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Teenage_Machinist
01-03-2009, 10:11 PM
How do you like to measure bores? There are telescoping and small hole gages, which are cheap if you already have the mike, and there are such things as caliper style bore mikes. What do you find to be the best system for an HSM to use>

I currently lack any and all bore measurement methods.

kf2qd
01-03-2009, 10:21 PM
If you do much work in the shop you will need at leat 1" & 2" mics, and a set of telescope gages will do a good job fo precision measurements. I use my digital or dial calipers for measurements that don't need better than plus or minus 0.005 but when it gets closer i tend towards my telescope gages. I have ID mics and rarely use them because the telecsope gages are easier to use.

Fasttrack
01-03-2009, 10:22 PM
For rough work, I use my dial calipers. For larger diameters that are deeper and may have a taper or egg shape, I measure with a mic and a set of telescoping gauges. Takes a bit of practice to get accurate readings with the telescoping gauges.

Then there are the bore gauges. Too expensive for me to afford! And, of course, plug gauges for small sizes. Those can sometimes be had for a very reasonable amount at auction.

wierdscience
01-03-2009, 10:30 PM
If you use a ring gauge of a known demension the ID jaws of your calipers can be plenty accurate for most things.

An example of cheap accurate ring guages are new un-used ball bearing inner races.

Lets say you need to bore a 25mm hole,if you have a 25mm bore ball bearing handy just feel in the calipers to the bearing bore and set the dial/display to zero.Bore the hole until the calipers read zero and your there.

This method will get you as close if not closer than a set of telescope gauges and a mic.

For work I have a set of hole micometers for bores up to 3",then a set of inside mics for 3" up to 30"

The mics are Polish made and run $80-90 each and the inside mics I picked up used for $75.

An assorment of even Chinese ball bearings can be had for $30 or less and even they are held to +.00015 -.0000"

rbregn
01-04-2009, 12:55 AM
if you get telescoping gages, get starrett. don't waste your money on cheap ones. You'll hate them.

Doozer
01-04-2009, 01:09 AM
I bought some Brown & Sharpe telescoping gauges.
I thought I was buying good ones.
Nope. Turned out to be junk.
Grind the ends of the binding rods, as they
looked like they were nipped off with a pair
of pliers!?! Inexcusable for B&S.
I inherited a set of Lufkins. Very nice.
Also get some split-balls for measuring
the small stuff.

--Doozer

Flying-Phantom
01-04-2009, 01:30 AM
It all depends on the tolerance, speed, number of parts, and number of different size bores. One part, one hole, and brick tolerance (length of a brick close enough) go ahead and use calipers or telescopic gauges. One hole in 40 parts with + or - .00025, set the price high enough to recoup partial cost of a Fowler bore mike.

macona
01-04-2009, 02:20 AM
if you get telescoping gages, get starrett. don't waste your money on cheap ones. You'll hate them.

Mitutoyo are nice as well.

oldtiffie
01-04-2009, 02:23 AM
For "small stuff" (less than say 1/2" or so), use the "expanding ball" type. They are cheap, very accurate and very reliable. For the "medium-larger" stuff, try a set of "old-fashioned" spring calipers. They too are very cheap, very reliable and very accurate.

I can hold 0.01mm (0.0004") easily and down to 0.005mm (0.0002") with a bit more effort and with a bit of practice and a lot of effort and concentration, I can hold 0.0025mm (0.0001").

For larger stuff, just make a "length guage" - a rod with tapered ends and a small hemisphere on the end. It costs nothing as it can be made from scrap. All I need is an outside micrometer. I have full range of 0-150mm (0 - 6") outside micrometers, and until a week or so ago, I never had a digital inside micrometer (see later).

