New to Pen Turning - Acrylic Blanks cracking???

[Weymouta]

I recently started turning pens and really enjoy it! Two completed! I found great acrylic blanlks of my favorite Ohio State Buckeyes colors too! But . . . When drilling the hole on my drill press it seems the last 1/2" of so, the acrylic cracks or "blows out". I have read what I can find on this site and I am looking for what to use to lubricate the drill bit?? I use a blank vise (Woodcraft) and have tried various levels of pressure. If anyone has had these same challenges and can offer up a newbie any help I sure would appreciate it! The last 3 blanks have now been thrown away! Bummer!!!!

 

[Kenny Durrant]

I don't lubricate when drilling. I go slow and bring the bit up to clear the shavings often. As far as blow out you can place a piece of wood under the blank to support the bottom or make the blank longer than necessary and don't drill all the way through. Then when you trim the end to expose the hole it will be nice and clean. With some practice you can feel the bit starting to go through and you can go extra slow and easy and not have to bother with the above.

 

[Weymouta]

I don't lubricate when drilling. I go slow and bring the bit up to clear the shavings often. As far as blow out you can place a piece of wood under the blank to support the bottom or make the blank longer than necessary and don't drill all the way through. Then when you trim the end to expose the hole it will be nice and clean. With some practice you can feel the bit starting to go through and you can go extra slow and easy and not have to bother with the above.

Awesome ideas! I think I will try keeping the blanks longer . . . I like that idea! Wish me luck . . . and THANKS!

 

[Brian G]

Welcome, Ann.

Inevitably, you'll receive lots of advice about using the lathe for drilling. That isn't your question, so I won't be "that guy."

Some thoughts:

-For a drill press, emphasis on "drill", and less on "press". Let the drill do the work.

-Going slow means drilling and clearing the swarf frequently, not setting the speed low and grinding away. Use a drill speed chart to help guide your speed selection.

-Heat is an enemy of acrylic acetate. Are your drills sharp? New doesn't necessarily mean sharp. Dull drills generate heat, create powdery swarf that doesn't clear, gets packed in the hole, and risks cracks.

-Kenny gave you good advice. Also consider setting the depth stop so that you just barely make an exit dimple to prevent blasting through the exit.

Good luck!

 

[Displaced Canadian]

The best option I've found is to leave them long and cut and trim after you have drilled them.

 

[Ted iin Michigan]

Ann - I've been doing pens for a while and I'd give the same response(s) as Kenny and Brian (esp Brian). I'll offer that brad point bits are best suited for wood and standard twist drill bits work better for acrylics (might get some discussion on that one), but in any case sharper is better.
Also - there are quite a few types of "acrylic" blanks out there and some are more brittle and prone to blow out, but they give a beautiful finish when polished. You might want to try some of the Rhino plastic blanks. Exotic Blanks has a gazillion different types and their prices and service are superior.

 

[TonyL]

welcome! I keep drilling between 600 and 900 rpms for non-woods, no more than 3/4" penetrations at a time. I do use blade-cote on every plunge, and if the material is really propone to blow-outs, I will place a level block of something at the end or not drill all of the way through. I have had much success with this process. I do keep my bits very sharp too.

Dry Spray Lubricant, Blade-Cote, 10.75 oz.

Bostik, Inc. V206501 Dry Spray Lubricant, Blade-Cote, 10.75 oz.

www.woodworkerexpress.com

A can will last you about 300 or more blanks.

 

[howsitwork]

Ann

firstly Welcome from the UK contingent on here !

Secondly the advice above from Kenny , Brian and Tony is first class. I would go so far as to say withdraw the drill bit every 1/4" on plastic blanks to keep it chip free and cool .

The chips gather round the drill creating friction and heat. This expands them causing more issue and they may melt and fuse to the drill ( don't ask me how I know that ) or they block the flutes and the resulting expansion blows the blank.

As much support around the blank as you can easily get helps resist this tendency but you're better off removing it at source by frequent clearing of shavings / chips.

I put plywood under the blank to resist the end pressure too but take your time, keep it cool and use sharp drill bits NOT brad point ones as , from practical experience , these cause more issues with plastics than they solve.

