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ID bore inspection tools

viper

Titanium
Joined
May 18, 2007
Location
nowhereville
We have been presented with making a few parts that have some tight tolerance bores in them. I will need a fast and accurate way to check them without breaking the bank. IDs range from .375-1.50" with a tolerance of +/-.0003". I feel we can stay in that window with the lathe with careful programming but will need to inspect each one accurately.


Will a quality ID mic do the job here? I understood that because of the 2 point contact design, they did not tell the whole story.
 
Check out Comtorgage: http://www.comtorgage.com/index.html

The system consists of an amplifier, a gage plug for the specific ID you want to check, and a setting master ring for the size of your gage plug. I am sure it is not cheap, but the amplifiers (including a gage plug that is unlikely to be what you need) often come up on eBay for a song. They will definitely allow you to check your parts, despite your close tolerance, in a quick and repeatable fashion. I also consider them quite rugged. I have bore gages that push a tenth indicator, but they do not compare with a Comtorgage in speed or repeatability.
 
Thanks for that reply. that might be what we need. I will call them. I bet their rangs is like .010in thus must have an adaptor for everything!
 
You know, I have seen those in several shops and they are super slick! One local company has one at every machine because they only make bushings. I am not sure if you have to get adapters for every size range or what but they are nice. Wish they were a little more portable though for checking things that are bulky.
 
These are the sunnen gages we use, pretty broad range and very portable.

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http://www.sunnen.com/ProductDetails.aspx?ProductID=23&NavID=666
 
You know, I have seen those in several shops and they are super slick! One local company has one at every machine because they only make bushings. I am not sure if you have to get adapters for every size range or what but they are nice. Wish they were a little more portable though for checking things that are bulky.

No adapters needed, though they make specials.
 
+/- .0003 is a six tenth window. Easily in the three point micrometer range. I have SEVERAL different ways to measure bore sizes- Comtor gages for every size bearing bore in my line, Brown and Sharpe intrimiks to 7 inches, Standard Brand bore gages, Deltronic Pin sets in tenths, and Diatest bore gages. Since you're only trying to make parts to 1 1/2 inches, at least measuring to high accuracy- you're lucky.

The Diatest sets are really nice, with included rings in fairly small increments. I TEND to use these more than the others. If you only have a few sizes of holes, the Deltronics TENTHS sets are also very nice. Pins in tenth increments. I have these pins in the common sizes I grind parts to. With a bore gage and pin set, I know I'm within a tenth.

The Brown and Sharpe intrimics are available down to .350. These also are quite capable of measuring to your tolerances. For my large bearings, I use these along with a ring gage for all my bearings. The Intrimics are a THREE POINT micrometer, which is a little easier to get centered. I HAVE COMTORS for every size too, but for some reason, have more of a comfort zone with the Intrimics. The real key for accuracy is a certified ring gage so you KNOW what the correct dimension should read.

Comtor bore gages have been around a LONG time, and since they have, there's been a TON of them on ebay. I bought out a machine tool company, and got ALL of their bearing sized Comtors. What a score! Comtors are SUPPOSED to be idiot proof, but I still think they need a feel to get them square. I have brand new Comtors, that I couldn't get to repeat each time- not off by much, but still they wouldn't repeat. The Standard brand bore gages for my large sizes with .0001 indicators, I like a lot. When I do bearing bores, I tend to check and recheck using MORE than one instrument.
 
The Sunnen bore gauges don't really require a feel. They are self centering, plop it in the bore, swing it until you get the smallest reading, and you are there. The Sunnen setting tool is pretty near foolproof too, no feel or technique required and comes with a ring gage to double check it. Takes all the stress out of measuring small IDs, and makes most other bore gages look like toys.
 
The Sunnen bore gauges don't really require a feel. They are self centering, plop it in the bore, swing it until you get the smallest reading, and you are there.

Add a Tesa ".00005 digital indicator that latches on to the min and end even more doubt.
 
A little herasy here. +/- 0.0003" is an everyday tolerance for dial indicating bore gages. These gages work via linkage from the movable gaging tip to the dial indicator on the end of an axial handle. You set them from a stack of Jo blocks or from a master ring. They have a centering feature that insures you get a true diameter. Here's a cheesy chinese set that if properly checked out and accurately set may just do your job. Here's the cheap version. A simple ugrade would be a better indicator.

http://cgi.ebay.com/ENGINE-CYLINDER...in_0?hash=item35a3bce7bd&_trksid=p3286.c0.m14

Or for prime bore gaging equipment:

http://cgi.ebay.com/Mitutoyo-Dial-B...in_0?hash=item414928b296&_trksid=p3286.c0.m14

The lower diameter limit for these gages seems to be about 3/4. Bore gages overlap ranges with split probe bore gages. Split probe bore gages have a probe with a split ball shape. In the center of the split is a gap which "pinches" a tapered feature on a rod causing an axial movement pf the central rod. It's motion registers on a dial indicator. These have to be set from a ring gages although some can be set from a gage block stack. This link takes you to one of my fav split probe bore gaging sets. Good but pricey. It's not the right range for the OPs needs but it gives you the idea. So long as they are clean and used as a comparative gage they give consistant results in the 0.0001" range.

http://cgi.ebay.com/DIATEST-DIAL-BO...in_0?hash=item1c0caf7304&_trksid=p3286.c0.m14

I've used both over the years and worked consistantly to 0.0001" repeatability provided I had a Jo-block stack handy or a setting ring gage for ready reference before and after gaging the part.

