Dial Caliper Repair (2019)
longislandindicator.com
longislandindicator.com
> I have personally repaired over 35,000 indicators in the years that I have been working. My father easily matched that number along with tens of thousands of dial calipers and micrometers which he and my brother have repaired. What I learned during all these years has all been put into this repository: www.longislandindicator.com Here you will find charts of manufacturers’ specifications and spare parts lists, critical evaluations of brands and models, instructions for cleaning, servicing and calibrating indicators and hundreds of web pages of information which often exceed what manufacturers’ catalogs provide. In fact, we have had manufacturers refer to our website to learn things about their own products!
> We don't carry spare parts or we just have a dislike for some of these brands, so please do not send the following ... Alina, Craftsman, Helios, Kanon, Peacock, NSK, Fowler, Starrett, Sylvac, SPI, Scherr-Tumico ... Anything made in China.
Digital Caliper, Adoric 0-6" Calipers Measuring Tool - Electronic Micrometer Caliper with Large LCD Screen, Auto-Off Feature, Inch and Millimeter Conversion https://a.co/d/1YBFS00
Of course you can go up to $50-60 for some more accurate all metal ones before taking the jump to serious $250+ precision instruments.
Just the mere thermal expansion coefficient of abs, 100 * 10^-6 m/(m C), is enough to tell you that across a very conservative range of 50 degrees the full scale measurement of 10 cm will expand by L0 * alpha * DeltaT = 0.1m * 100 * 10^(-6) * (50 C) = 0.5mm. (Units don't check out, I just added them here and there so you know what's what). Even if you use fiber-glass reinforced ABS that's still 31% of that, 0.155mm > 0.1mm. And who knows if the digital scale is even printed so it's accurate at any point in time - for all you know they just took a random other inaccurate tool to check against. And this does not account for any mechanical slop or for deformations from using what's essentially a slightly colder bar of chocolate to clamp down on hard metal.
Accuracy: if you measure something with this tool, and then with a standard, it's going to come up with the same number, "down to 0.1mm of accuracy". As we've shown above, this thing is not accurate.
Precision: if you measure something with this tool, and then measure the same thing with this tool again later on, then it's going to shoe you the same number. And even here, this tool isn't really "precise", but we can assume that for all intents and purposes you won't be using it to measure things years apart (wear and tear can change its shape easily) or during massive temperature swings.
Moral of the story:
Accuracy /= Precision
Edit: at least tools made out of chocolate can be eaten https://www.thisiswhyimbroke.com/edible-chocolate-tools/
For DIY, you often need to make measurements that are a little bit more accurate than 1 mm, but not much, as well as measurements where 1 mm is plenty accurate but you need a reliable way to measure it, provided by the inner and outer jaws of the calipers. Even cheap calipers are excellent for this purpose, and the point is that people should not be scared off from them because they are not calibrated.
Also, no, 50C is not a very conservative range for that purpose, that would be ±5C around the steady 20C temperature inside the average house.
> Also, no, 50C is not a very conservative range for that purpose, that would be ±5C around the steady 20C temperature inside the average house.
That is true until you realize many people keep their tools in the garage or in a cellar or an attic, where the temperature can go anywhere between -20C and +45C. Then you measure a small nut or screw as often used in, exactly, home appliances, and between the thermal coefficient, slop, bad geometry, and an inaccurate digital potentiometer you arrive at 4.8mm instead of 4.1mm and you order a 5mm replacement for your 4mm screw and have to wait another week or two after you figure that out. I've had this exact story happen to me in the past, and my tools were stored in, as you say, "±5C around the steady 20C temperature inside the average house" and not out of plastic - just still not accurate enough.
I don't know where you got your numbers from. I doubt it's anything other than you thought the numbers just looked fine and illustrated your point.
My point was that the ultra cheap caliper is suitable for measuring basic things where you can't get a good reading using just a steel ruler with 1mm increment measurements on it by eyeball, and maybe you might want to measure something a bit more precisely than 1mm increments. And it might be suitable for basic home DIY purposes. As I said, if I wanted a serious caliper I'd go spend $250 on one.
A cheap caliper like this, for example, might be suitable to tell me if a stripped copper wire's diameter really matches 23AWG or if it is 24AWG which is hard to see by eyeball.
What would it take to retrofit a digital mechanism onto vintage vernier calipers?
https://www.electroschematics.com/digital-caliper/
> There are several rectangular patterns etched onto a copper strip underneath the main scale (the part of the caliper along which the read head/slider moves). With the printed patterns on the bottom of the main circuit board, this forms a grid of capacitors. As the sliding jaw travels along the main scale, the capacitance of the printed patterns changes, the controller (chip-on-board) detects the resulting shifts in electrical charge, processes the signals and finally displays the readings on the LCD.
