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Drilling acrylic blanks

PhillH

Little Grandad
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Well, following my nice Pink Flamingo from Merv which went well, I had some others that I got at the same time.

I now have 3 less :sob: as they are in bits all over the shed floor.

Got 2/3 way through each one and they smashed like seaside rock.

So, what did I do ? I ran a 10.5 mm drill through slowly and cleared the flutes regularly ( I think ). On a pillar drill btw.

Was I too ambitious in doing it in one go ? Should I have put a pilot through at say 6-7 mm ?

Advice gratefully received.
 

bellringer

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Well when I drill my I get the whole way though and normal end up dropping them on the floor that y I don't do them as much
 

bluntchisel

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Hi Phil,
A few f the possible factors - are you using a sharp drill bit? Was your bit long enough to go through in one attempt, or ( like my setup) did you have to raise the blank in the vice and start drilling again? If this was the case did you (a) notice a wobble because now the vice is gripping a smaller section of the blank, or (b) ensure that you continued drilling with the same section of blank facing you? If you drilled as slowly as you infer then it's not heat - which is another cause of fracture.
Regards,
Bob.
 

Grump

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notice a wobble because now the vice is gripping a smaller section of the blank
Not if you leave the blank in the vice and lift the table up the drill bit that would ensure drilling through the same hole (Head for thinking feet for dancing as George would say)
 

Woody

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I found with drilling round blanks on a pillar drill it is best to drill a hole through a piece of 2" x 3" soft wood the same size as the blank from the 2" side then cut it in half put it round the blank in the vise and drill away sometimes these blanks can be a bit to brittle hope this helps mate
 

rowdyyates115

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I always cut my acrylic blanks to size first then drill slowly on my lathe 350-450 revs withdrawing regularly and cleaning the drill bit. I hope this helps
 

Woody

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I have found this can be a problem with home made blanks no matter how professionally they are made you do get the od batch that is to brittle or to soft I have turned home made blanks from quite a few different people and each one of them for some reason turned out brittle blanks as well as some that are to soft so I have stopped buying them now but I'm not saying this is definitely what was wrong with your blank even though it sounds like it was the problem that is why I made up the bits of wood it did stop them falling apart or exploding it gave full support were as a drill vice only supports two sidea and allows for movement
 

PhillH

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Some good advice and tips there folks thanks for your help.

I need to get my chuck adaptor for the Nova, as the new lathe is 1" and the sip was 5/8 - 3/4 i think, different anyway.

Will give them a go in the lathe with the couple that are left and I may well try the wood surround idea with 1, the 2 points of contact was worrying me to be honest.

I moved the table up to drill the second length, leaving the drill in place as a guide, so no wobble that I noticed.

As you say maybe just a tad brittle.

Onwards and Upwards.
 

Penpal

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How many wings does an Angel have.

We here in Australia used to watch a program called hypotheticals.

Personally I would dice the Pillar drill with insufficient depth capacity then check your lathe do you have to unlock the tailstock to acheive full depth of that throw?. What type of drill did you use?, what speed do you normally use?, is the chuck on the pillar drill simply stemmed with a morse taper post? or is that held in the quill by a threaded rod?, has your chuck ever dropped out? and down by itself at speed?. When you bring your dead tail stock dead centre to the head stock dead centre with a thinnish feeler guage in between the two points does the feeler deviate in any direction? having locked the tail stock in position doing this a few times if there is slop in the guide rails for the tail stock?. Is the alignment true?. Is your pillar drill as accurately ie the platform plate right angles to the drill in all directions?, your form of vice locking firmly not over tightening?. I have never forgotten my mate firing up his RC plane, he said hang on to this I Did and crushed the lightweight body a bit not realiizing enough is enough pressure to hold before crushing, he forgave me.

Now I drill with a pillar drill for preference sometimes in timber and I mean tough stuff noted as some of the toughest in the world, some as brittle as any found anywhere eg Imported Snake wood, African Ebony etc etc sometimes non stop for up to one to two hundred blanks of all shapes and sizes. I have never altered the speed from fairly fast ever for any material plastics, wood, metal. So why this diatribe well it works for me including 1/2 inch Corian. I have never placed a sacrificial piece of anything under any blank, reason cause I dont need to, have no need and like to physically watch the exit of the drill to guage the downward pressure which I believe is gained by keeping all things in perspective and gaining a feel for the throw of the drill. I try to use one type known quality drill DEWalt Extreme 2 available in metric sizes made in the USA with a drill point that is a tiny conventional drill point in front. I hear you say but you cannot sharpen them I say I have drilled even over 400 blanks with the one drill this tells me each one cost micro cents to do so when blunt consign them to the bin. I also use a variety of other drill makes with success. View the Rebar Pen into that particular steel yes I used the DeWalt type 2 7mm same old spec HSS-Din 338.

Now I am not touting for any brand ,any method, any lathe, any pillar drill my Taiwanese Drill has drilled countless thousands of everything in the last thirty plus years. Step one at purchase I ripped out the rubbish bearings fitted top line one cheap as from my known supplier, threw the rubbish chuck in the bin fitted a medium cost chuck to a new post tapered with a threaded end locking it up the quill with a 3/8 threaded rod it dropped the old one three times on me (change of underwear time) I had bought a morse taper reamer to firmly clean, make sure best fit for the post holding the chuck.

Ok by now I hear silly old fart what would he know about anything what does who does he think he is. Well he is an average bloke been around the block a number of times with this thought starting from scratch with each item in the making chain of events making pens trying to standardise on all my equipment to enable ease of comfort of repeatable use. I then chucked the Taiwanese crap underpowered motor with dare I say it a British solid steel 1 hp motor with a steel pulley or Australian counterpart because I listened to advice given by workshop folk who do this for a living.

Having touched on the subject of drilling blanks and only lightly describing what I do i also have experienced real crap plastic blanks and turned some real expensive ones where the pucker factor is elevated to extreme and I felt sorry you have lost three blanks and do trust this percentage of losses will improve, have fun I do.

Kind regards Peter.:thinks:
 

PhillH

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Ok by now I hear silly old fart what would he know about anything what does who does he think he is.

For one thing, you will never hear that from me.

I value the years of experience that people have on here and that's one of the reasons I like the place so much.

You all will have seen everything that is new to me, so the knowledge to be gained by asking questions is invaluable.

I will give the remaining ones a go in the lathe I think and see how it goes.

All part of the learning curve.
 

Grump

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Stick with it Phil if you find the others doing the same after you have sussed out the best method for you, it may well be the blanks themseves and not you.
Have a word with Merv he is a reasonable guy and well experienced in making these blanks aswell as turning them himself.
Don't throw them away he may well take one look and issue replacements, or give you a call to tell you what your doing wrong if anything.
Its good to talk init?
I have met him he is a nice guy with a well equiped workshop and his own high street shop he is not running away ask him what he thinks.
 

Maurice

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I drill my acrylic /wooden blanks held in my Nova 3 chuck and use Colt Pen drills from Stiles & Bates. They are not cheap but they do what they say in the advert.
If you go to Youtube and type in Colt Pen Blank Drill you can see a video of them being used. They do not have all the sizes that people may need but they cover quite a number.
I sold my pillar drill because I could not drill right through my blanks in one go. This has been solved by drilling on the lathe. Todate I have not had a blank split with these drills. (hope I haven't spoken
too soon).
Hope this helps.

Happy turning
 
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