Inside measuring - Bore gages?
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  1. #1
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    Default Inside measuring - Bore gages?

    Trying to put together a decent set of tools for measuring machine work that gets me past a .001" outside micrometer and a so-so digital .0005" caliper.
    I don't machine for a living, if I did I would spare no expense for what I consider essential tools for accurate work. It's mostly personal use so I can't raid the till too hard.
    So far I bought an older set of 0-6" Mitutoyo outside micrometers (103-907) in nice condition that read to tenths. An Asian set of 6-12" outside micrometers (tenths), nothing like the Mitutoyos but most things I do are under 6". So I should be able to get by on outside measurements 0-12".
    The problem now is what to get for inside measurements? It seems for inside or bore measurements the instruments get more diverse, complicated and expensive. Initially I thought a set of plain telescoping bore gages would be a place to start and use the mics to measure. I picked up a .312-6" set of telescoping gages cheap at a flea market but they are offshore junk.
    I don't mind spending $150.00 for a good set of Mitutoyo or Starrett telescoping gages but while looking around at other options I'm considering putting the money toward dial bore gages. The question is which set to get. I read quite a bit about the various brands, the lack of quality despite the name brand, and those that say some imports are good and some are not.
    I know the saying "you get what you pay for" most likely applies here. I've been searching Ebay for used but it's hit or miss and I don't know the quality of some brands I've never heard of. There was a DoAll .5-2.375" bore gage that looked like it was well made but in doubt I didn't bid.
    I think what I'm after is two point measuring for general purpose. Any suggestions, comments, recommendations are welcome and I'm listening.

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    For general machining I.D. mics, telescoping gages, and small hole gages will be more convenient than dial bore gages. For inside mics NSK are my favorite over the Starrett rod type which does not have a lock for the spindle. NSK does not make them anymore, but they can be found used. I have abandoned small hole gages for gage pins but they have there place.

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    Telescope gages are great for working a hole up to size within a few tenths. Once there though you usually will switch to an attribute gage such as a plug gage or the actual part that will go into the hole. Barring the actual part, a bore gage set to the appropriate size using gage blocks is standard practice. Given that you are making stuff for your own use you would probably be OK with anything that Enco or the other catalogs sell. The gage blocks are the key though, as long as you have a repeatable zero on your gage at the necesary size. There are also the old fashion micrometer style internal gages with several extensions for checking holes from 1" -12". I have a couple of sets (inherited) that I haven't ever used in 35 years. -Mike

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    My Starrett 4" to 32" set (tubular type) has a spindle lock. The smaller set doesn't. B&S makes a 1-1/2" min set that locks. I dislike telescoping gages for any thing over 3". I've used B&S, general, Mititoyo, Harbor freight, Starret. My preference is single plunger Starrett. I have a dial bore gage but the only thing I use it for is checking bronze bearings for wear and tapers.
    My work tools were all bought new before ebay. By being patient I've bought like new or new
    Starrett on ebay for very good prices for my home shop.

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    As always dial gauges are comparators not absolute measuring instruments.
    The long stick is great for checking long holes but, having noted the variation, you have to establish what the actual "nominal" size is by checking against something calibrated. Preferably gauge block stack to micrometer to bore gauge.
    For larger stuff an inside mike is, to my mind less trouble.
    With anything poked down a hole tilt error is a big problem. Takes a while to get the feel and the relatively heavy bore gauge or inside mike set-up makes it harder to feel the true diameter position as the darn thing tends to keep swinging during the feel around process.
    I scored both small and large sets of old line Moore & Wright telescopic gauges off E-Bay which are head and shoulders above the cheap imports I used to use. Its all in the lock. Also got a set of 6 M & W small bore gauges of the ball type. Nice but need an educated feel.

    Clive

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    Thanks all for some great information.
    I decided to stick with the plain telescoping gages for the time being. I got a very good deal on Ebay for a new Mitutoyo 0-6" (155-903) set. I'll use them with the Mit micrometers. I hope the Mit gages work better than the cheapo China set. May take a lot of repeat measurements to get the feel for using them but as long as things fit properly I'll deal with it.
    I'll keep my eyes open for inside mics and or bore gages but for now my eyes (and brain) need a break. I have plenty to learn yet so I'll get what I need as needed.
    Ernie F.

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    Telescoping gages require practice to get repeatable results. Get some known standards to check yourself against before doing critical work, especially if you're not using them on a regular basis. In a pinch various size bearings work well and are made to tight tolerance. Mfg specs can be looked up.

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    Quote Originally Posted by winger View Post
    Telescoping gages require practice to get repeatable results. Get some known standards to check yourself against before doing critical work, especially if you're not using them on a regular basis. In a pinch various size bearings work well and are made to tight tolerance. Mfg specs can be looked up.
    Not on a regular basis...that would be me. I like the bearing idea I will do that. I can see where the finish of bores will have an effect on results also.
    Ernie F.


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