# Acrylic blank issues



## Big (Oct 17, 2014)

I understand that there is PR (Poly Resin) and Alumilite and that the different blanks have different properties. I have learned that some acrylic blanks turn very easily and seem to be "soft" while others seem to be very hard and brittle. I seem to be having issues with brittle acrylic blanks. A couple have cracked badly when drilling them. Others have had blow outs when turning them. I had one today that I was excited about and thought it was going to make a beautiful pen. Drilled it, glued the tube in, and mounted it for turning. Started turning about about 1800 and it was almost like dust was coming off. Then, a big chunk chipped off and that was the end of that blank. So, realizing that I am still completely a rookie, what is the secret to dealing with brittle blanks and turning them. Heck, what is the secret to working with them overall?


----------



## Jim Burr (Oct 17, 2014)

A common mistake is to drill through the whole blank. Always, 100%, no exceptions...a bad idea. Leave the blank long, drill just past depth (tape on the bit works well here) and then cut the blank to length on the band saw. Any acrylic with have micro fractures in the end if you cut then drill through. These fractures amplify when turning then "POW!!"
Keep it up!!


----------



## ElMostro (Oct 17, 2014)

How sharp is your tool?  "Dust" is sometimes a indication of a dull tool.  A sharp tool should be producing shavings.  Carbide or HSS?
Eugene.


----------



## wyone (Oct 17, 2014)

What do you use to drill the acrylic?  I had a LOT of failures until I found a pen vice (used and cheap) and started using it with my drill press.  I think it has to do with drilling with the sides fully supported that made a big difference, at least for me.  I also drill very slowly and only about a 1/4 at a time, then clean out, and blow the hole and the bit off.  Actually I keep a flow of air going across the drill bit most of the time I am drilling, and I think it cleans as well as cools the bit and the blank.


----------



## Rodnall (Oct 17, 2014)

When drilling, I use a drill press with a drill press vice with a piece of wood under the blank to prevent blowouts. As far as turning acrylics,especially inlace acrylester, I use a round carbide tool. I use it in the scraping position, just slightly below center of the blank, with the handle slightly higher than the tip. One hand on the handle and the other hand holding the bar riding along the tool rest, acting as a guide to prevent the tool from grabbing, taking very, very light cuts. When I get close to the bushings, I switch over to my delrin finishing bushings and sand the rest of the way.


----------



## NittanyLion (Oct 17, 2014)

While turning, make sure you start your tool in the center of the blank and work to the end of the blank.  Never start your tool at the end working in or you are more prone to fractures.  Hope this helps.


----------



## ed4copies (Oct 17, 2014)

NittanyLion said:


> While turning, make sure you start your tool in the center of the blank and work to the end of the blank.  Never start your tool at the end working in or you are more prone to fractures.  Hope this helps.



Can I ask what the basis is of this assertion?

If you turn "toward the middle" you have material supporting the material you are cutting off.  When you turn from the middle to the end, the final cut has no material supporting it---doesn't that create more likelihood that it will "chip off"?

Always willing to be re-educated!!
Ed


----------



## Ted iin Michigan (Oct 17, 2014)

Gotta jump in here! Couple things about drilling: First, I prefer standard twist drill bits. I have had bad luck using brad point bits. Second, make sure the drill bit is SHARP. You shouldn't have to exert much pressure while drilling if the bit is sharp. Third, beware of the heat generated when you drill. It can be significant and it will weaken the blank making it prone to failure. While this is especially true for Tru-stone, it is also an issue for acrylics, etc. I'm of the opinion that too slow a feed rate causes excessive heat buildup. Except at the end of the cut. I do leave extra at the end of the blank, but when I get close, I slow way down and "feel" my way through the end.

About turning: +1 re comments on sharp tools. Really sharp. If you're not getting pretty curly shavings, it is probably time to sharpen. +1 about the need to take light cuts. I said LIGHT CUTS! And here, too, a word about pressure. If your tool is sharp, you shouldn't have to force it to cut.


----------



## wyone (Oct 17, 2014)

I have been using COLT bits.  They are made differently than a brad point bit.  I think they have 4 flutes instead of two and really do pull the waste out of the hole pretty well.


----------



## Tiger (Oct 18, 2014)

ed4copies said:


> NittanyLion said:
> 
> 
> > While turning, make sure you start your tool in the center of the blank and work to the end of the blank.  Never start your tool at the end working in or you are more prone to fractures.  Hope this helps.
> ...


I've tried it both ways, definitely turn toward the middle. Chip off much more likely when you turn toward the end.


