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Screw Fastening Systems |
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| 5.2.1 | Self-Drilling Screw Selection Guide |
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| 5.2.1.1 DRILL POINT SELECTION |
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Drill Flute
The length of the drill flute determines the metal thickness that can be drilled. The flute itself provides a channel for chip removal during drilling action. If it becomes completely imbedded in material, drill chips will be trapped in the flute and cutting action will cease. This will cause the point to burn up or break. |
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Point Length
The unthreaded section from the point to the first thread should be long enough to assure the drilling action is complete before the first thread engages the drilled metal. Screw threads advance at a rate of up to ten times faster than the drill flute can remove metal. All drilling therefore should be complete before threads begin to form. |
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Drilling Through
Wood to Metal If your application calls for drilling through wood over 1/2" in thickness, a clearance hole is required. Select a fastener with breakaway wings for this type of job. The wings will ream a clearance hole and break-off when they contact metal surface (minimum metal thickness .090") to be drilled. |
| Drilling Capacity |
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Standard
Fasteners
| Applications | Drill Flute Size | Screw Diameter
Size in. |
Optimal Drilling
Range in. |
Point
Length in./decimal |
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| Light Gauge Metals |
Self-drilling #2 |
6 | .035 to .090 | 9/64 | .140 |
| 8 | .035 to .100 | 5/32 | .156 | ||
| 10 | .035 to .110 | 13/64 | .203 | ||
| 12 | .035 to .140 | 15/64 | .234 | ||
| Medium Gauge Metals |
Self-drilling #3 |
8 | .100 to .140 | 13/64 | .203 |
| 10 | .110 to .175 | 1/4 | .250 | ||
| 12 | .110 to .210 | 9/32 | .281 | ||
| 1/4 | .110 to .250 | 5/16 | .312 | ||
| Heavy Gauge Metals |
Self-drilling #4 |
12 (wood) | .090 to .210 | 9/32 | .281 |
| 1/4 (wood) | .090 to .250 | 5/16 | .312 | ||
| 12 x 7/8 (steel) | .210 to .312 | 3/8 | .375 | ||
| 12 x 11/4 (steel) | .210 to .375 | 7/16 | .440 | ||
| Very Heavy Gauge Metals |
Dril-It Self-drilling #5  |
12 12 |
.250 to .425 .250 to .500 |
5/8 3/4 |
.625 .750 |
| Note: The above chart covers the Hilti standard self-drilling screw program. For information on specialty fasteners contact your Hilti representative. |
| 5.2.1.2 THREAD SELECTION |
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Thread Length Always choose a fastener with sufficient threads to fully engage in the base metal. For example: If you are fastening into 1/4" steel, the fastener should have at least 1/4" of threads. It is helpful, but not critical, that the threads also engage in the material being fastened. The head of the fastener provides the holding power for the material being fastened, while the threads provide the holding power in the base material. |
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Thread Pitch The thickness of material being fastened and diameter of the screw determine the type of thread pitch to be used. In general, the thinner the fastened materials, the fewer the number of threads. The thicker the material, the greater the number of threads. This principle is due to two primary methods of thread engagement/holding power: Clamping and Threading. In light gauge metal, the materials are actually being clamped together by the upper and lower threads. |
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Clamping Therefore, the thinner the material, the coarser the thread pitch must be to assure proper clamping. The thicker the material, the finer the threads must be. In very thick metal (3/8" - 1/2" thick), a fine thread is adviseable. This will allow the thread to "tap" into the base material with less installation torque than a coarse thread. |
Conversion
Tables
Metal Gauge
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Fraction to
Decimal
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| 5.2.1.3 HEAD STYLE SELECTION |
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HWH Hex Washer Head: Washer face provides a bearing surface for the driving sockets. |
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SHWH Slotted Hex Washer Head: Slot head offers ease of serviceability after installation. |
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PPH Phillips Pan Head: Conventional head for general applications and provides low profile fastening. |
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PFH Phillips Flat Head: Used primarily in wood to countersink and seat flush without splintering the wood. |
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PWH Phillips Wafer Head: Large head provides the bearing surface necessary to seat flush in soft materials. |
| 5.2.1.4 SEALING CRITERIA |
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| The Flo-Seal™ sealing screws offer weatherproof fastenings where moisture or condensation is a factor. The integrated washer/head design seals the hole to prevent moisture from dripping into the fastener threads, reducing corrosive build-up. As added protection against corrosion, all Flo-Seal sealing screws come standard with Stalgard® coating. The torque control and adjustment of the Kwik-Tapper electric screwdrivers help ensure that the optimal seal is applied. |
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| If you underdrive, the compression ring design results in a low torque seal. | If you overdrive, the compression ring, outer skirt, and rugged washer prevents spinout and the one-piece head design completely eliminates the possibility of washer inversion. | If you angle-drive, the design of the fastener head, outer skirt, and compression ring, along with the special washer, still helps provide a positive seal. |
| 5.2.1.5 DRIVING CRITERIA |
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| For optimal
performance and proper setting of self-drilling screws,
it is important that proper depth location and torque
setting be used. Varying the depth control is accomplished by rotating the locking collar. When the nosepiece contacts the fastened material, the driving clutch disengages and the driver no longer turns the screw. The torque control limits the torque (power) output of the Kwik-Tapper screwdriver. The drive motor will "ratchet" when the desired torque is reached, helping to prevent overdriving or stripping of the screw. This becomes very important when fastening into thin or soft metals as well as using the Flo-Seal screws. For best results, hold the Kwik-Tapper screwdriver perpendicular to the work surface. Exert only enough pressure to engage the clutch and then trigger the tool. In driving, remember that the self-drilling screw must first perform a drilling operation. This requires only a nominal amount of pressure--let the Kwik-Tapper and drill point do the work. The variable speed switch allows you to control the drill speed to prevent "walking" of the screwpoint. |
Socket
and Bit Sizes
| Screw Size | Magnetic Nut Setter Size |
Phillips Bit Size |
| 6 | 1/4" | 2 |
| 8 | 1/4" | 2 |
| 10 | 5/16" | 2 |
| 12 | 5/16" | 3 |
| 1/4" | 3/8" | 3 |
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