How Do You Measure Your Holes?

[Nick HulmeParticipant @nickhulme30114]

I started out with curved calipers, set to the bore then measured with micrometers.

I subsequently flirted with telescopic and expanding "bell" gauges, again set then measure with micrometers

Later I did get an old style internal micrometer, great for bigger stuff but the minimum size is a bit of a limitation.

Recently I bought a 5-30mm internal micrometer that has pins instead of anvils and that's great for accurately measuring bores but only at the first few mm from the surface and only above 5mm.

Last week I picked up a few very reasonably priced Diatest split ball bore gauge sets and added a digital indicator, with a bit of fiddling I've worked out how to set the indicator for a direct reading of the bore up to 25mm, with sizes starting under .040"/1mm

I've found myself wondering what others use and if there are any other good options out there?

– Nick

[Nick HulmeParticipant @nickhulme30114]

[pgk pgkParticipant @pgkpgk17461]

I suppose it depends on the size range and accuracy you need. At my level I use drill bits as slip gauges and mike them for the smaller holes. A pin gauge set would be an extravagance. I have telescope gauges for the larger holes and accept they can be a fiddle – or make a test gauge if I need to bore a fit.

[HansParticipant @hans86050]

I use a Starrett 269a taper gauge for holes from 0.100" – 0.500", and drill bits for holes smaller than 0.100"

~Hans

[Neil WyattModerator @neilwyatt]

I have calipers, internal telescope gauges and an internal mic, but with only one anvil so its range is a bit limited 3/4" to 1"! (I must make some anvils for it).

For smaller holes i use drill bits or turn a test diameter to fit. Where extreme accuracy isn't essential (i.e. I just want to get close before finishing to fit) I use a digital caliper internal jaws and add a fudge factor depending how small the hole is.

But as far as possible I try to avoid the need for accurately measuring holes.

Neil

[pgk pgkParticipant @pgkpgk17461]

Posted by Neil Wyatt on 13/12/2016 14:13:25:….

But as far as possible I try to avoid the need for accurately measuring holes.

Neil

Farmers around here use the same method: If it won't go in with a gentle tap – get a bigger hammer.

[EmgeeParticipant @emgee]

A few months ago I had the opportunity to buy sets of HSS Drill blanks, 1-6mm and 6-10mm by 0.10mm increments for a very low price. Since having them have found they are very useful not only for hole diameters but also for measuring slots cut on the milling machine.

Emgee

[Chris Evans 6Participant @chrisevans6]

Plus one for the drill blanks. After that it is small bore gauges and telescopic gauges plus luck but usually close enough for things I make.

[john carruthersParticipant @johncarruthers46255]

I have an internal caliper dial type bore gauge, old but good, £3 at a boot fair.

[Anonymous]

I try and avoid measuring small holes. If absolutely necessary I'll use drill shanks (taking into account that they're undersize) or use expanding "bell" gauges. For larger sizes I've got a range of internal micrometers from 1" to ~36".

If I'm machining a bore to size I usually make a gauge beforehand on the cylindrical grinder. With a few spark out passes and some tweaking of the table it's not difficult to make a gauge to size, and parallel, to within a tenth or two.

Andrew

[JAParticipant @ja]

Generally I use a pin or plug as already mentioned. I have bought a couple of dial bore gauges (not cheap) and used them when necessary. They take some time to set up but are particularly useful for measuring the taper, ovality etc of long holes such as cylinder bores.

[edit] If you making mating items, such as a bush and its housing or piston and cylinder, machine the bore first.

JA

Edited By JA on 13/12/2016 17:31:17

[Tim StevensParticipant @timstevens64731]

I have found the following handy and cheap for holes below about 3mm:

Get a box, an assortment, of clockmakers brass taper pins. These are (were) used to connect the columns to the plates of clocks before screw threads were common, and they are straight, about an inch long (25mm) and very lightly tapered. Find one that will just go into your hole (eg in a carburettor jet) and check the diameter with a micrometer or calliper.

Try these for, er, size:

**LINK**

Other sizes and assortments are available.

Cheers, Tim

[colin vercoeParticipant @colinvercoe57719]

Small drill blanks used as plug gauges, as mentioned before tapered bore gauges.

Colin

[Bob Brown 1Participant @bobbrown1]

I use one of these

[David ColwillParticipant @davidcolwill19261]

For anything over 13mm I use Bowers 3 point bore micrometers. They are hellishly expensive new but I managed to pick up 3 for a reasonable price £80-£100 I think. I then collected odd ones off ebay and now can go from 13mm to 37mm in metric and from 1 1/2 inches to 4 inches in imperial. Well worth keeping your eyes open for them. Smaller holes I use various dowel pins, drill shanks and caliper guesswork.

David

[Dinosaur EngineerParticipant @dinosaurengineer]

It all depends on how accurate you want to measure. The 3 point bore mikes are quite accurate but expensive. Telescopic and small ( split ball type) are perfectly accurate for most users not wanting to go to the last "tenth" of a thou. Vernier and electronic calipers suffer from the flats on the the inside jaws not being sharp points and the general accuracy not being as good as a "mike". Slip gauges with the accessory ( rounded ends) are quite accurate but time consuming to use and expensive. For any precision hole requirement it's quite easy to make your own plug gauge ( With steps if you want some warning of approaching the size). The taper pins are quite good for very small holes.

[HopperParticipant @hopper]

Ball gauges below half inch, telescopic gauges above.

[Roderick JenkinsParticipant @roderickjenkins93242]

Many years ago I was given these:

and this:

I've never used them, it seems dodgy to me to measure a hole at the "corner" – too much chance of burrs or bellmouthing (nice bits of kit though).

One of these (from ARC) gets me as close as I need to be. I generally work in imperial but I've got a calculator

Cheers,

Rod

[Michael GilliganParticipant @michaelgilligan61133]

Just for idle amusement, here's a thought:

[assuming that it's a hole of known depth; either blind or through a plate]

Fill the hole with Wood's Metal and pare-it-off flush with the surface[s]

… some initiative may be required!

Then melt out the filler; weigh it; and do your sums.

MichaelG.

.

Yes, I know it's daft on several levels, but it might be useful.

[Ian S CParticipant @iansc]

Block one end if the bore is a through one, blow across the end and note the pitch of the note, should come out similar to filling with Wood's metal and weighing.

Ian S C

[pgk pgkParticipant @pgkpgk17461]

Adding to off-the-wall ideas:

I think it'd be easier to tape one side of the hole and measure how much liquid fills it… allowing for the meniscus of course. For really tiny holes one could try and calculate the rate of capillary filling with different viscosity fluids and angle of fill. For really small holes how about finding the maximum amplitude of a signal that will pass through?

[vintagengineerParticipant @vintagengineer]

The only way to measure a bore accurately is with a Bowers Bore gauge.

[Tony Pratt 1Participant @tonypratt1]

Posted by vintagengineer on 16/12/2016 21:52:32:

The only way to measure a bore accurately is with a Bowers Bore gauge.

Really, and what do you base that pearl of wisdom on?

Tony

[JAParticipant @ja]

I know in the British motorcycle industry pneumatic gauges were used to measure the bore of a cylinder. I can guess how they worked but would not like to put my guess into print without a lot of thought.

JA

[vintagengineerParticipant @vintagengineer]

Posted by Tony Pratt 1 on 16/12/2016 22:10:51:

Posted by vintagengineer on 16/12/2016 21:52:32:

The only way to measure a bore accurately is with a Bowers Bore gauge.

Really, and what do you base that pearl of wisdom on?

Tony

35 years as engineer and seen more inspection departments than I care to remember!

[Author]

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