Manual says to use drill bits as gauge but numbers?

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gdizzle

gdizzle

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Trying to fine tune the holley 1920 1bbl for the dddddddart 225.

In manual it says to use drill bits inbetween butterfly, but it gives strange numbers? How does this translate to regular bits? i.e. it says use a #52 bit? then it says to use a #38 bit? Any ideas?
 
Besides fractions drill bits can be called by numbers. The smaller the number the larger the dia. of the bit. A #1 drill bit is a few thousands larger than a 1/4" bit. There are also letter bits. Both letter and number drills are often call out as drill sizes for a hole that is to tapped. A good hardware store should have number drills, not real sure about letters. You should be able to drill charts on the internet to download.
Mike
 
Guess fractions were too difficult for the average 'home'-improving redneck so they started coming up with alternative charts. :)
Another area where the metric system would have solved 'cr@p' like that :)
 
You'll notice that most of the number/letter sizes are perfect to use as drills for various sizes of taps. If you work in the machining field these things become etched into your memory.

Most of this "crap" can be blamed on the British. For example the number drill sizes are based on the British "Stubs Steel Wire Gauge" from the 1800s.
 
69_340_GTS said:
You'll notice that most of the number/letter sizes are perfect to use as drills for various sizes of taps. If you work in the machining field these things become etched into your memory.

Most of this "crap" can be blamed on the British. For example the number drill sizes are based on the British "Stubs Steel Wire Gauge" from the 1800s.
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^^^this^^^buy a tap and bit set and you'll get a #25 bit for a 10-24 tap now go to your local tool store and try and replace the #25 .

PS you will notice that neither chart gives you an actual size that you can walk in and ask for as a replacement #25 but that 10-24 tap is one that I use a thousand times a year doing door hardware .
 
I sell them but don't stock them. Like as described before, they are mostly used in tap and die sets.
 
69_340_GTS said:
You'll notice that most of the number/letter sizes are perfect to use as drills for various sizes of taps. If you work in the machining field these things become etched into your memory.

Most of this "crap" can be blamed on the British. For example the number drill sizes are based on the British "Stubs Steel Wire Gauge" from the 1800s.
Click to expand...

Interesting. I never knew that.
So maybe you can tell me why an "E" drill is the same as 1/4" (.250)

Ted
 
Because the E in letter scale is .250 and one fourth in inch scale is also .250
Stranger things have happened.
 
cannucky said:
^^^this^^^buy a tap and bit set and you'll get a #25 bit for a 10-24 tap now go to your local tool store and try and replace the #25 .

PS you will notice that neither chart gives you an actual size that you can walk in and ask for as a replacement #25 but that 10-24 tap is one that I use a thousand times a year doing door hardware .
Click to expand...

You gotta be kidding me. Any tool store that does not stock common number-sized drill bits is not a real "tool store".
 
69_340_GTS said:
You gotta be kidding me. Any tool store that does not stock common number-sized drill bits is not a real "tool store".
Click to expand...

That reminds me of a favorite quote, " No lawnmowers, What kinda damn drugstore is this ?!?!? " Charlie Burnett
I did drive way across town to that one store that would have a special tool a few times.
Never for special diameter drill rod called out in a carb rebuild.
No real reason for the engineers to do that anyway :wack:
Unless.... International application played into it. Some have inch scale drills on hand while others have metric on hand. Call out neither ?
 
A #52 bit is .0635" which is 1 thousandth of a inch larger than a 1/16".
A #38 bit is .1015" which is .0079 (almost 8 thousands) smaller than 7/64" .
Are you setting float or choke pull off? Either way, I wouldn't worry about a few thousands of an inch.
 
RedFish said:
No real reason for the engineers to do that anyway :wack:
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Would you rather that they specify a pin gauge which costs $$$$$ instead????

A drill bit is basically a cheap pin gauge...
 
toolmanmike said:
A #52 bit is .0635" which is 1 thousandth of a inch larger than a 1/16".
A #38 bit is .1015" which is .0079 (almost 8 thousands) smaller than 7/64" .
Are you setting float or choke pull off? Either way, I wouldn't worry about a few thousands of an inch.
Click to expand...

Exactly.

Just get it in the ball park, then you may need to adjust a notch or two rich or lean, depending on how it runs... Then your "gauge point" is no longer the target, but a step in the right direction. Use it to zero in on the bulls-eye....
 
RedFish said:
No real reason for the engineers to do that anyway :wack:
Unless.... International application played into it. Some have inch scale drills on hand while others have metric on hand. Call out neither ?
Click to expand...

You must realize that this all started in the 1800s during the Industrial Revolution. There was no agreement as to what measuring system was to be used (Inch? Metric? Other?) so someone tried to standardize things by coming up with wire gauges. The drill sizes followed the wire gauges originally. Now we are stuck with it, just like we are stuck with metric and English measurement systems for everything you can think of, plus really confusing things like bushels and Imperial gallons! The number/letter drill sizes are just another measuring system.
 
69_340_GTS said:
You gotta be kidding me. Any tool store that does not stock common number-sized drill bits is not a real "tool store".
Click to expand...

Well around here none of the industrial supply house's like Granger or National Concrete stock them , they will of course order them in but that's a different story now isn't ? The same can be said for Homo Depot , Lowes , Cambodian Tire and all the local Lumber Yards which takes care of all the "Tool Stores" in this city .
 
69_340_GTS said:
You must realize that this all started in the 1800s during the Industrial Revolution. There was no agreement as to what measuring system was to be used (Inch? Metric? Other?) so someone tried to standardize things by coming up with wire gauges. The drill sizes followed the wire gauges originally. Now we are stuck with it, just like we are stuck with metric and English measurement systems for everything you can think of, plus really confusing things like bushels and Imperial gallons! The number/letter drill sizes are just another measuring system.
Click to expand...

Oh I do understand the where and why of letter and number sizes. Just speculating as to why the engineers chose to go there in this case. It's simply not that critical. Many times the carb rebuild kit will include cardboard gauges.
 
cannucky said:
Well around here none of the industrial supply house's like Granger or National Concrete stock them , they will of course order them in but that's a different story now isn't ? The same can be said for Homo Depot , Lowes , Cambodian Tire and all the local Lumber Yards which takes care of all the "Tool Stores" in this city .
Click to expand...

I see you are not in the U.S. Things are different here, I guess. I could find those drills at any True Value or Ace hardware store. Tool stores like MSC, and even Harbor Freight have them. I'm quite sure well-stocked NAPA stores have them too. And then there is Sears.
 
RedFish said:
Oh I do understand the where and why of letter and number sizes. Just speculating as to why the engineers chose to go there in this case...
Click to expand...

The engineers chose those drill sizes because if you walk into any machine shop in the country, these drill bits are standard equipment that they will all have.
 
69_340_GTS said:
The engineers chose those drill sizes because if you walk into any machine shop in the country, these drill bits are standard equipment that they will all have.
Click to expand...

They're are closer in size ranges than fractional bits. Do you want to build a engine with a micrometer or a yard stick?
 
Most of the "engineers" I work around pull that stuff out of a book and there *** and have never seen a drill bit.
 
Doesn't everybody have a whole set of number drills?
Never drilled carburetor jets to the sizes they need?
Ok, enough ballbusting.
Google is your friend, and so is your hardware store.
Also, about $50 buys a set of drill bits at Costco, Sam's Club, etc. that gets you fractional 1/16"-1/2", full set of letter, and numbers 1-60...
Yeah, they're Chinese, but I've been working with the same set for years. :coffee2:
 
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