 

[ed4copies]

This might help, its old, but still pertains:

 

[tomtedesco]

Welcome from Colorado. All good advice above.

 

[TDahl]

Welcome from California.

 

[RichAldrich]

Welcome from Colorado!

 

[Jans husband]

I solved the problem by drilling a centre hole with a centre drill, and then using 3 or 4 smaller drill bits increasing in size before drilling with the final size drill bit.
That means that the material is removed in smaller amounts as you progress through the sizes, hence less stress on the blank or collection of swarf on the drill bit.

It works for me.

Mike

 

[Bats]

I solved the problem by drilling a centre hole with a centre drill, and then using 3 or 4 smaller drill bits increasing in size before drilling with the final size drill bit.
That means that the material is removed in smaller amounts as you progress through the sizes, hence less stress on the blank or collection of swarf on the drill bit.

The one drawback I've found to this is that depending on how small your smaller drill bits go, they may be more flexible and prone to drift, at which point the larger drills will then tend to follow that hole.... although I suppose that's probably more of an issue with wood grain, which is something acrylics tend to lack..

 

[Jans husband]

The one drawback I've found to this is that depending on how small your smaller drill bits go, they may be more flexible and prone to drift, at which point the larger drills will then tend to follow that hole.... although I suppose that's probably more of an issue with wood grain, which is something acrylics tend to lack..

Centre bit, 5mm bit, 7mm bit, and then 10mm bit if your final drill is a larger diameter than that.
Essential to get the centring bit hole to start with, because I find that after that everything follows. I don't trust drills to give me a good concentric start. I always drill on the lathe, not a pillar drill. The blank stays in the same position throughout the drilling process, and I think that must mean you end up with a more accurately drilled hole.

As always, there will be other equal and validly argued proposals to the debate, but that is the point of our posts!!

Mike

 

[randyrls]

To Join the thread; Ann;
All the suggestions above are good ones. One thing to add to the thread; The blank likely shattered when the drill bit broke through the lower end of the blank. So don't allow the drill bit to break through the end of the blank. Cut long, drill short and trim to length: Cut the blank at least 1/4" longer than needed. Mark the length of the brass tube on the drill bit. Drill until the mark enters the hole. Stop and slip the tube into the hole to make sure it is deep enough. Now go and trim the UN-DRILLED end to the proper length. This adds an extra step but you wind up with a good blank.

 

[mmayo]

We all have a lathe and I can't figure out why more people with drilling issues don't use the correct tool already in your shop. Drill on the lathe!!!

If you use a drill press and have been successful skip further reading.

Here is a box elder burl blank drilled in the lathe. It took me about a minute. I entered slowly and exited slowly too. I cleared chips every 1/2" or so especially before the exit. The speed was 900 rpm. I use very good drill bits that are fairly new, see photo. I did not use a center bit (I have them) or cut the blank longer and trim it. I simply drilled it in the lathe.

If you have troubles with drilling your own blanks - start drilling on the lathe, buy good drill bits and become successful almost immediately.

The middle two photos were Diamond knurl ballpoint blanks - 3 Inlace acrylester and 2 acrylic acetate showing the entry and exit points. The last two photos are of ten pairs of Streamline/Saturn acrylic acetate pen bodies drilled just now. The photos are of entry and exit holes. Norseman drill bits were used and drilled on the lathe.

I know you can do this if you skip the drill press.

 

[magpens]

@mmayo

Your .... IMG_0720.MOV .... does not show any video for me, altho' there is sound.

With regard to your statement ...

"..all have a lathe and I can't figure out why more people with drilling issues don't use the correct tool already in your shop. Drill on the lathe!!!"

I too have had similar thoughts ..... but there may be reason(s) for many folks not drilling on the lathe. . . Could the reason be .....

.... The throat of their lathe headstock is too small to accept the blank to a sufficient depth to adequately grip the blank .... ?
or
.... The thought that the lathe is primarily intended for turning and not drilling .... ?
or
.... The lack of an adequate tailstock-mounted drill chuck .... ?
or
.... The difficulty (perceived or otherwise) of gripping a square blank in a headstock chuck which is primarily designed for cylindrical work .... ?

