Pen Blank Drilling Probs

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Julie

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I can not for the life of figure this out!!!! :(

I have been drilling pen blanks with a brad point bit. Now all of a sudden they are all drilling in a diagonal. Whats up? I have made a drilling jig so that the blanks are held horizontial.

What type of drill bits do you all use? [?]

I have been drilling curly maple, corian and stabilized blanks lately.

Thanks
Julie :)
 
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Scott

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Hi Julie!

First, look at your drill bit. See if it is uneven in any way. Is it sharp? Is the shaft bent, even a little? If you have extra drill bits (not a bad idea) try one of the others to see if you get the same results.

Next, even though you lined up your jig to be square, check it again. The table needs to be square to the shaft of the drill. Use this opportunity to check and see if you have inordinate runnout as you extend the quill. You can get a cheap dial indicator for this at Harbor Freight.

Even after this you can get some wandering. A 7mm drill bit is thin enough that it doesn't take much force to get it to wander off course. The best defense here is to use sharp bits, back the drill bit out often, keep it cool, and use the right speed for drilling. What's the right speed? Try different speeds until you get one that gives you the performance you want. BTW, it changes based on the material you're drilling.

I use a 7mm bullet bit I got from Craft Supplies. But I also use a regular 7mm twist bit on my other drill press because I'm able to keep it sharp.

I hope this helps! What it comes down to is that you can get some wandering anytime. But when it becomes consistent, then something is off with your equipment. Good Luck! Let us know what you find.

Scott.
 

RussFairfield

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I posted the answer on the Yahoo group because I saw it there first. Sorry about that Scott. I am repeating it here because I think it is worth having in the archives of this group. I also had a chance to edit in posting it here.

After all of the vise and vertical alignments of the drill press, table and fixtures have been taken care of, we are still not guaranteed a straight hole in a peece of wood. Many dilling problems can start at the initial entry of the drill bit into the wood. We are drilling onto end grain, and because of the varying density of the wood, the drill bit will want to take the path of least resistance, which is not always the one that we want it to start on. If the bit moves off of center at the start of the hole, chances are that it will continue to follow that path that is at an angle to the centerline of the drill press or lathe. The 7mm drill is flexible enough that it can be off as much as 1/8" or 3/16" in the length of a 2" long piece of wood.

There are three ways to prevent this from happening, and none of them
have anything to with how the wood is held in vertical alighment with
the drill bit........

Cut the end of the pen blank square to its length, and as smooth as possible. When this surface is square to the drill bit as it enters the wood, both sides of the bit will start cutting at the same time.
The smoother surface prevents surface ridges from influencing the drill bit at entry.

Once the hole has started, and IF the drill bit has pulled off-center enough that you can see it (Watch the tip of the drill as it enters the wood) - move the piece of wood around until everything is lined back up again before drilling on through the wood. Otherwise, the drill bit will continue to follow the line that is at an angle to the one you want. It may still want to wander as it goes down through the wood, but you will have at least started it straight. Being able to move the wood around is an advantage of the drill press. Not being able to re-orient the wood is a disadvantage of drilling in the lathe or having a fixed fixture for holding the wood in the drill press.

Use a drill bit that is the less suseptable to following the path of
least resistance as it goes into and down through the wood. I know
not everyone will agree with my opinion, but...

The standard twist drill is the most influenced by the wood grain, the most likely to get started off-center, and the most likely to follow the wood grain as it goes through end-grain wood. An advantage of these drills is that they are easily sharpened, but unless you use some type of jig that ensures that both sides are equal, the unequal
cutting edges from a "free hand" sharpening can make it worse than a new drill.

The "Bullet Point" drill is the least likely to be influenced by the wood grain at entry, and the least likely to be influenced by the grain as it goes through the wood. That little pilot hole in front of the main drill was a wonderful invention. I haven't figured how to sharpen one of them yet.

The brad point drill can be somewhere in between, but depending on the
wood can be worse than the standard twist drill at entry and as it goes down into the wood. If the wood has a strong grain, the sharp point on the center spur will skid to the side when you try entering the wood along a hard grain boundary. If a sharp nail driven into the end-grain will move to the side to find softer wood, the sharp point of the drill will do the same. Once started into the hole, the spurs at the OD of the bit are supposed to keep the point from following the grain. However, in end-grain wood that has a strong grain or in laminated wood, the sharp knife-like and unequal angles of the cutters will make them also want to follow the grain, and the result can be the worst of all drill bits.

Now, you will have to hold the wood in vertical alignment with the
drill bit, and that is a problem with the vise or whatever else you
are using and the table being square to the quill.

None of this will guarantee a perfect hole, but it will eliminate a
lot of the drilling problems.

Russ Fairfield
 

Scott

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Excellent response Russ! It really goes into the "reasons why" and gives some great advice on how to counteract these forces. Do you have this on your site? How about formatting it as an article and posting it here? Think about it.

Scott.
 

Julie

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Goose Creek, SC, USA.
Thank you very much for the quick answers. I really appreciate them. Now back out to the shop. everything looks good, better order a new drill bit..

Thanks
 

RussFairfield

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And, all bets are off if you are trying to drill a hole with a dull bit. That may be part of your problem if you are having the same problem with all materials.

There is another problem with plastics. Something that is easily forgotten when drilling a plastic is that these materials can start to melt at 150-degrees. If the drill bit is hot enough that you can't touch it, it could easily be at that temperature. The solution is to never let the drill get that hot.
 

pen-turners

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while drilling the corian it will get very hot. I use transmission oil to lubricate the bit while drilling. I have actually warped bits in my earlier days by letting them get too hot on corian.

Chris
 

RussFairfield

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Chris,
That transmission oil will work even better if you thin it with a little Kerosene. The kerosene will carry away the heat better than oil by itself.

Another option is to use soap water. Use real soap, bar or liquid, and Ivory is best (my opinion). Real soap has more lubricity that the liquid detergents. A 2 to 1 water and Ivory Snow or shavings from the bar is a good solution. Use a lot of it.
 

pen-turners

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I actually solved my problem with overheating by making a small drilling mold. I t is about 5x5 inches and has 2 gasketed holes on the side to let the clamp come through. I fill this mold with soapy water or just plain water and then as I am drilling my whole corian blank is submerged. It does really well although you can not see what you are drilling too easily. The blank is pretty much held in place by a small wood block on the bottom of the mold that has a 5/8 x 5/8 square cut into it that the corian blank fits down into. This keeps the blank from spinning while drilling so the only thing the clamps have to do is keep the blank upright. The other thing I found most helpful with corian is to have my Drill Doctor close at hand and sharpen every few blanks!!

Chris
 
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