Here is a pic of the "ball type", (top left, which I like), the "telescopic" type (top right, which I don't like under 1/2" but need to be careful with, so generally OK) and the internal spring caliper which I really do like (bottom left).

http://i200.photobucket.com/albums/aa294/oldtiffie/idmeasdevice1.jpg

Here is the math for the "length guage" and the internal spring calipers:
http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Stickgauge1.jpg

If you have the mating part (shaft) for the bore you want to do, you can use a digital caliper (no need to turn it on as I am only using the blades - not the screen - as a gauge) to accurate "span" (but NOT measure) the shaft so that the gap between the blades matches the diameter of the shaft. Now by using the "expanding ball" (WITHOUT the "stick" math/chart) you can very accurately measure the bore.

Next up, you can use the telescopic guages or the "stick" guage (WITH the "stick" math/chart) you can very accurately measure the bore.

For diameters over 6" up to 12" I use my digital height guage on any convenient flat surface to set my "caliper/s".

http://i200.photobucket.com/albums/aa294/oldtiffie/Dig_Ht_Gg1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Dig_Ht_Gg2.jpg

This is the digital 10 -30mm (~0.400" - 1.200") caliper I referred to previously. It is NOT cheap (AU$340 x 0.7 ~ AU$240).
https://www.machineryhouse.com.au/Products?stockCode=Q244

It is accurate to 0.01mm/0.0005" but must be set for each reading/diameter. I find it easier to set with an outside micrometer than with slip-guages. I use the slip guages to check the micrometer.

Here are the pics:
http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Digital_caliper1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Digital_caliper2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Digital_caliper3.jpg

Here are the instructions etc.
http://measumax.com/InstruSheets/33-239_33-246.pdf

They are pretty convoluted at best - a lot of "Chingle-ish" - but as usual when you need them they are hard to follow and when you master it, it all makes sense and you (I) don't need the instructions etc.

It is as good as it says - 0.01mm/0.0005" - every time. Setting is a bit of a PITA and frankly, I can do better quicker with mt spring calipers and a micrometer. I bought it to "see what it was like" and it did what I wanted and despite the price, I am happy with it.

This applies to most "internal" mearurements - which includes widths of slots, spaces between parallel faces etc.

So, all-in-all you can do very with little cost and a bit of ingenuity and lateral thinking.

dp
01-04-2009, 03:22 AM
I bought a set if expanding piston calipers and have been fine tuning the ends and de-burring them. They are junk as they sit on the shelf but are rhinestones in the rough. The mechanisms are adequate and when the ends are polished they're acceptable.

I also use dial calipers for inside dimensions and often do so as Tiffie suggests, using them as a dimension capturing tool that is later measured with a good micrometer.

BadDog
01-04-2009, 03:37 AM
Wow, checking holes is a subject unto itself.

"How do I like to measure holes?" Not very much thank you. :D If I must, then how about a scale, or just a pair of calipers? ;)

In truth, as stated, it all depends on your needs, your access to tools, and the physical realities of the hole in question. Not only accuracy required (hand held scale, or calibrated air gage in temp controlled room?), but absolute size as well. Measuring a 0.030 hole is a completely different thing from measuring a 1" hole, which is still different than measuring a 10" hole. How deep is the hole, and what is it's aspect ratio? Chamfered? Tapered? Finish? Accessibility? And so on...

If it's a deep or through hole, it's hard to beat a "quick check" cones or the Starrett long taper scales. Accurate and couldn't be easier, if it is in range and accessibility/depth is not a problem.

Very small holes, almost exclusively the domain of pins.

Smallish holes, then Quick Check cones or "small hole gages" or perhaps precision balls?

More moderately sized holes, Split Ball bore gages (Mahr), finger bore gages (Federal or Standard), "T" gages, inside mics, some tube/bar mics, Tri-Mics. Perhaps comparator gages like Tiffie shows (but dial, not digital). Pin/Plug gages can still be used if you have them. Calipers of course, both sliding and classic spring or even firm joint. Perhaps even a scale is "good enough"? Might even use an adjustable parallel if the chord of the flats is not an issue.

