Drill Bit Sizes

[Wheaties]

I am still perplexed by the ridiculous drill bit sizes and have already asked about that in another tread. Now I am wondering (because I have never tried it, and am new) how big of difference is 0.008" when drilling the blank, if the 0.008" is on the larger side compared to the recommended size for the tube. I know many people here have said 0.003" or less. Some have said 0.001". But we are talking some really really small differences. So my question is can it be seen, or does it make it difficult to glue the blank?

Here's what brought about the question. I was looking at the reference sheet in the library and noticed the 0.008" difference between 10mm and 27/64, and 12.5mm and 1/2".

I will end up buying the needed bits just because I like doing things right, but I wanted to know if anyone has tried this.

 

[KenV]

You can check the thickness with your calipers (you do have a direct reading calipers -- either digital or dial, don't you?? If not put it on your list with transfer punches). Memory is that card stock is about 0.008-0.010 in thickness. Commerical veneer is about 0.020. So the difference is small. What is important is how thick the turning will be and for thin wood covering, what kind of glue you use, and how precise is your work practices.

The recommended sizes tend to provide adequate space, but alternative that are a few thousand different can be used. Sometimes people like the alternatives, and some times they do not work successfully.

For me, tight tolerances have been more hassle than the cost of a drill bit.

 

[jkeithrussell]

Some people use the slightly larger sizes for various purposes. I sometimes use them when I plan to paint the tube and inside of the hole in the blank. I also sometimes use them when I plan to use Gorilla Glue (which I prefer for segmented wood blanks) or epoxy (which I prefer for anything other than wood). The point is that you don't want the tube to have any room to move around in the blank or the bond could fail. If you are going to use CA to glue in a tube, I think you should use the recommended size of drill bit, generally speaking.

 

[Randy_]

Some time ago I complied data on about 60 pen kits and compared tube ODs with the recommended drill bit sizes.

I found that the recommended sizes ranged from a min. of 0.003" over to a max. of 0.019" over. The great majority were in the neighborhood of 0.008" to 0.012" over.

You will probably get some difference of opinion on this question.......some of it just personal preference and some of it based on variations in materials and adhesives. Personally, I like to have the holes on the smaller end of the range for most applications and have a little more thickness for the barrel material.

Do keep in mind that changing drill bits by only a few thousandths could cause a real problem. It is the size of the hole relative to the size of the tube that is critical. If you use a bit that is slightly smaller than the recommended bit and the recommended bit is already at the low end of the range, you will end up with a hole that is too snug. Conversely, where the recommended bit is at the high end of the range already, you could end up with a hole that is way too loose.

Best way to check this out is drill a test hole in a block of scrap wood and try the actual kit tube to see how well it fits.

 

[maxwell_smart007]

Too snug will cause glue starvation, but if one uses thick glue, moving up 2 tenths of a millimetre cannot cause much difference, can it?

I'm planning on using a good quality 1/2" drill bit for the statesman cap, rather than buy a brand new drill bit that I'll use very infrequently....i'll let you know how it works...

(plus, once I add a layer of paint to the inside of the tube, it'll be close to the same thickness as if I used a regular bit and didn't paint it, I figure!)

Andrew

 

[Randy_]

Andrew.......get smart!!:wink:

0.2mm is 0.0078". Supposing you are working a kit where the recommended bit is already over-size by 0.019"and then you add another 0.008". Now you are 0.027" over. You will have a hole you could drive a tank through.

Each kit is different so there is no stock answer that will cover all possibilities.

 

[ed4copies]

Wanna different answer???

Look at the BUSHINGS!!! Yeah, look to see how much material you will have AFTER you turn. IF they have very little material --- BE CAREFUL!!

If you are doing a cigar (lots of material) -- live a little --- GREAT pen for experimenting. When you can see the tube at the nib end of the cigar (with resins) or it shatters (with wood), you will learn what tolerance is too close.

 

[JimB]

The best thing to do is to use scrap wood to test drill and see how the tube fits.

For me, there also seems to be 2 other things to consider. I can use the same bit on 2 different types of wood and get slightly different results. Also, drilling multiple blanks can also result in differences. I assume, but don't know, that this is due to heat build up in both the bit and wood. I generally only drill a few blanks and then let the bit cool off.

Before gluing in a tube I always test it in the drilled blank to be sure it goes in smooth without getting stuck or having too much wiggle room. I use thick CA and I have had expereinces with holes too tight and the CA starts curing before i get the tube in. I have also had tubes to loose resulting in voids with no CA between tube and wood results in blow out on the lathe. Experimentation, practice and expereince has now just about eliminated these problems.

 

[maxwell_smart007]

Andrew.......get smart!!:wink:

0.2mm is 0.0078".
Each kit is different so there is no stock answer that wikk civer all possibilities.

