Fastener Holding and Pre-Boring in Exotic Table Slabs
Securing a custom tabletop to its base requires careful attention to how the chosen species accepts metal fasteners. When mounting structural cleats, steel base plates, or figure-8 desktop fasteners to a solid timber or hybrid river tabletop, driving screws directly into the underside without proper preparation can result in split grain, snapped screw shanks, or stripped threads. CIRAD (Centre de Coopération Internationale en Recherche Agronomique pour le Développement) details the nailing and screwing properties of dozens of commercial and exotic species in its CIRAD Tropix 7 technical sheets. These ratings classify whether wood holds fasteners reliably, whether pre-boring is mandatory, or whether fastener performance is poor.
CIRAD Fastener Classifications by Species Group
CIRAD evaluates timbers based on mature wood performance, grouping them into distinct mechanical handling categories for nailing and screwing.
Species Requiring Pre-Boring
A substantial portion of imported hardwoods and high-density softwoods hold screws securely once seated, but their dense cell structure and grain resistance cause splitting or hardware failure if driven raw. CIRAD explicitly classifies these timbers as Good but pre-boring necessary:
- Exotic Hardwoods: African Padauk, Afzelia, Angelim pedra, Angelim vermelho, Ayan, Berlinia, Bilinga / Opepe, Billian, Cabreuva, Ceylon Satinwood, Chengal, Congotali, Cumaru / Tonka, Cupiuba, Ekki, Eyoum, Freijo, Garapa, Grenadillo / Grenadille d’Afrique, Iatandza, Itauba, Jequitiba, Keruing, Limbali, Makoré, Massaranduba, Mecrussé, Mengkulang, Merbau, Moabi, Mora, Muhuhu, Muirapiranga / Bloodwood, Mukulungu, Mutenye, Niove, Nyatoh, Okan, Ovangkol, Padauk amboina, Pau marfim, Pau mulato, Piquia, Preciosa, Pyinkado, Red balau, Red grandis, Rengas, Rosewood Para, Snakewood, Sonokeling Rosewood, Tamalan Rosewood, Tamarindo (Groçai-rosa), Tatajuba, Tauari, Wenge, Yellow balau, and Zebrano.
- Temperate and Plantation Timbers: European Ash, European Beech, European Larch, European Oak, Rubberwood, Sycamore Maple (Great Maple), and Tasmanian oak.
- Specialized Structures and Conifers: Atlas Cedar and Coconut wood.
Species Rated Good Without Pre-Boring
Woods rated simply as Good accept fasteners cleanly with standard direct insertion, showing sufficient toughness to prevent splitting while offering solid holding grip:
- African cordia, African walnut, Agba, Aningeria, Black Guarea (Bossé Foncé), Cerejeira, Curupixa, Dabema, Durian, Etimoe, European Walnut, Gedu nohor, Guanacaste, Haldu, Idigbo, Iroko, Izombe, Kauri, Kosipo, Mango (Machang), Niangon, Olon, Peruvian Walnut, Scented Guarea (Bossé Clair), Scots Pine, Senegal mahogany, Suren, Tchitola, Utile, and Yellowheart.
- Conditional Timber: Cryptomeria is classified as Good when specific gravity over 0.35.
Species Rated Poor
Certain species exhibit weak internal cohesion or low screw-holding resistance, classified by CIRAD as Poor:
- Black wattle, Cedrorana, Jacaranda, Jelutong, Louro vermelho, and Yemane.
| Wood | Nailing and screwing (CIRAD) |
|---|---|
| African Padauk | Good but pre-boring necessary |
| Afzelia | Good but pre-boring necessary |
| Angelim pedra | Good but pre-boring necessary |
| Angelim vermelho | Good but pre-boring necessary |
| Atlas Cedar | Good but pre-boring necessary |
| Ayan | Good but pre-boring necessary |
| Berlinia | Good but pre-boring necessary |
| Bilinga / Opepe | Good but pre-boring necessary |
| Billian | Good but pre-boring necessary |
| Bintangor | Good but pre-boring necessary |
| Cabreuva | Good but pre-boring necessary |
| Ceylon Satinwood | Good but pre-boring necessary |
| Chengal | Good but pre-boring necessary |
| Coconut wood | Good but pre-boring necessary |
| Congotali | Good but pre-boring necessary |
| Cumaru / Tonka | Good but pre-boring necessary |
| Cupiuba | Good but pre-boring necessary |
| Ekki | Good but pre-boring necessary |
| European Ash | Good but pre-boring necessary |
| European Beech | Good but pre-boring necessary |
| European Larch | Good but pre-boring necessary |
| European Oak | Good but pre-boring necessary |
| Eyoum | Good but pre-boring necessary |
| Freijo | Good but pre-boring necessary |
| Garapa | Good but pre-boring necessary |
| Grenadillo / Grenadille d’Afrique | Good but pre-boring necessary |
| Iatandza | Good but pre-boring necessary |
| Itauba | Good but pre-boring necessary |
| Jequitiba | Good but pre-boring necessary |
| Keruing | Good but pre-boring necessary |
| Limbali | Good but pre-boring necessary |
