If there’s anything more frustrating than mounting holes that don’t line up with the thing you’re mounting, we don’t know what it could be. You measure as carefully as possible, you drill the holes, and yet at least one hole ends up being just out of place. Sometimes you can fudge it, but other times you’ve got to start over again. It’s maddening.
Getting solid measurements of the distance between holes would help, which is where these neat snap-on attachments for digital calipers come in. [Chris Long] came up with the 3D printed tools to make this common shop task a little easier, and they look promising. The extensions have cone-shaped tips that align perfectly with the inside edge of the caliper jaws, which lines the jaws up with the center of each hole. You read the center-to-center distance directly off the caliper display, easy peasy.
Of course, there’s also the old machinist’s trick (last item) about zeroing out the calipers after reading the diameter of one of the holes and then measuring the outside-to-outside distance between the two holes. That works great when you’ve got plenty of clearance, but the shorter inside jaws might make measuring something like a populated PCB with this method tricky. For the price of a little filament and some print time, these might be just the tool to get you out of a bind.
Very nice, a simple and effective hack
Just measure from the other side of the “populated” PCB. No need to reinvent the wheel.
But there are other uses, than measuring PCBs.
It’s not about avoiding the components on a board. It’s entirely about measuring the true distance between centres of the holes directly instead of lining up the calipers and the edges of the holes by eye (inaccurately) and subtracting the width of the hole (also measured inaccurately).
I’ve done that a lot, and I’ve hated it. I’m printing myself a set of these right now.
With the errors and tolerances of 3D printing, and all the slop and misalignment over the caliper jaws, I wouldn’t be surprised that this thing is measuring a good half a millimeter off the mark – and that’s exactly how you get the hole placement just wrong enough that you can’t get the last screw in, or it’s chewing at the side of the hole on insertion.
The biggest problem I see is how to zero the calipers with these things. You don’t know how well they align with the actual jaws, and you have to remove the extensions every time you zero the calipers, so the alignment changes on re-insertion. To be sure, you’d need two test holes and measure what the calipers read for that known distance, then remember the offset for the holes you’re actually measuring – but this isn’t any easier than just taking the inside-to-inside distance between the holes and adding the hole diameter.
Why do you do it by eye? You’re supposed to find the shortest distance between two holes by closing the calipers in between the holes. For small holes, calipers aren’t accurate for measuring the inner diameter anyways, so you need to use hole gauges. Common sets of drill bits in 0.1 mm increments work fine.
Also, the way the guy is handling those calipers in the video reminds me of the old TV commercials with butter fingered people who can’t hold on to their bowls of popcorn or whatever.
Just put the board down on the table and do it properly.
Notice that he rounds. Do you normally see a lot of boards where the hole spacing is some odd fraction of a millimeter? I suppose maybe if the board was hand-drilled.
Also, you don’t need to measure the hole size at all.
If you measure the distance between two holes from the closest edges and the furthest edges, the difference between the two measurements is twice the hole diameter, and the average of the two is the center distance.
And by using this method then the printed extensions, you get to calibrate them. Speeding up you next set of measurements.
The only issue is that the zero point of your calipers keeps drifting, so if you want to make really accurate measurements you’d check your zero between each and reset if needed.
With the extensions in place, you can’t close the jaws so you have to remove them, then check your zero, then put the extensions back, then calibrate for alignment… it’s a chore.
Dude, I’m as cheap as they come.
How cheap are your calipers if they won’t return to zero reliably?
I’ve never seen $15 chinisium special that wouldn’t.
Unless of course gunk got onto the rack and your losing steps..
On point, I didn’t watch the clickbait, but up thread it’s said he’s dropping them regularly.
But the jaws are as bent a Bill’s junk or Hillary’s ethics.
Which brings us back to gunk on the rack. I digress.
Have you tried flipping the board? I heard that helps.
I regularly build measuring tools and jigs, and often use paper to make
an instant transfer jig, paper, scisors, tape, pencil.And then can get.holes or cuts where they need to be, but without any numbers.
Depending on the job and what is availible, micrometers can be disassembled and then ,the mic head, can be put into a shop made holder.
And right /left thread pairs of bolts, can be used to make inside
calipers or alignment tools, and or clamps and positioning jigs.
