exploding blank

[Anderson Creations]

Hello fellow turners, greeting and salutations. Happy Thanksgiving.

Ok time for bussiness. I am getting started on Pen turning. Bought my first resign blank. Bought a new brad point 3/8" drill. And I started to drill the hole thru the blank and it Shatters. I thought maybe I was going to fast and did clear the chips. So I try a secound time going slower and in steps. SAME THING. These blanks are expensive for me so I can't keep blowing blanks. What am I doing wrong?

 

[wwneko]

Can you post a video? Hard to tell without seeing/hearing what's happening. Could be dull bit, too much force.

 

[Anderson Creations]

I forgot to add. It is made of polyester resin and is called Acrylester Molten Metal 5/8" x 5/8"

Thanks
Dave

 

[Anderson Creations]

Can you post a video? Hard to tell without seeing/hearing what's happening. Could be dull bit, too much force.

I can try and make a video. But it means losing another blank. Could it be that the material is 5/8" square and I am drilling it with a 3/8 drill? It is a brand new bit. Bought it for this task only. And I was very gentle (for me anyway) with the speed and pressure.

 

[ElMostro]

I little more detail can get you a better answer. For example the type of resin; polyester resin, acrylester, urethane, etc. What speed are you drilling at? Are the blanks really cold bec they were in the shop?

The spurs on a brad point bit may be the problem, drilling too fast or too slow could be it, if the blanks are really cold (depending on the type of resin) this can make them more brittle. If the bit has some wobble that can cause a problem.

Hmm...so I guess I really don't have a specific answer.

Edit; I type too slow and some questions are already answered.

 

[Silverado]

I would not be using Brad point bits on Plastic. Start with a smaller bit like 3/16 ths drill slow and cool bit and blank often with a spray bottle of water.
Use a 5/16 regular bit and do the same cooling often with water. Then use a regular 3/8 bit and drill slow and cool bit and blank.
If possible make your blank slightly longer in case you have a minimal amount of blow out as bit exits blank.

Good luck!

 

[Jack Parker]

Welcome, Dave. Acrylester tends to be very brittle, ditto on not using a brad point bit on these blanks. Another thing that you could try is cutting your blanks a bit longer and not drilling all the way through the blank and cutting to final length after you drill. Ed Brown has a video posted for this method here : https://www.youtube.com/watch?v=4vxjMTtHLio . Let us know how you make out.

 

[Anderson Creations]

WOW, lots of patience from me looks like. Thank you for the advice and time. I will try again this weekend using your advice. I hope the end result is worth it. This is all new to me.

 

[bgio13]

Welcome Dave,

As others have pointed out acrylester is brittle. As a side note make sure your turning tools are sharp as well and go easy when turning, this stuff will chip out on you. You may also want to read up on painting the inside of your blank after you get the hole drilled, I am not sure how translucent the blank is, but you don't want to ruin another blank by having the tube show. Hope this helps,

Bill

 

[MTViper]

Dave,

I think you hit on the largest potential problem - a 3/8" bit through a 5/8" blank leaves very little room for error. Everything has to work just right for it to come out right. If you get just a little off center, that doesn't leave you a lot of wood on one end to turn your blank to the right size.

I use brad point bits on acrylic all the time and rarely have a blowout. I know about when the point should come through the far end and slow down cranking my bit through the blank to a crawl until I feel the end start to give. It's a feel you develop over time.

How are you drilling your blank? Drill Press? On the lathe? I drill everything on the lathe using pin jaws for my chuck and a drill chuck in the tailstock to hold the bit. I can ease the bit in a turn at a time to make sure I'm taking it easy. I clear the chips every 1/2-3/4" of drill bit advance. I also drill at 400 rpm or less.

That's how I do it.

 

[ed4copies]

Hey Dave!

Don't try to learn to walk with your treadmill set at 70 degrees and running speed!!

Acrylester is among the most difficult "plastics" to make a pen. Start with acrylic acetate (or AA in Berea language). It is much easier. Also start with 3/4" blanks. If you have not turned plastics, you will mess up the first part of turning these, but at least you have enough left when it becomes round, so you CAN make a pen--if you are a fast learner!!

Now, if you ignore all that, then watch this video: https://www.youtube.com/watch?v=wPJucXYtst0

IF you use the Popsicle stick method, you will succeed in drilling, but acrylester is very brittle, it is unlikely you will get a pen, on your first few tries.

FWIW,
Ed

 

[mredburn]

Is it blowing apart before you can get very far into the drilling? or when you are coming out the end.? What tempature is it where your at?
If your blowing out coming out the end that is one problem, If its blowing apart in the middle of drilling thats another.
If the blanks are cold, thermal expansion will cause them to explode, there have been times when the blanks were drilled in cold weather and the heat from drilling caused them to shatter.
Roll your drill bit on a flat surface like a piece or glass and make sure it isnt bent.
How are you supporting the blank while drilling?

