Poor mans lathe DRO's

[Toolmaker51]

Look closely at the cheap knock-offs on eBay. Most have a resolution to the nearest 0.001", while the real ones are good to 0.0005". eBay does not seem to be able to police these knock-offs very well. Dan L

YES, DanLins, 100%.
To All; I don't see policing by Ebay as a real thorough undertaking. If US Customs, Rolex, Gucci, any automaker, antique Colts, musical instruments; probably any item in the global market can't get a handle on trademarks, no one can monitor actual product. I'm certain a number of high volume sellers 'augment' their inventory with counterfeits; some unintentionally, usurped by low price wholesaler.
First clue to me? Just notice if they use a stock product photo. If 40 different sellers display 100's of identical rows upon row, THE PRODUCT IS THE SAME. Some are so unfamiliar with items, text is copy/ paste too. Or reminds you of poorly translated instruction manual. Steer clear. Caveat emptor.
If unsure, use those with some kind of brick and mortar presence, there are plenty.

[Paul Jones]

Toolmaker51,

I have a 6" Mitutoyo model 505-637 dial indicator I bought in 1970 and it has worked very well and accurately until about three years ago. I check my dial, electronic and 1" and 2" mics every six months with a series of gage blocks to check for wear and for peace of mind. That is when I discovered the Mitutoyo dial indicator was measuring 0.0015" too large between 0.450" and 0.550". I think the precision rack used for measurement must be more worn in this range but it took many years before it made any difference. Three years ago, I replaced the dial indicator with a Mitutoyo 6" Absolute AOS Digimatic model 500-170-30 electronic caliper. It works very well, does not eat batteries, knows how to maintain zero without checking at zero, turns off automatically when put back in the toolbox and other than the back of the plastic display case showing signs of wearing from sliding on the work bench when it is picked up, I have no complaints.

The cost of your time, reputation and materials can be easily lost when not using quality measurement tools so I think it is worthwhile paying more for precision measurement instruments you will keep for a lifetime and you will trust. The worst thing is doing your machining by the book and discovering your craftsmanship was compromised by your measuring instrument.

Thanks for listening,

Paul Jones

[Saltfever]

Electronics are wonderful but I am moving back to full mechanical. While I change all my batteries at the same time once a year I am phasing out electronic everything. There is much more peace of mind with a dormant mechanical instrument resting in a drawer. You can’t say the same thing for anything electrical. I can’t tell you how many devices have been ruined by Duracell batteries. They are complete crap. It took a while and the loss of some lovely tools but I finally caught on. I will never buy a Duracell anything. The company was purchased a few years ago and downgraded their manufacturing.

[Ed Weldon]

Marv - I'm becoming a fan of yours. Here's a tip for calibrating calipers. Several years ago I happened on to a nice old set of Pratt and Whitney square gauge blocks and followed those listings on eBay to fill out the missing pieces. Among the findings was a poorly cared for set of long blocks up to 6 inches long. Worthless for serious lab work but perfect for checking the calibration of dial calipers. Ed Weldon, Los Gatos, CA

[mklotz]

Marv - I'm becoming a fan of yours. Here's a tip for calibrating calipers. Several years ago I happened on to a nice old set of Pratt and Whitney square gauge blocks and followed those listings on eBay to fill out the missing pieces. Among the findings was a poorly cared for set of long blocks up to 6 inches long. Worthless for serious lab work but perfect for checking the calibration of dial calipers. Ed Weldon, Los Gatos, CA

If you're going to check a micrometer for accuracy, it's important to use a set of gage blocks that cause the spindle to seat at different orientations so drunken thread errors will be noticed. The preferred set for inch micrometers is: 0.105, 0.210, 0.315, 0.420, 0.500, 0.605, 0.710, 0.815, 0.920, 1.000. For metric micrometers the preferred set is: 3.1, 6.5, 9.7, 12.5, 15.8, 19.0, 21.9, 25.0.

This leads me to wonder if there is a preferred set of blocks to use when checking calipers. Since calipers don't use a thread as micrometers do the sets indicated above may not be the correct ones to use. Nevertheless they do use a scale with regularly spaced elements that are sensed electronically (or a rack for dial types). Such scales are liable to periodic errors just as a thread is. My intuition says that checking should be done at intervals that are not nice multiples of each other; checking every inch probably isn't the best. (Hmm, maybe the micrometer sequence or some subset of it isn't such a bad choice.)