Would be nice to have open firmware for digital calipers.
Personally, analog calipers are more trustworthy to me, because you can never be in a state where you forgot to press the zeroing button - which happened to someone running a modern machine shop right in front of my eyes. If you care about the outcome of a process, eliminating every step that can fully destroy the result yields massive dividends. There's something to be learned here about every process, be it technology, customer retention, sales funnels, you name it. Having less steps is so extremely powerful that it can easily outweigh additional functionality of some sort.
> LR44 starting voltage is about 1.500 Volts. SR44 starting voltage is about 1.550 Volts. Both are rated as 150 mA hours, but the discharge curves give very different operational life depending on the required voltage for the application. The LR44 voltage drops over the duration of usage. The SR44 remains flat (and above 1.5V) for most of its useful life. The calipers need at least 1.25 to operate.
> The LR44 drops below 1.3 Volts after about 50% usage. The SR44 drops below 1.5 Volts after about 95% usage. The SR44 start at a slightly higher voltage, and their flat discharge curve makes them far superior for low power, long operational life applications, like a caliper.
> Before we start, let's state outright that the best, most reliable, and most useful caliper you can own is a vernier caliper. It isn't electronic and it doesn't have a dial ... Calipers should be frequently checked for accuracy using a gage block, or gage block combinations. To check for wear in the jaws do this: clean them and close them. Then hold them up to the light and if they're worn you'll see light shining through the gaps. At this point, measure with the unworn surfaces or have the calipers repaired. These jaws can be ground flat again.
Or they know they're more likely to be counterfeit.
The most recent supply scam I have personally had to deal with was the substitution for sale of alternate polymers as more expensive, engineering grade polymers.
Metric, imperial and woodworking-friendly fractions, https://www.homedepot.com/p/Husky-6-in-3-Mode-Digital-Fracti...
Since I'm just a lowly woodworker, I just buy second-hand dial calipers on eBay.
Power consumption analysis: http://www.davehylands.com/Machinist/Caliper-Batteries/
> The Mitutoyo caliper draws about 1/4 the power of the chinese caliper when on, and about 1/8 the power when off.
SR44 batteries should last longer than LR44. For infrequently used cheap calipers, one workaround for short battery life is to remove the battery between uses, https://www.garagejournal.com/forum/threads/electronic-calip...
> cheap calipers never actually turn off.. because the encoder they use is not an "absolute" encoder. You push the caliper all the way to the closed position, push "zero", and then the circuitry simply counts the number of pulses that goes by and figures out how far the caliper moved. If the caliper fully turned off, it would lose its position and you'd have to re-zero it every time you turned it on.
> Mitutoyo Digimatics have what they call an "absolute encoder". The sensor doesn't just count the number of pulses. They've put a special reference pattern on their encoder such that the caliper's circuitry can figure out where it is at any given time. With a Mitutoyo caliper, you can turn it off, take the battery out, slide it to a new position, put the battery back in, turn it on, and it will know exactly where it is. This "absolute encoder" allows the caliper to fully shut down when not in use, greatly increasing battery life.
Hacking a switch onto cheap calipers, https://www.instructables.com/Cheap-Caliper-Battery-Life-Hac... & https://www.youtube.com/watch?v=GcoUdIjZozY & http://www.surfacezero.com/g503/data/500/Digital_calipers_ad...
That sounds like you can buy an unbranded/off-branded one from Aliexpress or similar at a fraction of the price, with the exact same construction.
Veritas Set-Up Block (made in Canada) accuracy is rated at 0.002" (aluminum) and 0.0002" (steel), https://www.leevalley.com/en-us/shop/tools/hand-tools/markin... & https://www.leevalley.com/en-us/shop/tools/hand-tools/markin...
The set you're pointing to will be fine for most everything you'd do with calipers. With micrometers, it's harder to say. You'd buy from an established machinery / metrology supply if the work demands it, like Starrett. Or MSC, Enco, etc. if you don't need the best.
If you're just screwing around measuring the odd household object and / or using the calipers to get splinters out, Lee Valley will be more than adequate.
Also, estate sales are a good place to look for a set of gage blocks. Machinists often die with their stuff, and family has no idea what it is. The machinists would almost universally prefer it remain in use, in the hands of someone who knows how to use it.
Admittedly, this choice was a little more obvious before the recent inflation. Select your size and preferred units as required, of course. It was nice to see that even though mine is only Grade 0, it actually meets the Grade 00 standards. Not that that matters for me.
Now all this is reminding me that I should actually go and check out that sketchy micrometer that was borrowed and abused....