----------



## Big (Oct 18, 2014)

Thanks everyone, definitely some great and sound advice here. I have a better understanding of the issue and solutions now.


----------



## thewishman (Oct 18, 2014)

Jim Burr said:


> A common mistake is to drill through the whole blank. Always, 100%, no exceptions...a bad idea. Leave the blank long, drill just past depth (tape on the bit works well here) and then cut the blank to length on the band saw. Any acrylic with have micro fractures in the end if you cut then drill through. These fractures amplify when turning then "POW!!"
> Keep it up!!



I have to disagree. I always drill all the way through, from the center (the part that will be on the centerband of the completed pen) to the outside, and can't remember ever having a problem with "micro fractures." Some brittle blanks have issues with breaking out at the bottom of the hole - I just cut those blanks an extra 1/8" long. 

I drill on the lathe. When I get close to the end (last 1/8")of a blank, if I think it may be brittle enough to break out, I'll advance the bit slower than usual and back out the bit (about a 1/2 turn of the tailstock) for each advance (about a 1/4 to 1/3 turn of cutting).


----------



## Dave Turner (Oct 18, 2014)

Some really good tips on this thread that I'll have to try.  I always try to round off the square corners of a brittle acrylic blank as much as possible on my belt/disc sander prior to mounting it on my lathe for turning. I then use a SHARP roughing gouge to bring it to round. This seems to peel off ribbons better than other tools. Once rounded, I'll bevel both ends to about 45 degrees using my carbide cutter (EZ Wood Easy Rougher). This helps a lot to keep chunks from breaking off the ends. I'll bring the bevel down close to what my finished end diameters are. 

Then it's a matter of turning the blank down to the correct size. While I like using carbide tipped tools, I find that a sharp skew can remove the acrylic ribbons more quickly and with less chance of "grabbing" the acrylic. Once I get close to my finished size, I'll switch to the carbide tip Easy Rougher (or Woodchuck Pen Pro) to bring it to final shape and size using light cuts. I find a R4 radius edge on the carbide tip works best an acrylics (and wood). The R2 is too aggressive and tends to grab, and the square tips don't let you contour the surface without digging in the edge point.


----------



## NittanyLion (Oct 18, 2014)

I understand your point Ed....makes sense.  For me, turning with a skew, I've had trouble with brittle acrylic and punky wood by turning from outside in.  Maybe it's from the skew "catching"?  I really do not know.....but turning inside out I never have a problem.



ed4copies said:


> NittanyLion said:
> 
> 
> > While turning, make sure you start your tool in the center of the blank and work to the end of the blank.  Never start your tool at the end working in or you are more prone to fractures.  Hope this helps.
> ...


----------



## ed4copies (Oct 18, 2014)

A great deal of having success in turning is having confidence in what you are doing.

So, I have no quarrel with ANY technique that works for an individual penturner.  

When we decide to "teach", however, there should be sound logic to the technique--so that it is more probable that the student will succeed.  Giving advice on IAP is akin to teaching:  More of a "here is what I do and WHY it should succeed" rather than just "here is what I do and it works for me".

But, all input is good input---for someone!   So, if it works for you, certainly tell people "this is what I do, and it works for me---may or may NOT work for you"!!

FWIW,
Ed


----------



## Tiger (Oct 18, 2014)

With punky wood and brittle acrylics anything less than super sharp will give you problems, i find i have to hone the skew regularly to deal with these and if i slack off even slightly on having the skew razor sharp the result is chipping or when i have a bad day, a blowout.


----------



## Smitty37 (Oct 18, 2014)

*Not usually my bag but...*

I am going to interject something here.  My personal opinion is the problem of blowout is more in the turner than in the method.  

I know that I have difficulty with certain burls and certain acrylics and it's me.  How do I over come them....sand paper and patience.  

Once the pen is completed no one will even care how you got a good fit, just that you have one. So some materials I will take almost to final size with one of several tools, others I will take as much as the last 1/8th with sanding because I know that no matter what tool I use I'll get tear out on more than half my attempts and with sanding I will get none.


----------



## Jim Burr (Oct 18, 2014)

thewishman said:


> Jim Burr said:
> 
> 
> > A common mistake is to drill through the whole blank. Always, 100%, no exceptions...a bad idea. Leave the blank long, drill just past depth (tape on the bit works well here) and then cut the blank to length on the band saw. Any acrylic with have micro fractures in the end if you cut then drill through. These fractures amplify when turning then "POW!!"
> ...



