Acryilc Blank Drilling ???

[7miles]

Ok, folks hope you can help me out here. I thought I would try out my first acrylic pen today. Got all ready to rock. Had my 3/8 118 angel bit chucked up in the drill press. Speed was set low, to the tune of 540, not as low as it could be but it should work. Alright moving forward we are centered and ready to drill. Went at this, very slow I was getting nothing but chips. No melting at all so I knew it did not get hot, and i cleared the chip very often to prevent build up. I thought cool this is going good.
Then it happened just as I came thru it creaked...

I said ok, the only thing that I think I could of done better was to drill from both ends. So I went about a 1" in and flipped it over to drill the rest of the way. Was not worried about the line up, like I said was centered. However just as I joined the hole together it creaked .

Need I say, I was not pleased.

What did I do wrong here??

If someone has some hints I would be greatful.


Thanks

 

[DaveM]

My personal method for drilling acrylics is to set the blank up just a smidge longer than the pen. (Not possible with every style. This way, I don't have to drill out of the end of the blank. I just saw off the very end after I have drilled the hole.

If I can't do this with both halves of the blank, then I set the blank firmly against a waste piece of hard wood and drill through it into that. It isn't perfect, but it helps. I read one guy who actually glued a piece of scrap acrylic to the end of his blank if he had to drill through. I haven't tried it, but it might work.

I keep the speed low, the pressure light, and I only take a sixteenth or so at atime before backing out and clearing chips. Just a small bit of acrylic on the flutes of your drill bit can create havoc when punching through.

These are the things that work for me. I hope they help a bit.

Dave

 

[mrcook4570]

Don't drill an exit hole. Cut long, drill to depth, cut off.

 

[gerryr]

I probably don't drill acrylics like anyone else, but I drill at about 1200rpm and I drill pretty fast. Especially on blanks that are really translucent, I want the drill bit out of there as quickly as possible. But, I have a block of wood under the blank and I keep my drill bits very sharp. I rarely drill more than three acrylic blanks without sharpening the bit again, and splitting the point.

Did you have a waste block underneath the blank? Was the drill bit razor sharp? Those are the two major culprits when it comes to blowouts with plastic.

 

[7miles]

Thank guys, I 'm sure with the tips I will get.

The bit was very sharp just rolled of the drill doctor.

I did not have block under the blank, I will try that.

I also thought about cutting the blank long, drilling it then
cutting to size.

I'm sure that one of these will work.

Thanks

 

[maxwell_smart007]

Yep, just did the SAME thing myself yesterday.

Tried putting a sacrificial block below, and drilling from both ends, and clearing the chips, and it turned out fine.

 

[rherrell]

You should be getting long strands and not "chips". Sharpen your bit and up the speed a little.

 

[polarbear1]

If your drilling from both ends and it's cracking it does not sound like blowout. Is it possible the clamp your holding the blank in is too tight? When you drill out the center it makes one of the sides weaker and then cracks, I think that has happened to me before, some of the acrylic blanks are not as well made as others.

 

[Paul in OKC]

Cracking is still possible when drilling from both ends. The problem occurs (mostly) when the bit exits the blank, whether in the middle or the end. I always use a scrap block under the blank. Works 99.9% of the time. You still need to be aware of when the bit gets to the bottom and try to ease it through with smaller bites.

 

[Mikey]

Quick question.

When Acrylic is mentioned, is this commercial acryic from Craft Supplies or Berea, or PR that was hand poured from any number of sources?

I have found that the generic term for all plastic or PR blanks is Acrylic and the exact material does matter when trying to drill properly. Commercial blanks from CSUSA or Berea drill easily at that speed and you will get ribbons of material ejecting. I've never had a crack or blowout with any of those blanks. PR on the other hand will not product the same ribbons for me and if I drill through the PR, I get a blowout every time. The only way I have ever been able to get a decent blank drilled is to make the blank long, drill almost through, then trim the blank to length on the saw to expose the full size hole.

 

[7miles]

Both of my blank came from woodturningz.com

 

[rickstef]

Are you using a regular bit or one with a pilot or bullet tip, like the Colt bits from woodcraft?

I prefer to use the pilot tip bits, as they allow for cleaner entry, and exit on the blank, have not had a single blow out yet(knocking on wood)

Rick

 

[ed4copies]

Originally posted by 7miles
<br />Both of my blank came from woodturningz.com

Acylester is relatively brittle PR.

Don't drill through. Cut off the end, their blanks are long enough to do this with every pen I have made (I don't use these for closed-end, but you won't drill through a closed end, anyhow).

Yes, you CAN drill through without blowing out the blank - SOMETIMES!!

But, Why try??? Your failure rate will be high.

 

[RONB]

I drill all of my blanks, wood or acrylic on the lathe.The best thing I bought was a Jacobs chuck for the tail stock end. Works great with lots of control on the feed rate, which seems to be the culprit when exiting a blank.Everything is centered also.There are lots of ways to skin a cat.[]

 

[fuzzydog]

I do much like RonB. I mount the entire blank in jaw chuck on the head stock, the proper size drill bit in a Jacobs chuck on tail stock and begin drilling. I mark the outside of the blank with the length of the brass tube and once I've drilled past that point I cut that section off, giving me a piece with no blow out. Then continue drill the second tube if you have one. This allows me to have very close grain match both above and below any center band.
David

 

[jhs494]

In the Library section of the IAP forum, Ed Davidson has many videos.
One titled making a Sierra Pen. It shows his technique on acrylic, he does not drill thru, he drills short and cuts off the end on his bandsaw.
I just watched this video lastnight and felt it was very helpful.

 

[sparhawk]

I had drilled a few blanks of acrylic with no problems just a block of wood at the exit end to help with blowout. Then came home with one of the new blanks from woodcraft and crack;there went the blank. so now i clamp the balenk in my vise with a block of wood at the exit end,and clamp 2 blocks of wood together on either side of the blank that is open from the vise. All four sides are clamped and havent had any problems since. (Yeh I know i need to get a drill press or another chuck for my lathe but right now the "eyeballing it" method is working ok. Maybe Christmas?

 

[thewishman]

I drill those acrylester (and all other materials)blanks on the lathe at 500 rpm. I drill all the way through the blanks, but will usually wrap the far end (exit end, on the outside-not bottom of the blank) with electrical tape to hold it together. The chips build up fast on that material, especially near the end - you can hear and feel when the flutes get clogged.

Good luck. We've all blown out a few in the learning process.

Chris

 

[jwalt191]

I drill my acrylic blanks (not PR blanks) between 1100 & 1720 rpm. I regrind my drill bits to a 135 degree spit point. As I am drilling I also keep the heat down and lubricate the bit with a bit of soap mixed in water. I have made somewhere between 90-115 acrylic pens in the past couple of years with less than a 10% failure rate. When I do blow it out, it is usally quite spectular, last christmas I actually broke 2 drill bits in 1 style of acrylic blanks from WC.

I have quite a few pictures on my web site.

Hope this helps.

Jim Walter
www.jilly-bella.com

 

[byounghusband]

I have done a dozen or so Acrylic blanks. All from Beartooth Woods... I drill high speed and do about 1/8" to 1/4" at a time to clear shavings. I use a scrap piece of wood at the bottom and have never has a crack or blowout. The only issue I ever had was the one in my post yeaterday where I think I left the bit inside the blank too long and melted it around the bit.[:I]
In two years of turning, I have had maybe two blanks turn out bad, regardless of material. But I may have jinxed myself with this comment....[8]

My thought is you might be going too slow. But YRMV.....