I'm not 100% sure that I used the correct title for what I'm looking for. I need an accurate bore to set up the calibration of the probe on my CNC mill. Does anyone have one they want to sell. Anything from .375" to about 3" would be suitable. The photo is a random example of what I'm looking for. Can anyone think of something that might work as a substitute that might be found locally.
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Wanted: Bore gauge setting ring
- Thread starter Upnorth
- Start date
I don't know what accuracy you need. But you asked for alternatives. If you have a lathe, you could make something. The hard part is honing or better yet grinding the center hole. But depending on the accuracy you need, perhaps even reaming might meet your needs.
If I understand what you are looking for, the dimension isn't critical. Any dimension will work as long as you can accurately measure it, and mark it and the inside surface is smooth and consistent.
Not obvious in your photo is the line on the gauge. That's where the measurement has to be taken.
The other part is the temperature. The ID changes with temp so the dimension they provide is only valid at that temp.
May I ask why an ID is required for calibration? Wouldn't an OD be the same as far as coordinates are concerned - just opposite? And wouldn't a gauge block provide a superior calibration for that purpose?
PS - I have seen them from time to time on Kijiji. Usually with an inside gauge of some sort.
If I understand what you are looking for, the dimension isn't critical. Any dimension will work as long as you can accurately measure it, and mark it and the inside surface is smooth and consistent.
Not obvious in your photo is the line on the gauge. That's where the measurement has to be taken.
The other part is the temperature. The ID changes with temp so the dimension they provide is only valid at that temp.
May I ask why an ID is required for calibration? Wouldn't an OD be the same as far as coordinates are concerned - just opposite? And wouldn't a gauge block provide a superior calibration for that purpose?
PS - I have seen them from time to time on Kijiji. Usually with an inside gauge of some sort.
Dan Dubeau
Ultra Member
You could use the inner race of a suitable sized bearing. Probably the most accurate thing available that is reasonably price and readily available to the masses.
Correct the actual dimension does not matter it's accounted for during the probe calibration procedure. You measure a known bore diameter then mathematically set the diameter of the probe. This is to account for the difference between the diameter of the probe tip and when it actually triggers. I used to borrow a part a friend of mine had that was ground to size for a bearing fit. The part has gone AWOL in his shop so I can't use it anymore. I want to start with something of a known diameter to eliminate any source of error. I did not know that those ring gauges have to be measure at the lines. It's likely though that they are accurate enough. For most of my work I like to aim for less than .001" tolerance. .001" is probably more accurate than the probe I use is capable of. That is closer than I need for almost everything but I prefer to stay close as I can to keep in practice. There are long gaps between me making things. Temperature should not be an issue as my shop is heated and almost always at or near 20C.
As for why do I need an ID and not an OD for probe calibration. The only answer I have to that is the manual for calibrating the probe says so. I think when measuring the OD it only looks at one axis at a time. When measuring ID like a bore it uses both the X and Y axis when probing.
This might be the way to go. I do have a few bearings kicking around that I will never use.
I wasn't really suggesting an OD. That was just the quick way to explain why I was really suggesting a gauge block. The problem with IDs and ODs is tangent error. A gauge block doesn't have that kind of error.
But I get why you want to stick with the manual and I love @Dan Dubeau's idea of using a bearing race.
I also get @gerritv's explanation of the speed of the method. I assume his explanation ignores tangent error because it cancels out when making the opposite measurement. Clearly, that wouldn't work so easily on an OD or a flat surface cuz you have to go around.
I'm just an old school manual guy and I don't give a rat's ass about speed.
Glad you got the idea you needed.
I have been thinking about this. I think another issue with this would be that if the gauge block might be if you don't have it in the vise perfect it could introduce errors if it's not perfectly aligned with the axis. Another advantage of a round bore is it allows you to run a full probe test. There is a calibration where you can test your probe at all angles to see how far it is out at other angles. As an example it measure at 0 degrees then 10, then 20 and so on until it makes a complete circle. Then it generates a graph to show you if your probe is not accurate on a particular axis.
If your vise is not aligned you have bigger problems than any calibrated probe can fix!
But yes, I can see the advantages of using an ID. I've never set my DRO that way. Maybe I'll try it next time.
I think there are strengths and weaknesses with any approach.
I think an ID approach would not work well with small IDs. In any case, your probe accuracy is gunna limit what you can do.
Makes me glad I don't ever plan to do CNC.