Drilling 12.5 mm hole

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TonyL

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I saw a post about blowing blanks when drilling 12.5 mm holes searched for it but couldn't find it. When of the members recommended a bore bit. Does anyone know about these bits?
 
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TonyL

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I drilled 3 true stones and blew12.5 sections - the 10.5's were fine.

What speed Dan?

Still interested in the bore bit.

Thank you.
 

Dan Masshardt

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I've only done a couple tru-stone so I'm no expert there. Have done that size though. I usually drill around 600, but am experimenting with higher speeds as well. The interesting question is whether it's a size hole issue or a trustone issue What kind of bit are you using?
 
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TonyL

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Some bit I bought from one of our pen vendors (about $10) , but tell me what to buy...I am all ears.
 

Monty

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I believe a set up like this is what he was referring to.
I use one for odd sizes larger that 1/2". I drill first with a regular bit that is close to the size I want, then I sneak up on the final size with a boring bar.

edit in. Haven't used mine on Trustone, just wood, so I don't know how it would work.
 
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Jim Burr

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Is there a good reason you can't drill a blank? It's easy...Chuck the bit, turn on the lathe and turn the tailstock wheel. Add a spray bottle and slow...like 150 rpm and the isn't a problem. Your previous post show you do this all the time.
 

toddlajoie

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I'm guessing that the real issue is likely a combination of the larger hole being drilled, and how the remaining material is supported. As you drill the hole, there is stress being put on the material, trying to twist it in the direction of drilling by the drill bit. At the same time, most blank vises or lathe chucks hold 2 corners of the blanks, effectively leaving 2 corners unsupported, but more importantly, relatively long side profiles of the blank also unsupported, and if the vice/chuck is tightened on 2 of the corners, you are squeezing those sides. Look at the blank from the end after you drill a hole and notice the thin part in the center of the sides of the blank where the hole comes closest to the edge. Think of what stress squeezing two opposite corners causes along those sides and especially at that very thin part. It can quite easily cause the blank to distort a bit, making your nice round hole a bit oval. Add that to the stress mentioned from the drill bit trying to pull the blank in the direction it is turning, and with a hard, yet brittle material like tru-stone, these many stresses can cause problems...

In the end, everyone's general drilling suggestions are key, the VERY slow drilling speed is a HUGE help in reducing the largest source of stress. VERY sharp bits is another big help, and advancing the bit VERY slowly goes another step. But one thing that can be often overlooked, especially when drilling larger holes, is not to crank down the vice/chuck too tight, once the hole is drilled, that is going to squeeze the remaining material. It is important to have the blank held firmly but not squeezed too much. The vice ONLY needs to keep the blank from turning or sliding, anything else is adding to the circus of stress...
 

TonyL

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Thank you Todd(?). I was definitely drilling too fast and holding the blank too tightly in the jaws.
 

MikeinSC

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The only times I've had problems were caused by me. Either from letting the piece get loose or not waiting the 5 seconds it takes for the drill press to stop before getting the piece out while the bitnis still in.
 

TonyL

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I just learned something...I did not know that you are supposed to stop the drill/lathe (wait for it to stop rotating) before removing the bit from the blank. I thought allowing it to continue turning was the way to ensure the bit does NOT get stuck. I have to try this with some less expensive blanks...thanks!
 
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Gotta weigh in on this issue with yet another consideration. Heat generated by the drilling process is normally not an issue with a wood blank (I said NORMALLY). Somewhat more problematic with acrylics, but manageable. Tru-stone, however, seems to generate a lot more heat when drilled. At the same time the material seems to soften considerably as it heats up. A perfect storm for a blowout.
 

flyitfast

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With Truestone heat and speed are your enemy!! Drill slowly with some kind of lubricant - water, PAM, etc. Drill a little bit, retract the drill, walk away and do something else for a few minutes, and then come back and repeat the process until you have made it through the blank. Heat will melt Truestone. Also the heat rears its head again while you are cutting it, especially when making the final cuts as the material gets thin. They sure do make a beautiful pen though.
gordon
 

TonyL

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Gordon..... I experienced exactly what you stated especially with darker tones.
 

tgsean

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I thought I should just add a technique that Old fox told me to try for some of his pine cone blanks, now I use it all the time, and it really works well. Its very simple, but yet so effective. I agree with all the points made so far, they are all important and I practice all of them but with this one additional trick. After cutting the blank, before actually drilling, cover the opposite end of the blank with masking tape all around and the bottom as well. I found this really helps keep it together. Of course not without all other tips that have been mentioned already.
 

