Blank Splitting...what am I doing wrong?

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WildcatHollow

WildcatHollow

Member
Joined
Nov 4, 2009
Messages
104
Location
Boyce, Virginia, USA
I'm very new to pen turning. I've started three Designer pens. I get to the step where I'm required to square the faces of the blanks and brass tubes using a new 7mm barrel trimmer with a carbide blade. I use a drill press at 520 rpm. The trimmer makes very little headway, and eventually with any kind of pressure at all, I split the blank lengthwise.

What am I doing wrong?

Thinking the wood might be the problem, I've used three different blanks: zebrawood, cocobolo, and redheart. Split them all.

More information: I examined the end of the brass tube that was part of the event. There are two very small "bites" in the edge of the brass where it looks like the cutting surface of the pen mill came in contact with it.

I'm starting to think I had my drill press turning too slow at 520 rpm.

New information: I just spoke with a technical support representative at Penn State Industries from whence I bought the two blade carbide cutter. He suggested I toss it and replace it with the four cutter steel head. He very kindly offered to send me one for free. Nice people, those PSI guys.

He told me the two sharp blades tend to shave the wood really well, but have a tendency to bite into the brass, causing the kind of "explosion" I described to him.

I'll update this thread with new information after I try the steel pen mill.

I used Titebond Polyurethane Liquid Glue which recommends using water as an accelerator. I sprayed a little water into the drill hole. I had already scuffed the tube with 240 grit sandpaper. I coated the tube with glue, and spread it evenly over the tube with my fingers. I had latex gloves on, and I was working over a sheet of waxed freezer paper. The tube was on a tube insertion tool, and I inserted into the blank with a twisting and sliding motion.

I was examining the tube and the exploded blank and the surfaces seem to be very evenly coated from end to end.

By, the way, I studied all the material here and on YouTube, in addition to reading "Turning Pens and Pencils" before buying any tools or equipment or attempting my first pen.

I'm very grateful for all the information that's been put into the public domain. Thank you for sharing.

Thank you for your help.

Regards,

t.
 
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You don't say what the blank is...I've split a few segmented blanks this way.. usually one of the laminates.... with a carbide tip on your mill I would think you get a pretty good cut action... I don't use the carbide tipped mills (Just don't have one.. but think they are great idea).. I do run run my drill press at about 1100 rpms... I drill and mill at the same speed. I use just enough pressure to allow the mill to cut.. varies with the blank.
 
It sounds like either the wood or the glue is the problem. the first thing i would try is to use more glue to connet the tube to the wood. I dont use a drill press, i just throw the blank in a vise and trim it with a hand drill, maybe the drill pressure is creating too much pressure at an angle or something.
 
Thinking the wood might be the problem, I've used three different blanks: zebrawood, cocobolo, and redheart. Split them all.

PS: Where can I find designer pen tubes that are already cut?

Thank you.

t.
 
Is your pen mill sharp? I have lost a couple blanks due to forging ahead with a dull mill. I now make it a practice to sharpen at the least hint of dullness and I haven't had a problem since.
Edit to say: Ooops...I see it is carbide; probably not a sharpness issue then. sorry.
 
More information: I examined the end of the brass tube that was part of the event. There are two very small "bites" in the edge of the brass where it looks like the cutting surface of the pen mill came in contact with it.

I'm starting to think I had my drill press turning too slow at 520 rpm.

Thoughts?

Thank you.

t.

PS: Found extra tubes at PSI. Ordered two bags full, just in case.
 
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Problems...

I had some segemented pens that did the same... I discovered that if I wrap them with painters tape it helps... Then when you turn just turn the tape away... I also am using my hand drill and holding it in a vise... I found the drill press too agressive...
 
New information: I just spoke with a technical support representative at Penn State Industries from whence I bought the two blade carbide cutter. He suggested I toss it and replace it with the four cutter steel head. He very kindly offered to send me one for free. Nice people, those PSI guys.

He told me the two sharp blades tend to shave the wood really well, but have a tendency to bite into the brass, causing the kind of "explosion" I described to him.

I'll update this thread with new information after I try the steel pen mill.

