STEW MAC CALIPERS - Inaccurate!

[spindlebox]

I have sent these back 2x already.  What am I doing wrong?  I have decided it MUST be me, although my cheap Amazon calipers don't do it.

I don't know what to do.  Please help!

 

[Bizman62]

To me that looks like the depth measuring "stick" of the StewMac is a couple of millimetres too short. No question about that. You should get the same readings when measuring the thickness of an object like you did with the case. The notch is irrelevant as the stick is meant for measuring the depth of tight holes.

[curtisa]

I've personally never really paid much attention to the extension measurement at the base of a set of calipers, but I think you need to avoid using the movement of the jaws as a baseline reference for the movement of the tail. You're better off using it independently of the jaws altogether - moving the tail so that it butts up against a reference surface first, zeroing the caliper readout and then extending the tail to make your  measurement.

On all but the most expensive, precision calipers there is no guarantee that all three moving pieces have zeros that are equal. Use and zero each one independently of the others. I'd personally have more faith that the inner/outer pairs of jaws will be machined with equal zero points.

Edit: When you look at the 'custom fret crown notch' thingy Stewmac add to it, it's all the more important to not use the opening of the jaws as a baseline for the tail measurement (image credit: Stewmac):

 

The notch means that the tail needs more room to slide back into the body to allow for negative measurements. The upshot of this is that the tail will always extend further from the base than the jaws will open, and the tail will always give you a longer measurement unless you zero it first.

[spindlebox]

2 hours ago, Bizman62 said:

To me that looks like the depth measuring "stick" of the StewMac is a couple of millimetres too short. No question about that. You should get the same readings when measuring the thickness of an object like you did with the case. The notch is irrelevant as the stick is meant for measuring the depth of tight holes.

I just can't believe it is that off.  This is literally the 3rd pair of Calipers that is exactly off like that.  Unfortunately, this has messed me up, because I expect that measurement to transfer to other measuring tools, at least within a few hundredths of a MM.

It's also hard to believe nobody else has complained about it and they don't know about it!

Edited February 23 by spindlebox

[spindlebox]

56 minutes ago, curtisa said:

I've personally never really paid much attention to the extension measurement at the base of a set of calipers, but I think you need to avoid using the movement of the jaws as a baseline reference for the movement of the tail. You're better off using it independently of the jaws altogether - moving the tail so that it butts up against a reference surface first, zeroing the caliper readout and then extending the tail to make your  measurement.

On all but the most expensive, precision calipers there is no guarantee that all three moving pieces have zeros that are equal. Use and zero each one independently of the others. I'd personally have more faith that the inner/outer pairs of jaws will be machined with equal zero points.

Edit: When you look at the 'custom fret crown notch' thingy Stewmac add to it, it's all the more important to not use the opening of the jaws as a baseline for the tail measurement (image credit: Stewmac):

 

The notch means that the tail needs more room to slide back into the body to allow for negative measurements. The upshot of this is that the tail will always extend further from the base than the jaws will open, and the tail will always give you a longer measurement unless you zero it first.

I don't know.  A measuring tool should be at least SIMILAR in measurements regardless of features, REGARDLESS of where you take the  measurement from - because that measurement needs to transfer to other cutting and measuring tools.  It should Not 2 MM off like this.  I use that tail measurement ALL the time.

Edited February 23 by spindlebox

[curtisa]

I don't see the issue. The tool has been modified to include the ability to measure the crown height of the fret when it's installed in the fret board. To do that the tail needs to slide deeper into the body, which has the byproduct of offsetting the tail from the end by that extra depth, hence the couple of mm difference.

To get around it you just need to zero the tail before using it, which for absolute accuracy you'd typically do with any set of calipers anyway.

8 minutes ago, spindlebox said:

It's also hard to believe nobody else has complained about it and they don't know about it!

I don't think it's 'off' in any way. It's been deliberately modified to offer a feature that other calipers can't do as easily. It just requires a slight modification to your method of usage to continue using it in a more 'traditional' sense.

[spindlebox]

1 hour ago, curtisa said:

I don't see the issue. The tool has been modified to include the ability to measure the crown height of the fret when it's installed in the fret board. To do that the tail needs to slide deeper into the body, which has the byproduct of offsetting the tail from the end by that extra depth, hence the couple of mm difference.

To get around it you just need to zero the tail before using it, which for absolute accuracy you'd typically do with any set of calipers anyway.

