Test Indicator HELP

C

chuck williams

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i cant find a test indicator longer than 1/2" where do you get a longer arm for your indicators or a new indicator with a longer arm. thanks.

chuck
 
DO A SEARCH ON "INDICATORS" ON THIS FORUM.
MSC WHEN THEY DO A 30% off, otherwise the east coast company listed in the search.
interapid series
mitsutoyo makes a small body

mike in co
 
Chuck
Go to MSC/JL catalog V77 page 1467A , they list test indicator contact points there. on the internet go to mscjlmetalworking.com and do a search for order no. 99046633 for interapid. hope this helps.

Glenn
 
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thanks a bunch for the help

thanks for the help guys.

chuck
 
Mitutoyo 513-504 (if you add a T to the end of the part number you get a full kit with mounting attachments and adapters)
.0001 graduations
can reach into chamber ~1.9"
the body on this indicator is small enough to enter into most chambers
.375 OD body
1.35 body length
.600 stylus length
1.9 body+stylus

Interapid 74 111965
.0005 graduations
can reach into chamber ~2.70
2.70 stylus length
 
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Be careful adding a longer stylus to your indicator that came with a short one. It will change the resolution of your indicator.
 
Joe said:
Be careful adding a longer stylus to your indicator that came with a short one. It will change the resolution of your indicator.
Click to expand...

A longer than supplied stylus will make the indicator "lie".....it will show a distance as less than it actually is, by a ratio equal to the length difference between the original and new stylus. For indicating a barrel on the lathe it won't really matter, since you're not looking to measure a specific distance.......just keep in mind that a little wiggle of the pointer is significant, because of the loss of resolution Joe tells of.

-Dave-:)
 
thanks guys

thanks again guys. i ended up finding two mitutoyo round body 513-512t indicators on ebay for $50 each shipped! they are new in the box. they are the same as the 513-504 but in .0005 increments. i think this will work fine for me since a .001 indicator has been pulling duty thus far. best of both worlds in guess since it is a short stylus and long reach without changing the stylus. should be more accurate than a .0001 indicator that had the stylus changed?

chuck
 
I did an interesting little test today.
It involved two Brown & Sharp Bestest indicators in .0001" resolution. Both came with standard 1/2" long contact points.
I set them up over carbide gage blocks on a granite surface plate.
Built in to the gage blocks I had a step of .0001" and .0005".
Both indicators read almost perfectly while passing over the steps in the gage block setup with their 1/2" contact points. Repeated 10 times each.

I then replaced the contact points with 1 7/16" long contact points.

While passing over the first step of .0001", both indicators read .00005" almost exactly half of the supposed resolution.
While passing over the second step of .0005", both indicators showed only slightly more movement than .0002". Considerably more than half.

Bottom line............if you replace your contact point with a longer one than the original, you are getting more movement than the indicator is showing you.
Be careful to get the dial to read as close to "zero" as you can.
 
Joe said:
While passing over the first step of .0001", both indicators read .00005" almost exactly half of the supposed resolution.
While passing over the second step of .0005", both indicators showed only slightly more movement than .0002". Considerably more than half.

Bottom line............if you replace your contact point with a longer one than the original, you are getting more movement than the indicator is showing you.
Be careful to get the dial to read as close to "zero" as you can.
Click to expand...

Joe,
This is exactly what I posted 3 days ago..........If you extend the stylus the readings will be reduced to less than the actual measurement by an amount equal to the percentage of change from the contact point to the pivot (not the attachment point). The ratio won't show as exact when measuring a small difference in heights like you used in your experiment, because the resolution claimed is dramatically reduced because of the extended point.

-Dave-:)
Click to expand...
 
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You're right Dave, you did post it. It was on my mind since and I wanted to do a test to see how much it would actually affect the actual reading. I thought the readers here might like to see some actual numbers. Interesting stuff.
 
Three factors that come into play and are magnified by the longer stylus:
*Accuracy
*Resolution
*Repeatability

All things considered, What Joe said is the bottom line......try to get the pointer to read as near a flat zero as you possibly can.

Forget worrying about one vs. two tenths; there are a number of factors that you can't see or account for that put that last tenth into the "rainbow chasing" realm.

-Dave-:)
 
If you are trying to measure actual measure (distance) then the stylus the indicator was built for is essential. Example, in a barrel bore, measuring the distance between the lands and the grooves, rise and fall.

If, as in the barrel bore, you are trying to measure runout, and you are wanting to measure that runout at the, to be or finished, chamber neck, then a longer than normal stylus is required. Many gunsmiths use the Interapid indicator and a 2"-3" long stylus. This allows measuring runout, which is what you want, even though the actual amount indicated on the dial is incorrect. Remember, you are not concerned with how much the runout is, you are just concerned if there is runout .
 
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