Drilling Acrylic fail!

[Kengar]

I've tried several drill speeds and the blank is secured well to the press.
I have the depth set to where the bit bottoms out right at the base and then cut the last 1/8 off on the ban saw.
Any advise would be appreciated.

Ken

 

[ed4copies]

My first inclination: Replace your bandsaw blade.

However, the RIGHT answer is: Look at the blank after your have completed your drilling process. Is there a crack running up the side? If not, your bandsaw is breaking it and the above is the correct advice.

IF you see a crack, after drilling, but before taking the end off, sharpen your drill bit.

 

[Kengar]

I'm sorry with my wording this happenes while I'm Drilling the blank.

 

[pianomanpj]

Drill with a slow feed rate, a slow RPM, clear the chips often, and make sure the bit is SHARP!!

 

[walshjp17]

After blowing up too many blanks, I began drilling them on the lathe. I use a dedicated blank drilling chick from PSI, but you can use other chicks as well (long jaws, e.g.).

Put the blank into the chuck on the head stock, turn the speed down to 300 to 400 RPM, put a drill chuck and appropriately sized drill bit in the tail stock and slowly turn the crank. Have not blown out a single acrylic, stone, wood or other material blank since I started doing this 6 months ago.

 

[Kengar]

Thanks, my speed is way to fast! I may just have to go the lathe route.

 

[gbpens]

Use very sharp drill bits and go very slow as you near the bottom of the blank and make sure you have a piece of scrap to back up the blanks as the bit comes through. Cracks tend to occur due to heat build up which is usually related to dull or clogged bits and high drilling speed.

 

[Joe S.]

I glue a bit of scrap wood to the end and drill all the way through.

 

[jttheclockman]

You left alot of details out. You say you are drilling on the drillpress. Is the blank secured in some way that there is no movement??? Does your drillpress drill straight or is there runout??? How fast were you drilling??? Has this happened before??? Are your bits sharp???

When people drill on the lathe what they do not realize is they are actually taking out certain factors such as runout of the drillpress which can cause vibration and movement that does not happen because the blank is secured. In a lathe you do not have this. So follow some of the things mentioned above and you will get it straightened out. There could have been a surface crack in the blank from the beginning.

Now I will get yelled out again for suggesting this topic is in the wrong forum but who am I??? Just my opinion

 

[CharlesJohnson]

In addition to the above, I use several drops of dish detergent in my quart of turning water. This fills the hole every 1/2" inch or so in acrylics. To lube a bit and cool. No rinse after mm. No difference. Thanks to others . Drill press "or" lathe. I have got to follow 2 or more forums to see requests for help and answers? Having fun learning all "I" can remember. But it helps that all questions seem to repeat. Thanks every body. Whether asking or answering, you're teaching us a lot.

 

[Kengar]

Thanks for all the advice. Blank is secure, no run out at least I don't notice it.

 

[butchf18a]

I don't blow out blanks!! Joe S. saved me a lot of writing. All the advice provided is good. The fractures (blowout) occurs as the bit exits the blank. By gluing a scrap on the end of your blank you continue the forces into the scrap and not on the weak portion (the end) of your blank.

While keeping your blank long and stopping prior to going all the way through will have the same effect, it can result in excessive waste on expensive blank. I will glue a piece of backer to any acrylic, poly resin or similar blank regardless of whether I'm using a drill press or drilling on the lathe.

 

[John Doyle]

You are not just a pretty face i think that is a brilliant idea and would solve most problems of drilling failures. I have been wrestling with this problem and how to fix it for some time.
John Doyle (Australia)

 

[pensbydesign]

most times i see this happen its been the feed rate if your pushing faster than the bit can cut you get cracks and blow out, heat will do this also if your not clearing out chips fast enough

 

[Ian Thorn]

I made a jig to slide betwen the bed set to the hight of my blanks witha fence on top L shaped as a back stop jacobs chuck in headstock with bit then slowly feed black to bit clearing often and dont get breakouts ,just another way of doing it that works for me

Ian

 

[KenV]

Thanks for all the advice. Blank is secure, no run out at least I don't notice it.

You can have what a machinist would consider a lot of runout on a drill chuck (drill press) and not detect it with your eyes. The cheaper the drill press, the greater the odds that precision is not part of the package.

The extra length is measured from the point and especially on larger bits needs to be more towards 1/4 inch to assure the point of the drill bit does not exit. Once the tip exits, the chance of a "grab and break" goes up fast.

Many of us have had to learn that a truly "sharp drill bit" is not something one normally finds in a hardware store or in the cheap Asian import sets.

Most every turning club (AAW Chapter) has a few members with skills or gear to sharpen (really sharp and centered tips) drill bits.

 

[Russknan]

Where to get GOOD drill bits

Thanks for all the advice. Blank is secure, no run out at least I don't notice it.

