Exploding Pen Blanks

[Alzey]

This past weekend I had 5 pen blacks blow up on me when trying to use the pen mill on them to square them up. After 2 blow outs, i slowed down the drill press and sharpened the pen press per a video I found on YouTube ( Capn' Eddie). Still had a couple more blow outs.

Since I am only turning slimlines right now, I trimmed down the blanks from 3/4 or 7/8 down to 5/8. I plan to use the trimmed off pieces to make laminated blanks. I chuck the pin mill into my 1936 Delta Drill press. I use a crescent wrench to control the blank and a block of 2x3 to apply upward pressure to the blank. The mill will spin in the blank then all of the sudden it would grab and rip the blank apart. I did have one black that was still a 3/4 blank of Black Walnut do the same thing. The pin mill only had about a dozen uses on it before this weekend.

Are my blanks too small?
Am I running too slow on the press (680-2400 rpm, can go to 4800)?
Do I have a cheap mill (part of a PSI starter kit sold by Amazon)?

Thought I would ask and see what more experienced people have to say before I blow up any more blanks

PS. I don't have the option of sanding the blanks square.

Thanks

 

[G1Pens]

Too much pressure on the blank with the mill ???

 

[maxwell_smart007]

I found that if you're having to take enough off to warrant a drill press, you're cutting your blanks too long.

I use a hobby knife to clean out the glue and - rarely - a mill chucked in a drill turning very slowly (while the blank is held in a vice) to true up the ends...but I don't use the mill anymore.

I actually stopped using the mill entirely because of the 'catching' issue - I just use the hobby knife and a small 30 dollar disc sander I got on clearance somewhere - either Canadian Tire or Harbor Freight.

 

[Gary Beasley]

I've found too fast, and it doesn't cut, too slow it catches. Why do you not run the DP down to the blank? You have more control of the pressure and would have less chance of a catch too.

 

[sbarton22]

I use a cordless and mount the blank in the end vise on my bench. It supports the blank and the bit pretty much guides itself in the barrel.

 

[nava1uni]

I have found that taking light cuts by hand works really well. Use can also use a flat surface with sand paper if you don't have a disc sander. I mount sticky back sandpaper to a piece of thick glass and I use this to sand all kinds of things so that they are flat and even. I get glass scraps from a glass company and have different grits on them. It works very well.

 

[StephenM]

Are you using CA? I found that once a litle CA builds up on the mill tube, it either pulls the brass tube out or the blank "explodes". A couple of things to try:

Switch to a vice to hold the blank and use a hand drill for the mill. The variable speed on a hand drill works great for fine tuning the clean out. Move it in and out and if you see any CA building up on the mill tube, clean it off.

Switch to 5 minute epoxy. Since I've done that, I haven't had a single problem.

 

[pensbydesign]

i would check to make sure the blank was glued in completely, if you have a spot with to little glue in can easily be torn off. I use my pen mill at 17oo rpm or higher. also check to make sure the mill is cutting with all 4 wings if one is higher than the others its doing all the cutting.

 

[JD Combs Sr]

I use two different size mills depending on the tube size and I make sure the mill "guide" rod just fits the tube (I will make a bushing if necessary). I have always held the blank in my gloved left hand and used a variable speed cordless drill at low to medium speed to drive the mill. I have never blown out a blank, wood or acrylic during the milling process. I have however blown out a half dozen or so when drilling and/or turning by being overly aggressive. BTW both my mills have been resharpened manually so I know the tines are probably not all the same but they still seem to work fine.

 

[sumterdad]

Yeah I agree with the cordless drill technique

 

[pianomanpj]

I just watched a video of Curtis (MesquiteMan) turning a pen where he squared his blank on the lathe. He had a block of MDF drilled and tapped to fit his headstock, and self-adhesive sandpaper attached to it. In the tailstock, he had a Jacob's chuck holding a knockout punch that was sized to the tube. He put the blank onto the knockout punch and brought the tailstock up to the headstock. With the lathe running, he slid the blank up the punch to the sandpaper to square up the end. I'll be trying this idea soon!

 

[Alzey]

Well I took what everyone said here and put my own twist to it and I think I found something that work. First, I put the pen blank back into the my modified drill vice that i use to drill the blanks with. Then I chuck my pen mill into my cordless drill and set the clutch to 11. Now the vice supports the outer walls of the blank and clutch will slip when the mill grabs. Why I didn't think of it earlier, I don't know. Guess I was fixated on using the drill press for all my drilling.

Thanks everyone

 

[Ted iin Michigan]

This is an interesting (to me) conversation. I've been using a pen mill exclusively for a couple years and never had an issue that wasn't due to "operator error". I do try to keep the mill sharp. Maybe that's the difference.
Alzey, I know you said the mill was pretty new, but you might want to check and see if the angle on the cutting surfaces is right, they're all sharp and they're all the same length (put it on a flat surface and see if it'll wobble). Any one of those being deficient could cause the problem.

 

[wouldentu2?]

I hold the blank in my hand and use a battery powered drill and have only had that problem twice when I use doing heavily spalted material.