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What is clinching?

How does clinching work?

The Clinchlok joint is formed when the upper tooling squeezes the two ply of material joined between the punch and die. The amount of squeeze is very important to the strength of the clinchlok joint and to the life expectancy of the punch and die. Note that the die is of a very special design that allows the Clinchlok to "mushroom". The punch is also a special design and unlike a normal punch the edge of the punch is not sharp, but is rounded. This is known as the punch tip radius. Neither the punch or die can be sharpened.

 

If different thicknesses are to be joined, the best results occur when the thicker material is on the upper (punch) side of the two ply. The thicker material should not be more than twice the thickness of the thinner material. The combined thickness of the two ply should not exceed the combined maximum thickness recommended for the die. Other materials can be joined with the SURELOK II as long as they are not harder than commercial quality mild steel. In most cases both ply should be of the same hardness. If a different hardness is used for each ply (not recommended) the harder material should be on the upper (punch side) if possible.

Joint Strengths

There are two ways to measure the strength of a Clinchlok joint, pull and peel. Pull is almost always stronger than peel and is less sensitive to die adjustment.

Typical joint strengths are given for commercial quality mild steel.

These should be used as a guide only. Different materials will affect the joint strength. If the materialis softer than mild steel these strengths will be reduced according to the strength of the material.

Legend
  Light Duty - 0.12" (3.0mm) Round or [Not Available in Rectangular]
  Medium Duty - 0.18" (4.6mm) Round or 0.12" (3.0mm) Rectangular
  Heavy Duty - 0.25" (6.4mm) Round or 0.18" (4.6mm) Rectangular

Mild Galvanized Steel:

Mat. Thickness (each,2-ply) inch [mm]
Strength (Pull) lbs [N]
Strength (Peel) lbs [N]
Recommended Die
0.012" (32g) [0.30]
120 [534]
15 [67]
#20
0.016" (30g) [0.41]
150 [667]
18 [80]
#20
0.019" (28g) [0.67]
165 [734]
20 [89]
#25
0.022" (26g) [0.56]
180 [801]
25 [111]
#25/#30
0.028" (24g) [0.71]
200 [890]
30 [133]
#30
0.022" (26g) [0.56]
285 [1268]
70 [311]
#30
0.028" (24g) [0.71]
325 [1446]
85 [378]
#30/#40
0.034" (22g) [0.86]
375 [1668]
100 [445]
#40
0.040" (20g) [1.02]
400 [1779]
120 [534]
#40/#50
0.052" (18g) [1.32]
430[1913]
150 [667]
#50
0.063" (16g) [1.60]
475 [2113]
175 [778]
#50
0.028" (24g) [0.71]
550 [2447]
190 [845]
#40
0.040" (20g) [1.02]
600 [2669]
200 [890]
#40
0.052" (18g) [1.32]
700 [3114]
220 [979]
#40/#50
 0.063" (16g) [1.60]
800 [3559]
250 [1112]
#50/#60
0.080" (14g) [2.03]
1000 [4448]
300 [1334]
#60
0.105" (12g) [2.67]
1200 [5338]
400 [1779]
#70
0.138" (10g) [3.51]
1400 [6228]
500 [2224]
#70/#80


Aluminum:

Mat. Thickness (Punch->Die) inch [mm]
Strength (Pull) lbs [N]
Strength (Peel) lbs [N]
Recommended Die
0.032"->0.032" [0.81 ->0.81]
160 [712]
55 [245]
#30
0.040"->0.040" [1.02 ->1.02]
175 [778]
60 [267]
#30
0.050"->0.050" [1.27 ->1.27]
260 [1157]
85 [378]
#30
0.063"->0.063" [1.60 ->1.60]
240 [1068]
72 [320]
#30
0.080"->0.080" [2.03 ->2.03]
265 [1179]
90 [400]
#40
0.090"->0.090" [2.29 ->2.29]
225 [1001]
150 [667]
#40
0.063"->0.040" [1.02 ->1.60]
270 [1201]
50 [222]
#30
0.040"->0.063" [1.60 ->1.02]
140 [623]
45 [200]
#30
0.063"->0.090" [2.29 ->1.60]
210 [934]
48 [214]
#40
0.090"->0.063" [1.60 ->2.29]
240 [1068]
95 [423]
#40

Stainless Steel Clinching (Rectangular or Lance type)

Clinching stainless steel typically requires the use of a rectangular clinching type, often referred to as "Lance" clinching.

The Lance tooling option is available on most machines, and involves very accurate alignment concentrically, but also in the parallel direction. Typical strengths, in pounds, for stainless steel clinches are listed below.


Legend
  Light Duty - 0.12" (3.0mm) Round or [Not Available in Rectangular]
  Medium Duty - 0.18" (4.6mm) Round or 0.12" (3.0mm) Rectangular
  Heavy Duty - 0.25" (6.4mm) Round or 0.18" (4.6mm) Rectangular


Mat. Thickness
Transverse (Pull) lbs [N]
Parallel (Pull) lbs [N]
Transverse (Peel) lbs [N]
Parallel (Peel) lbs [N]
Recommended Die
16g
1400 [6228]
720 [3203]
220 [979]
250 [1112]
#90
18g
1080 [4804]
590 [2624]
180 [801]
215 [956]
#70
20g
650 [2891]
520 [2313]
85 [378]
95 [423]
#60
22g
430 [1913]
380 [1690]
75 [334]
90 [400]
#50
24g
340 [1512]
270 [1201]
40 [178]
50 [222]
#50

 

Testing Joint Strengths

The best method of testing joint strength is to pull the joint apart in both pull and peel, and measure the force required with a pull tester. In production however an indication of the joint strength can be found by measuring the diameter of the button cap (the "mushroom") on the die side of the joint. If a joint is tested in pull and peel with a pull tester and the upper and lower limits of joint strength are found, the cap diameters for these two limits can be measured. Calipers or a GO-NOGO gauge can then be used in production to see if the cap diameter is within the measured limits.

If the material changes or the die # is changed the cap diameters will change. When using the button cap, diameter shear and peel tests should also be used occasionally to confirm strengths.

Due to the overwhelming number of possible button diameters (various thicknesses, various gauge of material, etc.) Norlok does not typically supply these devices. The best method is to determine the acceptable joint strength for your particular application and fabricate one for yourself. Norlok can be of assistance in determining ideal pull strengths if required.