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Posted

is there a source of drill bits smaller than #80?

if a 1/25th scale inch is 40 thousanths (.040), then a quarter inch is 10 thousanths (.010). a #80 drill measures about 12.5 thousanths (.0125) if i'm reading the dial caliper correctly. when i use the drill for .010 brass wire the hole yields a reall sloppy fit.

help appreciated.

j

Posted

I wonder if just heating the wire and pushing it through the styrene would work. Naturally I would suggest using neddle nosed pliers in trying this method.

Bob :shock:

Posted

According to the chart on this site

http://www.madison.k12.wi.us/toki/teched/codrills.htm

you need a #87 drill. Were you get one is a different story. I didn't know that they existed that small. they would be fragile little suckers

Thanks

Carl Avis

edit:

Here is an excerpt from that above site:

Continuous Drill Bit Sizes

Measurement Systems

(Include: fractions, letters, wire gauge numbers and metric sizes

Drill bits from zero to one half inch are sized in four ways; fractions, wire gauge numbers, letters, and metric in millimeters. You will see drill bits with a fraction, number, letter or metric number stamped on their shank indicating their size. The fractions range from 1/64 inch to 32/64 inch. The numbers range from 107, (smallest) to 1 (largest). Where the number 1 drill bit leaves off the letter A (smallest) begins and continues through the letter Z (largest). The metric sizes are dispursed throughout. All of these drill bits are different in size except for the 90 and .22mm which are both 0.0087 inches in diameter, the 85 and the .28mm which are both 0.0110 inches in diameter, the 13 and the 4.7mm which are both 0.1850 inches in diameter, the 4.8mm and the 12 which are both 0.1890 inches in diameter, and the 1/4 inch and letter E bits which are both 0.250 inches in diameter. All of the drill bits are listed below with their decimal equivalents.

Drill Decimal

Bit Dia. Equivalent

107 0.0019

106 0.0023

105 0.0027

104 0.0031

103 0.0035

102 0.0039

101 0.0043

100 0.0047

99 0.0051

98 0.0055

97 0.0059

96 0.0063

95 0.0067

94 0.0071

93 0.0075

92 0.0079

.2mm 0.0079

91 0.0083

90 0.0087

.22mm 0.0087

89 0.0091

88 0.0095

.25mm 0.0098

87 0.0100

86 0.0105

85 0.0110

.28mm 0.0110

84 0.0115

.3mm 0.0118

83 0.0120

82 0.0125

.32mm 0.0126

81 0.0130

80 0.0135

.35mm 0.0138

79 0.0145

1/64 0.0156

.4mm 0.0157

78 0.0160

.45mm 0.0177

77 0.0180

.5mm 0.0197

76 0.0200

75 0.0210

Posted

ahhh, a #80 drill bit is actually 0.0135, better get yur eyes checked for :shock: glasses man :lol: yu sound like me...farsighted. :wink:

or perhaps yu should resize yur drill bit to fit tha 0.010 brass wire, tha number drill for that wire is #39, which is actually 0.0995. I mean, yur not using "1/25th scale" brass wire are yu j? :twisted:

Guest Anthony Oteri
Posted
  zebm1 said:
ahhh, a #80 drill bit is actually 0.0135, better get yur eyes checked for :shock: glasses man :lol: yu sound like me...farsighted. :wink:

or perhaps yu should resize yur drill bit to fit tha 0.010 brass wire, tha number drill for that wire is #39, which is actually 0.0995. I mean, yur not using "1/25th scale" brass wire are yu j? :twisted:

Boy Zeb u sur r good wit numbrs! :wink: :wink:
Posted

admittedly i am not using a journeyman's quality dial caliper [general fiberglass - $22 at the big box stores].

the wire i use is by Detail Associates [our friend in the model railroad section]. the wire was marked .010. i used the dial caliper as a "go - no go" guage and both the bit i used and wire made a snug fit.

the best i could guess [the dial is divided in .010 increments] is an approximation of .0125 so maybe your .0135 measurement is more accurate than mine eyes can extrapolate.

could the loose fit [of the wire in the hole - material = styrene] be attributed to radial thrust while drilling? i am using a pin vise.

i don't understand where the #39 drill bit came from...?

but my original question was: Where could I get drill bits smaller than #80?.

it's okay; sometimes "I don't know" IS the correct answer!

Posted

For very small drill bits, check out what Dremel has to offer. I am not sure the dinensions of these bits but the smallest is very SMALL. I picked mine up at the Home Depot. they come in a metal case for easy storage.

Bob :shock:

Posted

J....according to my drill bit lists, there is no actual 0.010 thousandths drill. The closest is a number drill - #39, which is 0.0995 thousandths dia. As to yur loosy-goosy fit, I'd say that yu are correct J, radial (side-ways) thrust is always a problem when using a pin-vise drill holder. Tha only way I can think of to make sure that yur hole has no radial thrust wuld be to chuck tha drill in a minature lathe and use a clamp mount on yur tail stock. :D But that would only work on small pieces.

As to a drill bit smaller than a #80, I've never seen nor heard of one. Yu'd probably need an electron microscope to see tha lands on tha cutting edges of a drill that small. :D

Zeb

Posted

oh Lordy; now i have to go out an' buy a lathe, too????

i should have stuck with military models......

Carl, thanks for the good technical supplement; i printed it for reference.

j

  • 6 months later...
Posted

Sorry I am responding 6 months after you asked. The Hobby shop stuff stops at #80. I would suggest machine tool supply places. There may be some online places too. I found a #87 drill bit for $13.00 !!!!!!!!!! :D I would use that #80. All you need is some sort of drill press to drill straight holes. You don't need a lathe! :( Can't recommend the heated poker thing. I can't imagine the wire retaining enough heat to sink through the plastic.

Posted
  Modelmartin said:
Sorry I am responding 6 months after you asked. The Hobby shop stuff stops at #80. I would suggest machine tool supply places. There may be some online places too. I found a #87 drill bit for $13.00 !!!!!!!!!! :o I would use that #80. All you need is some sort of drill press to drill straight holes. You don't need a lathe! :) Can't recommend the heated poker thing. I can't imagine the wire retaining enough heat to sink through the plastic.

Don't worry Andy, a hundred years from now when people look at this site, six months won't seem like much. ;)

To answer the original question, when I need a hole to match a specific rod, I use the rod to make a drill bit. Use a short piece of the rod and grind half the length to half it's diameter. Then grind the half round end to a point using two different angles. The shallow angle will scrape the bottom of the hole. The chips will exit the hole through the hollowed part of the rod. If using this bit in a motor tool it will be important to get the two angles on the correct sides. If using a pin vise, just turn the other direction.

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