Build it, use it , forget it, my shop is littered with stuff that I know I made
and used, but draws a blank as to what for, and then some of the things
have strong memories attached
Write on the jigs that you make, with a Sharpie, or other writing tool, its purpose. You can also indicate how to position it, in case you have forgotten.
I am not sure to put this extensions is more convenient then measure the distance of the nearest points of holes by “unextended” caliper, then measure the inner diameter one of the holes (supposing those are equal) and then add that diameter value and distance. But “calculation” is not so complex in case of different holes either :-). (Add the mean value of the twoo diameters.) By the way it is geometrically even more correct then the possible “unparallel” position against the surface of the plate since the conic tuch of the caliper extension, in case of holes with differend diameters. (Do not reinvent the wheel. The principles of measurements by and clear construction of the caliper are based on a very-very long time parctical experience. Those are not ad-hoc …)
Solid metal (mine are SS) tips for measuring hole center distances have been around for as long as calipers. They are essential to making accurate measurements of center to center hole distances for the common case of holes of the same size. If the holes are not the same size then different techniques are used.
Close attention to mounting them is essential to accuracy. Mine are clamped to the caliper by set screws. The ones in the article are suitable for use with $2 plastic digital calipers such as I used to put a 2 axis DRO on a $50 HF drill press with a $35 XY table. 0.01 mm DRO for $5 USD.
These are useful if you’re spotting holes to mount a PCB. The limit of accuracy of these is larger than 0.1 mm at best. Solid, time honored concept. But 3D printing doesn’t provide accuracy or precision.
I use my SS ones any time I’m being fussy or have lots of distances to measure. For casual work I just eyeball the jaws at the midpoints. Mine move the zero to 0.375”.
The concept is important, but these are very limited by the loss of accuracy inherent in their fabrication. Slots for jaws MUST be accurate depth and diameters must be equally accurate.
3D printing has many uses, but metrology is not its strong suite. People who use calipers should know about these and I suspect anyone doing machining does. But a 0.001” caliper is only good to 0.002-3” per inch best case. Thermal expansion eats your lunch if you measure over a distance of 4-5 inches or more.
Here’s a simpler way I learned from a machinist years ago and I’ve used it countless times…
-Use the other side of the calipers to measure the size of the inside of the hole. You don’t need to keep track of this, just press the ZERO button on the calipers.
-Use the normal side of the calipers to pinch the inside edges of holes that you want the spacing between.
-The number on the display is the exact center-to-center dimension between the holes.
Easy, no math required to invoke mistakes, and extremely accurate.
All of my criticisms have been stated already, i.e. zero drift, inaccurate print tolerances, etc. One additional consideration is that the cone centerlines need to be parallel to get an accurate measurement. I’m a fan of measuring the minimum and maximum distances and then subtracting half the difference.
I’m a big fan of making unnecessary tools – just ask my boss after he sees me wasting time yet again on the mill or lathe – but if you want to drill matching holes, accurately, then you could set up the PCB board, or whatever hole pattern, on your material and use a set of transfer punches to mark the holes? They will give you a pretty accurate center point so long as the right size is used. You can then use the center point to start your drill, or if you’ve done this on a separate material you can measure the center distance for a design or model.
Meh,
you won’t get the full accuracy of a digital caliper, but those things tend to have a resolution and accuracy that far exceeds a whole lot of usage cases. For example I used vernier calipers for many years, and they were already accurate enough, but I’m now switching to digital calipers, because I do not need glasses to read those numbers. The extra factor of 10 accuracy is mostly irrelevant. (I have one Mitutoy digital calipers, and a few from Terma, which seems decent quality for around EUR50)
These 3D printed jaws can be quite useful to speed up your measurements if you do a lot of this type of measurements. For the rest, Several manufacturers of digital calipers have specialized accessories for measurements like this, and other calipers too, for example calipers in which one jaw can be moved for offset measurements, or calipers that fit in very narrow grooves.
Digital calipers are not micrometers.
I don’t know where your getting an extra x10 of accuracy.
The criticisms here make sense. But.. if it is working for him then they are wrong. I have questions too but it looks worth a try.
I hate taking that measurement, I hate re-printing when it’s not quite right and I don’t understand why boards and other vitamins so often don’t come with that information.
Or better yet.. put it on the silkscreen!
I hadn’t thought of that before… that’s going to be regular practice for me now, dimensions and hole positions on the silkscreen!