Probably need to find an instrument repair shop with spares. -- Regards, Steve Saling aka The Garlic Dude Gilroy, CA The Garlic Capital of The World http://www.pulsareng.com/ |
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#26
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Dial Test Indicator Pointers
"Garlicdude" wrote in message ... Charlie Gary wrote: Have you tried a Lufkin catalog or web site? If it's anything like my B&S, the part number on the indicator (I hope there is one) should be specific to the length of stem it came with. Knowing that, you should be able to determine which one it needs. If I'm really lazy, I just dial 1-800-734-9099 and ask for Mike. I tell him what I've got, and he looks it up in his vast library of resources. Perhaps he can do the same for you. If he can find it, he can also probably get it for you, delivered right to your door. Visa and Mastercard gladly accepted. Later, Charlie fix the e-mail address and it will get to me Charlie, Lufkin has been out of business for a long time. Probably need to find an instrument repair shop with spares. Regards, Steve Saling aka The Garlic Dude Gilroy, CA The Garlic Capital of The World http://www.pulsareng.com/ Bummer. I'd still call Mike, though, 'cause he seems to know who the repair people are, too. At least in my area. :-) -- Later, Charlie fix the e-mail address and it will get to me |
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#27
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Dial Test Indicator Pointers
On Sat, 14 Feb 2004 23:26:29 GMT,
,"C harlie Gary" said: "Gunner" wrote in message .. . A probably really stupid question about dial test indicators. I stumbled across a minty Lufkin LARGE dial, dial test indicator (.0001) for $5 the other day. Crystal is good, everything moves smoothly..but the "pointer" was missing. A customer gave me one that screws in just fine..but here is the question...and Im blushing to ask.. How long are the pointers supposed to be? Perhaps Ive had a stroke or its a case of brain fade..but doesnt the length of the pointer make a difference as to the actual measurement displayed on the dial? Length of lever and all that stuff. Gunner "To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas Yes, it matters if you have to measure in specific units. If all you want to check is straightness or concentricity, any needle of the right thread size should work, but if it has to be an accurate number, it needs to be the correct length stem for the indicator. Agreed. For comparison use it doesn't matter. I try to avoid taking readings from the DTI face if at all possible. Work to zero and take the reading from the height gauge/machine readout. If you must read from the dial keep the stylus arm as straight to the indicator body as you can to avoid cosine error. More angle=more error. Cigi. -- Give Peas a Chance |
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#28
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Dial Test Indicator Pointers
Hey Jim,
SNIP you said: If it is a type similar to a last word, where the pointer swings in an arc, then the dial reading will indeed depend on the length of the pointer from pivot to tip. The longer the pointer, the more sensitive it will be, ie, for a given tip deflection, you will see a bigger dial reading. Hmmm.. Want to have another run at this? The longer the lever, the LESS sensitive it will be. Smoother for sure, but less sensitive. Take care. Brian Lawson, Bothwell, Ontario. |
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#29
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Dial Test Indicator Pointers
In article , Brian Lawson says...