Large holes, there are some common, and some very different options. Calipers in various flavors of course. Or tube mics (or anything similar) in direct reading if you have the length, or chordal calculation if you don't.

.RC.
01-04-2009, 03:52 AM
How do I measure holes??? Not very easily when you want it measured accurately....

I generally use a set of mitutoyo telescopic gauges and can try to get to 0.01mm but lets be realistic here, when someone comes along and says they can measure a bore to microns in a general workshop they are talking out their arse...The smallest temperature change will totally stuff up any measurement they have...Take yesterday for example...I was machining down some steel using carbide and when I finished it was over 100C..I measured it and then measured it when it was room temperature...The difference was in the order of 0.1mm..

Sorry but it irks me when people make outlandish claims about what they can measure...(or when their radial arm saw come surface grinder can hold tolerances of 0.0000001mm) :D

dp
01-04-2009, 04:00 AM
Sorry but it irks me when people make outlandish claims about what they can measure...(or when their radial arm saw come surface grinder can hold tolerances of 0.0000001mm) :D

I made no such claim of tolerances regarding my grinder - I said it suited me for the purpose. If that purpose was a tolerance of 0.125 that is a figger I'll take to my grave :)

It does much better than that, though, and produces a nice flat finish I can't achieve with any of my other tools.

.RC.
01-04-2009, 04:34 AM
heh heh don't worry I was only taking the piss with the radial arm saw statement... :)

oldtiffie
01-04-2009, 06:49 AM
Wow, checking holes is a subject unto itself.

"How do I like to measure holes?" Not very much thank you. :D If I must, then how about a scale, or just a pair of calipers? ;)

In truth, as stated, it all depends on your needs, your access to tools, and the physical realities of the hole in question. Not only accuracy required (hand held scale, or calibrated air gage in temp controlled room?), but absolute size as well. Measuring a 0.030 hole is a completely different thing from measuring a 1" hole, which is still different than measuring a 10" hole. How deep is the hole, and what is it's aspect ratio? Chamfered? Tapered? Finish? Accessibility? And so on...

If it's a deep or through hole, it's hard to beat a "quick check" cones or the Starrett long taper scales. Accurate and couldn't be easier, if it is in range and accessibility/depth is not a problem.

Very small holes, almost exclusively the domain of pins.

Smallish holes, then Quick Check cones or "small hole gages" or perhaps precision balls?

More moderately sized holes, Split Ball bore gages (Mahr), finger bore gages (Federal or Standard), "T" gages, inside mics, some tube/bar mics, Tri-Mics. Perhaps comparator gages like Tiffie shows (but dial, not digital). Pin/Plug gages can still be used if you have them. Calipers of course, both sliding and classic spring or even firm joint. Perhaps even a scale is "good enough"? Might even use an adjustable parallel if the chord of the flats is not an issue.

Large holes, there are some common, and some very different options. Calipers in various flavors of course. Or tube mics (or anything similar) in direct reading if you have the length, or chordal calculation if you don't.

Thanks BD - I agree with everything you say - its "horses for courses" - depends on what tolls etc. you have to measure what-ever hole to what-ever accuracy for what-ever purpose.


Might even use an adjustable parallel if the chord of the flats is not an issue.

I presume that this is what you mean:
http://www.cdcotools.com/item.php?itemid=14

I have a set of those and have contemplated the diagonals, corner radius as well as the diagonals etc. with regard to using them for measuring the diameters of holes.

There is a fair bit of math to it - but that should not be insurmountable - its on my "get around tuit" list.

I intend to get another set and to grind a convex radius on each measuring face of each pair with the radius being jut a bit less than half the distance across the measuring faces. I had them when I was an Apprentice and later as they were standard tool in the shops and Tool-room. Just slide them in, get them snug, measure with an outside micrometer - job done - almost. They could only detect "taper" by the/any "swing" that remained at one end. We had "rules of thumb" for evaluating that too - not too unlike the "stick" method I posted earlier.

I have to get a radius profile wheel-dresser for my grinders - but they are expensive.