Just curious .... !!

I use a metal-turning lathe of the Sieg type. . The headstock has a through-bore of about 0.84" diameter to a depth of about 5.5"
I routinely drill my blanks on the lathe but I first round the blank to a diameter of about 0.825" or less.

Now, you might ask, why not mount the square cross-section blank in the headstock without first rounding the blank ?
In my case, a common square blank has an edge-to-edge diagonal of about 1.2".
Using, in my case, a 4" 4-jaw chuck, such a blank will go in only about 0.75", and so about 1.75" of a Sierra-length blank still protrudes.
I do not regard that situation as adequate for drilling the square-cross-section blank accurately without wobble.

And so, I round the blank down to an appropriate diameter before attempting to drill it.

I am aware that the headstock of a wood-turning lathe may not have a through-bore.
Or if it does, the diameter of the through-bore may be too small to accept a round blank of diameter needed for a pen.

I would be interested, as I am sure @mmayo would, in hearing from people who would like to drill on the lathe but are unable to do so.

Just curious about reasons for not doing the blank drilling on the lathe. .
@mmayo is obviously successful at doing it .... even for square-cross-section blanks of size needed for pens.

 

[KenB259]

@mmayo

Your .... IMG_0720.MOV .... does not show any video for me, altho' there is sound.

With regard to your statement ...

"..all have a lathe and I can't figure out why more people with drilling issues don't use the correct tool already in your shop. Drill on the lathe!!!"

I too have had similar thoughts ..... but there may be reason(s) for many folks not drilling on the lathe. . . Could the reason be .....

.... The throat of their lathe headstock is too small to accept the blank to a sufficient depth to adequately grip the blank .... ?
or
.... The thought that the lathe is primarily intended for turning and not drilling .... ?
or
.... The lack of an adequate tailstock-mounted drill chuck .... ?
or
.... The difficulty (perceived or otherwise) of gripping a square blank in a headstock chuck which is primarily designed for cylindrical work .... ?

Just curious .... !!

I use a metal-turning lathe of the Sieg type. . The headstock has a through-bore of about 0.84" diameter to a depth of about 5.5"
I routinely drill my blanks on the lathe but I first round the blank to a diameter of about 0.825" or less.

Now, you might ask, why not mount the square cross-section blank in the headstock without first rounding the blank ?
In my case, a common square blank has an edge-to-edge diagonal of about 1.2".
Using, in my case, a 4" 4-jaw chuck, such a blank will go in only about 0.75", and so about 1.75" of a Sierra-length blank still protrudes.
I do not regard that situation as adequate for drilling the square-cross-section blank accurately without wobble.

And so, I round the blank down to an appropriate diameter before attempting to drill it.

I am aware that the headstock of a wood-turning lathe may not have a through-bore.
Or if it does, the diameter of the through-bore may be too small to accept a round blank of diameter needed for a pen.

I would be interested, as I am sure @mmayo would, in hearing from people who would like to drill on the lathe but are unable to do so.

Just curious about reasons for not doing the blank drilling on the lathe. .
@mmayo is obviously successful at doing it .... even for square-cross-section blanks of size needed for pens.

My suspicion on why some don't like drilling on the lathe lies in the fact that to be successful, on a non rounded blank, the pen blank has to be very square. That's especially important on a segmented blank. I use a Nova G3, with a set of Nova pen jaws. They are a set of two, square blanks a must, if you're not rounding. They will accept a round blank as well, so you can go either way. I have not found any downfalls with them. Perhaps people don't like changing the belt positions to gear the lathe down. I used to drill on my drill press, when I didn't have the needed equipment to drill on the lathe. Personally, I'll always drill on the lathe. I would also be interested in hearing why some are adamant about not drilling on their lathe.

 

[mmayo]

@mmayo

Your .... IMG_0720.MOV .... does not show any video for me, altho' there is sound.

With regard to your statement ...

"..all have a lathe and I can't figure out why more people with drilling issues don't use the correct tool already in your shop. Drill on the lathe!!!"

