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Pen Blank Drilling ('Dot Theory' Debunked)

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Blog entry by rance posted 03-23-2013 09:36 PM 1945 reads 2 times favorited 8 comments Add to Favorites Watch

I am on a few wood-related mailing lists that send out their weekly e-letters. I am continually amazed at the less than stellar information that is propogated. And the latest one is from a major magazine. It spurred my interest again about a particular aspect of pen making that just keeps being propogated as fact. Where in fact, it is really in error. It has to do with aligning the holes between two halves of a pen blank. Like you would do with a Cigar pen.

When preparing a pen blank for drilling, we often add a witness mark down the side of the blank, spanning where we plan on cutting it:

This make it easier to realign the grain later:

We flip the top piece over:

And then we mark adjacent corners with another witness mark, a dot:

Rotate and ready for the vise:

This dot helps us properly orient the blanks into the vise. We align the dot on the blank with an arbitrary dot we put on one jaw of the vise. Now if we properly align the vise to drill perfectly in the center of the blank, then we have no problem:

Sometimes however, we find that for whatever reason, the setting has wandered and the hole is slightly off center on the first blank:

We’ve been told though, that if we align the dot on the second blank with that same dot on our vise, then the offset will be cancelled out. This would be fine if it actually worked. Actually, it WILL work if the error is in the direction of the other jaw. The problem comes when the bit wanders in ANY other direction, such as shown in the previous picture.

If we drill the second blank with the same setting, the hole will be located at the Red mark, which would be wrong. The proper location would be to drill it at the Green mark:

In the Green location, it would correctly align the grain of the two blanks.

Conclusion: Mark your pen blanks but don’t bother with the ‘Dot Theory’. Just do a better job of setting up your drill press. Or just use your lathe for the drilling. Hope this helps someone out. And I hope I havn’t stepped on any toes out there.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--



8 comments so far

View Deycart's profile

Deycart

402 posts in 1006 days


#1 posted 03-23-2013 10:10 PM

I don’t turn pens, but your explanation makes sense. I really appreciate the time you spent in sketchup. I use it all the time to try out my hair brained ideas before I waste shop time and money. If I ever get into pen making I will have to keep it in mind.

View William's profile

William

9271 posts in 1590 days


#2 posted 03-24-2013 12:53 AM

I am new to turning pens. I am really enjoying it though.
This is the first I’ve heard of the dot theory, and am somewhat baffled by it.
I carefully set each blank up in the drill press to start drilling on the end where I cut the blank. Then, I carefully set things up to drill as perfectly on center as I can get. I mark this using a center finder and then locate point of my bit to it.
Here’s my problem. The bit, depending on grain direction, and a variety of other things, sometimes wanders a tiny bit anyway. That’s why we trim the ends isn’t it? To make sure the ends are square with the tube?
Anyway, if I do everything right as I described, I haven’t had any issue yet with lining the grain back up beautifully after turning the blanks.
I just fail to see how this dot theory could make things any more accurate, at least as far as I think the human eye could see. If there is a point to it besides an exercise in frustration, I hope someone would enlighten me.

-- http://wddsrfinewoodworks.blogspot.com/

View NormG's profile

NormG

4510 posts in 1752 days


#3 posted 03-24-2013 01:26 AM

I use a centering vice, combines with the witness markings as my reference point

-- Norman

View Monte Pittman's profile

Monte Pittman

15455 posts in 1086 days


#4 posted 03-24-2013 01:45 AM

Your explanation makes sense from when I worked in a machine shop. However, your last comment makes the most sense, do a better job lining up your parts when drilling.

-- Mother Nature created it, I just assemble it.

View woodbutcherbynight's profile

woodbutcherbynight

1311 posts in 1157 days


#5 posted 03-24-2013 03:28 AM

I agree with Monte on this, set up is the key and attention to detail is important. But…..if the grain does not match up the way you want it save both blanks, make two more from a different wood and mix and match. Crazy I know but I sell more of those pens than the matching one’s. I glue up all the acrylic cut off’s and make a pen from them and it usually gets sold first.

Why, have no idea but I make such wonders purposefully because they sell. At the end of the season I walk away with a nice profit for my winters worth of work and can get all those nice new tools I drooled over all winter…. (laughing)

-- Live to tell the stories, they sound better that way.

View rance's profile

rance

4147 posts in 1908 days


#6 posted 03-27-2013 08:41 PM

William, If your bit wanders(sometimes mine do too), no amount of squaring the ends will fix that. What you want to do is compensate when drilling your 2nd blank to make it match the first. Squaring the ends with your pen mill only makes them smooth, flat, and perpendicular to the tube. It makes sure the mating brass hardware fits flush all the way around the pen.

Norman, Using a centering vise gives you consistency from one blank to the next. If the vise is aligned perfectly, then no use for the witness marks in the first place. If the vise is not perfectly aligned, then no amount of witness marks etc. will compensate for the error. Fwiw, using witness lines when mounting a blank in the vise is the same as the ‘Dot Theory’. Hope this helps.

Woodbutcherbynight, You are right. When I blow out a blank and have to fix it, I then have to sell it for more because it took more time, AND it usually looks better. So funny. Per your suggestion, I think I’m gonna stop turning plain pens and have ALL mine customized. Thanks for your input.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View William's profile

William

9271 posts in 1590 days


#7 posted 03-27-2013 10:08 PM

Thank you for explaining that.
I’ve never had my bit wander enough yet to justify all this. I will keep this thread in mind to refer back to in a case it happens to me on some kind of material that I can stand the thought of wasting.

-- http://wddsrfinewoodworks.blogspot.com/

View Jim Jakosh's profile

Jim Jakosh

12349 posts in 1853 days


#8 posted 03-28-2013 02:41 AM

Hi Rance,
I don’t make pens, but I think the centering is very important. I always use a center drill to start a hole in wood because a twist drill will “walk” when it hits the grain. One thing I think I would do is to first drill the part through past the cut line a bit. Then cut it it half and continue drilling in the partial hole through the second half to the other end. That way the hole is exactly aligned with the first half. You could mark the cut line so you have those two ends come together on the actual pen so the grain pattern is continuous.

Also. I made some blanks for a friend who turns pens in Illinois. I did not use a pen vice because the jaws are too short for the long blanks. I clamped them in a long angle plate I made for the drill press that has a long vertical square corner in which I clamped the blanks. This holds them true so the drill has a better chance of holding the center from one end to the other

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

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