This should do the job:
http://www.cdcotools.com/item.php?itemid=32

This one is a bit small:
http://www.cdcotools.com/item.php?itemid=284

This one is WAY too expensive. ~AUD1,300 x 0.70 ~ USD900!!!:
https://www.machineryhouse.com.au/Products?stockCode=P360

Precision is everything in this job - or perhaps its just a good excuse to buy a new tool without having a good reason!!

oldtiffie
01-04-2009, 06:51 AM
heh heh don't worry I was only taking the piss with the radial arm saw statement... :)

Ringer,

I suspect that you won't be able to take the pi$$ out of yourself until you open your hand. Grip it any longer or harder and you will strangle it.

oldtiffie
01-04-2009, 07:10 AM
How do I measure holes??? Not very easily when you want it measured accurately....

I generally use a set of mitutoyo telescopic gauges and can try to get to 0.01mm but lets be realistic here, when someone comes along and says they can measure a bore to microns in a general workshop they are talking out their arse...The smallest temperature change will totally stuff up any measurement they have...Take yesterday for example...I was machining down some steel using carbide and when I finished it was over 100C..I measured it and then measured it when it was room temperature...The difference was in the order of 0.1mm..

Sorry but it irks me when people make outlandish claims about what they can measure...(or when their radial arm saw come surface grinder can hold tolerances of 0.0000001mm) :D

Ringer,
I hope and trust that you are talking with your tongue in the cheek in your face and not else-where.

If there was a temperature differential of say 75 degree C between your job (100 deg C) and the shop ambient temperature of (say 25 degree C) at which the micrometer probably was, of course you will get a "temperature error".

If you use your micrometer at those temperatures - good luck to you. But it won't happen here.

Measuring to a "tenth" (of a "thou") is not all that hard although it might be at or beyond the limits of capability in many HSM - and Commercial "Jobbing" shops. But there are 100 of those microns in that "tenth".

Measuring a bore - or anything else - to 0.01mm (~0.0004") should not be beyond the easy reach of a good machinist or Fitter/Mechanic with standard tools. Some with more specialised tools can do quite considerably better consistently (say 0.005mm ~ 0.0002") - "two tenths" - or better.

Ed Tipton
01-04-2009, 07:44 AM
Having never had to accurately measure what I consider to be a "large" hole, I have no preferred metheod. For smaller holes that must be very accurately measured, I prefer to use pin gauges. I have a complete set that ranges from about .050 up to 0.500 in .001 increments. I trust these and have a high confidence in them for any measurement where .001 is accurate enough. I am always somewhat leery of using any device with a spring since I have in the past caused some deflection with the Mike "compressing" the spring tension. I have used the telescoping gauges, split ball gauges, and the internal calipers, and all are good for quick and dirty measurement, but if I need close measurement, the pin gauges do it for me.I've tried not being so heavy handed, but regardless, I don't trust my technique, and feel more comfortable using the solid pin. I found my pin gauge set at auction for $50.00, and consider them to have been worth the money.

Teenage_Machinist
01-04-2009, 03:23 PM
I was really talking about holes from about an eighth or so to an inch or two.


Right now I have a good dial indicator, soon to have a half-thous BesTest, surface plate, calipers, a depth gage mike, and a 0-1 inch Helios tenths mike with rusty spindle and anvil, and no reference to calibrate it. Most of my work is pretty rough but sometimes I do need to split thousandths such as for bearings. I have not thought about this until I needed to do a job that involved boring to a precise size, not a common size, and had to jury rig things with a chuck and the micrometer collar of the lathe.

I was assuming that telescoping gages were the preferred. So, time to make small hole gages and buy telescoping ones, I guess.

