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Strange Question Time...

I have a question that ought to fall into the dumb category, but I am getting "answers" to it that are inconsistent.
 
OK, back in the dark ages (1968) I bought two :sets: of metric drill bits. As I recall (and it was 50 years ago now) the primary set ran from 0.5mm to 15mm and the secondary "set" ran from 15mm through 35 mm. I have spoken with 3 Aerican Drill Bit Manufacturing Companies and am being told that 17.5 mm is the largest diameter metric drill bit they make. This seems irrational to me!

Now what I am doing is creating a spreadsheet where you can enter a "Hole size" and it will tell you what the nearest three Drill Sizes (next smaller, closest to indicated diameter, and next larger) are. What I have says that Drill sizes 0.35mm to 2.5mm are supplied in 0.05mm increments and 2.5mm through 10mm are supplied in 0.1mm increments. and 10mm through 14mm in 0.2mm increments and 14mm through 17.5mm in 0.25mm increments. Now, mind you, these "data" comes from American Drill Bit Manufacturing companies. (A) Is this data generally correct and (B) are there any generally accepted "extensions" to it?

Irrational minds want to know!
 

simonb65

Alibre Super User
Why just metric? My Zeus pocket book includes imperial, letter and number sizes which will get you a better hole size match?
 
Why just metric? My Zeus pocket book includes imperial, letter and number sizes which will get you a better hole size match?
I have all the "US standard" drill bit sizes already. However, there used to be (at least) a "set of standard" metric drill bit sizes you could assume most machine shops had in stock. That is what I am looking to find.
 

iwanttoslot

Member
Over time I have seen a lot of rationalisation of drill sizes and styles from manufacturers and with buy outs and acquisitions there have been significant changes to what drills are available.
Brands like Dormer and Guhring have changed significantly over the last few years.
Added to that the different machining methods and type of machines available has also had an influence on what
drills are available.

With that in mind i have not seen a drill bit or what we down here call a jobber drill over 20mm in dia from any supplier we have.
 
Over time I have seen a lot of rationalisation of drill sizes and styles from manufacturers and with buy outs and acquisitions there have been significant changes to what drills are available.
Brands like Dormer and Guhring have changed significantly over the last few years.
Added to that the different machining methods and type of machines available has also had an influence on what
drills are available.

With that in mind i have not seen a drill bit or what we down here call a jobber drill over 20mm in dia from any supplier we have.
I have no leg to stand on to disagree with you. I know that whereas I can buy drill bits as large as 3.500 inches, few shops stock drill bits larger than 1.500 inches in diameter as it is simple to set up a boring bar for anything larger than (say) 1.375 inches in diameter. I would assume that a similar "judgement call" apples to the metric side of the universe, I am just unaware what that "judgement" is -- though I am willing to learn!
 

albie0803

Alibre Super User
We used to have a wide range of large drills but these days we use tipped "cam" drills or "U" drills which blast through material in a fraction of the time that the old drills used to take. So basically the large drills are just not feasible any more.
 
We used to have a wide range of large drills but these days we use tipped "cam" drills or "U" drills which blast through material in a fraction of the time that the old drills used to take. So basically the large drills are just not feasible any more.
I shan't disagree about the (Factory of the Future) developments im drilling technplogy, bit sizes amaller than (say) .750 still tend towards more conventional Drill Bits.
 
OK, here is the inch drill sizing system. The Drill Bits Size Matching.7z archive contains a spreadsheet (in Excel and OpenOffice Calc formats) that takes a desired hole diameter between ø.0.135 anr ø1.500 inches (value entered in Cell B8), Finds the three closest values and returns the closest value in Cell J8. I developed this as part of assigning appropriate tap "Pilot Hole" drill sizes, but you may find this useful.
 

Attachments

  • Inch Drill Bit Sizes.zip
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JST

Alibre Super User
Generally drilling is the lowest cost way to remove material from a hole. So large drills do make sense.

Not sure how that affects Alibre, other than the hole bottom shape....
 
Generally drilling is the lowest cost way to remove material from a hole. So large drills do make sense.
It is not so much the material removal speed as it is the resulting accuracy of the hole size when using llarge diameter drill bits (as well as the cost to acquire and maintain them).
 

JST

Alibre Super User
Drilling is not generally famous for hole size accuracy. Nor location , roundness, or straightness either.

But drilling makes a cheap hole.
 
Drilling is not generally famous for hole size accuracy. Nor location , roundness, or straightness either.

But drilling makes a cheap hole.
Any machinist worth their salt knows how to improve the accuracy and precision of twist drill created holes. The problem is that machinist's worth their salt are overseen by incompetent mis-managers at leat 90% of the time.
 
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