Air gages and LDVT gaging equipment are more sensitive and almost immune to stiction error but they are not without quirks of their own. They can also be quite expensive for a shop starting from scratch. An LDVT system consists of a gaging cartridge and a gage amplifier and head. This link shows a typical gage head with selectable ranges. The actual measurement is taken by the indicatorlike gadget in the foreground. This particular gage cartruidge is use exactly like a dial test indicator except its far more sensitive. In device isn't suited for a bore gage.

A gage cartridge dimensionally replaces a dial indicator stem end but is sensitive to millionths. Instead of a dial on the other end, a cord comes out to connect with the gage amp. Gage cartridges have to be matched to the head they are used with; a Federal cartridge with a Federal gage head, Starrett to Starrett for examples. Quite often the signal connectors are unique to the brand. PITA but that's engineered exclusivity.

http://cgi.ebay.com/FEDERAL-230-EAS...in_0?hash=item5632b1fc6d&_trksid=p3286.c0.m14

And a link to a gage cartridge:

http://cgi.ebay.com/Federal-Digital...0?hash=item3c9bc6dc87&_trksid=p3286.m20.l1116

The cartridge looks like a hunk of barstock hanging from the signal cord. The digital amp is pretty primitive but you can live with it. This is a pretty good deal if you like flashing numbers. I find digital amos hard to read. OTH I think this unit can be hooked to a data collection system. .

It's best to educate yourself before committing to any gaging system and that includes checking with competent authority. Anything you read on a message board should be taken with a grain of salt - even my immortal words.
 
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I know I am just a noob here, but I work in the boring dept. at work.
We bore everything from .3752" to 10.5000" bores. Usually 4140HR, 4150HR, 306SS, 304SS, 8620Q+T and 1018HR.
Our 3 point digital Mito's usually do the trick on everything under 4". We actually used to use old school no digitals up until 2 years ago. There seems to be more ways of scrapping a bore due to process than measuring difficulties.
Our tolerances are +/-.00015.
I have run into a few different issues like calibrating my mic's with an inspection ring that was on the shop floor at a sweltering 92F mid-summer, so be careful with calibrating your mics. Also, coolant temperature is important. I like to run the inspection ring in the coolant from the lathe I am using for 5 or so minutes.
In addition, stick to 3 clicks on the ratchet only....every time.

The MOST important part of boring is a solid boring bar set-up. Using the biggest bar
that will fit into a bore is best.
We typically leave the bores undersized .015" and then start the fine cuts (.003-.005) making sure to cool the part after each cut while re-calibrate your DRO each time.
As soon as I get to within .0015" of the finish ID, it's time to sand the bore with 220grit cloth. Cool the part after every sanding. When I am .0002-.0003" under tolerance, I used a red scotchbright pad to polish the bores. They look like glass and measure perfect every time. Hope this helps.
 
How do you polish your bores? Scotchbrite will give a nice finish but not polished and just not sure of your methods. WE commonly use a 3 stone hone and wrap it with scotchbrite and spin it with a drill but not sure how to automate anything with the lathe. Sounds like you guys are running manuals over there. We would run a bunch of coolant and probably seek to just run near max tolerance with a warm part so it would come back to perfect when cool. We just need to move faster. I feel pretty good about our Jap lathes holding this kind of tolerance.
 
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My vote goes for Sunnen PG gages instead of the portable usints.
I have those for milled parts, but turnings go strictly on the PG.
The PG800 goes from .375 through 3.5" and is reliable as anything for the .0003 range.
 
Viper, Maritool has some very good prices on bore mics, if you want to go that way I have two of them and think they are very well made. I dont have any way to quantify them but I just set them with the ring gage supplied and use them.

Will your customer gage each one or just use them? That may make a difference as to what gage you use.

Charles
 
For a .0006 limit, I use either my Standard bore gages or my Mahr split-probe gages, both set to a ring.
While I have a few Comtors, I generally use those on dowel holes as they are a little more difficult to detect out of round and taper.
I use a Marposs E4 LVTT column for closer than .0003; Marposs suggests two XX master rings for setting so it's a little pricey though it is quite sensitive, it'll easily display the size differences between two XXmaster rings.
YMMV
 
I have (2) mitutoyo bore matic like brand new! #568-406 & 568-406 I purched at msc years ago. used on (2) different jobs twise very accurate.+ - .00005 Willing to sell at a reasonable price, if you still require them.(inter-changebil heads.
Vinny D
 
I'm in the 3 point inside mic camp here as well.

I have never used digital ones, but they would be a GOD send for checking to the tenths as they would be SO much easier to "zero" (set?).

I have spent WAY too much time trying to dial in the spool, but I finally give up and just remember that "This one is set .0001 small". Or was it big? Dang - gotta check it aggin! :willy_nilly:

Also note that rings are many times NOT right on! a 3/4 ring very well could be .74985 . You need to pay attention to the ring and not jist assume .75000 . Apparently perfection aint easy on their end either? ;)

You would definately want your ID mics set dead nutz on if having enyone else running them. You can't expect someone else to keep that .0001 discrepancy in mind.


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