I too have had similar thoughts ..... but there may be reason(s) for many folks not drilling on the lathe. . . Could the reason be .....

.... The throat of their lathe headstock is too small to accept the blank to a sufficient depth to adequately grip the blank .... ?
or
.... The thought that the lathe is primarily intended for turning and not drilling .... ?
or
.... The lack of an adequate tailstock-mounted drill chuck .... ?
or
.... The difficulty (perceived or otherwise) of gripping a square blank in a headstock chuck which is primarily designed for cylindrical work .... ?

Just curious .... !!

I use a metal-turning lathe of the Sieg type. . The headstock has a through-bore of about 0.84" diameter to a depth of about 5.5"
I routinely drill my blanks on the lathe but I first round the blank to a diameter of about 0.825" or less.

Now, you might ask, why not mount the square cross-section blank in the headstock without first rounding the blank ?
In my case, a common square blank has an edge-to-edge diagonal of about 1.2".
Using, in my case, a 4" 4-jaw chuck, such a blank will go in only about 0.75", and so about 1.75" of a Sierra-length blank still protrudes.
I do not regard that situation as adequate for drilling the square-cross-section blank accurately without wobble.

And so, I round the blank down to an appropriate diameter before attempting to drill it.

I am aware that the headstock of a wood-turning lathe may not have a through-bore.
Or if it does, the diameter of the through-bore may be too small to accept a round blank of diameter needed for a pen.

I would be interested, as I am sure @mmayo would, in hearing from people who would like to drill on the lathe but are unable to do so.

Just curious about reasons for not doing the blank drilling on the lathe. .
@mmayo is obviously successful at doing it .... even for square-cross-section blanks of size needed for pens.

It shows every time for me. I tested it several times to confirm Mal.

 

[mmayo]

I am guilty of squaring up EVERY blank with two passes through the table saw. I trust no vendor to do this.

I truly wish I knew what I know now. I could have avoided:

Drilling on the drill press
Barrel trimmers
Mandrels
Micromesh
Regular non TBC bushings
Cheap, from the pen kit vendor, drill bits
Trusting that the blanks you buy are square

 

[magpens]

@mmayo

"I am guilty of squaring up EVERY blank with two passes through the table saw. I trust no vendor to do this."

I fully appreciate why you go through that, Mark. . . Absolutely no need to express guilt about doing that !! . .
I neglected to mention in my post above the IMPORTANCE of starting with an accurately square blank b4 drilling on the lathe.
You and Ken have both emphasized that, when you attempt to drill a non-rounded blank on your lathe.

You can do the drilling on the lathe with an "approximately square" blank but that results in compromises in the accuracy of the result.

But the other thing of importance, it seems to me, is how far you can insert your blank-to-be-drilled into your headstock chuck.

Since you have shown how very excellent your drilling results are, @mmayo, I'd like to know the insertion depth on your lathe, please.

 

[KenB259]

@mmayo

"I am guilty of squaring up EVERY blank with two passes through the table saw. I trust no vendor to do this."

I fully appreciate why you go through that, Mark. . . Absolutely no need to express guilt about doing that !! . .
I neglected to mention in my post above the IMPORTANCE of starting with an accurately square blank b4 drilling on the lathe.
You and Ken have both emphasized that, when you attempt to drill a non-rounded blank on your lathe.

You can do the drilling on the lathe with an "approximately square" blank but that results in compromises in the accuracy of the result.

But the other thing of importance, it seems to me, is how far you can insert your blank-to-be-drilled into your headstock chuck.

Since you have shown how very excellent your drilling results are, @mmayo, I'd like to know the insertion depth on your lathe, please.

I know you didn't ask me, but the pen jaws are advertised to be able to hold a length of ten inches. I am not at home, so I can't measure mine, but it's got to be close to two inches of length that can be inserted.

 

[magpens]

I know you didn't ask me, but the pen jaws are advertised to be able to hold a length of ten inches. I am not at home, so I can't measure mine, but it's got to be close to two inches of length that can be inserted.