 

[jttheclockman]

Hello Dave

I started this thread a couple years ago and it mainly was for segmenting blanks but there is some information in there that may help you even with a basic blank.

http://www.penturners.org/forum/f179/why-blanks-go-boom-110385/


I am not a fan of brad point bits for what we do. The blank you are drilling requires patience and a sharp bit for sure. It also needs to be drilled in a manner where there is no chatter from the drill bit produced by an out of round drill bit or drill motor. The blank must be held steady and firmly but not to the point of crushing because there is no meat left when drilled and you are putting pressure on the sides. The best case scenario here would be if the blank were round and you mount it in a collet chuck and drill on the lathe. Many of those things are now controlled better and the results should be better.

 

[mecompco]

I love the Molten Metal blanks, have made a few pens with it (just sold one, as a matter of fact). I gave up on brad-point bits long ago. I use a center drill to start, then go to a jobber drill bit. It is a brittle blank, but comes out so nice when done. I drill on the lathe, at around 400 RPMs. Clear the chips regularly and don't let the blank get too hot (I hit the bit w/DNA if it seems to be getting hot).

As mentioned above, a 3/8 hole in a 5/8 blank leaves little room for error. Good luck and make sure to show off your pen when you get it right.

Regards,
Michael

PS: Here's one of Smitty's Click pens on a Molten Metal blank I made--either 27/64 or 3/8 from a 5/8 blank.



PPS: NEVER drill through the blank--drill it, then cut it on the band saw!

 

[CREID]

Welcome, Dave. Acrylester tends to be very brittle, ditto on not using a brad point bit on these blanks. Another thing that you could try is cutting your blanks a bit longer and not drilling all the way through the blank and cutting to final length after you drill. Ed Brown has a video posted for this method here : https://www.youtube.com/watch?v=4vxjMTtHLio . Let us know how you make out.

What Jack say's, When I first started, I had trouble with acrylester and learned it is not the best to start with, try some other softer resin, learn your techniques and then go back to it. On all resin blanks, I cut them over long and then drill, because of the possibility of breakout on the end. So best advice is watch the video he recommended and get a softer resin and keep at it. You will get the hang of it shortly, just don't give up.

Curt

 

[Skie_M]

I grabbed some Acrylester "Pot of Gold" when PSI had it on sale at 2.95 apiece... I found that it turns extremely chippy and seems to be very brittle. In order to get a decent round surface for my chuck to grip, I had to resort to wet 220 grit sandpaper and sand off around half a millimeter to get a good clean round surface (backed with a piece of glass).

In order for me to drill my blanks, I turn them round between centers first, and then chuck them in my 3-jaw scrolling chuck. I then cut to length (for this stuff, I add 1/8th of an inch), and re-chuck the pieces I am going to use, face it and put a dimple in the center by hand to guide my bit. I drill with a bullet tip style acrylic bit, which I have found tends to reduce blow out at the end, but I don't have a 7mm version of this yet, so when I first made one of these I used the brad point bit and lost about 1/8th of an inch to blow out at the back end.

While drilling, I cooled the bit frequently, and used the lowest speed my lathe was capable of. I slowed down considerably towards the end, and it still chipped big chunks out at the end. I held the bit in a bit holder - hand held. It takes a steady hand, and gentle pressure, and a sharp bit is a great idea. To make my bit holder, I went to Harbor Freight and bought a corded drill with a hand tightening chuck, and removed the chuck. The chuck itself can't be attached to the lathe, but it fits quite comfortably in my hand, and holds up to 10mm bits... I still use this occasionally to drill when I just want a quick hole in the center and the final dimensions aren't critical yet.


While turning on the mandrel, I got the barrels as close as I dared to their finish profiles with my scraper, which didn't chip nearly as bad as my bowl gouges ... I re-ground my chisel profiles after this point to get better results, as the original profiles provided by Harbor Freight just weren't up to scratch. I finished the final half mm or so just using sandpaper, and graduated up to micromesh and Plast-X for the final polish.


I do have to say that the results of the acrylester is quite stunning, but it's a pain to work with all those chips flying up into my face while I work. I bought a face shield just for turning these plastics.


These days, I will turn these with a face shield and a fan blowing a good amount of air from the side (to reduce the fog in my mask and my glasses) ... I turn it at high speed with a carbide bit (2" radius) and take light passes till it's round. I now drill using a MT#1 drill chuck in the tailstock, but I still use hand pressure to push the bit into the work after I start the hole. I turn the barrels with carbide till it's close, though scrapers for larger curves works for me too ... still finish with wet sanding and Plast-X.