You can try Chris...but dozens of posts on the exact same subject, with the exact same problem resolve the same solution. Sharp bits are a given...who would drill without them? The steps provided work all the time and have been recommended by many...uhhh...more approved members? It's just one of those things that works according to a high percentage of membership. And since you can't drill from the center...it looks like you may have another agenda? Just sayin'


----------



## Smitty37 (Oct 18, 2014)

Jim Burr said:


> thewishman said:
> 
> 
> > Jim Burr said:
> ...


  I personally took this to mean drilling toward the tip on single barrel pens and from the center end on both barrels of two bbl pens.  I could be wrong an that interpretation but at least on multi bbl kits you can drill frome the center.

I also drill most wood blanks all the way through.  Some acrylics not but most I just cut long and cut to length after drilling.


----------



## Tom T (Oct 18, 2014)

I drill on a small drill press.  An important thing for me has been to make sure the pen vise is snug on the blank but not tight.  I have had issues with cracking the blank if to tight.  I use colt bits and have no issues with drilling.  Very light touch and cut 1/4 and back out.  Ted said keep the blank from getting hot.  Very important for sure as he says on true stone and acrylics as well, true stone is worse for heating up.  I some time drill about half of the blank and come back and drill the other 1/2 an hour later.  So it does not get to hot. Because I have cracked some nice blanks and frozen the bit on to other blanks.  I some times do use a fan when drilling.  One of the guys on here sprays water on his from a spray bottle.  I was thinking rust so I have not tried that.  I always drill all the way through the blank.  When I started turning pens I did not know I was not suppose to drill through, so it has never been an issue for me.  Always have a wood strip under the blank between the blank and the vise.  I never use a pen mill any more.  I did for a while and blew out lots of acrylic, even with new ones.  The 4 bladed one did work way better then the 2 bladed one.   I now us a 4 in delta disc sander to square the ends.  The I put sand paper in the head stock and put a ..... Pin the tube diameter in the tail stock and make it extra square on fatter pens.  I use a roughing gouge all way down to the sanding stage as a skew is not safe in my hands.  As Smitty said some times I start sending way sooner.  On computer pens from WC  Wall Street 3.  I sand them first on the disc sander , long side.  Then touch them up on the lathe with the roughing gouge and then sand the pen round.  They look great but they are 95% sanded.  As they are so brittle the chip out down to the brass.  Yes I blew out 3 or so before I mostly just started sanding.   Hope that helps some.


----------



## robutacion (Oct 18, 2014)

Well, I would like also to add something in here, we sometimes develop certain techniques that, regardless if "orthodox" or "normal", seems to work for us 99% of the time.  Sometimes we don't mind to talk about it, other times we do, some because they think they have discovered the "wheel" and want to keep it for themselves, which I call "greediness", and others, are most happy to share it around, and as much you may not agreed with, both options have its merits...!

I find it hilarious that, some people have so much trouble in admitting the use of something else to get the job done, apart from what we all would consider "normal" and within the "parameters/guidelines" of old workmanship tooling rules.

Particularly when it comes to the use of non-cutting tools to handle pen blanks, of any material and or nature.  Removing the square corners prior to mounting the blank/barrel on the lathe as a precaution (well conceived one) to "sand" the blank to the final size to avoid catches, shattering, etc., etc., I've seen often people referring 'it' as the, 80 grit, coarse sanding, block sanding, rasp sanding, file sanding and another half a dozen of other names people use.

The principal of all these "ways" to get things done without risking to lose the blanks, are the same, some a little more effective than others but, they are all used for the very same reason/intention/purpose, need and I have no problem with, if that is what allows them to get the result they want.

While I have made this thought known, for a long time, I have also brought the attention to some of the problems using such techniques, not only the amount of time require, with some of them but, the inconsistent and in more times than not, the inevitable results of some of those approaches so, what are those problems...!

Sanding produces heat, the finer the grit, the worse it gets, some materials don't react too well with that sort of heat, some brass tubes glue-ups will not hold its adhesion, as the heat destroys it and off-course, it results in all the problems that follow.

And, the worse of all these results is, the out of round the barrel gets as a result.  Even if you have a perfectly round and centered blank, but the time you get to final size, it will be all over the place, more noticeable at the bushing ends but also, throughout the entire barrel body.  Again, some people think that is good enough and if you are making $20.00 pens, those buying them may not notice a thing but, somewhere in the handling/inspecting/admiring of that pen by others, the chances are, someone will point out the flaws and the poor workmanship.

Now, here is when things get "tricky", there is nothing wrong about people making $20 pens nor I am to criticise the reason why they make the $20 pens, and this is what I want to make very clear to everyone however, most of the time (as far as I'm aware of), they need to find a way to make them fast, and not spend all day working to make a $20 pen, right...???

