Drilling Acrylic Blanks

[PenTurner]

Hello To all, I am new to this site, but I have done some pen turning, I purchased acrylic blanks and when I try drilling them I am sucessful until the very end bit, at that point all my patience in drilling is undone, the bit grabs and crack!! another blank hits the dust. Can someone give me advice on this, I have also had this happen when drilling Black Palm. thanks. Amos

[lubbing5cherubs]

I was having this problem too but now I make sure it is square and also make sure the blanks not getting too hot. I also place a round of insulation tape around the bottom and top of blank to support it while the drill goes through
as added support
hth some
Toni

[Jude A]

What speed are you using on your drill press?? I assume you are using a drill press. I usualy use the slowest speed. With acrlics you have to be very slow and back out alot, the same with red palm. Both will do as you know, crack or blow apart. Another thing is to use a brad point drill bit this will help. I allways get a little blow out at the bottom of my acrlics kinda like a pit around the hole so I add a little more when size the blank.
So all I can say is go slow/ back out alot/ clean debris off everytime you back out. Hope this helps.

[PenTurner]

Thanks for the advice, I will get a Brad point drill, also tape the ends, I am already making the blanks longer and using slowest speed on drill press , Amos

[floobyduster]

Standard metal working drill bits are not suitable for drilling plastics (acrylics) as the angles they are ground to are wrong. You can modify a standard drill bit to give a much better result. Speed of drilling, pressure and lubrication are also things to watch for.

Do a search on the net for more info. Here are a couple of pages to start with:
http://www.plasticsmag.com/features....sue=Sep/Oct-01
http://www.wingsandwheels.com/Installation.htm

[soundman]

I have no problem with standard twist bits on acrillic. actualy I find them better than brad point.
BUT... they must be sharp.
It is true that there are better grinding angles for acrillic but standard grind will work fine with care..... they must be sharp.

All plastics vastly exagerate all drilling method faults so you must be reightous.

I find the right speed is the key.... too slow is a problem too.

the blank must be firmly held and a firm preasure onto a backing block helps.

stop and wait for cooling and very easy does it near the end. some colours are more brittle than others.

If you have a bust out think about cutting ans shutting the blank with epoxy.
part off the gammy bit and glue up a bit of same colour scrap or acontrast like black, or thats another key ring

cheers

[PenTurner]

Thanks again for the info, The drill bit was brand new, what speed would you suggest as a ball park figure? Amos:confused:

[goodwoody]

Plastic bits should have a zero or negative rake angle. They scrape and dont cut.

[Skew ChiDAMN!!]

With a brad point on the lathe, I drill @ 750rpm for resin, 1100 for acrylic. They're the two lowest speeds on my non-var pen lathe. [shrug]

For non-timber blanks (inc. corian) I actually prefer to use my 5-speed drill-press running on the middle pulleys... no idea what RPM it is. I don't use my press-vice though, instead I use a home-made clamping jig that supports the end of the blank to reduce chip-out. ie. the bit drills through the blank into the timber.

[Touchwood]

I try drilling them I am sucessful until the very end bit, at that point all my patience in drilling is undone, the bit grabs and crack!!

Know the feeling well .. I am told that I need to get a spray bottle and keep spraying while drilling .......

a 4x2 teacher (AKA wood work teacher) says it is to do with plastic not getting rid of the heat fast enough and so I must go slower and keep it (and me too I think ) cool!

I have managed to reglue broken with with 2 part 'poxy glue and keep going .... otherwise they make good key rings!

JD

[Froggie40]

G'day all,
As you are all aware I love acrylics, I have made about 50 of them.
I use a parabolic flute drill it is by far the best drill bit I have used on my acrylics but there isnt to much but be very careful and slow down as you punch through the other end.
Let the drill bit do the work and take it easy as you go through.
I havent had any self distruct since I started using the parabolic flute drill.

Regards
Brett

[PenTurner]

Thanks, tried the suggestions last night with success, used a brad point on slow speed, taped the ends, poured in a little coolant, and easy as she goes and SUCCESS The only downer was that when I turned the pen the end of the pen was not in the bush (i thought it was) so after a beautiful finish it looked like I had tuned a dogs leg