# 1/64th Too Large?



## Tn-Steve (Apr 4, 2009)

Hey Gang,

I'm getting ready to do a Cambridge (Same bushings as the Churchhill / El Grande), and here's the rub..


Berea calls for a 33/64th bit (.5156 inch)
AS calls for a 13.3mm Bit (.5236)
The best I can find locally is 17/32nd  (.5313 inch) (which would be 34/64ths)
When I run the numbers, and measure it all out against the bushings here's what I end up with for the depth of the wood at the ends of the big bushings...

Berea .072 inches of wood at ends
AS .064 inches of wood at ends
Mine - .057 inches of wood at ends.
I know I'm close to the limits, do you think if I epoxy to make sure that I've got good coverage between the tube and the blank, and drizzle a little thin CA the blank to help stabilize it when I get down toward the final dimensions I can dodge a bullet on this one, or should I suck up, wait until I get the 33/64ths bit before I attempt this one?

I KNOW I should have checked the directions BEFORE I left the woodcraft shop that's only 70 miles from the house, but I figured that it would be more exciting this way. (Yea, that's my story, I'm sticking with it)

Thanks in advance

Steve


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## johnnycnc (Apr 4, 2009)

From what I have seen, the thickness on these is dicey, anyway.
My free nickel's worth of advice..get the correct bit.:biggrin:


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## Constant Laubscher (Apr 4, 2009)

I would go with a 13.33 mm the 33/64 is to tight. I had to redo 250 Puzzle kits because of that.


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## ed4copies (Apr 4, 2009)

Save the trip.

Use the SMALLER hole, then use a file to ream it out.

OR sandpaper, attached to a dowel.

Go til it fits nicely, then use gap filling glue (your hole won't be perfectly round)


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## ed4copies (Apr 4, 2009)

IF you are going to make a wood pen, don't make this fit TOO tight.  Remember wood moves (shrinks) and will crack if you make it too tight.


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## wdcav1952 (Apr 4, 2009)

When you do get the correct bit, it will be a 13.3mm, trust Constant and me on that.


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## mick (Apr 4, 2009)

Don't go with the over sized bit....DAMHIKT. Do as Ed suggests and drill the smaller hole and file or sand. I make a fair number of Churchills and one of the holes, I can't recall if its the barrel or cap, is always tight so I wrap sandpaper around a dowel, put it in my Jacobs chuck and sand until I've got a loose fit. There's virtually no wood left on a Churchill barrel. So if the tubes too tight you're just asking it to split when the wood moves.


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## bitshird (Apr 4, 2009)

I wish I'd found a 13.3 mm drill, I've only had a 17/32 bit, I've done about a dozen Churchills/El Grandes, used wood trustone and Ed's alternative Ivory, with out any problems yet. but it does get pretty thin I also use Gorilla glue on all of them, Here is a place that has the 13.3mm drill bits cheap  http://www.wttool.com/product-exec/..._Shank_Silver_Deming_Metric_Drills_WT_Import_ they list the price as $3.50, not sure what their shipping is though, or the quality of the bits,


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## Randy_ (Apr 4, 2009)

Tn-Steve said:


> .....When I run the numbers, and measure it all out against the bushings here's what I end up with for the depth of the wood at the ends of the big bushings...
> 
> Berea .072 inches of wood at ends
> AS .064 inches of wood at ends
> Mine - .057 inches of wood at ends.


Steve: I don't know if you have ever done a slimline or not; but they only have about 1mm of wood on the barrels and you don't ever hear folks worry about how thin they are. 

1mm is right at 0.039" so your calculated thicknesses are much thicker than what is on a slimline. (if your figures are correct) No real need to worry about special efforts to reinforce the wood IMO. 
 
But do pay attention to what has been said previously about tight holes.  They can be a real problem.


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## Tn-Steve (Apr 4, 2009)

Ok, so I've got some pretty strong arguments, from some very experienced people, suggesting 2 contradictory paths. One goes for the 13.3, to allow for wood movement, the other says go as small as possible, and sand to allow for a fit if needed. Both sides make perfect sense, and I am confident are backed up by practical experience. (and I mean this in all sincerity). 

The diameter of the brass tube for the top section is 0.510 (Gotta love a digital caliper, even a non-machinist like myself can get good repeatable reads with it). 

