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.