Thank you.

Regards,

t.
 
I also use a hand drill in a vise.

I go as fast as possible and make very short light cuts. as soon asa I see chips fly I pull off. Gorilla glue on the tubes also helped me out with this problem.
 
Try to use the barrel trimmer in a cordless drill. Do it by hand, thats what I do. I can control it better that way. Also make sure your not trimming a ton of material to square the blank. Simply ensure the blank is really close to the brass tube size to eliminate having to remove too much material when squaring off the blank.
 
i use my drill press also, and really think at least a big part of the prob is the speed. Crank that bad boy on up a bit more.. 1500 or so.

Also, if you are taking enough material to "bite" the tube, you may be getting a bit too aggressive. You want to ever so barely touch the tube with the mill. Alot of people say: If you have shiny brass, you went too far.
 
Put thin CA on both ends BEFORE you trim. Then, again, after you trim successfully. Wait at least two hours, or use an accelerator on the thin CA.
 
WildcatHollow said:
The trimmer makes very little headway, and eventually with any kind of pressure at all, I split the blank lengthwise
Click to expand...

Toby; The other suggestions are good ones.
Inspect the blank and tube, did the glue separate from the tube, or the blank? Is the glue spread over the entire glue surface?

If there isn't any glue on the brass tube, make sure you "scuff" the brass tube with sandpaper so the glue stick well. As glue, use Polyurethane (Gorilla) glue or thick superglue. Epoxy is also a good choice.

Superglue doesn't fill gaps very well under any circumstances, so superglue needs to have a close fit between the hole and tube.

If there are gaps in the glue, try to use more glue. I block the one tube end with wax, or play-dough. Put a dollop of glue inside the blank, and spread glue on the outside of the brass tube at the end you will insert into the blank. Insert the tube with a twisting, sliding motion. Glue should push out the other end. Use paper under where you are working and don't do this over the dining room table. DAMHIKT!:frown:
 
I've been having a similar problem with some acrylic blanks recently. I use the 4-blade barrel trimmer in my hand drill. I think I was probably just pushing too hard against the blank as I trimmed. Probably better to do lighter, easier cuts, even if it takes longer.
 
a TWO BLADE trimmer? That doesn't even sound like a good idea. I wasn't happy
with the four blade, so I went to a six. Two blades just sounds like there's little
possibility of holding it straight onto the tube. At least with four ,you're more likely
to hold it square..
 
NewLondon88 said:
a TWO BLADE trimmer? That doesn't even sound like a good idea. I wasn't happy
with the four blade, so I went to a six. Two blades just sounds like there's little
possibility of holding it straight onto the tube. At least with four ,you're more likely
to hold it square..
Click to expand...
While I agree that a two-edge mill sounds like a recipe for disaster, it should still give a square edge (if it doesn't esplode). After all, the shaft is going to ensure that the cut edge is square to the tube.
 
The problem I see with a two blade cutter is that it would try to take to much of a bite with those two teeth. Four blade would require less pressure per tooth with that thinking. As well 6 blade would be even less. But actually using the cutter heads I have not found this to be the case for me at least. I get the consistently best results with a 4 blade head I get more tear out with a 6 blade so I am not completely sure just what all is coming into play. I do trim at a low speed and am careful to increase pressure slowly until the blades start cutting. Also keep in mind the mill is not a drill bit and will not cut all that fast at best.
 
Additional Information

I used Titebond Polyurethane Liquid Glue which recommends using water as an accelerator. I sprayed a little water into the drill hole. I had already scuffed the tube with 240 grit sandpaper. I coated the tube with glue, and spread it evenly over the tube with my fingers. I had latex gloves on, and I was working over a sheet of waxed freezer paper. The tube was on a tube insertion tool, and I inserted into the blank with a twisting and sliding motion.

I was examining the tube and the exploded blank and the surfaces seem to be very evenly coated from end to end.

By, the way, I studied all the material here and on YouTube, in addition to reading "Turning Pens and Pencils" before buying any tools or equipment or attempting my first pen.

I'm very grateful for all the information that's been put into the public domain. Thank you for sharing.

Regards,

t.
 
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