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How Do You Measure Your Holes?

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Nick Hulme13/12/2016 13:53:06
750 forum posts
37 photos

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

pgk pgk13/12/2016 14:03:06
2661 forum posts
294 photos

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.

Hans13/12/2016 14:10:02
7 forum posts

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 Wyatt13/12/2016 14:13:25
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19226 forum posts
749 photos
86 articles

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 pgk13/12/2016 14:17:05
2661 forum posts
294 photos
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.

Emgee13/12/2016 14:55:23
2610 forum posts
312 photos

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

dormer drill blanks 6.0 to 10.0 x .10mm.jpg

dormer drill blanks 1.0 to 6.0 x 0.10mm.jpg

Chris Evans 613/12/2016 15:53:46
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2156 forum posts

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 carruthers13/12/2016 16:29:33
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617 forum posts
180 photos

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

Andrew Johnston13/12/2016 17:21:20
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7061 forum posts
719 photos

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

JA13/12/2016 17:28:05
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1605 forum posts
83 photos

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 Stevens13/12/2016 19:04:02
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1779 forum posts
1 photos

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 vercoe13/12/2016 19:41:14
72 forum posts

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

Colin

Bob Brown 113/12/2016 19:43:58
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1022 forum posts
127 photos

I use one of these image00003.jpg

David Colwill13/12/2016 21:57:46
782 forum posts
40 photos

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 Engineer14/12/2016 00:59:41
147 forum posts
4 photos

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.

Hopper14/12/2016 05:01:05
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7881 forum posts
397 photos

Ball gauges below half inch, telescopic gauges above.

Roderick Jenkins14/12/2016 11:04:45
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2376 forum posts
800 photos

Many years ago I was given these:

bg1.jpg

and this:

bg2.jpg

bg3.jpg

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 smiley

bg4.jpg

Cheers,

Rod

Michael Gilligan14/12/2016 13:47:54
avatar
23121 forum posts
1360 photos

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 C15/12/2016 10:24:30
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7468 forum posts
230 photos

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 pgk15/12/2016 10:32:26
2661 forum posts
294 photos

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?

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