Heli-Coil Insert Specifications
 
  • Size and location of notch, shape of tang, reduced first coil (if any) and all dimensions not shown will be Heli-Coil standards.
  • Count number of free coils 90° from tang.
 
HELI-COIL INSERT SPECIFICATIONS, FINE THREAD
NOMINAL
THREAD SIZE
TYPE SIZE
DESIG-
NATION
"Q" NOMINAL LENGTH
"A" OUTSIDE DIAMETER
"Q" NUMBER OF COILS
NOMINAL LENGTH
Screw-Lock
Insert No.
1D 1 1/2D 2D 2 1/2D 3D Min. Max. 1D 1 1/2D 2D 2 1/2D 3D
3(.099)-56 3591 03CN 0.099 0.148 0.198 0.248 0.297 .131 .146 3-3/8 5-5/8 8 10-3/8 12-5/8
4(.112)-48 3591 04CN 0.112 0.168 0.224 0.280 0.336 .147 .162 3-3/8 5-5/8 7-7/8 10-1/4 12-1/2
6(.138)-40 3591 06CN 0.138 0.207 0.276 0.345 0.414 .173 .193 3-1/2 6 8-3/8 10-3/4 13-1/4
8(.164)-36 3591 2CN 0.164 0.246 0.328 0.410 0.492 .204 .224 3-7/8 6-1/2 9-1/8 11-5/8 14-1/4
10(.190)-32 3591 3CN 0.190 0.285 0.380 0.475 0.570 .236 .256 4-1/8 6-7/8 9-1/2 12-1/4 14-7/8
1/4(.2500)-28 3591 4CN 0.250 0.375 0.500 0.625 0.750 .306 .326 5 8-1/4 11-3/8 14-1/2 17-5/8
5/16(3.125)-24 3591 5CN 0.312 0.469 0.625 0.781 0.938 .380 .400 5-1/2 8-7/8 12-1/4 15-5/8 19
3/8(.3750)-24 3591 6CN 0.375 0.562 0.750 0.938 1.125 .448 .468 6-7/8 11 15 19-1/8 23-1/8
7/16(.4375)-20 3591 7CN 0.438 0.656 0.875 1.094 1.312 .524 .549 6-5/8 10-5/8 14-5/8 18-1/2 22-1/2
1/2(.5000)-20 3591 8CN 0.500 0.750 1.000 1.250 1.500 .592 .617 7-7/8 12-3/8 16-7/8 21-3/8 25-7/8
9/16(.5625)-18 3591 9CN 0.562 0.844 1.125 1.406 1.688 .666 .691 8 12-1/2 17-1/8 21-3/4 26-1/4
5/8(.6250)-18 3591 10CN 0.625 0.938 1.250 1.562 1.875 .733 .758 9 14-1/8 19-1/4 24-1/4 29-3/8
3/4(.7500)-16 3591 12CN 0.750 1.125 1.500 1.875 2.250 .876 .901 9-3/4 15-1/8 20-5/8 26 31-1/2
7/8(.8750)-14 3591 14CN 0.875 1.312 1.750 2.188 2.625 1.021 1.051 9-7/8 15-1/2 21-1/8 26-5/8 32-1/4
1(1.0000)-14* 3591 16CN 1.000 1.500 2.000 2.500 3.000 1.156 1.186 11-1/2 17-7/8 24-1/4 30-5/8 37
1(1.0000)-12 3591 161CN 1.000 1.500 2.000 2.500 3.000 1.169 1.199 9-5/8 15 20-1/2 26 31-1/2
1-1/8(1.1250)-12 3591 18CN 1.125 1.688 2.250 2.812 3.375 1.304 1.334 11-1/8 17-1/4 23-3/8 29-1/2 35-3/4
1-1/14(1.2500)-12 3591 20CN 1.250 1.875 2.500 3.125 3.750 1.439 1.469 12-1/2 19-3/8 26-1/4 33 39-7/8
1-3/8(1.3750)-12 3591 22CN 1.375 2.062 2.750 3.438 4.125 1.575 1.610 13-3/4 21-3/8 28-7/8 36-1/2 44
1-1/2(1.5000)-12 3591 24CN 1.500 2.250 3.000 3.750 4.500 1.710 1.745 15-1/4 23-1/2 31-5/8 39-7/8 48-1/8
*Inactive for new design.
 

COMPLETE PART NO. EXAMPLE:
1/4-20 x .375 standard (free running) stainless steel insert.
3591-4CN-375
TYPE SIZE
DESIGNATION
MATERIAL LENGTH
3591 Standard, UNC (Coarse Thread) See Above Chart CN-Stainless Steel
BN-Phosphor Bronze
TN-Iconel X
See Above Chart    
3591 Standard, UNF (Fine Thread)
3585 Screw-Lock, UNC
3591 Screw-Lock, UNF

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Notes on Insert Specifications:
  • Insert Nominal Length is a computed value and cannot be measured. It is the actual assembled length + 1/2 pitch.
  • The number of coils are counted 90° from the tang.
  • Grip Coil(s) Location: For 1,1 1/2, and 2 diameter long inserts, Grip Coil Location=1/2 the number of free coils. For 2 1/2 and 3 diameter long inserts, Grip Coil Location (distance from the tang) is the same as 2 diameter long inserts.
  • Phosphor Bronze Inserts - Not available in sizes 2-56, 3-48, and 3-56. 1 diameter long Screw-Lock Inserts not available in sizes 4-48 and 4-40 thru 1/4-20 UNC.
  • Iconel X Inserts - 1 diameter long Screw-Lock Inserts not available in sizes 3-56, 4-48, and 2-56 thru 1/4-20 UNC.