Well, if it didn't have that 8 in there, it would have been 007, so I would have HAD to try it...

But what you're saying is that forgetting to order the drill bits was a BAD thing eh? I wonder if my large set of drill bits has the .5 sizes...unlikely eh?

Andrew

 

[mickr]

for any drill bit under a 1/2 inch buy the popular sets that are everywhere..get in inch & metric if you wish..then you have tons of choices and can be happy with the diversity

 

[wdcav1952]

Take some time and count the number of drill bits needed to make the kits you wish to make. I have been turning for 5 or 6 years, and I have less than 2 dozen drills, some of which are standard sizes that could be bought anywhere. I consider the drills to be part of the cost of this hobby/craft/art form. I also consider the cost of my lathes, blanks, turning tools, finishing supplies and likely other things that I likely left out. Even if I had paid $10 per drill bit, which is certainly more than I actually paid, my drill expense is still less than the cost of a decent mini lathe.

 

[RussFairfield]

The best pens will always be those where the drilled hole is the closest fit with the brass tube, and the closer the fit, the better.

There are a couple problems with oversized drills. The 1st is that most of the glues we use don't fill gaps very well. A good glueline is a gap of only a couple 1/1000's of an inch. Anything greater than that and there can be a problem keeping the tube in the wood until we can get the pen barrel turned and finished.

The bigger problem is that a large gap usually means that the tube will not be centered in the hole. That means the wood is thicker on one side than the other and this starts a chain reaction of potential problems, from a difference in wood movement with the diference in thickness that can accelerate cracking, to being one of the causes of oval pen barrels.

 

[Randy_]

Take some time and count the number of drill bits needed to make the kits you wish to make. I have been turning for 5 or 6 years, and I have less than 2 dozen drills, some of which are standard sizes that could be bought anywhere. I consider the drills to be part of the cost of this hobby/craft/art form. I also consider the cost of my lathes, blanks, turning tools, finishing supplies and likely other things that I likely left out. Even if I had paid $10 per drill bit, which is certainly more than I actually paid, my drill expense is still less than the cost of a decent mini lathe.

Nicely stated!!

Other point is that if all pen kits could be constructed with only few different bits, they would all start to look the same. The fact that we have several hundred different choices of kits available is partially a function of the fact that there are so many different tube sizes.

For those that are concerned about how many different drill bits they need, there is an easy solution. Buy just two bits.....the 7mm and the 10mm.....and make nothing but slimlines and cigars. Bet that will get "old" in a hurry!!

 

[Randy_]

.....
The bigger problem is that a large gap usually means that the tube will not be centered in the hole. That means the wood is thicker on one side than the other and this starts a chain reaction of potential problems, from a difference in wood movement with the difference in thickness that can accelerate cracking, to being one of the causes of oval pen barrels.

I've seen that theory posted before and have given it a lot of thought. And the more I think about it, the less I understand it. I sure would like for someone to explain how that can happen.

Seems to me that if you have a blank spinning on a straight mandrel with accurate bushings, the resultant barrel will be round and outer surface will be concentric with the long axis of the mandrel. If the tube is not centered in the blank, I can understand that the final thickness of the blank will not be uniform; but I don't understand how the exterior surface will be oval?? It seems to me that if the blank is spinning accurately, then the cutting tool will take off only the high spots of the blank and leave a perfectly round surface.

 

[DCBluesman]

Using the diagram below, square the blank against the tube, then turn round. You will definitely have a thick side and a thin side to the wood. If it is pronounced enough, you may even turn through the blank itself. FYI, this is just three-degrees off! Note: The barrel is not really oval, but it is eccentric (non-concentric).

 

[nava1uni]

Before I say anything I want to comment on Cav's new dancing chili with green sneakers. Very HOT Heh, Heh. I find that having different bits for penturning is really no different then having different sizes for different size screws, bolt, etc that I use in every phase of repair, building, inventing. The only difference is that I keep my pen drill bits in plastic cases so they remain sharp. I find that the correct size bit makes for much better gluing and decreased blow outs or tubes coming loose while turning.

 

[Randy_]

Using the diagram below, square the blank against the tube, then turn round. You will definitely have a thick side and a thin side to the wood. If it is pronounced enough, you may even turn through the blank itself. FYI, this is just three-degrees off! Note: The barrel is not really oval, but it is eccentric (non-concentric).

Lou: I certainly agree that you will end up with a barrel that does not have a uniformly thick wood, acrylic or whatever "skin"; but the barrel should still be round and match up well with the hardware if a turner's other crafting skills and his tools are correct. It looks like we agree that an angled tube would not cause a barrel to be oval.