You can have what a machinist would consider a lot of runout on a drill chuck (drill press) and not detect it with your eyes. The cheaper the drill press, the greater the odds that precision is not part of the package.

The extra length is measured from the point and especially on larger bits needs to be more towards 1/4 inch to assure the point of the drill bit does not exit. Once the tip exits, the chance of a "grab and break" goes up fast.

Many of us have had to learn that a truly "sharp drill bit" is not something one normally finds in a hardware store or in the cheap Asian import sets.

Most every turning club (AAW Chapter) has a few members with skills or gear to sharpen (really sharp and centered tips) drill bits.

I realize that this is hijacking the thread a little but, Ken, your post brought back an impulse. I've wanted, for some time, to ask you as a machinist for a recommendation on where to get reasonably straight drill bits. I've been using brad point sets and realize that that prevents me from keeping them sharp on my Drill Doctor. Also, the ones I have seem to have a bit of Daniel Boone in them, in that they tend to want to explore places other than the dead center of my blanks. Russ

 

[ashaw]

I drill only on a drill press. Many because I am in production mode. I run at the slowest rpm on my dp. I also drill a pilot hole 8mm. Then drill with the final drill bit size. It stops the breakage of the blank also stops the oval shaped hole because the bit heats up. When you are using the lathe or dp always go slow. I do use water and dish soap when I am doing a large production run.

Alan

 

[CabinetMaker]

I leave my acrylic blanks as long as I can. I then drill just deep enough for the tube. I use a slow speed and a sharp bit and I have had good luck with that approach.

 

[monark88]

I leave my acrylic blanks as long as I can. I then drill just deep enough for the tube. I use a slow speed and a sharp bit and I have had good luck with that approach.

I do all this with acrylic and tru stone. I mix dawn soap, corn oil, and water and use a lot, drilling 1/4" to 3/8" max between adding mixture.

I've never had a blow out unless I try to hurry the drilling, which I did last summer on a tru stone blank.
Russ

 

[ianjwebster]

My 2c's worth. I had terrible trouble drilling acrylic at first. What worked for me was making the hole in two passes. The first with a bit a few sizes smaller than required. The second the required size. Clear the chips OFTEN and mist the drill bit with water each time to keep it cool. Finally turn the lather off (I drill all my blanks on the lathe using the PSI chuck) when 're-entering' the hole after clearing the chips. I have had a 100% success rate since adopting the above method.

 

[Richard Gibson]

Just looking at your picture, it appears that you are not drilling straight. (The picture shows more acrylic on two side than on the other two side.) I use to have the same problem and solved it by drilling on the lathe instead of my bench drill press.

 

[NewLondon88]

Many of us have had to learn that a truly "sharp drill bit" is not something one normally finds in a hardware store or in the cheap Asian import sets. .

First thing I do with a brand new drill bit is to sharpen it.

 

[NewLondon88]

lots of good advice here.
Two things not to read and go "yeah, yeah.. i know that" are
1) drill slow and clear out the chips
2) Keep the bit cool

Keeping the bit cool is easy enough to check. Grab a scrap blank, start
drilling and after 1/2" remove the bit and hold your fingers on it for 5 seconds.
If you can't, then there's no reason to think your acrylic blank will hold up
to that kind of heat either.

Drilling slow and clearing the chips both relate back to heat buildup.
If the chips are not clearing out of the blank, they tend to hold in
the heat generated by the bit. And every bit of material still in that
hole adds to the friction. And the faster the bit moves, the more
heat is generated. (either in/out or by speed of rotation)

The water/detergent idea helps to reduce friction and dissipate
heat, too. Works very well with non porous materials like acrylic

 

[Donovan]

My 2c's worth. I had terrible trouble drilling acrylic at first. What worked for me was making the hole in two passes. The first with a bit a few sizes smaller than required. The second the required size. Clear the chips OFTEN and mist the drill bit with water each time to keep it cool. Finally turn the lather off (I drill all my blanks on the lathe using the PSI chuck) when 're-entering' the hole after clearing the chips. I have had a 100% success rate since adopting the above method.

Same here I also drill a plot hole first and then the correct size never broke a blank since doing that

Donovan

 

[Kengar]

This is great info, I'm definitely doing severally thins wrong.

 

[PenMan1]

Step 1: SELL you drill press. (you are about 1/4" inch between where the hole started and where it ends up, this is too much "drift", even for a slimline).

Step 2: TAKE the money from step 1 and invest in a dedicated pen drilling chuck and a Jacobs Drill chuck on a taper for the tail stock of your lathe.

Step 3: DON'T look back. Drill perfect holes every time.

Respectfully submitted.

 

[Phillip Kelley]

Too fast...

