3/8's Tube Trouble

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BillyBoy63

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Joined
May 14, 2017
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54
Location
Heyworth IL
:eek: I have a problem when I go to make a pen using a 3/8's tube
when I use the 3/8's inch bit the hole ends up being to big you can see to much day light between the blank and the outside of the tube .
Being new to turning the bigger tubed pens what size bit should I use
to get the right sized hole
BillyBoy63
 
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There could be other things causing the oversize hole.
However, I generally measure the tube OD and find a bit that is about .004" larger, or around that.
 
Hmm, haven't seen that problem (yet). First, two questions - How do you drill the holes, and have you measured the tubes and the bit for correct size? Second, if it's not a huge gap you might use Gorilla Glue for the tubes since it expands as it cures.
 
Maybe, try a different 3/8 bit - assuming you haven't tried that. Would you mind sharing a few of the kits that this was affected by?
 
Another simple solution:

1. get a set of good metal calipers from Harbor Freight
2. measure the outside of your tube
3. look at a drill chart such as this one - http://content.penturners.org/library/general_reference/drillchart1.pdf
Go down the chart until you find the size closest to the tube, but a smidgen larger;
4. look for a bit that is close but larger than the tube

THAT SAID, it seems like you may not be using proper drilling techniques. Something seems loose. It is also possible that you were given the wrong bit. If you are sure of the bit size, then the problem is with either the drill or drilling technique.
 
Check out drill bit sizes using this chart:

Drill Size Conversion Table

and select (and buy if you have to) a drill bit smaller than 3/8" and about 0.005" bigger in diameter than the measured brass tube (with digital calipers .... buy them also - $25 - and you will use them a lot)
 
William; This comes up quite often in the forums. I often find the sizes of drill bits that give me the best fit are NOT the ones on the instructions. The drill bits specified are the closest most common available size.

I have a 115 piece drill bit set ($50) and a 25 piece metric set. When starting on a new style/model, I drill a hole that is smaller than I think is correct. If the tube doesn't fit, step up to the next size larger until the tube just fits. Then write down that drill bit size on the instructions for the pen. As Hank and others have commented, go and download a drill bit size chart from the library

Sometimes there is a difference in the drill bit needed for wood vs synthetic. Just my OCD showing up!

Roll your drill bit on a smooth flat surface to make sure it is not bent.
Drill no more than 1/2" at a time. All the other suggestions are good ones.
 
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Hank's post reminded me - If you register for a free account at Starrett, you can order free literature. I have their pocket - size Decimal and Metric Equivalent cards and a giant wall poster of the Inch/Metric Tap Drill Sizes And Decimal Equivalents. Great reference material!
 
Most of the time I use the lathe but sometimes I use the drill press.
I didn't not measure the tube I have done gear shift and bolt action these are the only two I have made
I'm learning I have done most of my pens / letter openers using 7mm
I didn't know there would be a big difference I just went off of what the instructions told me.
BillyBoy63
 
BillyBoy63 said:
Most of the time I use the lathe but sometimes I use the drill press.
I didn't not measure the tube I have done gear shift and bolt action these are the only two I have made
Click to expand...

Lathe - drill press....same results with both? Try a different 3/8th bit if the results are the same. Can I ask why are you using to different drilling methods. If one technique is consistent...stick with it.
The gear and bolt are good kits to work with. (single tube).
If you are lathe drilling is the head and tailstock centered?
 
If the bit is wobbly (usually due to a bent bit), the hole may end up being bigger than it should. Also, if you are holding the blank too tight in the chuck/vise, you could end up with an oval hole (this is especially true with acrylic blanks and thin-walled blanks).
 
Drill Bits

The times I used the drill press was before I got my pen jaws for the lathe
Now I use the lathe because I have better control of what is going on and it is centered better because when I used the drill press the 7mm holes would not go through straight
BillyBoy63
 
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