Want to have another run at this? The longer the lever, the LESS sensitive it will be. Smoother for sure, but less sensitive. Hoo boy, I think now *everyone* has weighed in on this. Probably more than actually replied to gunner! For the record, and for the last time: f/x PA system echo N O W H E A R T H I S : Yep, I screwed up. Happens sometimes! Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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#30
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Dial Test Indicator Pointers
In article ,
jim rozen wrote: In article , Brian Lawson says... Want to have another run at this? The longer the lever, the LESS sensitive it will be. Smoother for sure, but less sensitive. Hoo boy, I think now *everyone* has weighed in on this. Probably more than actually replied to gunner! Don't you know that the best way to get lots of posts in answer to a question is to post a wrong answer? :-) I didn't weigh in -- but only because I saw that several others had already followed up, and a quick check showed that they had already entered the correction. (One advantage of being late catching up on the newsgroup. :-) Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
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Dial Test Indicator Pointers
In article ,
Cigi wrote: [ ... ] Agreed. For comparison use it doesn't matter. I try to avoid taking readings from the DTI face if at all possible. Work to zero and take the reading from the height gauge/machine readout. If you must read from the dial keep the stylus arm as straight to the indicator body as you can to avoid cosine error. More angle=more error. Note that some makers design so the proper reading is given at a specific angle -- not necessarily 90 or 0 degrees to the work surface. An angle of 30 degrees will give a 2:1 motion modification -- and will hold the pivot point clear of the work surface (if you are dealing with a large radius), so some makers design for it to be correct at such an angle. All the more reason for you to chase up an old Lufkin catalog and find out both what length and what angle you need to use. Or you could set it up on a stable surface, then slide a piece of shim stock under it to deflect it a known amount. This will show you how many marks it goes for say 0.001" of pointer motion -- and you can try different angles to find one which works well. (You could probably even find a combination of angles and pointer length to give your readings i Metric units, should you so desire. Good Luck, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
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Dial Test Indicator Pointers
On 15 Feb 2004 18:38:53 -0800, jim rozen wrote: In article , Brian Lawson says... Want to have another run at this? The longer the lever, the LESS sensitive it will be. Smoother for sure, but less sensitive. Hoo boy, I think now *everyone* has weighed in on this. Probably more than actually replied to gunner! For the record, and for the last time: f/x PA system echo N O W H E A R T H I S : Yep, I screwed up. Happens sometimes! Jim Hey Jim, Yeah, but not too often. So it's noteworthy. And just shows you that we all read your posts! Anyway, I'm sorry I did write, because I had 367 incoming rcm's to read, and Gunners and your reply were early on, and I wrote then. I see after I got through more than about 50 of them that you did get quite a few "comments" on what happened. Take care. Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXXXXX ================================================= = please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================= = |
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Dial Test Indicator Pointers
In article , DoN. Nichols says...
Don't you know that the best way to get lots of posts in answer to a question is to post a wrong answer? :-) Hee hee. I joke about this, but it's true. You could win the nobel prize and nobody'd hear about it, but walk around for five minutes with my pants zipper down, and the pa system here cranks up with "now hear this!!" Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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Dial Test Indicator Pointers
"DoN. Nichols" wrote: Note that some makers design so the proper reading is given at a specific angle -- not necessarily 90 or 0 degrees to the work surface. DoN: This is true. Interapid test indicators seem to be one brand that is most accurate when the contact point is at 12 degrees rather than parallel to the work surface. http://www.longislandindicator.com/c...tion.html#Test Indicators An excerpt from the above site: =============================================== Test indicators can also be calibrated on a surface plate using certified gage blocks. The indicator is securely fastened to a stand and the contact point is brought in contact with a gage block of a given size. The contact point must be parallel with the surface of the block for most manufacturers. Interapid test indicators are an exception and should be at a 12-degree angle, approximately. ================================================ Here is a cosine error chart from the same site with a correction factor to be used for various indicator tip angles. (If it doesn't copy correctly just go to the site) ================================================ About the cosine error: for test indicators excluding Interapid models. If the contact point