[mklotz]

Electronics are wonderful but I am moving back to full mechanical. While I change all my batteries at the same time once a year I am phasing out electronic everything. There is much more peace of mind with a dormant mechanical instrument resting in a drawer. You can’t say the same thing for anything electrical. I can’t tell you how many devices have been ruined by Duracell batteries. They are complete crap. It took a while and the loss of some lovely tools but I finally caught on. I will never buy a Duracell anything. The company was purchased a few years ago and downgraded their manufacturing.

I'm sure there are poorly made batteries but so far I haven't been able to single out a manufacturer. I've had several flashlights ruined by leaking Duracells as well as other name brands of batteries. I've never had a leaking Japanese battery but that might be coincidental.

I have dozens of devices that use "coin" batteries (e.g. CR2016, CR2032) and I never have had a leaker. Is it the chemistry or the case construction that makes these so device-friendly?

[Paul Jones]

Marv,

You are correct about not using nice multiples of measurement intervals to check the accuracy of the calipers. That is how I found the error in may gently worn 6" Mitutoyo model 505-637 dial indicator. I had suspected there may be an error in the range under 1" because of machining some parts with a sliding fit and finding my micrometer and caliper did not agree. I went about "bracketing" the location of the error by measuring at 0.415" intervals with gage blocks offset with 0.5" and 1.0" intervals and quickly discover the error was consistently at the lower range of the dial caliper and then subdivided again the bracket until I found the error was between 0.450" and 0.550". I think the precision rack used for measurement must be more worn down in this range. I still use the calipers but know now know where I have a measurement problem.

Paul

[mklotz]

Marv,

You are correct about not using nice multiples of measurement intervals to check the accuracy of the calipers. That is how I found the error in may gently worn 6" Mitutoyo model 505-637 dial indicator. I had suspected there may be an error in the range under 1" because of machining some parts with a sliding fit and finding my micrometer and caliper did not agree. I went about "bracketing" the location of the error by measuring at 0.415" intervals with gage blocks offset with 0.5" and 1.0" intervals and quickly discover the error was consistently at the lower range of the dial caliper and then subdivided again the bracket until I found the error was between 0.450" and 0.550". I think the precision rack used for measurement must be more worn down in this range. I still use the calipers but know now know where I have a measurement problem.

Paul

Absent any detailed knowledge of the caliper rack (mechanical or digital) construction, I would be inclined to use test standards based on a progression of the prime numbers - 1,2,3,5,7,11,13...- multiplied by a suitable power of ten to provide, say, five to ten measurement points in the intervals of interest.

Using Jo blocks for test standards may tempt folks to use the single blocks because they don't want to spend the time wringing blocks together to get a series like the ones I've discussed. Plug gauges come in increments of thousandths but most folks only have sets that go up to 0.5" or so. Perhaps the solution is plug gauges used in conjunction with a Jo block.

Folks are going to think us crazy to devote such effort to calibrating a tool that most of us use where accuracy of a thousandth is sufficient. But, as you noted, the idea is to locate suspect areas in the tool's range where wear, damage, or construction creates an error "zone" with greater than average error. With this in mind, I would calibrate the 0-1" range of the calipers very closely since, if my work is any indication, that's where the tool is most often used.

[Saltfever]

I am not angry, only disappointed in myself for being brand-phobic and hanging on too long. I have lost $$thousands in equipment to Duracell. The warrantee is not! All you can get is the cost of the batteries. Just one, of many examples; how about $3.00 for a $1,200 aviation GPS . . . I could go on. I post here only because I value you and this site too much to not pass on a warning. I will not bring up the issue again.

Notice the expiration date is irrelevant! 2017, 2023 all go bad!

[Saltfever]

. . . If you're going to check a micrometer for accuracy, it's important to use a set of gage blocks that cause the spindle to seat at different orientations so drunken thread errors will be noticed. The preferred set for inch micrometers is: 0.105, 0.210, 0.315, 0.420, 0.500, 0.605, 0.710, 0.815, 0.920, 1.000 . . . .

Marv, I notice your preferred increment is 0.105" each time. On a typical 40 thread mic that would be 4.2 threads. Anything special about 4.2 threads every time?