Educate me please.
I'd like to directly measure small holes in the .200 to 1" range in particular but I guess the same questions apply to larger work as well. I've been watching the auction site for Intrimiks and the variations on that style tool from Etalon and Tesa. I'd like to measure to ." and it'd be great to have as much as 3" of reach into the hole if that's possible.
What do I need to know about these instruments and what brands to look for and which to avoid? How about wear and calibration on used tools? They seem a bit complicated and look delicate.
What about the dial types? Others I've not listed?
I don't have a load of cash to spend on this but I'll buy good tools when I need them.
Thanks,
Henry
. ????
WOW.
To properly gauge that tolerance, you'll probably have to use an air-gauging system, or ultra-precission pin gauges.
Intramikes read to ., but depending on the users "Feel", everyone will get a different reading. 3 guys will get 3 different measurements.
Bore gauges have the same problem. You can get one with a . indicator on it, but 3 guys will still get 3 different measurements.
. is hard to hold, and even harder to measure.
That's why machinists and inspectors are always at each others throats.....
If you're strapped for cash, then your best bet would be a set of pin gauges. If you need a special +/-. pin, then you might have to grind it yourself.
Random thoughts: All the shops seem to use Mitutoyo.
I think Etalon is the same a B&S and Tesa now-a-days.
A three anvil will read the more consistantly but a two anvil is easier to handle. If you buy used make sure it's comes with the standards.
If I had to measure to tenths I would buy a standard the same size as the bore.
The anvils do wear with use thus the need for standards.
The precision and thus the accuracy to which you can read is highly dependent on the surface finish of the bore.
I don't see a problem measuring to tenths if I have a standard sitting next to the work that is the same size as the bore. Just go back and forth between the standard and the work until you're sure of the same feel between the two. Thinking you are going to get tenths buy just walking up cold, gaging the bore and reading the dial is pie-in-the-sky.
OK,
Lets pretend that I have a drilled and reamed or bored hole that is ." and I want to make it .". Assume that I made the hole with parallel sides and that it is round. I'll need to measure the hole before and as I work on it to enlarge it.
I don't need to measure an entire bore over a 3" length. I might need to measure a hole right at the end of the part or it might be an inch or two in. I want the ability to measure either one or in between.
I understand that it takes care and skill to measure properly. I can measure o.d. with a micrometer to . and unless I'm sadly mistaken I think I can figure out the technique for i.d. but I've never owned the tools for this nor used any enough to know much about what is good or bad. I've made pins or slugged the hole and measured. I want to avoid that if I can.
I'd like to know about the tools used, which are good and which are not so good. I'll be buying used and I don't mind buying individual tools to build a set. I'm thinking Intrimiks or similar but I need some education about the tools first.
If your planning to machine and measure to ." you will need a climate controlled shop and the work will have to be stabilized to the ambient temp before measuring it. All this takes time and money and a machine to machine to that tolerance is expensive and the instruments to measure that are expensive.
You have to keep a constant temp and humidity in your shop 24/7 and that is expensive. Once you take the part out into the real world the dimensions will change. That is why the shop and the inspection people are always at odds.
Unless your making parts for NASA or some such company it's not needed.
EDIT: just read the above post and what you probably need is a set of pin gages but your still up against temp changes. Things are not always the same and you can come back tomorrow and the pin gage may not fit the hole as it did yesterday. Oh, and you will have a hell of a time taking out just ." to enlarge a bore with a standard mill. You are having a pipe dream Henry.
I must not be writing this clearly........
I'll most likely be lapping to final size in a lathe.
I'm not making a part that is to be inspected under standard controlled inspection conditions, sent to the moon or a run of parts that have to be +_ . or anything like that. I want to measure a danged hole and have control over how much larger I make it.
If I can't measure it I can't know what I'm doing to it.
So, as an example, I start with a hole that measures . and I want to enlarge it to .. I want to measure it directly as I work on it. I am aware that as I work on the part the temperature change will change the dimensions. I am aware that the hole will measure differently at 70 degrees and at 90 degrees or 110 degrees.
Please tell me about the instruments I'm asking about that are used to measure the hole.
Buy ten oversize reamers and ream one bore with each. Mark the one that gives you the size closest to your target. Or, use a lap.
Here is a training guide more detailed and correct than I could write:http://www.uiitraining.com/b51a/100/bore_gage.htm
And this site has infomation on the various manufacturers: http://longislandindicator.com/index.html
I would trust using a standard dial bore gage like the Mitutoyo to compare the work bore to a standard rather than using a direct reading gage like the Intrimik. While convenient, the direct reading gages can easily fool you if the bore is dirty or the surface finish is rough or the anvils are worn or etc. Like others have said you give three different people an Intrimik and they will get three different readings but with a standard dial bore gage you are forced to use a standard.
The Intrimik and the B&S are made by Tesa in Sweden.
...
So, as an example, I start with a hole that measures . and I want to enlarge it to ..
...
If you tell a machinist you want a dimension of 0. and you don't give a tolerance then rules say he has to assume plus or minus 0.". Don't yell at the machinist when he starts talking about air gaging and controlled environment. If all you need is "a little over" then just say so.