LES A W HARRIS
01-04-2009, 05:07 PM
If you have gage pins, the 3 pin check is also very accurate.

http://i37.photobucket.com/albums/e97/CURVIC9/07%20SHOPSTUFF/3pinchck01.jpg

Marv has a download on his site, "PLUG"? that will run the numbers. For rough work keeping the spread of pins to a "thou", a guestimate equation;

D = ((average of 3 pins) / cos 30)+(d (avg))

eg. 0.2310"+0.2320"+0.2330") = avg 0.2320"/ cos 30 + 0.2320" = 0.4999". (0.49989052" rough calc)

Actual calc with Marv's "PLUG" = 0.4998959".

Cheers,

Teenage_Machinist
01-04-2009, 07:09 PM
Well, I guess I know. I was figuring people would use the telescope gages, but I did not know.

Fasttrack
01-04-2009, 07:21 PM
3-pin check - thats pretty neat. I don't think I've seen that before. I'll have to remember it. Seems like a good, quick way of getting a pretty decent measurement.

lunkenheimer
01-04-2009, 10:16 PM
When measuring a hole there are some considerations-

1. What depth are you measuring at? Near the surface, deep in the hole, or several depths? Some tools have little reach (such as dial/vernier/digital calipers) and others have deep reach such as bore gages.

2. What diameter are you measuring? Many tools have a very limited range (like bore gages) and others have broad ranges.

3. Why are you measuring? Do you care how round the hole is? A hole can have a constant diameter but be far from cylindrical ( see for example Reuleaux triangle). For some purposes this doesn't matter too much but for others it is critical. Two-point measurement tools won't catch this but three-point tools may. Note that ordinary twist drills can make holes that are not round but have a constant diameter, under some conditions.

I think maybe you are asking for guidance on buying a good general purpose hole measuring device. What I use is some spring calipers and good mikes, which takes a bit of practice to develop 'feel'. But, this is only good for some situations and you need to know about the cases where it will give you bad results (such as the non-round holes of constant diameter case). It is economical and flexible, however.

Spin Doctor
01-04-2009, 11:01 PM
All in all it depends on just what I am mearsuring. At work when I am inspecting the bearing housings and mounting diameters on shafts a lot of the bearings we ar using have at a minimum 80mmID for some of the needle bearings we use. Main bearing diameters and thrust bearing diameters on some of the machines we work on get quite a bit bigger. So a lot of the holes I have to check are done with an inside micrometer that is then checked against a regular micrometer. Bore and shaft specs call for H6 and m7 fits so we may have 180mm diameter shafts that are allowed up to 70 IIRC. My fit manual is at work right now. Rarely do we run into situations where the type of machines we work on have angular contact bearings and when we do they are invariably installed Face-to-Face. because a DF mount allows for greater axial misalignment in the bearing alignments.

oldtiffie
01-05-2009, 03:54 AM
If you have gage pins, the 3 pin check is also very accurate.

http://i37.photobucket.com/albums/e97/CURVIC9/07%20SHOPSTUFF/3pinchck01.jpg

Marv has a download on his site, "PLUG"? that will run the numbers. For rough work keeping the spread of pins to a "thou", a guestimate equation;

D = ((average of 3 pins) / cos 30)+(d (avg))

eg. 0.2310"+0.2320"+0.2330") = avg 0.2320"/ cos 30 + 0.2320" = 0.4999". (0.49989052" rough calc)

Actual calc with Marv's "PLUG" = 0.4998959".

Cheers,

Very good advice indeed Les.

Many thanks.

Only or main problem I had was the cost of a set from 0.011" to 1.000" in increments of 0.001" (set of 990 pieces) is USD616 at CDCO
http://www.cdcotools.com

Other problem - perhaps for some - is that Marv's utilities are made to run under "DOS" (I use the Windows DOS-emulator under "cmd" command/utility). I have no problem with DOS as it was my "native" OS prior to "Windows".

I really do like your elegant math solution. Your "rough"???? answer was about 9 microns away from Marv's "precise" answer.

Given that there are 100 microns/micro-inches in a "tenth of a thou" I doubt that too many will be able to accurately dispute - or find - your "error".