can not be kept parallel to the work surface then you will have to make a mathematical adjustment to the dial reading. contact correction point angle factor 10° 0.98 15° 0.97 20° 0.94 30° 0.87 40° 0.77 50° 0.64 60° 0.50 From this chart you will notice that a contact point held at a 60-degree angle results in one-half the dial reading. Once you determine the angle, simply multiply the dial reading by the corresponding correction factor. For example, an indicator reading of .0085" at an angle of 30-degrees is equivalent to .0085" x .87 = .0074" =============================================== Some indicators used to be made with involute "balls" (sort of pear shaped tips) that automatically corrected for minor cosine error. But I haven't seen any in years. Or you could set it up on a stable surface, then slide a piece of shim stock under it to deflect it a known amount. Using shim stock to try and calibrate your indicator is probably not such a hot idea. Especially with a .0001 indicator. Shim stock not only varies in thickness but can be bent, or burred. That's what Jo blocks and Height Masters are for. If you don't have a Height Master or Jo blocks then in a pinch you could use pin gages. Mic them first to see what they actually measure. -- BottleBob http://home.earthlink.net/~bottlbob |
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Dial Test Indicator Pointers
In article ,
BottleBob wrote: "DoN. Nichols" wrote: Note that some makers design so the proper reading is given at a specific angle -- not necessarily 90 or 0 degrees to the work surface. [ ... ] This is true. Interapid test indicators seem to be one brand that is most accurate when the contact point is at 12 degrees rather than parallel to the work surface. O.K. I knew that I had encountered at least one such brand. [ ... ] Here is a cosine error chart from the same site with a correction factor to be used for various indicator tip angles. (If it doesn't copy correctly just go to the site) [ ... ] contact correction point angle factor 10° 0.98 15° 0.97 20° 0.94 30° 0.87 40° 0.77 50° 0.64 60° 0.50 That is simply the cosine of the angle. Something which can be looked up in tables, or with a scientific calculator, had at the press of a button -- to finer steps than are given above. (Though getting that close a measurement of the angle of the tip is a bit problematical. :-) [ ... ] Some indicators used to be made with involute "balls" (sort of pear shaped tips) that automatically corrected for minor cosine error. But I haven't seen any in years. I suspect that they wore faster than the spherical ones, and were more expensive to replace. Or you could set it up on a stable surface, then slide a piece of shim stock under it to deflect it a known amount. Using shim stock to try and calibrate your indicator is probably not such a hot idea. Especially with a .0001 indicator. Shim stock not only varies in thickness but can be bent, or burred. But -- shim stocks (or feeler gauges) might be present in a shop which doesn't have a set of Jo blocks (or equivalent), though a cheap Chinese set would be good enough for the purpose. Ideally, the shim or feeler gauge would be placed between a ball contact and the ball on the indicator, to eliminate the problem with bent or burred examples. And all things considered (including the cosine errors), you really don't want to be depending on such tools for truly accurate measurements, anyway. A plunger style would be better, as it has no cosine error if set up square to the surface being measured. Shim stock would be good enough to get an order-of-magnitude indication of the sensitivity of the indicator -- for such things as telling whether you have the right length feeler arm on the indicator. That's what Jo blocks and Height Masters are for. If you don't have a Height Master or Jo blocks then in a pinch you could use pin gages. Mic them first to see what they actually measure. Again -- I doubt that you would be using that style of indicator for precision measurements -- unless the access to the point to be measured precludes anything else. I would agree to the use of Jo blocks for checking a plunger style indicator -- especially a tenths-reading one (or more sensitive, if you are really lucky.) Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
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Dial Test Indicator Pointers
Gunner wrote:
OOOH! I like that...Gunnerinos! Chuckle..I need to use a DTI for measuring TIR of rotating collet closer bodies. How do I actually measure .0005 runout with a DTI? Actual tenths..not Gunnerinos. G This is why I asked the question about pointer/lever length Sorry to burst your gunnerinios, Gunner; but Tom's not correct. The point length does matter. What an indicator actually measures is angles. The angular deflection of the pointer touching the work is magnified by the gears into a larger angle when the needle moves around the dial. The linear distance (tenths, thousandths, or whatever) that you read is just a convenient conversion from degrees, which is accomplished by making the marks on the face of the indicator match the angles produced by the pointer and gears. Here's a real simple example: Think of an indicator on a surface gauge, with it's pointer arranged to be perfectly horizontal, while touching the top of a stack of gauge blocks. The pointer is exactly 1" long, from the point where it's ball touches the gauge blocks to the center of little axle it rotates on. To move the pointer one degree, you'd need to change the stack of gauge blocks by 17.5 thousandths. 