Pen Mill Blank Exploding

[chuybregts]

Hey guys,

So I'm pretty new to this, I have 12 pens under the belt now. In the 26 half blanks that I've trimmed up, I've had 2 blanks essentially explode (one literally, the other just tore really bad).

This happens right as the pen mill starts to kiss the blank.

My question is, when using a pen mill, should i just expect this to happen? or is it likely I'm doing something wrong? (as in, I'm applying too much pressure initially?)

Thanks everyone!

Chris

 

[keithkarl2007]

burled blanks may do this if they are not stabilised

 

[Lulanrt]

Cross cut blanks are real bad about doing this as well. Try soaking the end with water thin CA first works for me.
Traivs

 

[Monty]

Are you using the mill by hand or in a power drill? If you are using a drill, too fast and a catch can result in a blowout.

 

[Jim Smith]

I've also had some acrylic blanks shatter when touched with pen mill, especially the more brittle ones Going slowly, taking very small bites and clearing the blades is how I usually avoid it.

Jim Smith

 

[chuybregts]

Okay, I use the drill by hand (don't have a drill press yet) but butt it against the work bench. The wood was fairly reasonable (just straight up maple) and was going into the face grain.

I think I must be applying too much pressure to start with, either that or my pen mill is crap and could be sharper? (it's a woodcraft one)

Thanks guys!

 

[jkeithrussell]

Lots of different types of blanks will do this with a pen mill. I switched to using my Rigid belt sander with a squaring jig and it has made life a lot easier. Save the pen mill to use by hand to clean up the ends after you've finished the pen.

 

[Skye]

Do any of the mill's cutting edges reach beyond the edges of the blank? You know, is it wider on any side than the blank. Sometimes if that's the case, it'll bite into the wood and cause it to chip. If the blank is larger than the 4 cutting edges, then you'll cut a nice hole into the blank with less chipouts.

 

[lwalden]

Paul Huffman does a great job of putting a nice sharp edge on pen mill cutter heads- it's amazing what a difference that makes, and he gets them turned around pretty quickly as well. I've got multiple cutterheads, and will normally hold a couple in reserve while sending him the others.

 

[CaptG]

If you are using the mill by hand as indicated and butting up against a solid workbench, you are putting way to much pressure on the blank. The cutting edges of your mill are digging in DEEP and getting a hard bite that will rip chunks out. Just hold the blank in your other hand as long as you are not using power and turn mill with light pressure untill you are getting the smooth cut you want. Hope this helps. Let us know.

 

[TellicoTurning]

If you are using the mill by hand as indicated and butting up against a solid workbench, you are putting way to much pressure on the blank. The cutting edges of your mill are digging in DEEP and getting a hard bite that will rip chunks out. Just hold the blank in your other hand as long as you are not using power and turn mill with light pressure untill you are getting the smooth cut you want. Hope this helps. Let us know.

This was my thoughts too, too much pressure and the hand drill speed is waaaaay too fast. I use a drill press at about 1100 rpm or less, light pressure.

 

[chuybregts]

This was my thoughts too, too much pressure and the hand drill speed is waaaaay too fast. I use a drill press at about 1100 rpm or less, light pressure.

Cool I will definitely try it lighter/slower. Guess I'm still learning about the characteristics of wood

Thanks everyone!

 

[maxwell_smart007]

That's why I hated my pen mill - it got dull very quickly, and tore out the blank once it did...

I now use my hobby-sized disk sander...works much better.

Andrew

 

[Chris Bar]

Had this happen a few times so I apply CA now. But reading about catches on a lathe, most if not all folks say max speed will allow fewer catches than slow speed. So, why not for pen mills? I always use fast motor speed, keep the blade sharp and approach the work slowly ( which is a good tactic for any work :biggrin. I speak out of turn (honest, not intended) though...novice that I am.

 

[Daniel]

Chris, it is all an interaction of cutting edge, tool diameter, and the forces that are created on the work. think about a 3/4 inch drill bit. you would slow the drill press down considerable for such a large bit. In this case I believe it is actual experience with the tool that causes people to recognize that it works better at slower speed though. for the pen mill I know higher speed will start up a vibration that will leave an uneven surface. that probably has more to do with being a 4 or 6 cutter tool.

 

[JimB]

I have the Woodcraft mill as well. At about the same point you are at I experienced the same thing. Once I sharpened it everything was OK again.

 

[Billman]

My question is, when using a pen mill, should i just expect this to happen?

Sorta...

Any material has the potential for it to happen.

Generally, if the cutter is nice and sharp, and doesn't reach past the sides of the blank, and you are not using a in-lay kit or a cross-cut laminated blank, then you shouldn't have many problems. But even if you avoided all the things that can cause an explosion or blowout when milling, you have no guarantee that it won't happen again.

I had the basic same issue as you... I could do many end mills with no problem, then seemingly out of no where, I'd destroy one for no obvious reason.

To solve that, I went to PSI's Universal Pen Squaring Jig to use on a combo disk/belt sander.

I have not had problem since.

 

[rlharding]

What they said. Also, have you looked at the tube? Is there glue where the blank has exploded? There might be nothing holding the blank to the tube.

 

[shull]

I have never met a woodworking hand tool with an edge that wasn't benefited by honing the edge. Pen mills usually 4 edges. There is a very good article in the library on sharpening a mill.

Steve

 

[chuybregts]

Excellent, I'll attempt to sharpen the mill, as well as slow the speed down. Thanks guys!

 

[bitshird]

also consider a sanding mills, a couple of members are making them, sandpaper wont cause your blank to explode

 

[chuybregts]

Well, this morning I took some 600 grit sand paper, put it on my workbench, and followed the instructions posted in our library. WOW, holy crap that made a huge difference. I now get paper thin shavings without applying that much pressure at all! I think I won't have a explosion like I did again unless the wood is just that weak.

Thanks guys, every time something like this is discovered (through your help of course) It makes me smile

Chris