So, you will find that, most of the turners using this "hand sanding" method, are the ones working with expensive and sometimes fragile blanks that, they simply can't afford to wrack/destroy the blank so, sure, they can spend all day taking their time the sand it bit by bit and adjust any out of rounds with some, "with the length" sanding on the high spots.

They may have the  time and be most happy to take their time, to make sure a finished pen is what they endup with, and nothing else. Now, is anything wrong with this...??? absolutely not, they have made that choice based upon expensive failures from trying to be "technically correct" and within the "normal protocols" that some other turners, prefer to follow, and that is OK to me, also.

So, what in the hell, am I trying to say here...???

It is OK to use "sanding" to get your pens done however, if that is your choice (for whatever the reasons...!), you could achieve much faster, more accurate results, using the "Flap disc system" http://www.penturners.org/forum/f30/blowouts-my-solution-110460/ in one of its fews variations.

Unsupported drilling can, very easily create very small cracks that are invisible to the naked eye, particularly on acrylics and Resifills, any blanks that has wood and resin (PR, Polyester, mainly) combinations, are very susceptible to these cracks or even separation of the resin to the wood, the results can be catastrophic when the blank is put in the lathe for turning...!.

Sure, alumalite is a much softer material to turn, PR by nature is a much harder and brittle material that makes turning a much more trickier job however, the PR hardness/brittleness, can be considerably controlled by the "maker" however, as a blank maker myself, I would be interested in create PR blanks that are as soft as any Alumilite ones.

There is not much to it, really, if you use 1/4 or less of Catalyst as per the MINIMUM factory recommendation, allow the molds to stay in the pressure pot for 4 days, allow the molds to be put aside in a cool place (never exposed to the sun) for at least 4 weeks, before you touch them, you wouldn't believe they were made with PR.  Yes, I have done this as a test to make sure my thoughts were correct.

Now, is this a safe way to make soft PR pen blanks...??? think carefully, what would you think that would happen if the easy to turn pen you made, was all of a certain exposed to the hot sun...??? Yep, not a good result...!

OK so, and to wrap this up, I have nothing against normal cutting/turning tool, hell, I use them almost everyday however, if you experiencing problems turning a particular type of blank(s), use the alternative flap disk system as your best friend, if you prefer to learn out to handle those same blanks using traditional turning tools, get yourself some inexpensive pieces of the material you are having problems with, and practise, practise, if other can do it, so do you...!

Sometimes in life, is better to take a step back, use an alternative solution to get the situation resolved for the time been, regroup and try again...!

Did I mention that you need "sharp tools"...????:wink::biggrin:

Good luck,

Cheers
George


----------



## OZturner (Oct 19, 2014)

I do not intend to hi-jack "Big's" post, but I believe it is appropriate to the subject at hand.
I like most, subscribe to properly sharpened drill bits.
I recently watched a YouTube presentation on Drilling Plastic and Brass.
I found it enlightening, I haven't had an opportunity of trying it out for myself, but it sure looked authentic, and though it somewhat shattered my long held belief, I will let you see it for yourself, and make up your own mind.
https://www.youtube.com/watch?v=8Ri6poVpQM8
C & C's would be most welcome.
Brian.


----------



## StuartCovey (Oct 19, 2014)

Ted iin Michigan said:


> Gotta jump in here! Couple things about drilling: First, I prefer standard twist drill bits. I have had bad luck using brad point bits. Second, make sure the drill bit is SHARP. You shouldn't have to exert much pressure while drilling if the bit is sharp. Third, beware of the heat generated when you drill. It can be significant and it will weaken the blank making it prone to failure. While this is especially true for Tru-stone, it is also an issue for acrylics, etc. I'm of the opinion that too slow a feed rate causes excessive heat buildup. Except at the end of the cut. I do leave extra at the end of the blank, but when I get close, I slow way down and "feel" my way through the end.
> 
> About turning: +1 re comments on sharp tools. Really sharp. If you're not getting pretty curly shavings, it is probably time to sharpen. +1 about the need to take light cuts. I said LIGHT CUTS! And here, too, a word about pressure. If your tool is sharp, you shouldn't have to force it to cut.




This is pretty much exactly what my approach is.  
I have always drilled completely through the blank and just go extra slow through the end.  I don't think I have ever had an acrylic blank blow out on me while turning, other than my first couple.
But not drilling completely through the blank is definitely something to try and see what results you get.


