7mm

[Jake Byrd]

Hey Guys,

Does anyone know what a 7mm drill bit converts to in standard(like 7/16 or whatever)?

Thanks a lot,
Jake Byrd

 

[Fred in NC]

Jake, look at the table in the home page reference files:

http://www.penturners.org/content/HUTDrills.pdf

7 mm drill = .2756"
"J" drill = .2770"
9/32" drill = .2812" (too much bigger for my taste)

 

[Jake Byrd]

Thanks Fred, by the way, did you get my email?

 

[BogBean]

Hi Jake,
I use a 9/32 for 7mm but I also use Gorilla Glue to glue in the tubes because it expands. 9/32 is .2812 and 7mm is around .2770.

 

[woodpens]

Originally posted by Fred in NC
<br />9/32" drill = .2812" (too much bigger for my taste)

I guess 35/128 is pretty close, eh? [] You still might have to ream it out a little to get the tubes in.

Jake, it is worth buying the drill bit from your pen kit supplier. You'll get your money's worth from it.

 

[Jake Byrd]

I got what they called a Slimline bit and it was WAY to big.

 

[Fred in NC]

I agree with Jim, get the right bit for the kit, and get a good quality one! The tube is not supossed to fit in very tight, there has to be some space for the glue. But NOT too much space!
And that depends on the glue. For epoxy or CA, the 7 mm drill is just right, or you can use the "J" size which is just a hair larger. (1 hair = 2 smidgens)

 

[jwoodwright]

I had read all of Russ Fairfields articles on Pen Making...

Here's what Russ Has to say about 9/32 and Poly:

"The drill bit is a 9/32" Bullet-Point as made by Black and Decker. The "bullet" type bit is used because it is more immune from being steered by the wood grain, and is less likely to drill a curved , crooked, or oval hole than some of the other types of drill bits.

The larger 9/32" drill is used because we are going to use Polyurethane Glue to hold the brass tube in the wood. The Poly Glue expands to fill the void and has sufficient elasticity to keep the finished pen barrels from cracking during use. "

Now, I've tried this and have been very successful.[:I]

 

[KKingery]

I also use the B&D 9/32 for my 7mm kits. Works fine everytime!

 

[woodscavenger]

I don't like the "cracking during use" idea. How oftern is this really a problem? Have I just wasted my time and money on my first 30 pens because I used CA insted of gorilla glue?

 

[jwoodwright]

CA will stress fracture. It's not for anything where you need tensile strengh. Polyurethane actually bonds with the wood fibers and the Foam is part of its strengh. Epoxy is another choice.[]

Not too worry, your pens will be ok. Everyone used CA and many still only use CA....

 

[DCBluesman]

It really doesn't matter how you scuff the brass tubes. It's a matter of convenience. What matters is that you get a surface that is free from dirt and oils.

Most of our tubes are fairly highly polished, minimizing the adhesion surface. Additionally, most are coated with a lubricant during manufacture such that they go through the machinery more easily. They don't oxidize with the lubricant coating and that's why they look shiny and new when they come out of the bag. We scuff the surface of our brass tubes to both add more surface holding strength and to remove the light layer of lubricant. This allows the glue of choice to work more efficiently.

<b>More info than you probably want to know</b>

Glue only works in two ways: direct bonding and contact bonding. In direct bonding you apply the adhesive directly between two surfaces. In contact bonding, you apply a layer of adhesive to each surface, and then the two layers of adhesive are put in contact to stick to each other. Contact bonding is not often used in craft work as the bond is near permanent the moment the two adhesive surfaces touch.

The glues most commonly used in woodworking fall into three categories: water based, solvent based and chemical curing.

Most wood glues are water based and cure through evaporation. They stick best to highly porous surfaces (such as wood) and thus are not a good choice for plastics and metals. Poly and CA glues are solvent based and also work by evaporation. They work best with less porous surfaces such as metals and plastics. Epoxy is a chemical curing glue that involves a physical change when a hardener is introduced to a resin. This is a fast bond, but can be slowed by the introduction of a third chemical to increase the amount of time the chemical reaction takes. Epoxy works well on a wide variety of surfaces.

With all of this in mind you can more easily select the appropriate glue for your need, BUT, regardless of the glue the surface needs to be clean and free from lubricants (other than water).

Originally posted by woodscavenger
<br />I don't like the "cracking during use" idea. How oftern is this really a problem? Have I just wasted my time and money on my first 30 pens because I used CA insted of gorilla glue?