0.017452 inches, actually. That's the sine of one degree. If the gears in the indicator multiply the angle by, say, a factor of ten, then 17.5 thousandths on the gauge blocks, which produces one degree of motion on the pointer, will become ten degrees of needle motion on the face of the indicator. In order for the indicator to work properly, the marks on it's face have to be arranged so that 10 degrees equals 17.5 thousandths when you read it. Or, the .001" marks on the indicator need to be exactly .5714 degrees apart. If this same indicator had a 1/2 inch pointer, and you changed the gauge blocks by 17.5 thousands, that would create an angular motion in the pointer of 2.006 degrees, instead of one degree. When the gears multiplied it by ten, this would become 20.06 degrees of needle motion on the indicator face. If the marks on the face are still .5741 degrees apart, then 20.06 degrees would look like 34.8 thousandths, even though the gauge blocks had only changed by 17.5. Bad news, of course. For some kinds of measurements, you don't really care about any of the marks on the indicator face except the zero. Concentricity can be one of these. Whether the indicator reads accurately as it moves isn't really an issue. All you care about is that it repeats to one particular position. In that case, pointer length doesn't matter as much; but it still affects (multiplies or divides) the sensitivity of the indicator. Unless your readings really ARE zero, you won't be able to tell precisely what they mean. With too short a pointer, the needle will move too much in response to even the slightest provocation. If the pointer's too long, the needle won't move enough to tell you whether you're really as close to zero as you want to be. The other factor, which makes all of this a little less perfect than it might appear, is cosine error. As I'm sure most folks here are aware, it's often pretty tough to set up your indicator as described above, with the pointer exactly parallel to the surface plate, or tangent to the diameter you're measuring, or whatever. That affects the accuracy of measurement substantially. And, the affect grows trigonometrically as you try to read larger and larger values on the indicator dial. It might not mean much when you're looking at a difference on the dial between zero and .001; but it can mean a lot when the needle needs to move from zero to .010 or beyond. Hope this helps! KG -- I'm sick of spam. The 2 in my address doesn't belong there. |
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Dial Test Indicator Pointers
Gunner wrote:
Chuckle..I need to use a DTI for measuring TIR of rotating collet closer bodies. How do I actually measure .0005 runout with a DTI? Actual tenths..not Gunnerinos. G This is why I asked the question about pointer/lever length While I'm at it... You can calibrate your indicator, no matter what the pointer length is, as long as you plan to use it only for concentricity, or for measurements that involve only small movements of the needle. Mount the indicator on a surface gauge. Set it up so the pointer is as close to horizontal as you can get it, while zeroed on a stack of good gauge blocks. Then carefully increase and decrease the height of the gauge blocks by increments. Say, plus a thousanth, then minus a thousandth. Then plus two, then minus two, etc. Write down the results of each measurement, including the gauge block changes AND the actual needle readings you get from the indicator dial. These will produce a kind of "conversion table" for the indicator with any particular pointer. If each .001 change on the blocks gets you a .0015 change on the indicator dial, for example, then you can use the indicator accurately (over small ranges of motion) just by converting with a factor of 1.5. KG -- I'm sick of spam. The 2 in my address doesn't belong there. |
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Dial Test Indicator Pointers
In article , BottleBob says...
Some indicators used to be made with involute "balls" (sort of pear shaped tips) that automatically corrected for minor cosine error. But I haven't seen any in years. Federal's electronic gaging heads still come with that feature. Works well. Jim ================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================== |
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Dial Test Indicator Pointers
mikee wrote in message ...
You might want to consider calling Luftkin and asking if they can supply the correct size. Good luck, Gunner. Mike Eberlein That Lufkin is long out of business. -- Cliff |
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Dial Test Indicator Pointers
In article , Gunner
writes: How do I determine the correct stem lenght? Measure something *known* and trig it out. Simple. For small deflections it's also almost linear (sine in radins ~~ angle in radins). .001" shim stock may come to mind .... or a feeler guage. http://www.longislandindicator.com/dialindicators.html [ Lufkin never actually manufactured their own instruments. Dial indicators were made by Federal Gage. Repairs: not economical Sales: discontinued Parts: no longer available Information: unavailable ] Try Federal's Site? http://www.mahrfederal.com/frameset.htm -- Cliff |
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