I think that what I will do is distill the pure knowledge that drips from this forum each and every day (everybody got there boots on?), and split the difference in half. I'll get the 33/64th bit (which is just barely over 0.51 and probably too tight), and then use some sand paper on a dowel to get a little bit of breathing room, but not as much as the 13.3 would give me. The Woodcraft store is only about a 1/2 hour away from where I work, so I can pop over there some evening and pick up the bit.

Looking at the bushing it's pretty clear that there isn't a lot of wood left over at the ends when you're done turning the pen. One would almost wonder why this kit wasn't designed with a slightly smaller tube, perhaps someone can shed some light on that issue for me.

Thanks for all the advice and suggestions,

Steve


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## thewishman (Apr 4, 2009)

I use a 1/2" bit and file the hole out just a bit.


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## thewishman (Apr 4, 2009)

The difference in the cap and body are very small. To allow for the nib to fit inside the cap, the cap must be a bit larger. The brass tube is much thinner in the cap which saves a bit of room. 

My problem is that the recommended bit for the body seems too large to me, the tube is too loose and doesn't center perfectly.


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## Randy_ (Apr 5, 2009)

Tn-Steve said:


> Ok, so I've got some pretty strong arguments, from some very experienced people, suggesting 2 contradictory paths. One goes for the 13.3, to allow for wood movement, the other says go as small as possible, and sand to allow for a fit if needed. Both sides make perfect sense, and I am confident are backed up by practical experience. (and I mean this in all sincerity).....


 
I don't see any contradiction at all.  Everyone is telling you that you need a proper sized hole.  They are just proposing different ways of getting there.  
 
When I was working on my pen reference chart, I compiled a little chart comparing recommended drill size with tube OD.  What i discovered,s that the majority of the kits had a recommended drill size that produced a hole that was anywhere from 0.006" to 0.013" larger than the tube OD.  There were a few recommendations where the drill size was as much as 0.019" over; but I suspect those are the kits for which drill bit recommendations have been subsequently revised.  I have not gone back and review the original data since I first put it together.    
 
I think 0.006" is probably a little tight.  That leaves a clearance that is only about the thickness of a sheet of newspaper.  My feeling is that you probably should be looking for holes that are in the neighborhood of 0.01" over.


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## Tn-Steve (Apr 5, 2009)

Randy_ said:


> I don't see any contradiction at all. Everyone is telling you that you need a proper sized hole. They are just proposing different ways of getting there.
> 
> When I was working on my pen reference chart, I compiled a little chart comparing recommended drill size with tube OD. What i discovered,s that the majority of the kits had a recommended drill size that produced a hole that was anywhere from 0.006" to 0.013" larger than the tube OD. There were a few recommendations where the drill size was as much as 0.019" over; but I suspect those are the kits for which drill bit recommendations have been subsequently revised. I have not gone back and review the original data since I first put it together.
> 
> I think 0.006" is probably a little tight. That leaves a clearance that is only about the thickness of a sheet of newspaper. My feeling is that you probably should be looking for holes that are in the neighborhood of 0.01" over.


 
Perhaps my choice of the word "contradictory" was a poor one. :redface: Your posting what you've discovered while you were developing your chart is VERY helpful, I wondered what kind of room you wanted for a "good fit", and that helps out a bunch. Looks like I'll probably go with the 33/64ths and then just use some sandpaper on a dowel as has been suggest to get a fit where the tube can 'fall thru' the blank, but no bigger than it has to be for a friction free fit. That should allow room to let the wood move, but keeping enough wood to work with, and to help minimize any problems with centering the tube in the blank. Plus, I can pick up the 33/64ths bit down in Nashville after work, I suspect that without going on-line like I would for the 13.3, (and buying one thing like a drill bit KILLS ya on shipping). I noticed that the WTTool.com site they have Metric bits (US Made) sized pretty much in 0.1mm steps. Looks like a great resource.

Thanks for the general guidance on "tube to hole" fit. That is something I'm going to copy out and past into my pen note book, because I suspect that it will come in very handy in the future.

Cheers,

Steve


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## TurnaPen (Apr 5, 2009)

I use 13.3mil and 5 minute epoxy to put the tube in place, I also coat the inside before insertion, and there is usually no problems then. Amos


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## jackrichington (Apr 5, 2009)

the best thing I ever did was get a huge asst of drill bits..in metric and fractional..I measure the tube then find bit that is closest..has made my choices easy..