I don't think it's 'off' in any way. It's been deliberately modified to offer a feature that other calipers can't do as easily. It just requires a slight modification to your method of usage to continue using it in a more 'traditional' sense.

No way you and I are gonna agree on this

[ADFinlayson]

I don't have the stewmac callipers, just some regular digital ones from my local store. I use them for measuring the really precise things like bridge holes, tuner locations etc. So always zero the callipers every time I measure anything. I do also use them to measure crown height with the tail so the little cut-out stewmac do is unnecessary IMO.

[spindlebox]

27 minutes ago, ADFinlayson said:

I don't have the stewmac callipers, just some regular digital ones from my local store. I use them for measuring the really precise things like bridge holes, tuner locations etc. So always zero the callipers every time I measure anything. I do also use them to measure crown height with the tail so the little cut-out stewmac do is unnecessary IMO.

Yeah, I've never really used that little Crown crown height measurement, I use that tail height measurement ALL the time. To me. It's more important to have all 3 measurements accurate and compatible.  It most certainly is within a couple hundredths on my cheap $20 Amazon caliper.  It's actually shocking to me that it is that far off.

[Bizman62]

4 hours ago, curtisa said:

zero each one independently of the others.

That combined with the fret measuring notch. Didn't realize the notch being of importance but obviously it's a feature.

2 hours ago, ADFinlayson said:

So always zero the callipers every time I measure anything.

That. For some reason the digital callipers seem to wander, with the jaws pushed together the reading is not always 0. Guess that's why they have the zero button.

[spindlebox]

10 minutes ago, Bizman62 said:

That combined with the fret measuring notch. Didn't realize the notch being of importance but obviously it's a feature.

That. For some reason the digital callipers seem to wander, with the jaws pushed together the reading is not always 0. Guess that's why they have the zero button.

If you watched the video I focused on making sure things were zeroed out.  Still inaccurate.

[Bizman62]

53 minutes ago, spindlebox said:

If you watched the video I focused on making sure things were zeroed out.

I did. But now that it's been said that the stick part has been deliberately shortened for measuring fret heights you'll have to zero it separately for using the depth measuring stick. That will leave the jaws open by a few millimetres. Stand the end on a flat surface and slide the stick down, then zero it for measuring depths.

For ordinary people like you and me such things can be confusing. The tool looks similar, acts similar but has a difference that doesn't seem to make sense.

Agreed, the notch makes measuring fret height more accurate as the solid part will stand on two feet to eliminate errors caused by an angled callipers but then again, why would anyone want to measure the height of individual frets? A fret rocker would be more accurate as it doesn't care whether the fretboard is level or not. For measuring a fret to find a suitable replacement regular callipers should be accurate enough.

[henrim]

It is simply a tool modified for luthier work. It looks like there is also a slot in the upper jaw. Which can be used for measuring the crown height of an uninstalled fret. Features that make quick fretwire readings easier.

My experience with digital calipers is that you better always zero them before taking measurements. And measure twice to make sure the measurement is right. But I rather use manual calipers anyway.

[spindlebox]

Well, this was explained to me by Stew Mac. I wish they had explained this when I first contacted them about it.  I didn't see it on the instructions that came with it Either. it's not exactly intuitive.  To me anyway.

[Bizman62]

2 hours ago, spindlebox said:

Well, this was explained to me by Stew Mac. I wish they had explained this when I first contacted them about it.  I didn't see it on the instructions that came with it Either. it's not exactly intuitive. 

Guess they have a YouTube video with Dan Erlewine telling how wonderful that calliper is, explaining all the modifications. So why bother printing an illustrated manual.

It seems to be more of a rule that the customer service guys don't actually understand what the real problem is. They simply apoligize and send you a new item. The guys at StewMac know how their tools work and they automatically assume that if someone buys a luthier tool they also know all the details. Why would they buy something if they don't know what it is or how to properly use it? Manuals are for sissies anyway...

[spindlebox]

Actually the guy at Stew Mac is going to make a recommendation about the whole thing to the technical team - He said he himself did not know about it.  A simple piece of paper explaining the features will be all that would be necessary.

[Bizman62]

That reminds me about the different marketing styles or rather attitudes, don't know if there's actual terms for those. Anyhoo... Back in the day when PC's were new and mostly sold to companies for a stellar price, the sales personnel were engineers speaking tech jargon about how powerful their products were etc. instead of trying to figure out how and what for the customer would need them. Engineer driven marketing instead of customer experience, the terms were something like that IIRC. Heck, that was some 40 years ago! But that's still an issue, nerds make a product that has all sorts of features which require the end user to be a similar nerd to intuitively figure out how to properly utilize all the features.