@KenB259

I am quite sure you understand my concern about this issue, Ken.
If the headstock chuck can only grip the "near" 3/4" of your blank, then drilling the "far" end .... 2.5" or so away .... has potential for wobble.
That's the rough picture on my lathe.
I know that wood-lathe headstock chuck jaws can have a gripping length of more than 3/4", so the situation could be better for wood-lathe.

HOWEVER, I would never trust ANY chuck jaws to hold ... at the end ... a 7/8" dowel accurately parallel to the lathe bed for a 10" length.

 

[KenB259]

@KenB259

I am quite sure you understand my concern about this issue, Ken.
If the headstock chuck can only grip the "near" 3/4" of your blank, then drilling the "far" end .... 2.5" or so away .... has potential for wobble.
That's the rough picture on my lathe.
I know that wood-lathe headstock chuck jaws can have a gripping length of more than 3/4", so the situation could be better for wood-lathe.

HOWEVER, I would never trust ANY chuck jaws to hold ... at the end ... a 7/8" dowel accurately parallel to the lathe bed for a 10" length.

I wouldn't try it that far out either. Good thing they don't make foot long pens

 

[Bats]

I know you didn't ask me, but the pen jaws are advertised to be able to hold a length of ten inches. I am not at home, so I can't measure mine, but it's got to be close to two inches of length that can be inserted.

That's if you have pen jaws. And a chuck that can handle pen jaws (I don't know if that's even a practical option for a Sieg).... And if your pen jaws are actually straight, which I'm beginning to strongly suspect mine aren't.

HOWEVER, I would never trust ANY chuck jaws to hold ... at the end ... a 7/8" dowel accurately parallel to the lathe bed for a 10" length.

Regardless of the chuck jaws, I don't know that I'd trust the dowel to remain straight once things start spinning, either - sounds like a recipe for whip.

I wouldn't try it that far out either. Good thing they don't make foot long pens

(seems to me I saw one of the newer users post one about three times as long recently, too)

 

[mmayo]

@mmayo

"I am guilty of squaring up EVERY blank with two passes through the table saw. I trust no vendor to do this."

I fully appreciate why you go through that, Mark. . . Absolutely no need to express guilt about doing that !! . .
I neglected to mention in my post above the IMPORTANCE of starting with an accurately square blank b4 drilling on the lathe.
You and Ken have both emphasized that, when you attempt to drill a non-rounded blank on your lathe.

You can do the drilling on the lathe with an "approximately square" blank but that results in compromises in the accuracy of the result.

But the other thing of importance, it seems to me, is how far you can insert your blank-to-be-drilled into your headstock chuck.

Since you have shown how very excellent your drilling results are, @mmayo, I'd like to know the insertion depth on your lathe, please.

My pen jaws are about 2". I usually have a small space at the back to allow the drill to clear and that last disk of acrylic to fall off.

I'm not better than anyone else and if your (whoever you are) method achieves consistently good results, don't change. The folks like the author of this thread are not successful and my comments could help them get past drilling which is an early step to enjoy beautiful finished pens.

 

[KenB259]

My pen jaws are about 2". I usually have a small space at the back to allow the drill to clear and that last disk of acrylic to fall off.

I'm not better than anyone else and if your (whoever you are) method achieves consistently good results, don't change. The folks like the author of this thread are not successful and my comments could help them get past drilling which is an early step to enjoy beautiful finished pens.

I agree, use what works for you. No wrong answer here

 

[magpens]

@mmayo

Thank you for your replies, Mark ..... it's very helpful for ALL of us to read your posts !! . .

 

[Weymouta]

Ann - I've been doing pens for a while and I'd give the same response(s) as Kenny and Brian (esp Brian). I'll offer that brad point bits are best suited for wood and standard twist drill bits work better for acrylics (might get some discussion on that one), but in any case sharper is better.
Also - there are quite a few types of "acrylic" blanks out there and some are more brittle and prone to blow out, but they give a beautiful finish when polished. You might want to try some of the Rhino plastic blanks. Exotic Blanks has a gazillion different types and their prices and service are superior.

Thanks Ted . . . sorry for delay in responding but I have to respond to you as I found "Buckeye Pride" acrylics from Beartooth Woods and can't wait to make these! I am from Dayton originally, huge Buckeye's fan and Chicago Bears also. Pretty excited about Justin Field's with the Bears!
Hoping to find time to get back out in my workroom and try again!!!! Go Buckeyes!!

