# What size is a "O" drill bit?



## Squeaky1

I just ordered a pen kit and it needs an "O" size drill bit.  The pen kit also has a letter opener kit which I bought too. It will arrive in 10 days.

I am using a dremel drill so I need to know what size "O" is? Thanks

Being a newbie  I do not have all the drill bits except a 7mm so I am confused on this new drill bit size.


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## EN Pens

O is 8.2 mm. An 8mm bit will probably work and a number of kits are 8mm.
Good luck


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## mredburn

Here is a link to the library article that will help you, I saved it to my desk top and have printed it out and taped it to my drill holder.
http://content.penturners.org/library/general_reference/conversions.pdf


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## its_virgil

I say this not to scold.  Our library here is invaluable and should be required reading for membership acceptance. The reference section has several drill bit size charts. I have a couple printed and hanging in my shop. One is by the drill press and one by the lathe. Oh, and a third by my pen kit cabinet.
Do a good turn daily!
Don

Sent from my Samsung Galaxy 4 using Forum Runner


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## nativewooder

An "O" bit is between a "N" and a "P" bit!:biggrin:


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## Smitty37

If you need an "O" size drill bit...get an "O" size bit.  They are not hard to come by, Your local hardware store might have them and if they don't, you can easily find one on line..

Just for your Information Drill bits are usually sized 3 ways: 
Fractional by 1/64th increments.  
Metric
Number and letter gauge, which include "O".  

You can easily find conversion charts on line by searching for *drill bit sizes *  - 8mm might work but is a tad small however that small difference could almost fall in the manufacturing tolerance of the bit.  O falls between 5/16 and 21/64 fractional sizes - probably neither of them will work.


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## Squeaky1

*Thanks for the Quick Reply*

I printed out that drill bit size list.  Oh was that really helpful.  I guess you get to ask questions,  I feel more confident about ordering new pen kits because I can get pass only  7mm now.  Thanks 



Squeaky1 said:


> I just ordered a pen kit and it needs an "O" size drill bit.  The pen kit also has a letter opener kit which I bought too. It will arrive in 10 days.
> 
> I am using a dremel drill so I need to know what size "O" is? Thanks
> 
> Being a newbie  I do not have all the drill bits except a 7mm so I am confused on this new drill bit size.


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## Dan Masshardt

Woodcraft sells this bit too.


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## New Bill

If you have an iPhone get the iEngineer app. (free when I got it - may still be). It has a drill chart. Very handy. I use it almost daily. 

5/16 = .3125
8mm = .3150
O = .3160
8.10 = .3189
8.20 = .3228


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## Acelectric

I just use an 8mm bit for the O size kits.  Works just fine.


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## Smitty37

Acelectric said:


> I just use an 8mm bit for the O size kits.  Works just fine.


Most of the time it will..but not for all applications.


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