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Drill pen blanks? (Read 454 times)
 
Glenn Jacobs
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Drill pen blanks?
May 21st, 2017 at 11:59am
 
HELP!! I am trying to drill acrylic pen blanks. Have 7 mm drill bit (new) and an accurate holder for the blanks. At what speed and rate should I have the drill set for? And why does the drill want to wonder?

Glenn J.   Angry
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Ed Weber
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Re: Drill pen blanks?
Reply #1 - May 21st, 2017 at 3:38pm
 
Speed depends partially on what type of tip the bit has (special plastic drilling bits) as well as the material to be drilled. Without knowing what type of bit you're using, I'd say 1800 - 2000 rpm is a good medium speed for acrylic.
I can't really speak to the wandering, there may be imperfections or in consistencies in the material letting the bit follow the path of least resistance.
good luck
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Grant Wilkinson
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Re: Drill pen blanks?
Reply #2 - May 21st, 2017 at 7:54pm
 
As Ed said, much depends on the bit you are using and the material you are drilling.There are many different acrylic used in the commercially available pen blanks. Generally, though, I would go even slower than Ed. I drill most acrylics at something less than 1000. Also, I back out every 1/4" or so, and fill the hole with a water/alcohol mix to keep the acrylic from melting.
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Grant Wilkinson
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Steve Kniffen
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Re: Drill pen blanks?
Reply #3 - May 21st, 2017 at 8:54pm
 
I drill wood and acrylic on the lathe using pen jaws to hold the blank.  I drill at 400 rpm or less, usually around 300.  I back out every half inch and clear the swarf from the big.  I do not use any cooling fluids and have no trouble with wandering bits.

When I did use the drill press to drill blanks, I had it on the lowest speed - around 400 rpm I think.
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Ed Weber
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Re: Drill pen blanks?
Reply #4 - May 21st, 2017 at 9:47pm
 
I should mention that I was talking about a acrylic point bit. These are usually a 60 degree included angle (like a pencil point). Brad point bits and the similar pen makers bits are usually used at a slower speed 1000 - 1200.

EVERYONE seems to drill blanks differently, obviously I'm no different in this case.
Some drill at 400 rpm, some drill 1/4" at a time, and so on.
Acrylics can be tricky, too slow with excess pressure can cause heating and melting, too fast with a slow feed rate can cause heating and melting.
Know your material as much as possible and read what the bit manufacturer indicates for speed, other than that, it experiment time.
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Re: Drill pen blanks?
Reply #5 - May 21st, 2017 at 10:10pm
 
Glenn, I drill at slower speeds.  No readout of speed, but estimate in the range of 300 rpm.

Wandering goes down when I make a starting dimple with a machinist centering bit or the long point of a skew.  The bit starts on center and tends to stay on center. 

New bit is usually, but not always centered and sharp.  Had one that had the point way way off center.   Brad point is not a favorite for me, especially with acrylics.

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Glenn Jacobs
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Re: Drill pen blanks?
Reply #6 - May 22nd, 2017 at 12:30pm
 
Thanks for the ideas. After I posted this, I went back out and tried harder! I increased speed and reduced feed rate, ,backing out and letting the blank cool off before continuing on. this helped. seems no matter what I tried, I got melting. I kind of like the idea of coolant, just don't like the mess it causes. Will look at getting a "plastic" drill to do the rest of the blanks I have.

Thank you all for the input.

A less frustrated turner,
Glenn J.
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Re: Drill pen blanks?
Reply #7 - Jun 1st, 2017 at 2:11pm
 
Glen

I only drill down 1/2" at a time and bring it back up to eject the shavings or they will plug up the flutes and cause it to get hot or blow out the blank or any number of things.  Also when I used a drill press I only did so at 250rpm and I remember Berry Gross said the same thing.

When drilling to fast it will melt the plastic.  When I turn them on the lathe I go as fast as the lathe will go or 2000 rpm or more but when sanding I go 500 with water to keep the heat down and so it will sand better
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Tom Coghill
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Re: Drill pen blanks?
Reply #8 - Jun 1st, 2017 at 3:17pm
 
For any type of acrylic or plastic or other material that is not organic, one should be very mindful of the temperatures.  This would apply to drilling, sanding or even riding the bevel of a spindle gouge.

With acrylics as with UHMW materials, I avoid scraping.  Rather I favor cutting with a gouge or skew.  The acrylic, much more than UHMW plastic, can chatter and/or chip.

Keep it cool and take small slicing cuts  Thumbs Up
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Glenn Jacobs
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Re: Drill pen blanks?
Reply #9 - Jun 2nd, 2017 at 11:30am
 

for me acrylics are not fun! They do look nice when finished, but getting there is going to be a journey. So far have made 3 pens from acrylic and not happy with any of them. I will take the information shred here and apply it. Will get back to on my results.

Thank you for the instructions and patience.

Glenn J.
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Ed Weber
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Re: Drill pen blanks?
Reply #10 - Jun 2nd, 2017 at 12:28pm
 
Glenn, good luck.
My only advice is to use a bit "designed" for the product you're drilling.
Many people have had less than good experiences using wood or steel cutting bits.
Bits for plastics are ground much differently and are less aggressive. Using the correct bi, running at the correct speed will reduce the need for peck drilling.
Multimedia File Viewing and Clickable Links are available for Registered Members only!!  You need to Login or Register for drilling acrylic sheets, but the main principals are the same.
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