# Sierra Pens Tubes.



## Mather323

I have found that using a 10.5mm drill bit makes a much better fit than using the 27/64 drill bit that they recomend much better fit, to much slop.


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## Mack C.

Mather323 said:


> I have found that using a 10.5mm drill bit makes a much better fit than using the 27/67 drill bit that they recomend much better fit, to much slop.


 Hi Mather; I assume you meant to say 27/64 drill bit. I don't recall having a problem with my Sierras, but there could be some merit to your suggestion since the 10.5 mm bit is about 8½ thou. smaller. 

Are 10.5 mm bits readily available?


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## leehljp

On a few pens I have used the 10.5 but I usually go back to the 27/64. The 10.5 is too tight in some cases - I have drilled a 10.5 hole is some blanks and the fit was so tight for some reason that the tube was difficult to get in. In cases like this, it means that there will be too little space for glue as glue will be pushed out, or the glue will end up inside the tube.


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## Mather323

It could be the big bench top drill press that my dad bought at the state fair years ago, I am sure that he did not pay over $5 dollars for it.  Ha Ha   I have noticed that when drilling the acrylics and acrylesters that I have seen the biggest difference.  Both drill bits are colts, I guess that I could even have a bad bit, since the 10.5mm drills so nice and the 27/64 looks like a hog walked thru it when I am done drilling.  Any recomendiations for a new drill press?    I found the 10.5mm drill bit at Craft Supply USA for $14 dollars.   Mike


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## Mack C.

Mather323 said:


> Any recomendiations for a new drill press?
> 
> 
> 
> Hi Mike; I think the big question is what's your budget. Floor model or bench top?
> 
> I've got a Delta Model 17-901 floor type that has served me for years. I do all of my blank drilling on the lathe now!
Click to expand...


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## randyrls

leehljp said:


> On a few pens I have used the 10.5 but I usually go back to the 27/64. The 10.5 is too tight in some cases - I have drilled a 10.5 hole is some blanks and the fit was so tight for some reason that the tube was difficult to get in. In cases like this, it means that there will be too little space for glue as glue will be pushed out, or the glue will end up inside the tube.




To join the thread;  10.5 drill bits are commonly available in metric sets that go from 3mm to 13mm in .5 mm steps.

Hank;  I prefer to drill my blanks with a snug, just sliding fit.  I many times use a different drill bit than the one recommended.  

Twist drill bits have a tendency to "unwind" and drill a hole from .001 to .005 larger or smaller depending on the material, drilling speed, and whether you are enlarging a hole or drilling a hole in one go. 

This is only my opinion and understand the differences will be less than ten thousandths inch.  
Wood drills a smaller hole.  Acrylic holes will be slightly larger.
Slow speed drills a smaller hole.  Faster drills a larger hole.
When enlarging a hole the hole will be smaller than drilling in one go with the same bit.

I use a VS milling machine to drill holes.  It is very accurate and drills holes dead on!


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## maxwell_smart007

Seems like too tight of a fit will remove all of hte glue!


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## Mather323

Bench Top.


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## grub32

I agree 10.5 mm is much more accurate!! Big difference in size!!

Grub32


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## JimB

I found the same problem using the 27/64. I was getting gaps between the wood and tube and some slop. I used a lettered "Z" bit from my HF set on my last 5 Sierras without any problems. I believe both the "Z" and the 10.5mm are .413 inches. It beats spending $14 on one bit.


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## avbill

First  
the drill size 27/64     = 0.4219
the drill size 10.5mm  = 0.4134  10.5mm being .0085 smaller 
the O.D. of a Sierra tube is = 0.4105  its also 2.4300 inches long. 

a Z drill is = 0.4130 

just the measurements!


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## Paul in OKC

JimB said:


> I found the same problem using the 27/64. I was getting gaps between the wood and tube and some slop. I used a lettered "Z" bit from my HF set on my last 5 Sierras without any problems. I believe both the "Z" and the 10.5mm are .413 inches. It beats spending $14 on one bit.



Same here, letter 'Z'.


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## leehljp

avbill said:


> First
> the drill size 27/64     = 0.4219
> the drill size 10.5mm  = 0.4134  10.5mm being .0085 smaller
> the O.D. of a Sierra tube is = 0.4105  its also 2.4300 inches long.
> 
> a Z drill is = 0.4130
> 
> just the measurements!



10.6 mm = 4.173
10.7 mm = 4.2125

I can get them here but they are roughly $35.00 / $40.00 each!


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## Texatdurango

If my feeble memory is working, I recall about a year ago some of the vendors were including instructions to use a 10.5mm bit and they switched to the 27/64 bit because it was more readily available and everyone was complaining about blanks blowing apart when turning and most found no glue between the brass and blank when they examined the remnants of a blow out.

Do whatever floats your boat but as for me, I'd just as soon have a bit of glue left between the brass and blank after squishing them together.


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## toolcrazy

13/32" _(0.4063) (--0.0071)_
Z _(0.4130) (--0.0004)_
*10.5mm (0.4134)*
27/64" _(0.4219) (+0.0085)_
11mm _(0.4331) (+0.0197)_


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## nava1uni

I have 13" Rikon drill press that is very nice.  I would recommend it.


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