Brass tubes and drill bits

[knowltoh]

I hope this question isn't totally obvious to everyone but me! I don't understand why so many drill bit sizes are used. It seems the tube sizes available are 7mm, 8mm, 3/8" and 10mm, at least from wood-N-Whimsies. If I wanted to buy extra tubes for a kit that recommends an "O" bit, would I not buy the 8mm tubes, and could I not use a 5/16, "O", or 8mm bit to bore the blank?

Sorry if this is a stupid question----am I missing something?

 

[leehljp]

No, you are not. Quite a few think this way, and it has been a common complaint over the past few years.

 

[Daniel]

I have never heard of a comparison of actual tubes, but my suspicion is you are correct. since the fit of the parts are dependent on the I.D. of the tube I would be careful about swapping tube sizes. as far as drill bits, I am of the opinion that 8mm and O bits are the same thing as far as drilling the blank are concerned. If you look through the catalogs of P.S.I, CSUSA and Berea you will find about 35 different bit sizes listed. break those down into what are basically repeat bits and you actually have about 27.

 

[DCBluesman]

It's not a stupid question, but you are missing something. It's called proprietary sizing and it happens everywhere. Why don't all headlights fit any car? Why are there two different bases for candelabra light bulbs? Why do we have electonics and toys that run on combinations of 1.5, 3, 6 and 9 volts? Why don't all charger adapters have the same plugs?

Economically, the manufacturers do not want you to be able to shop replacement parts based on lowest price. Have you ever tried to put a 8.1mm (basically an O size) in an 8mm hole. It won't work. And if you have a 8mm outside diameter tube where the inside diameter does not match the kit design, you will not have a proper pressure fitting.

And if you think drill bits and tubes sizes are complex, wait until you try to make sense of threading.

And how about the fact that Lamy Safari fountain pens take a proprietary cartridge?

And did you know that nibs are not interchangeable, even if they are sized the same? Check out the Waterman nib with the tiny locking flange.

Marketing, sales, price maintenance, proprietary specs. They are all part of the sales game. Just look at Microsoft and Apple!

 

[gwilki]

Daniel: No offence meant, but an O and an 8mm are not the same and are not interchangeable. As Lou said, the O is about 8.1mm. A tube needing an O bore will not fit if the bit used is an 8mm. And if you use an O where you need an 8mm bit, the bore will be too big. You can fill it with Gorilla or epoxy, but there's a big risk of getting it cockeyed.

 

[maxwell_smart007]

Sure it'll work - you just need my drill press with .1mm of slop!

Andrew

 

[knowltoh]

Lets say I have a blowout on a blank I am just finishing. I want to purchase some extra tubes so I can start over and still use the kit. The original blank was bored using an "O" bit. I can only buy 8mm tubes. I know I can't change the tube size the kit uses, but it seems like the tube will fit whether the hole is drilled with an O bit, 5/16 bit, or 8mm bit.

Would an 8mm tube from different vendors be identical? It sounds like some are saying if I have a problem with, lets say, a Berea kit, I should order extra tube specifically for that kit from Berea rather than generic tubes from PSI. Would the ID of a 8mm tube vary from supplier to supplier?

I am not trying to be difficult here--it just seems that 4 bits should suffice for drilling 7mm, 8mm, 3/8, and 10mm. There is no "O" size tube.

Hopefully I have made my question more clear.

Thanks for the replies. This is a great forum.

Herb

 

[wdcav1952]

Sure it'll work - you just need my drill press with .1mm of slop!

Andrew

Andrew,

ROTFLMAO!!!!

 

[Daniel]

A piece of copier paper is 3-4 thousandths (4/1000) of an inch thick. just to give some of you a mental picture of what sort of gap 1/1000 of an inch would be.
Bit sizes as compared to 8mm
5/16 bit is .3125 or -0.0025 (2.5/1000) not even one thickness of paper
8mm bit measures 0.3150 inches
O bit measures 0.3160, or +0.001 (1/1000) 1/3 to 1/4 the thickness of a piece of paper.
an 8.1 mm bit is 0.3189, +0.0039 (39/10000) or about the thickness of 1 pieces of copier paper. for tube fit 0.02 (2/100)has been just about the limit in gap for me and still that is a personal feel type of thing.
looking at that would an 8mm tube fit in a hole drilled by a 5/16 inch bit? in truth it probably would since a bit does not drill a hole exactly the size of the bit but for me the fit of the tube might be to tight.
Also an 8mm tube does not measure 0.3150 inches. it is a tube that is ment to fit into a hole of that size. it is smaller by as much as 0.019 inches according to another thread along these lines recently. that is a difference of 19/1000 right there. I do not think that the 4/1000 of an inch between the 5/16 bit and the O bit is going to be much of a problem.

As far as the comment above about there being no O size tube. has anyone actually measured a tube from a kit that says it is 8mm and one from a kit that says it is O?
I'm thinking they could be the same size.

 

[MobilMan]

Herb. The Hart Double Twist calls for an 'O' size bit. Never bothered to measure it, just bought the bit. Now you've got me to wondering if another bit would have done the trick. Just a note. I did find out that 7mm tubes are not all the same ID. Had some cheaper kits from CSUSA & [which I normally don't do] tubed 4 sets of blanks & was going to use the CSUSA kits. But one set was nicer than I expected so got a out a better kit from Woodcraft. The nib & cap just slid in the tube.

 

[gwilki]

Keith. If you blew out the blank, just turn it down to the tube and start over again. You don't need to buy new tubes. If you want new tubes, you can buy replacement tubes for kits.

Daniel: I just measured a O tube from a cigar kit and an 8mm tube and they are not the same o.d. Close, but no cigar.

Andrew: You've got me there.