Chiping on PR ends

[Rick1708]

I've had something happen to me twice so I think there might be something wrong with my technique. Any suggestions welcome:

When I'm down to the right size on the end of a pen blank, I notice small chips out of the blank. I thought it was from taking too much with a bite with a gouge, but this last time, I used sand paper for the last .10".

I suspect it might be my drilling and it's causing stress in the blank before I ever start working on it. I don't notice the chips until I get close to finishing. I drill on a drill press at the slowest speed and keep everything cool. I drill then trim down the blank. Next time, my plan is to step drill with progressively larger bits.

Has anyone dealt with this?

A different but related question. If I take off 1/32" off the end of the blank on the nib of a gent, is there enough tolerance to still fit the pen? It looks like it, but it also looks really tight.

Thanks in advance.

 

[ed4copies]

Too many possible answers to list.

Start by stopping your lathe and inspecting the blank, from time to time. Decide WHEN the chipping is happening. That will help determine WHAT is causing it.

 

[HSTurning]

What are you using to trim the blank? I was using a 2 tooth carbide trimmer for mine and it was tearing the end of the blank up. I use a 4 tooth steel and use a hand drill on high now and it makes a much cleaner cut. I have a couple 6 tooth cutters coming.

Just a thought

 

[randyrls]

Rick; I cut the raw blank in half, then drill so the bit doesn't emerge from the end of the blank. Next cut the two ends off to the correct length for the tubes. This eliminates any blow-out when the bit emerges from the end of the blank.
Tip: Use a Sharpie to mark the tube length plus 1/8" on the side of the drill bit. When the mark disappears into the blank, the hole is deep enough.

 

[JimMc7]

I drill all PR on the lathe at ~800rpm. I drill ~1/2", retract and cool the bit to touch with high velocity air from a vacuum (10-15 seconds is all it takes) and repeat until through the end. No problems so far using this technique. I've also used water to cool the bit but that's a bit messy on the CI lathe bed.

 

[Rick1708]

What are you using to trim the blank?

Thanks for the suggestions. I'm using a barrel trimmer (PSI) to get close then sanding with a disk I made to use in place of the barrel trimmer cutter head.

When you don't drill all the way through, what do you use to cut to fit. I've been using a hand miter saw in stead of the various power saw options. One thought would be to use a disk sander before installing the tube.

 

[keandkafu]

I started to see the same thing, but not only in acrylics, but in wood also. I narrowed it down to a dull end mill that I use to true up the ends. Mine is a 4 blade carbide. I sharpened it and the problem went away. May not be the same for yours but it fixed mine.

Kevin

 

[glwalker]

I've really not had this problem because I think I prevent it. I use CA/Superglue on all the ends after I finish with my carbide PSI barrel trimmer. I saturate the ends with glue then after dry I again touch up each end lightly with the barrel trimmer just to smooth it down and get any glue I might have gotten inside the tube. This seems to work for me as I think it "stabilizes" the ends and ensures glue is present where the blank meets the tube at the ends.

Also, if I detect any chipping type problem as I'm turning down to the bushings I stop, remove the blank(s) from the mandrel, and apply a little glue by hand to saturate about a half inch from the ends of each blank where, when done, the wood will be the thinnest. I actually remove the bushings when I do this so that I don't glue the blank to the bushing. I might also retouch the barrel trimmer to each end if I think I got glue inside the tube(s). Obviously this process adds time, but I think its worth it and I try not to be in a hurry anyway. Hope this helps.

 

[fernhills]

I've had something happen to me twice so I think there might be something wrong with my technique. Any suggestions welcome:

When I'm down to the right size on the end of a pen blank, I notice small chips out of the blank. I thought it was from taking too much with a bite with a gouge, but this last time, I used sand paper for the last .10".

I suspect it might be my drilling and it's causing stress in the blank before I ever start working on it. I don't notice the chips until I get close to finishing. I drill on a drill press at the slowest speed and keep everything cool. I drill then trim down the blank. Next time, my plan is to step drill with progressively larger bits.

Has anyone dealt with this?

A different but related question. If I take off 1/32" off the end of the blank on the nib of a gent, is there enough tolerance to still fit the pen? It looks like it, but it also looks really tight.

Thanks in advance.

( Yes you should be fine ) Carl

 

[workinforwood]

I think what's happening is you are using a scraping motion rather than a cutting motion while you turn. A scraping motion, especially over PR will cause a chipping effect. Sharpen your chisel and lower the handle. Ribbons should be release, not dust. Don't get in too big a hurry removing too much material at a time, just gently pull ribbons off the blank. I believe it's all in technique and has nothing to do with your drilling or barrel trimming. If it had to do with either of those, you'd notice a problem before you even started.