Is there a reason why you don't just buy a new reamer the size you need and ream it. It will be damn close. I just did a bunch of holes at . with a carbide reamer bought to size and they all read just that on a vernier micrometer. I used an old set of adjustable half-ball hole gages from B&S to transfer the measurement to a chinese vernier micrometer. I knew the reamer was more accurate than my gaging but after measuring the holes and splitting the lines on every single one I am pretty certain they are right on size.
Most intramics are . graduated. I've used Mitutoyo and a set of SPI brand. Both were very similar and were very nice to use. I believe Brown & Sharpe makes some as well, but have never used them.
As far as bore gages, I've used Interapid, Federal, Mitutoyo, Sunnen, Fowler and even some Chinese made bore gages. They are all nice bore gages to use. Sunnen is my overall favorite, but that is because I love their master setting gage. It makes setting a bore gage, accurately, a real breeze. Out of all of the bore gages listed, I believe Sunnen will sit you back the most. They are extremely expensive.
In my shop (I'm on a low budget), I have a mix of used and new bore gages, including Interapid, Federal, Mitutoyo, Fowler and even a couple Chinese bore gages. Believe it or not, both Chinese bore gages that I have appear to measure accurately and are of fairly high quality. Most of my bore gages measure to . with the exception of the Interapid gages that are . reading.
I also have pin gages up to 1.00" which get the most use as many here have suggested.
Keep in mind that no matter which way you chose to go, you need to come up with a way to set these gages. Bore gages require either a setting master, or some way to hold a stack up of gage blocks for setting size, intramics call for ring masters.
Frank
www.randolphmach.com
Well Henry, since you are aware of the issues all I can add is to measure the ." increase in bore size you will need a gage that can read in ." on the dial. Mine and most bore dial gages read in ." increments and are supposed to be accurate to ." but a lot of the accuracy depends on the person using the tool.
I don't know where you can get a bore gage to read in ." or ." increments so I have to bow out of the discussion. I have never been able to hold that kind of tolerances on a lathe or mill so good luck. But then I never really had to or wanted to.
Henry, I did a google and here is your best bet http://www.sunnen.com/graphics/assets/documents/ed146da30bcc.pdf Sunnen is very good and may be the best for the money. On top of that it goes down to the sizes you want to measure.
I love the sunnen gauges also. Very acurate. I routinely deal with . tolerances and am lucky enough to work for a company that pays for everything I use. 2 companies not mentioned yet that also have great metrology equipment are Marposs and Kaefer. We have gauges that read to ." from both of those. I don't usually try to machine to a . tolerance. I usually get it to within .001 of final dimension & then manually hone it into tolerance using our sunnen honing machine and a J95 stone or even a cork *stone* depending on finish requirements.
Here's my two cents on bore gages. These are cheap chinese jobs, but veeeery accurate. Fowler and others put their label on them as well. They range from .275 through 10". These came from Shars. I've got over $.00 in them and have had great luck with them. They measure to ., but temperature of course is a factor. Never had a customer complaint from regular boring to jig grinding so I'm quite pleased.
A word of caution on the Sunnen gages, at least the ones I've worked with, or any other instrument that only measures two points on the profile ...
They will not show you a part that is out-of-round in three places due to chuck/collet over-pressure.
Because they only measure two points that are diametrally (sp?) opposed they will show the part to be good when it can be out of tolerance by a couple of thou'.
An air bore gauge with three or more orifices will detect this.
So will an ID mic with three contact points instead of two.
A pin gage, even a Deltronic set ... eh ... not so much.
A company I used to work for found this out to their chagrin.
It resulted in several thousand scrap parts and much rework when I detected the problem.
Just a word of caution ...
KillerB
I have never had that problem with the sunnen gauges. The (sunnen) gauges we have at our shop have a . resolution and can easily pick up any irregularities in a measured bore within a couple of tenths.
They will not show you a part that is out-of-round in three places due to chuck/collet over-pressure.
Because they only measure two points that are diametrally (sp?) opposed they will show the part to be good when it can be out of tolerance by a couple of thou'.
I would actually worry more if the bore was made with a 4 jawed chuck because opposing sides could more easily be misread by the gauge/user....the "couple of thou" would or at least *should* be easily picked up by any sunnen gauge with a . resolution even by an inexperienced user.
KillerB
I have never had that problem with the sunnen gauges. The (sunnen) gauges we have at our shop have a . resolution and can easily pick up any irregularities in a measured bore within a couple of tenths.
I would actually worry more if the bore was made with a 4 jawed chuck because opposing sides could more easily be misread by the gauge/user....the "couple of thou" would or at least *should* be easily picked up by any sunnen gauge with a . resolution even by an inexperienced user.
The resolution of the gage has nothing to do with it.
If your gage only measures between two points it can resolve to 8 decimal places and as long as the part maintains a constant distance between the two points being measured it can be out of round ... .001"? .005"? 1/8"?, who knows ... and the gage will not show it.
Put that same part on an air gage with three or more orifices, or check it in two places with a three-anvil bore mic and it's condition is immediately apparent.
BTDT
My boss at the time didn't believe me either ... until the parts were rejected by the customer.