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Thread: Dull Pen Blank Trimmer...

  1. #16
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    12,298
    Quote Originally Posted by Bob Bouis View Post
    Generally you wouldn't remove any wood (or very little), but you always have to remove the glue from the ends or the parts won't fit together right.

    But, yeah, sometimes the ends get out of square somehow. Could be stress being relieved when you cut the blank down, could be distortion from being clamped on the mandrel, heat from sanding -- who knows. Or maybe just weren't squared perfectly to begin with, but since it's right before you fit the parts, after finishing is the best time to square everything up once and for all.

    The trimmers don't always chip CA glue off, but it happens consistently enough to ruin your (my) day. Maybe if I sharpened it? I find it inexplicable that even an expensive trimmer like the whiteside is made from carbon steel.
    That makes sense. I've removed excess glue from the ends lightly with the trimmer but usually by hand with 600 grit paper. Maybe I haven't done enough pens to run into distortion. I can't imagine clamping hard enough to distort and my instinct tells me sanding heat would not be good for anything - I sand at low speeds to avoid any heat. I made conical bushings from HDPE just for finishing so excessive pressure is unlikely.

    About carbon steel vs HSS: we turners love our HSS but I understand the principle advantage is how they can take incredible heat in the hands of amateurs with bench grinders without losing hardness. In fact, machinist TubalCain says in one of his books that high carbon steel can be made both harder and sharper than HSS. (I think I can find the reference if anyone is interested.) You just can't grind it casually. Something like a pen trimmer probably won't be sharpened on a bench grinder so the carbon steel may be fine.

    JKJ

  2. #17
    Maybe it's possible to make carbon steel with edge retention as good as high speed steel, but it doesn't seem like they bother with that for pen trimmers. The ones I have dull really easily. I'd say they last about as long in wood as cheap HSS bits last in mild steel.

  3. #18
    Join Date
    Nov 2006
    Location
    TX, NM or on the road
    Posts
    845
    The easiest way is to turn the blank to 3/4 or 5/8 and use a collet chuck to drill the blank. Glue in the tube, then square it using a drill chuck in the tailstock with either a pen mill, a router bit or a sanding disc, or a Forstner bit with the nob ground off.

  4. #19
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    12,298
    Quote Originally Posted by Marvin Hasenak View Post
    The easiest way is to turn the blank to 3/4 or 5/8 and use a collet chuck to drill the blank. Glue in the tube, then square it using a drill chuck in the tailstock with either a pen mill, a router bit or a sanding disc, or a Forstner bit with the nob ground off.
    Just wondering (I haven't tried this). Why does the tip need to be ground off - won't it clear the inside of the tube?

  5. #20
    Join Date
    Nov 2006
    Location
    TX, NM or on the road
    Posts
    845
    I had the bit for for another project, the nob had already been ground off, also the outer cutters, It had been used as a facing bit to square up ends of spindles.

  6. #21
    Join Date
    Jan 2006
    Location
    Paducah, KY
    Posts
    112
    Count me in as one who uses a sander instead of a pen mill. I bought a Harbor Freight 1x30 belt sander and a set of transfer punches, and built a dedicated blank squaring station.

  7. #22
    Join Date
    Nov 2012
    Location
    UP of Michigan
    Posts
    354
    https://www.woodcraft.com/products/w...RoC_6IQAvD_BwE this is an excellent pen mill from Woodcraft. i had both PSI's and the tube fit is better on this mill.

  8. #23
    Join Date
    Feb 2006
    Location
    Southern Ontario Canada
    Posts
    430
    I gave up on pen mills about 5 years ago when it hit me I was going to need a bunch of different sized shafts for each tube type or turn a barrel to fit my slim shaft and each tube type, plus having to sharpen the mill which I never had much luck at. I took a small thin parting tool I had made with old planer blades and ground the tip to an angle a little less than 60 deg. I cut the blank close to the brass tube then using my turn between center bushings I turn the blank round and a little larger than final size. I then take it out of the bushings and mount it between my 60 deg. live and dead centers. Working on the assumption that the tubes are cut square and the dead center will come to rest on the inside of the tube slightly before the blank is cut even with the tube I take the parting tool I made and place it flat side up on the tool rest and trim the blank slowly to get it square and even with the end of the tube. I trim at the headstock end using a carbide tipped dead center then turn the blank around and trim the other end. While trimming I adjust the tailstock to keep the blank tight against the dead center in the headstock. This has worked well for me through 2 or 3 hundred pens since I started it and since I trim at about 1200 rpm I get nice clean cuts on wood, acrylics and truestone.
    Rick
    I support the Pens for Canadian Peacekeepers project

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