Next-Geeratio Screw Guide There s a whole ew twist o the latest fasteers. By Dari Lawrece The Now Havig worked i the fasteer idustry a doze years, it s hard ot to get upset whe someoe says there s othig ew i screws. O the oe had, they ve got a poit: the basic desig remais uchaged. A 15th cetury craftsma would t have ay problems drivig a 21st cetury screw. O the other had, the sciece ad techology behid this seemigly simple fasteer could fill libraries. Oe of the most sigificat chages ceters o the creatio of productio screws, fasteers maufactured for specific tasks. Cosiderig that the varieties umber i the hudreds of thousads, it s easy to feel overwhelmed. The way to hadle the ifo overload is to face the facts: productio screws are made for productio, Cut threads Thick shak Traditioal Tapered root ot ecessarily small-shop woodworkers. But that does t mea you ca t beefit from a trickle-dow techology. You do t eed a store-sized collectio of fasteers or a egieerig degree to get the Threads wider tha shak Rolled threads Productio Straight root job doe right. What you eed is the kowledge to pick ad choose a maageable screw assortmet for hadlig most woodworkig tasks, plus a few specialty fasteers to tackle specific applicatios. Drywall Screws: Do t Screw with 'Em Wat a easy way to reduce slippig, bridgig, ad breakig? Ditch your drywall screws. The characteristics that make these screws good for hagig gypsum to softwood studs become major liabilities whe joitig boards i the workshop. Drywall Screw Phillips recess slips (cams out) to prevet overtighteig. Bugle head siks ito gypsum without tearig paper. Fully-threaded shak ca cause bridgig/jackig. Torsioal stregth to breakig 25-32 i.-lbs. Productio Screw Square recess resists bit slippage (cam out). 82 taper desiged to match coutersiks. Thicker shak resists breakage. Smooth shak lets threads draw top board tight. Torsioal stregth to breakig 40-55 i.-lbs. 56 woodcraftmagazie.com Feb/Mar 2010
Head recesses You re ot the first perso to witess a traditioal screw slip off the driver or strip out. Maufacturers have searched for a slotted-head solutio sice the 1860s. Slotted screws work well for reproductios ad restoratios, but ewer recesses make drivig easier. Matchig the recess(es) to the driver is critical for your screws, driver bits, ad work. Slotted Proe to slippig ad easily strips out. Not suitable for power drivers. Phillips More positive egagemet tha a slot, but still proe to strippig. Square Resistat to cam out ad helps the screw stay o the driver. Combiatio Use a square-drive bit whe you ca, a Phillips whe you must. Pozi Watch for the cross. A Phillips driver will evetually ream out the recess. Poits Some productio screws sport tips ad threads desiged to reduce the eed for pilot holes. I additio to savig time, these tips reduce the amout of torque eeded to drive the screw ad decrease the chace of splittig the wood. Although helpful for certai istaces, predrillig remais the best choice for fie woodworkig. Pilot bits establish a precisely located hole ad protect agaist jackig, splittig, ad stripped heads. Metals ad coatigs Platigs ad other coatigs ca offer a decorative touch ad cheap isurace agaist stais ad/or fasteer failure that ca happe whe buildig outdoor projects or usig acidic woods. Although they cost more, corrosio-resistat metals offer the best defese, makig them a smart ivestmet for projects that eed to withstad the elemets. Corrosio-Resistat Metals Brass Soft ad easy to strip. A carefully-sized pilot hole ad pre-threadig the hole with a steel screw miimizes strippig ad breakage. Silico Broze The favorite for boat builders. Fasteers oxidize ad darke to bled i with wester red cedar ad redwood. Stailess Steel The ultimate i corrosio resistace, but at a price. Stailess is expesive ad softer tha hardeed steel screws. Sharp Poit Sigle Auger Double Auger Serrated Uplated Steel May be treated with a dry lube coatig to reduce drivig torque ad prevet i-trasit corrosio. Suitable for iterior use oly. Black Oxide/Phosphate Cotrolled oxidatio desiged to give fasteers a more decorative look. Miimal corrosio resistace. Plated Clear Zic Silver color provides some corrosio resistace, but chose over yellow because color matches commo builder hardware. Yellow Zic Provides better defese tha clear, but color may ot match some hardware. Use with acidic woods, such as oak, whe pluggig to prevet staiig. Galvaized Te times more corrosio resistat tha zic but ca cause some staiig with acidic woods. Coatigs ca chip. Epoxy Coated Twety times more corrosio resistat tha zic. Colors bled with wood ad composites. Ca still cause some staiig with acidic woods. Illustratio: Mike Mader Feb/Mar 2010 woodcraftmagazie.com 57