 

[Gary]

Whew! You convinced me...now give me that Gorilla stuff! []

 

[Gary]

Originally posted by woodscavenger
<br />I don't like the "cracking during use" idea. How oftern is this really a problem? Have I just wasted my time and money on my first 30 pens because I used CA insted of gorilla glue?

I wouldn't toss what you've done. But, I would not continue to use CA to glue in tubes.

 

[Randy_]

Originally posted by DCBluesman
<br />.....Poly and CA glues are solvent based and also work by evaporation......

I have read in a number of posts that poly cures by reacting with the moisture in the air or in the glued materials. That seems to be at variance with what you are saying, Lou. What thoughts do you have??

 

[DCBluesman]

In realitym Randy, the two are not at odds. I took the short cut rather than give the complete, text book description. Here's the entire process from a chemist's perspective.

CA or cyanoacrylate is acrylic resin that cures (forms its strongest bond) almost instantly. The only trigger it requires is the hydroxyl ions in water, which is convenient since virtually any object you might wish to glue will have at least trace amounts of water on its surface. Even if the surface does not have water, there is typically sufficient vapor in the air for the reaction to take place. Cyanoacrylate molecules link up when they come into contact with the hydroxyl ions in water, and they whip around in chains to form a durable plastic mesh. The hydroxyl ions and the linking and whipping of the CA molecules releases energy in the form of heat, causing the glue to thicken and harden through evaporation until the thrashing molecular strands can no longer move.

Sorry for boring most of you to tears. [8D]

 

[RussFairfield]

Unless we live in a very humid climate, the inside of a shirt pocket inside of an air conditioned office building will cause the wood to drop in moisture content. That means it shrinks. Most wood will tolerate these changes and a rigid glue is not a problem. Some wood will not tolerate any stresses at all, and it will crack. For these woods, the larger hole and foaming Polyurethane glue is the better choice. If you aren't having a cracking problem, don't worry about it because you aren't using a problem wood.

I was making a lot of Ebony pens several years ago, and was losing 4 out of 5 within a year because of cracking. Not something I wanted to happen to a $100 fountain pen. I switched to the Poly glue and the problem went away.

My favorite Poly glue is the Franklin Titebond. It cures in half the time without using water, and there is less foaming. Less foaming means fewer problems with the tubes floating out of the wood when I'm not looking.

A problem that a lot of people have with the 7mm drill is that they let it get too hot, the hole is drilled in hot wood, the wood cools, the hole contracts and the brass tube is too tight a fit. The 9/32" hole solves this problem. We are only talking about 0.005" here, but it is enough to make a difference..

 

[jwoodwright]

The IAP is like one large tutorial... Open your Mind and you will Learn... []

 

[DCBluesman]

In the good old days (a couple of months ago) I had to take my blanks to my local Woodcraft to drill them. By the time I got them home, some of the holes had closed up until I couldn't insert the brass tube. I went back to Russ's articles and tutorials and started using the 9/32" bit. The problems went away! For the most part, when I run into problems, those articles straighten me out. When I find an issue with no "Russ answer" I come here and get to pick the brains of over 900 pen turners. I'm going to give the Titebond a try when I run out of Gorilla Glue. I'm not having any problems, but if it's good enough for Russ, it's good enough for me.

 

[Rifleman1776]

DCBluesman said &lt;&lt;The hydroxyl ions and the linking and whipping of the CA molecules releases energy in the form of heat, causing the glue to thicken and harden through evaporation until the thrashing molecular strands can no longer move.&gt;&gt;
I just had surgery with an 8" incision that was closed up with CA. I must have stopped whipping and thrashing so my molecular strands could no longer move. It works. My guts ain't falled out yet. [] Is this a great list, or what? Guts and pens in one forum.

 

[Randy_]

Lou:

Thanks for the details about the glue chemistry. Does poly glue work the same way??

 

[DCBluesman]

Polyurethane glues also fall into the category of solvent based glues. They all work through evaopration. The curing process for both CA and PU glues are very similar. While we think of evaopration as being the vaporization of water, in these cases it is the hydroxyl ions in water that accelerate the evaporation of the solvent. When the solvent evaporates, in both cases, a long-chain polymer (plastic to laymen) mesh is created. That's the bonding power.

Originally posted by Randy.
<br />Lou:

Thanks for the details about the glue chemistry. Does poly glue work the same way??

 

[Jake Byrd]

Wow, all this on a post about drill bit conversion. I love it!! Very interesting to.