If there is a slight taper - wider at the "front" - it will be very easy to "jamb" those pins in and not too easy to get them out. Finding and measuring a taper might not be too easy either.

Evan
01-05-2009, 10:04 AM
when someone comes along and says they can measure a bore to microns in a general workshop they are talking out their arse...The smallest temperature change will totally stuff up any measurement they have...

There are ways to deal with temperature differences.

One easy way to check a bored hole at the top is to use a tapered plug gauge. Make one up from the same material as being measured and set the compound to cut a taper of 2 degrees. The exact value doesn't matter. Or, you can use an existing item such as a morse taper if the circumstance will allow. The shallower the taper the more sensitive the measurement. Too shallow though and it will cause problems.

Blue the taper (a sharpie will do) and insert lightly in the bore. Remove and now you have the much easier job of measuring the OD where the mark is on the plug gauge.

If you make the plug guage accurately to a predetermined slope then you can make it direct reading. A 10" bar turned between centers with an offset at the tailstock of .050" (half angle) will have a taper of 1 in 100 along it's length. That means that every .1 inches the bar changes diameter by .001".

Set up a suitable round bar between centers. Cut a land at the headstock end of the bar a few thousandths of an inch larger than the bore to be measured. Then offset the tailstock by the required amount toward the user. Cut the taper for an inch or so at the headstock end starting at the land. Part off the new plug gauge and include enough material at the land to make it easy to handle. You now have a guage that will taper from the land OD by .001" every tenth of an inch. By measuring the length from the land of the plug gauge (known diameter) to the mark made in the bluing it is relatively easy to measure to .0001" diameter since that represents a distance change of .01" along the gauge.

Evan
01-05-2009, 10:07 AM
Given that there are 100 microns/micro-inches in a "tenth of a thou" I doubt that too many will be able to accurately dispute - or find - your "error".



Tiffie,

A micron is one millionth of a meter, not the same as a microinch.

John Stevenson
01-05-2009, 10:19 AM
Many thanks.

Only or main problem I had was the cost of a set from 0.011" to 1.000" in increments of 0.001" (set of 990 pieces) is USD616 at CDCO
http://www.cdcotools.com



So just use two identical dowel pins of a known size and a slip block.
No need for a computer just add the 3 sizes together but you may have to take your shoes and socks off if it's a large bore.

.

oldtiffie
01-05-2009, 10:28 AM
Oops.

You are right Evan. I saw it just as I typed it and both before and after I posted it. I meant to amend it - but didn't.

It was careless of me and I should not do it. I am glad you were there as the "catcher".

Thanks.

1 micron (1 millionth of a meter) while being 25.4 x 1 micro-inch (1 millionth of an inch) is a "size-able" difference in relative and absolute terms but I'd doubt that it would either need to be nor could be measured or noticed in most practical applications in many or most HSM shops.

But that doesn't excuse the fundamental mistake I made.

oldtiffie
01-05-2009, 10:48 AM
Originally Posted by oldtiffie
Many thanks.

Only or main problem I had was the cost of a set from 0.011" to 1.000" in increments of 0.001" (set of 990 pieces) is USD616 at CDCO
http://www.cdcotools.com


So just use two identical dowel pins of a known size and a slip block.
No need for a computer just add the 3 sizes together but you may have to take your shoes and socks off if it's a large bore.

.

Thanks John.

I've tried that and while it works, it can be a PITA with close fits.

I've done it with my adjustable parallels and to a better extent, they worked pretty well.
http://www.cdcotools.com/picture/14

I am sorely tempted to buy another set and a grinder profile dresser and to grind a diameter of just less than the over-all measurement of the least position on all of the adjustable parallels and I can "mike" to bore directly. I've pretty well promised myself I'd get a set ever since I used them so successfully so long ago.

I am toying with buying a set of those pin guages as well.

I guess it won't surprise you how often I say "nah - give it a miss" and sure as you like - I need it within a week or so - and have to f**k around with "jury-rigged" stuff.