BTW, the three degree angle you display is probably somewhat unrealistic. I got out my trig tables and did a little figuring. If you drill a hole that is 0.020" over-sized in a blank for a Sierra pen (which is a lot more generous that most folks are likely to go), the angular error is a bit less than 1/2°.

 

[Rifleman1776]

It took eight posts before someone actually suggested "test" your intended drill bit.
I agree, buying the weirdo size bits for new kits is both frustrating and an expense.
But, I am not of the school of thinking that oversized holes are OK. A good fit is part of making a good pen.
That said, be aware there is much confusion regarding proper bit sizes. Some vendors recommended sizes that are actually not the best for a given kit. If you bring it to their attention, some might send you a new, proper, bit. But, sadly, it doesn't always end there. Often (Yes, often, I have seen it.) even though the vendor knows their advertised bit size is incorrect,they fail to change the catalog, thus continuing the frustration and ruined pens for many customers.
I suggest using what works best for a given kit. That may require testing and buying more than one bit. When placing orders, I always call and ask if there are updates in specs from what is printed in the catalog.
Do use this forum for good information. Ask.
My bottom line recommendation? Don't do the oversize hole thing. That is a formula for sloppy looking pens. The test, experiment, learn curve may be frustrating and expensive but if good pens are your goal, there are no shortcuts.

 

[wdcav1952]

Before I say anything I want to comment on Cav's new dancing chili with green sneakers. Very HOT Heh, Heh. I find that having different bits for penturning is really no different then having different sizes for different size screws, bolt, etc that I use in every phase of repair, building, inventing. The only difference is that I keep my pen drill bits in plastic cases so they remain sharp. I find that the correct size bit makes for much better gluing and decreased blow outs or tubes coming loose while turning.

LOL, thanks, Cindy. It is supposed to be a gif. but I haven't messed with it enough to get it moving here on the site.

Randy and you made the point well that drills are a part of doing business. I particularly like Randy's point that if the manufacturers made all their kits around a few common drill sizes that the pens would tend to all resemble each other.

When I get back home tomorrow, I will try to get my pepper dancing and then it really will be hot!! :biggrin:

 

[Daniel]

I don't remember where I have put it but I once made a list of drill bits that basically are all the same bit where penturning is concerned. I know when I made the list I did not allow the bit to be within 0.01" of the tube size or larger than 0.03.
Keep in mind that the hole has two sides so a bit that is 0.03 over the size of the tube creats a gap this is 0.015.

 

[wdcav1952]

I don't remember where I have put it but I once made a list of drill bits that basically are all the same bit where penturning is concerned. I know when I made the list I did not allow the bit to be within 0.01" of the tube size or larger than 0.03.
Keep in mind that the hole has two sides so a bit that is 0.03 over the size of the tube creats a gap this is 0.015.

That is strange. I have noticed that the holes I drill don't have two sides; they are circular. Of course the tubes I use are circular so that works for me.

 

[Daniel]

Well I guess the idea that a hole has two sides was thought up by the same people that think that the extra length you leave on a pipe for the fitting is called the take off.
The fact still remains that the gap around the 1 side of the tube is on average 0.015 if you drilled the hole 0.03 inches larger.

 

[Randy_]

It took eight posts before someone actually suggested "test" your intended drill bit.....

Actually, Frank, it was the third response (post #4) where the suggestion was made to drill test holes.

 

[Randy_]

I don't remember where I have put it but I once made a list of drill bits that basically are all the same bit where penturning is concerned. I know when I made the list I did not allow the bit to be within 0.01" of the tube size or larger than 0.03.
Keep in mind that the hole has two sides so a bit that is 0.03 over the size of the tube creats a gap this is 0.015.

Every individual pencrafter has his own limits as far as what sort of slop s/he is comfortable with. In my data collecting on pen kits, I have never come across a drill bit recommendation from a manufacturer that was more than 0.019" over-size and I can't possibly imagine being satisfied with a hole that was 0.03" over-sized. Personally, I like to keep in the range of 0.006" to 0.010" over-size which represents a clearance between the tube and the blank of the thickness of a sheet of newsprint or a little more. (0.003"+)

One exception would be plastic blanks that are semi-transparent and need to have paint applied to either the tube or the blank and another is when using Corian. I've had a Corian blank or two crack when pressing in nibs and finials when the blanks were very tight. Also, I am experimenting with looser blanks and flexible adhesives to see if that has any effect on the cracking that seems to be associated with snakewood and ebony blanks.

 

[DCBluesman]

Lou: I certainly agree that you will end up with a barrel that does not have a uniformly thick wood, acrylic or whatever "skin"; but the barrel should still be round and match up well with the hardware if a turner's other crafting skills and his tools are correct.

No, this is incorrect. It you assume the tube is concentric with itself, the blank is eccentric to the tube and the findings are concentric with the tube, the barrel will never match up well with the hardware.

