Looking for a good depth gauge/depth micrometer/I-don't-know

Hi there

I'm wondering if someone can help me find a good depth gauge

It needs to have a 200mm length minimum and just needs to be pretty accurate, preferably better than 0.01mm accuracy. I assume the digital depth gauges are the best way to achieve this for not too many $. This tool is $170, I don't want to spend more than $200 really if possible.

This item has those attributes but it doesn't come with any kind of certification and there is no mention of international standards. How accurate do you think this would be if it's measurement graduations are 0.005mm? It's made in China, is that something to be concerned about.



Just wondering if someone could give me a heads up of good brands or where to look, Ive looked and it seems that SPI have a depth gauge that is fairly reasonable


Swiss Precision Instruments

Calibration cert but only a 0.01mm resolution which is probably at the limit of how precise I need to measure.

I guess if any of the following fit the bill (200mm length, but only need <5mm measuring range) It needs to be more accurate than 0.01mm
- depth micrometer
- depth gauge

Thanks in advance for any help.

Is electronic better than analog?

Digital is only better than analog if you like them better.

I have a older Starrett No.753 digital depth gauge and love it. Their newest iteration of it is the No.3753, and it's very nice. Of course a Mitutoyo Series 571 is the equivalent, and undoubtedly has better battery life and more-reliable electronics.

Starrett Catalog 32

Mitutoyo America Corporation

Try them both if you can and see which feels better to you. If willing to take a chance on the SPI one, it can be had for $75, shipped.

http://www.ebay.com/itm/SPI-Electro...004?pt=LH_DefaultDomain_0&hash=item27bdeb29b4

A couple of general observations...

First, note if a Certificate of Calibration (CoC or 'cal cert') is available for the product. Although you don't need to purchase it, the fact that it's available lends some credence to the specifications.

SPI has some decent products. Many of them are re-badged standards of other manufacturers. Their own stuff is made at various locations all around the world. BTW, they have nothing to do with Switzerland; they're in Singapore.

I always advocate buying the best quality you can afford. And consider used as well. A high-quality used instrument can be a better value than a new mediocre instrument.

- Leigh

Any of the gages(either digital, or analog), that have replaceable rods, should be calibrated each time it is assembled. They should, at least be set to
the major ranges of each rod, and better yet, set them with gage blocks, to the target dimension. I, found a set of Mitutoyo, extension rods, to be off by
nearly .001", on a couple rods.
Regards,
Bob

A lot of Chinese measuring instrument ( incl. DROs) manufacturers only quote the digital display resolution limit and never quote the instrument error . I wonder why that is - are they trying to hide something ? Surely the most important spec. parameter for a measuring instrument is it's accuracy ?

One of the things, that needs to be looked at, is the overall system accuracy. An example that I, saw at one time, was a custom gage, w/.0001"
jeweled indicator, mounted on a 24" Mitutoyo digital height gage, with an accuracy of .001"! :-/ ??????????
Regards,
Bob

RDCutter said:

An example that I, saw at one time, was a custom gage, w/.0001" jeweled indicator, mounted on a 24" Mitutoyo digital height gage, with an accuracy of .001"! :-/

Click to expand...

I don't see a problem with that.

The indicator zero can be set with gage blocks. The height gage is then just a support, probably a convenient one.

- Leigh

Hi all thanks for the replies, sorry for my slow response!

I emailed insize and they told me it's 0.03mm accurate. I never realised you'd need to calibrate with gauge blocks to get an accurate reading. That rules that out.

My 2nd thought (I spoke to a local engineering shop) was to get a piece of square solid steel tube about 1cm high 1cm wide and 20cm long and get one of the long flat surfaces machined flat. then get another long piece of square steel tube and get it ground to 195mm exactly (how fine a tolerance can an engineer cut/grind/machine a piece of steel to?

Then I would just place the long flat piece across the top (to act as the base of the depth gauge) and then use the 195mm long piece with machined flat top and bottom to act as the rod of the depth guage (obviously a static gauge) and use feeler gauges to measure the gap

I guess I should explain what I need to do.



This is what I'm trying to achieve, that is a factory tool for measuring the gear stack height of a transmission, The top of the T piece which is essentially a precision machined piece of metal is about 150mm wide and the | of the T piece is 195mm long exactly. The reading to be taken involves using feeler gauges to measure the clearance between the nut on the shaft and the bottom of the gearstack height tool. The tolerance range is 195-195.1mm so the tool needs to be pretty accurate (I wanted a 0.01mm accuracy so I could use the tool for another application)

Thanks for any help. It would be cool if I got these 2 bits of metal machined the guy was really nice and quoted me $40 bucks! Would the machine shop be able to plane the metal to less than 0.01mm error?