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High-Low Screw Thread
Specifications

For use in plastic, nylon, wood and other low density materials.


Phillips Flathead High-Low Self Tapping Head Dimensions Phillips Panhead High-Low Self Tapping Head Dimensions Hex Washer High-Low Self Tapping Head Dimensions



Thread and Hole Dimensions for High-Low Screw Threads - ANSI B18.6.4 / Elco
Screw Size D B P Pilot Hole Diameter
FlexuralModulus of Plastic		 Minimum
Torsional
Strength
(Lbb In)
High Thread
Diameter		 Low Thread
Diameter		 Point Diameter Up to
200,000 PSI		 200,000-400,000
PSI
2-32 .084-.090 .069 .050-.058 .0670 .0700
4-24 .105-.115 .086 .061-.070 .0810 .0860 4
6-19 .135-.145 .108 .080-.090 .1015 .1100 13
8-18 .160-.170 .130 .095-.105 .1200 .1285 18
10-16 .185-.195 .145 .099-.110 .1360 .1440 30
12-16 .210-.220 .167 .125-.137 .1570 .1660 39
1/4-15 .250-.260 .200 .161-.175 .1890 .2010 56
Length Tolerances: 1.0 inch and less = +0 -3/64, Over 1.0 inch = +0 -1/16

  • Description A thread forming screw with a double-lead, consisting of a low and a high thread. The lower thread varies in height from 1/3 to 1/2 that of the high thread, which is sharper and flatter than a standard thread.
  • Advantages and
    Applications     For use in plastic, nylon, wood or other low-density materials. Thread design reduces driving torques, enhances resistance to thread stripping, improves pullout strength and lessens risk of cracking the worpiece.
  • Material Steel: 1019-1022 or equivalent Stainless: 410 Martensitic Stainless Steel
  • Heat Treatment Steel: Quenched in liquid and then tempered by reheating to 650°F minimum Stainless: Annealed by heating to 1850-1950°F, held for at least 1/2 hour and rapid air or oil quenched the heheated to 525°F minimum for at least 1 hour and air cooled to provide the required tensile, yield and hardness properties.
  • Case Hardness Steel: Rockwell C45 to C50
  • Case Depth Steel: Nos. 2 thru 6 Dia. - .002-.007, Nos. 8 thru 10 dia. - .004 - .009, 1/4" - .005 - .011
  • Core Hardness Steel: Rockwell C28 - C36 after tempering Stainless: Rockwell C38 - 42 after tempering
  • Plating See plating page



Head and Drive Dimensions For Phillips Flathead High-Low Thread
Nominal
Size		 A H M G Driver
Size
Head Diameter Head
Height		 Recess Diameter Recess Depth
Max Min Ref Max Min Max Min
4 .225 .195 .062 .128 .115 .082 .066 1
6 .279 .224 .075 .174 .161 .095 .072 2
8 .332 .292 .091 .189 .176 .110 .087 2
10 .385 .340 .112 .204 .191 .125 .102 2



Head and Drive Dimensions For Phillips Panhead High-Low Thread
Nominal
Size		 A H M G Driver
Size
Head Diameter Head Height Recess Diameter Recess Depth
Max Min Max Min Max Min Max Min
2 .167 .155 .062 .053 .104 .091 .052 .034 1
4 .193 .180 .071 .062 .112 .099 .061 .043 1
6 .254 .240 .097 .087 .158 .145 .072 .046 2
8 .270 .256 .097 .087 .166 .153 .080 .055 2
10 .322 .306 .115 .105 .182 .169 .097 .071 2
12 .373 .357 .133 .122 .199 .186 .113 .089 2
1/4 .492 .473 .175 .162 .281 .268 .144 .118 3



Head and Drive Dimensions For Hex Washer Head High-Low Thread
Nominal
Size		 A T J H F U
Width
Across
Flats		 Slot Depth Slot Width Head
Height		 Washer
Diameter		 Washer
Thickness
Max Min Max Min Max Min Max Min Max Min Max Min
4 .125 .120 - - - - .055 .044 .177 .163 .016 .010
6 .187 .181 .049 .030 .043 .035 .070 .058 .260 .240 .025 .015
8 .250 .244 .053 .033 .048 .039 .093 .080 .328 .302 .025 .015
10 .250 .244 .074 .052 .054 .045 .110 .096 .348 .322 .031 .019
12 .312 .305 .103 .077 .067 .056 .155 .139 .432 .398 .039 .022
1/4 .375 .367 .111 .083 .075 .064 .190 .172 .520 .480 .050 .030
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Self Tapping Screws
Smith Fastener Company, A California Corporation - 3613 East Florence Avenue, Bell, California, 90201 - Phone: ( 323 ) 587-0382 - FAX: ( 323 ) 587-8712 - E-mail: sales@smithfast.com - Copyright © 2000 by Smith Fastener Company - Last updated: May 19th, 2006 - http://www.smithfast.com/hilow.htm