----------



## Sawdust1825 (Oct 20, 2014)

Not drilling all the way through seems to open the door to a new and different problem. If a blank isn't held exactly the same when you flip it end to end what is going to keep you from having a mismatch where the holes come together? Blanks are generally pretty uniform but if even a little variation in the exterior it seems like you just introduced a new issue. I am in the drill all the way through camp. Leave the blank a little long and support the end to help alleviate blow out. A piece of sacrificial wood can help with this. Good luck.


----------



## Dave Turner (Oct 20, 2014)

Sawdust1825 said:


> If a blank isn't held exactly the same when you flip it end to end what is going to keep you from having a mismatch where the holes come together?



You don't have to flip the blank. For instance, if you have a 2 1/2 in brass tube, you'll need a drilled blank a little less than 3 inches long. Cut your blank to 3 1/2 inches, then when you drill, stop your drill hole at the 3 1/4 inch mark. Now cut off the undrilled end of the blank so that your final drilled blank is the length you need.

While I've been in the drill all the way through camp so far, I can see where this drill "almost all the way trhough" method should work nicely if you have a blow-out problem. The only downside is the need for slightly more blank length. I'll have to give it a try.


----------



## Smitty37 (Oct 20, 2014)

Dave Turner said:


> Sawdust1825 said:
> 
> 
> > If a blank isn't held exactly the same when you flip it end to end what is going to keep you from having a mismatch where the holes come together?
> ...


Given those numbers, why stop.....you're starting with a blank 7/8 inch longer than you need, I doubt that drilling all the way then cutting off would really do anything to hurt you.

I suspect that if abody drills all the way through and cuts off a quarter of an inch it will prevent problems as well as not drilling all the way and cutting off a quarter of an inch.  The problem with that is people like to make 5 or  5 1/2 inch blanks and get two single barrel pens or one two barrel pen out of one blank, which can make cutting the blank long to start with a bit iffy at times.


----------



## ed4copies (Oct 20, 2014)

Trust me, a "break" as you exit can break more than an inch of material--especially some resins.

Drill any way you want to.  But the blank is NOT "defective" when you shatter it on exit.  Nor is it "defective" when it breaks while you are turning.  If you think a blank is "defective", do NOT cut it or drill it---simply return it, with the defect (crack or bubble) that you think exists, highlighted.

I have seen fewer than five truly defective "manufactured" blanks, in the tens of thousands I have turned or sold as blanks.


----------



## nativewooder (Oct 20, 2014)

I have used the "Colt" pen drilling bits since they were first available and find they are fantastic.  Expensive but well worth it!  Their instructions state that the cut should be completed before withdrawing the drill bit.  (Drilling on the lathe.)

Learn something new every day!!!


----------



## Smitty37 (Oct 20, 2014)

ed4copies said:


> Trust me, a "break" as you exit can break more than an inch of material--especially some resins.
> 
> Drill any way you want to.  But the blank is NOT "defective" when you shatter it on exit.  Nor is it "defective" when it breaks while you are turning.  If you think a blank is "defective", do NOT cut it or drill it---simply return it, with the defect (crack or bubble) that you think exists, highlighted.
> 
> I have seen fewer than five truly defective "manufactured" blanks, in the tens of thousands I have turned or sold as blanks.


Well Ed, I'll take your word for it, you have a whole lot more experience than I have with those things.  It would still seem to me like cutting a blank 7/8 in longer than you want is a bit of overkill. You sure don't need that much to avoid drilling through.


----------



## ed4copies (Oct 20, 2014)

I did not type that to be argumentative, Smitty.  Hope you didn't read it that way.

Particularly, trustone with matrix or web or PR that has used a lot of MEpK will shatter up the pattern, or up the blank.  A lot depends on how the blank is being held.  If it CAN move up the drill bit, more damage is done than will happen if the blank is not able to move.

I used to think I could tell which ones would survive the "exit wound".  Now, after being wrong several times, I only drill through on materials I know very well.

I HAVE observed that a sharp drill bit makes a BIG difference in the survival rate from "exit wounds".


----------



## Smitty37 (Oct 20, 2014)

ed4copies said:


> I did not type that to be argumentative, Smitty.  Hope you didn't read it that way.
> 
> Particularly, trustone with matrix or web or PR that has used a lot of MEpK will shatter up the pattern, or up the blank.  A lot depends on how the blank is being held.  If it CAN move up the drill bit, more damage is done than will happen if the blank is not able to move.
> 
> I used to think I could tell which ones would survive the "exit wound".  Now, after being wrong several times, I only drill through on materials I know very well.


 I didn't take it as anything other than what you were saying.  You do have a great deal more experience with that stuff than I do and I learned something.  I thought that cracks from drilling through would not extend more than a quarter inch or so.


----------