Specialty screws for special situatios You do t eed to blow ext year s tool budget o a catalog s worth of fasteers. I additio to a assortmet of #8 flathead screws, cosider a secod fasteer case stocked with specialists. Havig these fasteers o had will help you overcome some of the most commo assembly ad istallatio problems you might face i ad out of your workshop. Tip Alert As the thickess of the wood ad/or fasteer legth icreases, you ca reduce the 1:3 screw legth ratio dow to to 1:2. Geeral Purpose Screws Woodworkers do t always admit to tacklig projects outside the workshop, but for jig buildig (ad the occasioal outside project), it helps to have a few geeral-purpose screws. The auger tip ad self-sikig head ca t compare with a predrilled, coutersuk pilot hole, but it works well eough with pie ad plywood. Stock up o clear or yellow zic for iterior work ad epoxy coated or stailess steel for exterior work. Compared to the total cost of materials, ot to metio your time, you ll fid the price differece is icosequetial. Cabiet Hagig Screws The big brother of the smaller washer head screws, the cabiet hager has a large diameter shak to icrease holdig power ad accommodate the shear force of heavy cabiets. The auger poit drills through cabiet backs while deep threads ad loger shaks resist pullout ad esure maximum egagemet i softwood studs. Cabiet hager heads are typically plated or paited to provide a fiished look iside cabiets. Drawer Frot Screws Oversized washer head screws are desiged for use with a oversized clearace hole i order to make adjustmets, such as whe moutig drawer faces to drawer boxes. The lower head profile reduces the chace of catchig o the iside of the box. Igore the 1:3 screw legth rule. Select a legth that provides good egagemet but does't poke through the drawer frot. Pocket-Hole Screws Aother descedet of the washer head, pocket-hole screws have thier shaks ad shorter thread legths (compared to cabiet hagig screws) to egage the secod piece oly after clearig the first, miimizig the chace of jackig. The auger tip works like a pilot drill, reducig the likelihood of splittig or raisig a chip betwee the two pieces. Two basic head desigs exist. The larger washer-style head distributes pressure ad prevets overdrivig. The pa head does the same whe joiig thier (½" or less) materials, but the smaller head does t protrude past the pocket. 58 woodcraftmagazie.com Feb/Mar 2010
Trim Head Trim heads (or fiishig screws) work like a fiish ail but with a reverse switch. Capable of sikig ito oak without a pilot hole, these thi-shaked fasteers attach trim, cabiet backs, eve stair treads. You ca drive the screws below the surface, like a fiish ail. The square drive recess provides the positive bit egagemet you ca t get from a Phillips. Cofirmat Style Desiged for processed wood substrates such as MDF ad particleboard, the large diameter shoulder ad shak provide extra stregth ad stiffess while the self-sikig head pulls paels tightly together without pullig through. The thread agle resists withdrawal ad allows for reassembly without compromisig joit itegrity. Use the 7 50 mm screws with ¾" materials, ad the 5 40mm with ½" materials. Euro Like Cofimats, Euros are desiged aroud the poor holdig power of processed wood substrates. Used primarily for cabiet hardware, the screws have large shaks ad coarse threads to icrease holdig power ad allow removal ad reisertio. They may look similar, but Pozi-Drive recesses resist cam out better tha Phillips. Pilot Holes: The & Now Pilot bits defed agaist bridgig, splittig ad stripped heads, provided that you select the right pilot ad use it correctly. Traditioal woodworkig screws require tapered bits to match the root. To miimize splittig without affectig the holdig stregth, the pilot hole eeds to match the screw s diameter ad the peetratio depth of the screw. Drillig pilot holes for productio screws is t as fussy. Because of the uiform shaks ad arrow shafts, you ca get by with a straight pilot. Drill a clearace hole through the upper piece to prevet bridgig; drill deeper to prevet splittig. If you re usig moder screws ad still have tapered bits, it s time to make the switch. Whe used with a straight-root screw, the coical hole ca sacrifice holdig power. Traditioal Screw/ Tapered Pilot About the Author Before becomig techical director for McFeeley s, Dari Lawrece was a professioal luthier for ie years. He ow works as director of product developmet for Woodcraft. Productio Screw/ Straight Pilot Feb/Mar 2010 woodcraftmagazie.com 59
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