# whats the outside diameter of a 7mm pen tube?



## Krazekajin (Jan 5, 2015)

I don't have a set of calipers. What is the outside diameter of a 7mm pen tube?


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## JD Combs Sr (Jan 5, 2015)

Should be about 0.268".


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## ed4copies (Jan 5, 2015)

JD is EXACTLY  correct!

Which points out one of the inaccuracies of the terminology that is accepted in penturning.  We refer to the tubes by the size hole that is suggested.  

7mm=.2755"--the size of the hole.
The tube is .268" OD

This is fraught with danger, since the INSIDE diameter of tubes is critical so that all the parts "press fit".  But, we never refer to the actual size of the tube.  Is PennState's 7mm the same as CSUSA's 7mm??  When I made pens, the answer to this was "not exactly".  I don't know now.


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## nativewooder (Jan 5, 2015)

You can find all sorts of info like that in the library.  Look up at the top of the page.


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## ed4copies (Jan 5, 2015)

nativewooder said:


> You can find all sorts of info like that in the library.  Look up at the top of the page.



You are absolutely correct, Barry!!  But be careful, as CSUSA and Dayacom continue to look for cheaper sources, the published sizes can and will change from one shipment to the next.

The Junior Emperor used to take the nibs from the Jr. Gent or Jr. Statesman, even the Jr. Majestic fit.   I just had a customer who wanted to switch out, so I tried them all---NONE with a Rhodium plating fit!

This is likely to change often, before they standardize on one supplier, again.


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## walshjp17 (Jan 5, 2015)

ed4copies said:


> 7mm=.2755"--the size of the hole.
> The tube is .268" OD



Am I missing something here?  How can the OD be smaller than the ID?


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## ed4copies (Jan 5, 2015)

The point is* a 7mm tube is NOT 7mm!!*

The HOLE you drill is 7mm, so quite obviously the tube can't be that size.  But that is the "industry lingo".  I would love to see this change.


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## walshjp17 (Jan 5, 2015)

D'oh!


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## Wildman (Jan 6, 2015)

Harbor freight always has their digital calipers on sale below $20 check current flyer.  They measure in mm’s and fractions of an inch. Bring a pen tube with you and try before you buy!

Also find a drill bit size chart here in the library or on line and print it. 

Learned the hard way not all 7mm exactly 7mm could be more or less in thousands of an inch.  Would think either 7mm 0.2756 or wire size J 0.2770 drill bits should take care of any 7mm pen tube.  Then you run into those tube somewhere in between.

Learn this dealing with two different PSI resellers.  Back then did not know the big three major venders and their resellers.  Today not sure who sells what!


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## Brian G (Jan 6, 2015)

Out of curiousity, I measured the OD of "7 mm" tubes from different styles of PSI, Dayacom, Berea, and an unknown origin. I used a digital caliper. All 20 tubes that I measured were 0.265" OD.

I don't have a point. I was just curious.


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## Wildman (Jan 7, 2015)

How we measure, differences in one digital caliper from another, or type of caliper used, supplier of kit components all can affect reading you see and I see. 

Hopefully only talking about thousands of an inch or .268 minus .265 equals?  Or 7mm drill bit  drill bit chart says .2756 and after measuring your drill bit with calipers and reads .2755 is there a problem?


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## Krazekajin (Jan 8, 2015)

I feel a bit dumb.  Lol.  My post came from the fact I was thinking that a 7mm tube was the inside diameter.  Did not even think about the fact that I use a 7mm drill.  

I am wanting to make some arrow pens and was looking for the right size arrow that a 7mm fits best in.


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## loydstuts (Jan 11, 2015)

Does anyone know what the circumference of a 77mm tube?


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## ed4copies (Jan 11, 2015)

Diameter (.265") times 3.1416 (pi)=.8325" for a SEVEN (7) mm.

IF you really mean 77 mm, multiply .8325 times 11


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