This happened to me yesterday...I was drilling too fast & my vise was too tight! This morning (5:00 a.m.) I mixed a lot of water with some left over Windex & put in a few drops of detergent, didn't tighten the vise so tight, drilled slower & kept the bit lubricated with a lot of spray "coolant".

 

[butchf18a]

I don't blow out blanks

I've described this in the past. Methodology works well on drill press as well as on lathe as pictured. the blank shown issome expensive Italian acetate which is only .635" in diam. Accuracy is paramount, slow speed and sharp bits, as many others have advised, as it will melt if drill too fast.

In this particulr situation I simply ca glued a piece of dowel rod to the end of the blank prior to drilling. Square blank? Either piece of wood or what else you gonna do with all those cutoffs we all refuse to throw away?

 

[CharlesJohnson]

In this particular situation I simply ca glued a piece of dowel rod to the end of the blank prior to drilling. Square blank? Either piece of wood or what else you gonna do with all those cutoffs we all refuse to throw away?[/quote]


I have been seeing great looking segmented pens that have surely inspired Using up a lot of those nice cut offs. Having fun learning 'and' trying. As I have the time. Thanks for all the great ideas.
"Not bragging!" That would mess me up. I haven't yet had an end blow out. I think that is because at the end I "ALL WAYS" go threw the end "Very" slow!!! No matter what the material.

 

[Hexhead]

I too use a smaller drill bit first. I also use a machinist center drill to start the hole straight. Using a backer board helps even more.

 

[panamag8or]

A related tip, for removing chips... a can of compressed air keyboard cleaner, with the little extension straw. You'd be amazed at the amount of crud that blows out of the hole during drilling.

 

[Gary Beasley]

I agree with using water to cool the bit while drilling, and to clear the hole frequently. A machinist will generally put lubricant on a bit when drilling a hole in metal to help cool, preserve the cutting edge and make a smoother cut. Works the same with acrylic.

 

[low_48]

A related tip, for removing chips... a can of compressed air keyboard cleaner, with the little extension straw. You'd be amazed at the amount of crud that blows out of the hole during drilling.

Only in America would someone pay for a can of "air". Use a drinking straw and your breath and do the same thing, if you don't have an air compressor. All that manufacturing to make the can and ship it, makes that air about as wasteful as I can imagine.

 

[Leatherman1998]

Are you using a Brad point bit. They don't do well with plastics

Levi Woodard
Sent from my DROID RAZR using Forum Runner

 

[randyrls]

A related tip, for removing chips... a can of compressed air keyboard cleaner, with the little extension straw. You'd be amazed at the amount of crud that blows out of the hole during drilling.

I use a bent straw and lung power. Close your eyes when you start blowing. DAMHIKT!

 

[healeydays]

I too use a lathe. If I am concerned about blowout I will drill out the blank 2/3 of the way thru and reverse the blank and finish the job coming in from the other side. You need to be 100% sure the blank is square though...

 

[Paul in OKC]

I drill on the drill press with no problem. I don't run very slow. I do use a piece of scrap under the blank, and clear very often. Even as often as 1/8" per 'peck'. As a machinist the one place I don't buy bits is Harbor Freight. I think they do carry HSS, but......I would rather buy from MSC or Enco, or one of the suppliers. I don't have to have 'name' brand, but rarely buy import.

 

[mmayo]

I am no expert and many others on this forum are far more skilled, but I have had consistent success drilling acrylic acetate and inlace acrylester blanks without exit hole problems. Below is a sample of blanks drilled yesterday on the lathe - most used 7mm drills and two were 27/64" for a Mesa pen. For the 7mm I like to change to a different bit each time I drill to allow it to cool. I used a Colt (my favorite), two HSS and one carbide coated bit. I rotate the bits and pick another cool one for each hole. Each had smooth, chip free exit holes. The carbide is the slowest and the Colt the fastest. I extract chips when the binding noise starts. You might see a rough edge on the outside of the inlace acrylester - with that material I am still trying to find the best sawblade, but the holes are OK.

All the blanks are cut slightly oversized (1/16" - 1/8") so the can be sanded flush and smooth to the tubes.

 

[Pompeyite]

Hi Ken,
There has been a lot of good advice given before this, but here is my two penny worth for you to try,
I don't know if you can get the drills that I use over in the USA, but they work well for all the penturners I have trained in the UK.
They are Black and Decker Pirhana Bullet Tipped Drills. Note Bullet Tipped, as they have a small pilot tip which makes them drill true every time. Just set your depth on the drill press to just allow the tip to touch the wooden sacraficial piece or better stll stop short and cut off on the bandsaw as you have already been doing. I also use a woodpecker action( only drilling about 5mm then remove the drill from the blank to clear any swarf build up, before drilling a further 5mm and so on). I can drill a true 7mm hole dead centre in a piece of corian that measures just 12mm square without any blowout with this method. I hope that this is of help to you matey.