ExoticBlanks Diamond Knurl kit drill sizes?

[Smokey S]

I recently received my order of Exotic Blanks Diamond Knurl ballpoint pen kits. The instructions page identifies as "Making the Ellipse or Zodiac pen". For blank drilling the instructions state "Drill the blank with a 10.5mm (for plastics) or 27/64 (for wood blanks) drill bit". My curiosity is why such a difference in drill sizes between wood and plastic. I have never scene this difference on sizes stated in the instructions for any of the other pens that I have made in the last year or so.
Wood. 27/64. 0.421
Plastic. 10.5mm 0.413
Equals. 0.008 difference
TIA for any and all feedback. Sometimes I begin to wonder if it is just me! Just saying…………Smokey

 

[Darios]

I noticed something similar on the instructions for the Majestic JR this weekend.
Needs:
10.5 mm drill bit for lower barrel
0.492 inch drill bit for the upper.

0.492 inches equals 12.4968 mm for a difference of .0012.

 

[egnald]

As with all things in the machine tool world, typical "standard" drill bits are machined and thus have a tolerance. Most are targeted to be on the low side of the "nominal" dimension as most drills and drilling setups do not drill perfectly round holes. That's why in the machine tool world we use reamers whenever precise hole dimensions are necessary.

Part of the difference between the specified sizes in the instructions is likely due to the drilling stability of the material - with wood being less stable I would typically use a slightly larger bit if available (and practical). That being said, I often make the same choice when it comes to plastic blanks as the hole gets smaller depending on how thick and how many layers of paint I apply.

As a side note, I have found that most pen kit instruction sheets are not written using a highly technical vernacular. It is usually rare to see key dimensions even included for key components and it would be shocking if they included the tolerances.

I have also found that there are a lot of conversion rounding factors that come into play. As Darios pointed out, the 0.492 inches in the instructions has most likely been rounded or truncated from the mathematical conversion of 12.5mm. (12.5mm = 0.492126 inches).

On the kits that I use the most often, I create my own "Quick Reference Sheet" for drilling and assembly so that I can have a reference all of the dimensions and stuff at hand when I am working. As can be seen in the thumbnail attachment, I usually include a bracketed table for drill bit sizes so I can choose appropriately depending on the blank material I am using and since they too have an unspecified tolerance, on an empirical OD measurement of the actual brass tubes in the kit.

Regards,
Dave

Click on Thumbnail to Enlarge

 

[Darios]

And here I thought I was being fancy by scribbling down notes on the provided instruction sheets.
It's a shame that you aren't in the business of providing the instructions, because that right there would have saved me from the post 0.470 / nib 0.480 drama over <cough> JR kits.

And coincidentally I've a knurl in the works right now - two numbers if you would like : Knurl cap plate - aka - cabochon :
0.413 inch diameter / 0.058 width at edge.

 

[egnald]

And here I thought I was being fancy by scribbling down notes on the provided instruction sheets.
It's a shame that you aren't in the business of providing the instructions, because that right there would have saved me from the post 0.470 / nib 0.480 drama over <cough> JR kits.

And coincidentally I've a knurl in the works right now - two numbers if you would like : Knurl cap plate - aka - cabochon :
0.413 inch diameter / 0.058 width at edge.

The reason I have all of those details is because I have also suffered a lot of <cough> drama while making pens (especially on the junior gent styles).

 

[Darios]

I just didn't want to confess in public the number of times I made the /same/ mistake.

 

[ed4copies]

I wrote the instructions in question and I would defend them by simply saying drill a 10.5 mm hole in a piece of wood. If it is not REALLY DRY, the hole will close slightly and you will have to force your brass tube into it. Do the same with an acrylic and it will slide in and out.

So, I recognize this difference. In spite of the fact that I have seen instructions for decades and never was a distinction made.
I'd rather be right than follow the "norm"

You are perfectly within your rights to ignore me!!!!!!

Ed

 

[egnald]

I wrote the instructions in question and I would defend them by simply saying drill a 10.5 mm hole in a piece of wood. If it is not REALLY DRY, the hole will close slightly and you will have to force your brass tube into it. Do the same with an acrylic and it will slide in and out.

So, I recognize this difference. In spite of the fact that I have seen instructions for decades and never was a distinction made.
I'd rather be right than follow the "norm"

You are perfectly within your rights to ignore me!!!!!!

Ed

Hi Ed,

That was exactly what I was trying to get when I was talking about the hole size being related to drilling stability of the material, but you said it much better. As you know I do go a little overboard in my explanations and I only create my own versions reference sheets because I tend to screw up - a lot. I think it must be the college instructor and engineer in me.

I certainly hope I didn't offend you with anything in my posts in this thread. If I did, I sincerely apologize as it was by no way intended at all. I have the utmost respect for you and all of the support you give to all of us - your improved Cigar bushings for example, you are the only supplier that takes the initiative to do things like that. If I ever get the chance to make it back to the I94 corridor I would like to swing into Racine to meet you in person and shake your hand.

Regards,
Dave

 

[ed4copies]

Dave and everyone, FACTS will NEVER OFFEND ME!!!!!!!!!!!!!!!!!!

I try to explain my thinking, but you ALWAYS have EVERY RIGHT to think independently!
Oh, I did not take your comments as disagreeing, either!

All is GOOD!!

 

[Smokey S]

Quote-"I'd rather be right than follow the "norm"
A big thanks to Ed and all whom spoke up. And yes, I'm really want to do it right. That is exactly the reason I reached out to this fantastic group of turners. This hobby is really a learning experience daily and I have truely enjoyed every bit of it in this last 1 1/2 years. Thanks to all…Smokey

 

[Smokey S]

Oh, by the way, I like "All is GOOD". Just saying……

 

[bugradx2]

I wrote the instructions in question and I would defend them by simply saying drill a 10.5 mm hole in a piece of wood. If it is not REALLY DRY, the hole will close slightly and you will have to force your brass tube into it. Do the same with an acrylic and it will slide in and out.

So, I recognize this difference. In spite of the fact that I have seen instructions for decades and never was a distinction made.
I'd rather be right than follow the "norm"

You are perfectly within your rights to ignore me!!!!!!

Ed

Am I the only one reading Ed's comment "you are perfectly within your rights to ignore me" and adding "at your own peril" to the end of it and then laughing?