And yes, my three-degree example was an exaggeration such that folks could clearly visualize what happens with an oversized hole.

 

[Randy_]

No, this is incorrect. It you assume the tube is concentric with itself, the blank is eccentric to the tube and the findings are concentric with the tube, the barrel will never match up well with the hardware.

I suspect that if you think about this a little more, you will come to a different conclusion. I don't have software that will allow me to make a drawing and post it like you have done.

Please take a minute, if you wish, and add to your drawing a bit. Take the one with the tube that is cocked and chop off the ends as it the blank had been squared. Then draw in a couple of bushing that are proportionally correct as to size. Then draw a couple of lines that represent the surface that would be left if the blank was turned B2B.

I think you will see that you will get a perfectly cylindrical barrel whose outer surface will be perfectly concentric to the long axis of the tube. Because the tube was cocked originally, some areas of the wood "skin" will be thicker than others; but the difference will be filled with glue or will just be a gap.

In the meantime, I have an old version of Autocad and maybe I can figure out a way to do a drawing in it that I can post here??

And finally, note the hilited text in your comment. Is that a typo of some sort?? I'm not familiar with the term "findings" as you used it above??

 

[Daniel]

I also see that since the outside material will be turned away. how much of it is wood and how much of it is adhesive is the only issue. with everything else working correctly it would be concentric to the tube.
It would leave thicker wood on one side than the other and this could cause some serious problems when you consider that wood expends and contracts. basically you have a thicker portion that will move in proportion to it's thickness stressing the thinner portion. this very well could at times cause one area of the barrel to not match the fittings (thicker wood = larger expension). In effect creating an oval shape to the barrel.
I have noticed that on the scale of a pen and the tolerances needed for a correct fit. that even tiny differences in wood movement are noticeable. I have also noticed that even small amounts of moisture will cause a blank to crack. So much so that I have all but given up on anything but stabilized wood.

some random thought on another subject. Snakewood and Ebony cracking. All wood has internal stresses. basically the outer wood is keeping the inner wood in place.as the outer wood is removed these stresses are able to release actually causing a change int he shape of the wood (warping). I suspect that snakewood for sure is an extreme example of this and the problems it causes. this would also be part of the reason that boilng helps. Ebony could also fall into this catagory but I am not at all sure about it. I believe that the problem with Ebony is the amount it will move with moisture changes. The best fix I know for Ebony is African Blackwood.

 

[NewLondon88]

And finally, note the hilited text in your comment. Is that a typo of some sort?? I'm not familiar with the term "findings" as you used it above??

I'm guilty of using that word, too. I think it comes from the jewelry industry,
but it refers to the parts used to make something. I've been using it for
30+ years with regards to pens. .it usually refers to finials, nibs, center bands,
clips, jump rings, clasps, chains etc. etc.
Probably not many people in the public use the term, but I'm sure that
the manufacturers use it every day. Those are the people I got the term
from.

 

[rjwolfe3]

find·ing (fīn'dĭng)
n.

1. Something that has been found.
2. 1. A conclusion reached after examination or investigation: the finding of a grand jury; a coroner's findings.
   2. A statement or document containing an authoritative decision or conclusion: a presidential finding that authorized the covert operation.
3. findings Small tools and materials used by an artisan: a jeweler's findings.

The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.

(Cool I learned a new word today!)

 

[Ron in Drums PA]

Using the diagram below, square the blank against the tube, then turn round. You will definitely have a thick side and a thin side to the wood. If it is pronounced enough, you may even turn through the blank itself. FYI, this is just three-degrees off! Note: The barrel is not really oval, but it is eccentric (non-concentric).

Please take a minute, if you wish, and add to your drawing a bit. Take the one with the tube that is cocked and chop off the ends as it the blank had been squared. Then draw in a couple of bushing that are proportionally correct as to size. Then draw a couple of lines that represent the surface that would be left if the blank was turned B2B.

I think you will see that you will get a perfectly cylindrical barrel whose outer surface will be perfectly concentric to the long axis of the tube. Because the tube was cocked originally, some areas of the wood "skin" will be thicker than others; but the difference will be filled with glue or will just be a gap.

How many times have we heard that an over tightened or bent mandrel caused an oval pen.

The symptoms of a oval pen and a cocked tube can produce the same effect on a finished pen.

I'm thinking that the cocked tube is the more likely the culprit.

A few things to remember.
A dull bit will drill a larger hole than a sharp bit.
Not clearing the bit will cause the drill to make a larger hole.
Just because the drill is stamped 3/8" doesn't mean it is 3/8". I find this happens quite often with the cheap drill sets. Make sure the bit is the right size by measuring it before you drill with it.