| Makoré | Good but pre-boring necessary |
| Massaranduba | Good but pre-boring necessary |
| Mecrussé | Good but pre-boring necessary |
| Mengkulang | Good but pre-boring necessary |
| Merbau | Good but pre-boring necessary |
| Moabi | Good but pre-boring necessary |
| Mora | Good but pre-boring necessary |
| Muhuhu | Good but pre-boring necessary |
| Muirapiranga / Bloodwood | Good but pre-boring necessary |
| Mukulungu | Good but pre-boring necessary |
| Mutenye | Good but pre-boring necessary |
| Niove | Good but pre-boring necessary |
| Nyatoh | Good but pre-boring necessary |
| Okan | Good but pre-boring necessary |
| Ovangkol | Good but pre-boring necessary |
| Padauk amboina | Good but pre-boring necessary |
| Pau marfim | Good but pre-boring necessary |
| Pau mulato | Good but pre-boring necessary |
| Piquia | Good but pre-boring necessary |
| Preciosa | Good but pre-boring necessary |
| Pyinkado | Good but pre-boring necessary |
| Red balau | Good but pre-boring necessary |
| Red grandis | Good but pre-boring necessary |
| Rengas | Good but pre-boring necessary |
| Rosewood Para | Good but pre-boring necessary |
| Rubberwood | Good but pre-boring necessary |
| Snakewood | Good but pre-boring necessary |
| Sonokeling Rosewood | Good but pre-boring necessary |
| Sycamore Maple (Great Maple) | Good but pre-boring necessary |
| Tamalan Rosewood | Good but pre-boring necessary |
| Tamarindo (Groçai-rosa) | Good but pre-boring necessary |
| Tasmanian oak | Good but pre-boring necessary |
| Tatajuba | Good but pre-boring necessary |
| Tauari | Good but pre-boring necessary |
| Wenge | Good but pre-boring necessary |
| Yellow balau | Good but pre-boring necessary |
| Zebrano | Good but pre-boring necessary |
| African cordia | Good |
| African walnut | Good |
| Agba | Good |
| Aningeria | Good |
| Black Guarea (Bossé Foncé) | Good |
| Black wattle | Poor |
| Cedrorana | Poor |
| Cerejeira | Good |
| Cryptomeria | Good when specific gravity over 0.35 |
| Curupixa | Good |
| Dabema | Good |
| Durian | Good |
| Etimoe | Good |
| European Walnut | Good |
| Gedu nohor | Good |
| Guanacaste | Good |
| Haldu | Good |
| Idigbo | Good |
| Iroko | Good |
| Izombe | Good |
| Jacaranda | Poor |
| Jelutong | Poor |
| Kauri | Good |
| Kosipo | Good |
| Louro vermelho | Poor |
| Mango (Machang) | Good |
| Niangon | Good |
| Olon | Good |
| Peruvian Walnut | Good |
| Scented Guarea (Bossé Clair) | Good |
| Scots Pine | Good |
| Senegal mahogany | Good |
| Suren | Good |
| Tchitola | Good |
| Utile | Good |
| Yellowheart | Good |
| Yemane | Poor |
Data compiled by BigEpoxy from individual CIRAD Tropix 7 technical sheets (average values for mature wood).
Mounting Table Bases, Cleats, and Fasteners
Understanding these CIRAD classifications directly shapes how hardware should be installed on slab tabletops to maintain stability while allowing for natural seasonal wood movement.
Cleats and Slotted Mounting Brackets
Transverse wooden cleats and slotted metal aprons prevent slab cupping while permitting cross-grain expansion and contraction. When fastening cleats into woods listed as needing pre-boring (such as Wenge, Ekki, European Oak, or Cumaru), running screws without a pilot hole creates extreme radial pressure, easily checking the slab around the fastener hole. Pilot holes must clear the minor diameter of the screw threads. Conversely, in species rated Poor like Jelutong or Cedrorana, coarse-threaded fasteners or through-anchored inserts provide better security against stripping under the weight of heavy assemblies.
Figure-8 Desktop Fasteners
Figure-8 fasteners pivot slightly in a shallow mortise to accommodate wood movement across the tabletop width. Because they rely on a single screw driven into the underside of the slab near the edges, splitting risks are concentrated. For species categorized as Good but pre-boring necessary, failing to drill a pilot hole can crack the timber precisely along the mortised edge, ruining the perimeter joint. When working with woods rated Good, such as Iroko or European Walnut, standard screw driving remains safe, though pre-boring remains good practice when driving close to ends or epoxy-wood bond lines.
Sources
Published October 30, 2026. Sources are linked in the text.
Header image: original graphic by BigEpoxy.com.
Staff note: For Cryptomeria slabs, CIRAD specifically conditions its ‘Good’ rating on having a specific gravity over 0.35, meaning lighter, faster-grown stock may lack the density needed for reliable screw holding without specialized anchoring techniques. (Source: CIRAD Tropix 7 technical sheets (index).)