 

[Ted iin Michigan]

Thanks Ted . . . sorry for delay in responding but I have to respond to you as I found "Buckeye Pride" acrylics from Beartooth Woods and can't wait to make these! I am from Dayton originally, huge Buckeye's fan and Chicago Bears also. Pretty excited about Justin Field's with the Bears!
Hoping to find time to get back out in my workroom and try again!!!! Go Buckeyes!!

No worries on the delay. Life happens, y'know. I was in Dayton over the weekend and rode the "Tour de Donut" with my brother. What a hoot!
Best,
Ted

 

[egnald]

Greetings from Nebraska. Go Big Red (including the Wisconsin Badgers). Sorry I am a month late to the party this is what solved the "acrylic" blank blowouts for me:

As has already been mentioned, heat is the enemy. Drill, retract, cool, drill, retract, cool, take your time. Also if possible, cut the blank long and drill according to the depth you need plus some while still avoiding drilling all of the way through. The grabbing/catching that happens as the drill exits the blank can cause blowouts. Then saw the scrap end off. If not possible, make sure your drill is set to a low speed. This is especially critical when the bit is punching through the bottom. And, make sure the bottom is supported with a sacrificial piece of material so that you are not punching through into air.

Now for the overkill, I use drill bits that are specially designed and sharpened for drilling through plastics. I use the ones from McMaster Carr. They are a standard jobber length but have been ground with a steeper angle to allow for a more gradual penetration with less catching and chipping. (Where "standard" bits are ground at 118 degrees or 135 degrees, bits that are made for plastic are usually ground at 90 degrees).

Good luck with your blanks!
Dave

 

[greenacres2]

Only thing I can add is that Alumilite is a really easy non-wood turn. Especially McKenzie's DiamondCast in custom made ND Blue & Gold. Go IRISH!!
earl

 

[MyDadsPens]

I agree with everyone's suggestions above, BUT Just to add a contrary opinion:
if heat is the primary culprit to her problem I would suspect she would see evidence of that like burnt plastic near the fail zone - I suspect her issue is more with exit blowout from the blank not having a backer at the bottom. If I get lazy and don't find backers I have had this happen on weak woods like highly figured olive etc

As for drilling on the lathe, I have seen people get good straight holes BUT I still don't understand the physics of why a lathe should produce a straighter hole than a drill press. In fact it seem counter intuitive, if spinning helps keep something straighter (think riffled bullets) and the primary issue with straight hole is the small diameter drill bits deflecting in wood grain then spinning the bit would seemingly be better than spinning the wood

 

[MyDadsPens]

But I think we are all ignoring her biggest issue, why is an Ohioan a Bears fan ? I think some people from Cleveland and Cincinnati would be pretty upset

Be careful with lubricants as oily ones might interfere with gluing the barrel afterwards. water is probably ok for acrylics

Oh and I forgot to add to the -- why people don't drill on their lathes question

• Many people start out with mini pen lathes --- to drill you need to purchase a $100 lathe chuck, $30 chuck adapter for your lathe, $30 Pen blank vise jaws, a $50 Morse taper drill bit chuck AND change back and forth every time you want to drill a blank and then turn a blank. And if you dont like putting your pen jaws on your chuck and removing them when you want to turn bowls then you might end up buying 2 lathe chucks. If you started out with a $100 HF or Sears lathe you just paid double for the drilling accessories
• Many of the cheaper mini lathes (like harbor freight) have very little tail movement (throw), so its drill 3/4", turn off lathe, move and secure tail stock again, repeat 2 or even 3 times.
• lathe bearings are expensive and perhaps impossible to find for some makes and models - save them from the wear and tear of drilling.
• 9 out of 10 blanks don't need a perfectly straight hole (not counting segmented blanks), its quicker, easier to drill them on the drill press
• getting backer boards in a lathe chuck is tough - usually need to prepare small pieces that are smaller than your blank to fit inside the jaws, maybe even glue them to the bottom of your blank (PITA, compared to drill press)