Kudos to you for being patient with StewMac and kudos to the SM guy who's going to try to get a simple manual made.

[spindlebox]

It's actually very very common still.  I do studio engineering too, and have been teching myself for over 20 years.  When I first got into some of the forums, like Cakewalk, etc., trying to navigate things - some of the descriptions relied SO heavily on experience, forethougt and knowledge.  

It also has happened to me trying to learn how to build pedals, with electronics.  That's probably the worst.  If you can't read a schem - WHOO BOY.  Hahaha.

 

[soapbarstrat]

I just wish Walmart would get the freaking batteries for them back in stock.

[henrim]

2 minutes ago, soapbarstrat said:

I just wish Walmart would get the freaking batteries for them back in stock.

CR2032? I’d think they are widely available.

[spindlebox]

1 hour ago, henrim said:

CR2032? I’d think they are widely available.

They are totally widely available

[soapbarstrat]

Matter of convenience. 

[MiKro]

They are missing the tail part  ( cutout ) of the extension, thus making it shorter. Why? I have no clue.

Also there are four ways to measure on a set of calipers, not three. Using the step on the back side as well for depth or width.

Watch some videos on YT for more info. MK

 

[Bizman62]

11 minutes ago, MiKro said:

They are missing the tail part  ( cutout ) of the extension, thus making it shorter. Why? I have no clue.

@curtisa showed the explanation:

 

[Satchmoeddie]

The last StewMac calipers I used were rebranded I Gauging calipers. All of these cheap Chinese made calipers are of adequate quality for measuring but they are a long ways from being a truly high quality instrument for measuring anything very critical. They also eat batteries at an alarming rate too. The measuring part never really turns off. Only the LCD display actually turns off. A milliammeter will show current drain when the calipers are supposedly turned off. Mitutoyo calipers show zero current drain when they are turned off, but those are $250-$6200 calipers. I have the 8 inch carbide anvil Mitutoyo calipers which are about $500. They measure in .01mm and .ooo5" increments. I like having the 1/128th or 1/64th or 1/32nd or 1/16th or 1/8th or 1/4, or 1/2 of an inch measurements! Mitutoyo does not offer that feature in the carbide anvil sets.  You have to re-zero any caliper set, any micrometer and especially dial gauges every time you go to use them. Changes in temperature make the metal expand and contract enough to throw the measurements off, especially with dial gauges. We have an old wind up 8 day clock. In the summer it needs to be readjusted or it runs slow. In the winter it needs to be readjusted or it runs fast. What happens is the pendulum expands with the higher temp in summer making it longer so the weight takes longer to swing back and forth. In winter it contracts and the pendulum swings back and forth faster because that pendulum rod is shorter. My dial gauges' racks can grow or shrink by 50-200 1/10,000ths of an inch with seasonal temperature changes. I wish I could keep every part of room in the house at 74 degrees F, but it ain't ever gonna happen. And yes, that Ames Waltham dial gauge measures down to 5/100,000 of an inch and it is repeatable to 1/10,000 of an inch or 10x more repeatable and 20x more accurate than most micrometers and calipers. Waltham also made fine American watches.  For calipers that measure in fractions of an inch, I am using I Gauging. I also use I Gauging straight edges. For a while StewMac's straight edges were I Gauging's rejects. They were about 1/2 as accurate as an I Gauging straight edge but still accurate enough for luthrie, I guess. The I Gauging straight edges cost about 45-60% less too. I'd buy two 36 inch straight edges and cut them into pieces, so I had 6 inch, 12 inch 18 inch, 24 inch, and a 30 inch and some odds and ends pieces. I have a hand scraped Starette of two that are accurate to 1/1000th per 3 feet. Those are $3500+, and used for very fine machine work, like decking the heads on a Rolls Royce Merlin engine. I do NOT buy calipers, dial gauges, straight edges or micrometer from StewMac. I can get better quality stuff, even if it's Chinese made, non Mitutoyo stuff, cheaper elsewhere and the quality is almost always better that StewMac stuff,  by a factor of 100%.  These tools are NOT luthrie exclusive tools. Put the words "luthrie" or "gunsmith" in front of any tool's name and the price always goes way up.