doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Bore diameter measurement tools - Part 2

I've read the thread related to shotgun barrel blueprinting and it has a lot of good info on wall thickness measurement tools.

Now back to tools for measurment of bore diameter. I'm aware of the longer ones sold by Galazan and Brownells; also the short one that's 6" long one I see in magazine adverts. Is anyone aware of any other vendor of long measuring tools, something like 16" to 20" or so? I'm in the market for a good one and I want to consider all makes and models. Thanks. Silvers

I had Skeet's gun shop make me one with a 16" depth. I think that he did make them for Brownells at one time. Price was quite low and the bore gauge works well today.

Silvers,
If you have access to a little lathe and drillpress, you can modify one of the conventional bore gages that industrial machine tool inspection gages. I found a couple on ebay and have yet to lengthen them. It is a simple matter of making a longer tube and rod that actuates the dial, no real precise work at all. The rod has to be cut to the right length but it is very tolerant and can be filed to length.

here's a candidate. http://cgi.ebay.com/Hemco-Dial-BORE-Gage...1QQcmdZViewItem

Silvers,
Where is the blueprinting thread please?

Silvers,
Ignore my last post, I was looking TOO deeply into your post.I thought you meant there had been a more in depth article on the specific subject of 'Blueprinting Barrels'.

Twenty years ago I worked with a chap who was into computers in a BIG way.We had an engineering problem to measure a bored hole.I made up a tool to his instructions, which was basically a piece of wooden dowel with sensors attached.This was put into the bore hole at the mouth and zerode.One sensor was spring loaded and able to move away under spring pressure from the other sensor and its path plotted on a computer screen.
The probe was then pushed down the bore and the bore dia was plotted on the screen for its full length.
The resultant graph on the screen showed I.D. to 0.0001" and 0.001" increments down the bore.But I suppose with calibration he could have crunched any number I wanted.He was a real smart guy but I bet you guys out there think that is easy to do.Well I just wish I could do it now.
I've just followed Rabbits instructions and spent the night hanging from the Bay window curtain rail!!!!!!!!

Sal, Dr. Gaddy broke the chain by being something of a prophet in his own country. Perhaps rabbit doesn't imbue the subject with the same scholarly gravitas, LOL!

jack

While the specialized shotgun bore gages which I've seen, that were of the '3 balls against a tapered rod, running a dial indicator' design, are convenient and in most cases more than adequate for the average amateur or professional task at hand, they will not give an accurate account of an out-of-round condition.

In most cases, the bores are not far enough out-of-round to be of any concern. But, if it were, the reading from one of these type of gages would not be indicative of actual out-of-round condition since it essentially averages the three points.

The two point measureing type of bore gage (which often also employs two other non-measuring spring assist plungers to center) is the only way to get actual values of out-of-round, if that is needed.

And those two pointers are cheaper and more available in eight gauge sizes!! I think I'll get one of those in .750 to 1.000 for my eights and tens. The ones on the links to ebay are sure short though. I wonder if they come in 12" or 16" depth?

Murphy,
They have a simple tube and a rod to run the dial. A new longer tube and rod can be easily fabricated to any length desired. Buy an ebay used, quality name and you'll be happy.

Chuck,
thanks for the great tip on those ebay deals.I have the Skeets 12/16 one from Brownells,the 3 ball deal, but will look for one of the ones you suggested.When you say the tube and rod are easily fabricated is this from spare parts or some sort of machine tool work required?We will also have to be sure we all don't bid each other up (Murphy I will hold off on that on if you want it)as there seems to be more than enough to go around.
Dave K

Go for it. I'm not buying any more eight gauges any time soon.

The Egerton- Chubb 10-12-16-20 Multigauge is supplied cased with setting masters to ensure accurate reading from a dial gauge.The gauge is capable of measuring actual bore diameter to .001 inch or less. The gauge has an entry depth of upto 16 inches . The stem of the gauge is grooved to show the correct depth for checking proof diameter. This gauge is or was, the gauge of choice used by the British gun trade.Egerton-Chubb,is/ was located in London U.K.

Even the cheap Skeets comes with a ring gauge for calibration. Chuck, as usual I'm not seeing many bore gauges on eBay with capabilities in the shottygun range; most are 2-6".

jack

The Egerton-Chubb guage is available from Chubb's Ltd 132 White Lion Rd.,Little Chalfont,Amersham Bucks. HP7 9NQ Telephone UK 01494 762370 . I also have a Custom Shooting Products PO BOX 6148 Omaha NE68106 Shotgun bore and choke guage which as served me well since the '80's.Do they still make them? $400 seemed value for money to me.

Note; I would not be too concerned whether the gauge had two or three measurement points. An out of round shotgun bbl is most likely to be oval shaped. If you put in a two point tool & rotate 90° & get the same reading it is "Probably" round. On the other hand if you put in a three point tool & rotate 60° & take another reading & it reads the same it is almost of a certainty round. There is a situation in which a "3-lobed" cam can be built which will with a regular micrometer Mike "Round". The same situation can exist in a hole, but not apt to be encountered in a shotgun bbl. I would feel comfortable taking a measurement with either.