MikeinSC

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I just learned something...I did not know that you are supposed to stop the drill/lathe (wait for it to stop rotating) before removing the bit from the blank. I thought allowing it to continue turning was the way to ensure the bit does NOT get stuck. I have to try this with some less expensive blanks...thanks!

If a bit gets stuck I will turn back the chuck by hand. I'll then wait until it all cools down and ream out the hole real quick but only if the tubes don't fit. If the tubes fit, the blanks don't go back to the drill press.
I've not messed up any blanks by waiting but have messed up more by not.

Anything that is acrylic based or resin infused I drill in pulses to clear out chips and keep heat to a minimum. If it gets hot, I go stare at my phone for awhile.
 

toddlajoie

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Excellent comments on the heat issue, something I didn't get into with my post, but with difficult materials there are a LOT of factors coming to play. It's important to note that if you have a good strait alignment, and are drilling a clean strait hole, you will be generating heat even when you are not drilling, as long as the bit is in the hole while the blank is turning (friction on the sides of the drill bit...) The slow speed is your best defense against this, as well as not backing the bit out with the lathe spinning (sometimes you need to hand turn the blank to make it easier to back out if it is a nice tight fit..) PAM is an excellent tool also, works better than water, but be sure to clean the blank well before you glue up, cause I've heard that can affect the glue :biggrin:.
 

Lenny

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Never drill through the blank. Drill to the depth of the tube plus a little, trim back to the hole. Usually blowouts happen when the bit breaks through the other side.
 

RKB

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What a great thread. I know the library has lots of information and have read many of the entries, but sometimes it's so much better to just ask for help and advice. The library is static, however we are not and methods, tools and materials change and evolve. This is how we get better.:biggrin:
 
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mmyshrall

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Not static? That means we are DYNAMIC. I love it! Wait till I tell my wife!

(uh, not trying to be a jerk, Rod - engineer's attempt at humor)


Careful there, Ted. My SWMBO would tell me "Great, here's more to-do items for you since you are so dynamic. Shouldn't be a problem, should it???" :eek:

I watched my dad fall into that trap repeatedly... :frown:

Oh well, I look at as a chance for lively marital discussion... :biggrin:

Michael
 

sbell111

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I drill primarily with a drill press. My drilling method always comes down to this:

  • Sharp bit
  • Blank should be clamped down securely, but not too tight or you will crush it
  • Advance the bit slowly
  • Be mindful of the chips being ejected. If the bit clogs, badness will happen.
  • Heat is the enemy
  • You don't need to drill through the entire blank in one shove. Back out the bit to ensure that the flutes aren't getting clogged and to let it cool off.
 

MikeinSC

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I've found that I've been able to feel when the bit is close to coming through the end. When it gets to that point, I back off how fast I'm pushing through the blank and take little bites. 9 out of 10 I come away with a near perfect exit wound. That other time might be slightly large but the blanks are cut slightly longer to accommodate for any exit damage.

I don't have access to a disc sander but if I did, that would be used to square off the blank. I suspect that many of us don't have a disc sander either. That easy adjustment of slightly longer blanks saves me room by not having an extra piece of equipment and money too.

But someday that could change.
 

triw51

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Great post Todd, I would like to add one thing is backing out the drill bit ofter to keep the hole clean. When I started I had a few blow outs and a friend showed me where the chips had caused the blow out because of the build up od chips.
 

jsolie

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I keep a spray bottle of water handy for when I'm drilling plastic or similar media. I'll spritz both the hole being drilled and the drill bit to keep things cool.

Since I've started doing that, I've had a very good drilling experience. Plus I slow things down (either on the drill press or the lathe), and only drill a little bit at a time. If I'm drilling a big hole (12.5mm), sometimes I'll pre-drill. If the material looks like it might be kind of chippy, or pretty hard, I'll pre-drill.

With wood blanks, I'll pick the speed of the lathe or drill press up a bit, but still drill kind of slow (slow feed rate). And no water. I wouldn't want the wood absorbing some moisture and swelling, which could cause adhesion issues when gluing in the tubes, or run the risk of cracking.
 
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