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## bad (Apr 5, 2009)

I just bought a Cambridge pen kit myself and had the same problem. A year ago I picked up a 115 piece drill bit kit so I wouldn't have this problem. Except it only goes to .500" :-( After going out and buying a 33/64 drill bit I ran into another problem. So here's my question to you. What are you planning on using to square the ends of the blank after you get the tube glued in? If you're planning on using a pen mill then you don't have the right size. After some searching around online I found that one solution is to take a tube from another kit such as a cigar, glue that up and turn it down until it's the right size to fit inside the Cambridge tube and use that as an insert for your pen mill. If anybody else has any other suggestions I'd be interested in hearing them.


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## broitblat (Apr 5, 2009)

I don't think the advice you've received is contradictory.  I beleive that if you were to sand the hole until the tubes slide easily, you're going to end up very close to the 13.3 mm.

  -Barry


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## johnnycnc (Apr 5, 2009)

bad said:


> I just bought a Cambridge pen kit myself and had the same problem. A year ago I picked up a 115 piece drill bit kit so I wouldn't have this problem. Except it only goes to .500" :-( After going out and buying a 33/64 drill bit I ran into another problem. So here's my question to you. What are you planning on using to square the ends of the blank after you get the tube glued in? If you're planning on using a pen mill then you don't have the right size. After some searching around online I found that one solution is to take a tube from another kit such as a cigar, glue that up and turn it down until it's the right size to fit inside the Cambridge tube and use that as an insert for your pen mill. If anybody else has any other suggestions I'd be interested in hearing them.




I can make custom pilots for the pen mills. PM me if interested.


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## Tn-Steve (Apr 5, 2009)

broitblat said:


> I don't think the advice you've received is contradictory. I beleive that if you were to sand the hole until the tubes slide easily, you're going to end up very close to the 13.3 mm.
> 
> -Barry


Nod...  Yea, 'Contradictory' was probably a bad choice of words as I posted earlier.  Better to say that there were two routes that both get me to the same place. Think that I'm going the 33/64th and sand route, since I know they have that sized bit at WC.  

Steve W


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## Buzz (Apr 6, 2009)

Depends on how many you want to do.  Sanding out a too small a hole takes time and is a step we should not have to do.  I finished up getting the 13.3 mm.  What sort of a ridiculous size is that?  Makes you wonder about the designers of these kits.


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## skiprat (Apr 6, 2009)

I would try and avoid filing out any hole in a thin walled pen blank. No matter how careful you are, you will ALWAYS make the ends thinner than the middle, and of course its normally the ends that are most vulnerable.


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## themartaman (Apr 6, 2009)

You don't have to use a pen mill. I use the disc on my belt/disk sander with my miter gauge. Works good.


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## ed4copies (Apr 6, 2009)

skiprat said:


> I would try and avoid filing out any hole in a thin walled pen blank. No matter how careful you are, you will ALWAYS make the ends thinner than the middle, and of course its normally the ends that are most vulnerable.



This is an EXCELLENT point!!  

Also remember that wood moves, Resin, not so much.  So, since I build 95%+ resin pens, my tolerances are probably different from yours.

Now, if you switch to resins !!!!!
(Tempting another one to the "dark side"!!)


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## bad (Apr 6, 2009)

themartaman said:


> You don't have to use a pen mill. I use the disc on my belt/disk sander with my miter gauge. Works good.



Doesn't that assume that you've drilled the hole perfectly parallel to at least one of the sides? Not trying to start an argument I'm just asking. I've never done it that way.


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## Sabaharr (Apr 6, 2009)

I first used the brad point 33/64 bit and had to drive the tube in with a hammer. I purchased the 13.3mm but it was not brad point, which might contribute to a blowout if not drilled carefully. Since I now have both I drill with the 33/64 then run the 13.3mm to get the correct size hole. There is practically NO material left if you make this pen with straight sides. I found this out when I made my first Cambridge out of burl and had it explode on me. See my other thread on that subject. Anyway, if you want to use just one bit get the 13.3mm. Mine came from Bear Tooth Woods.
Stephen


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