Effect of Geometric Parameters of Finger Joint Profile on Ultimate Tensile Strength of Single Finger-Joined Boards


  • Shuzhan Rao
  • Meng Gong
  • Y. H. Chui
  • Mohammad Mohammad


Joint profile, slope, tip thickness, joint length, ultimate tensile strength, single finger-joined board


The feasibility of adopting a short finger profile for structural finger-joined lumber was studied by investigating the effect of geometric parameters of a finger joint profile on ultimate tensile strength (UTS) of single finger-joined boards. Six finger joint profiles were designed with three finger lengths (28.27, 15.88, and 12.70 mm). A commonly used finger profile was included as a control. Eastern white pine (Pinus strobus) lumber was used to fabricate single finger-joined boards that were joined using a polyvinyl acetate adhesive. Analysis of variance showed that the finger joint profile had a statistically significant influence on UTS of single finger-joined boards. Finger profile P2 showed the highest UTS value and had the shortest finger length among seven groups. With decreasing profile slope, UTS increased. Slope of 1:12 appeared to be the optimized value for finger jointing. UTS decreased with increasing tip width. It can be concluded that with the proper design of finger profile, a finger joint with short finger lengths can be used to fabricate finger-joined structural lumber without any loss of tensile strength compared with the finger length commonly used by the wood industry.


Ayarkwa J, Hirashima Y, Sasaki Y (2000) Effect of finger geometry and end pressure on the flexural properties of finger-jointed tropical African hardwoods. Forest Prod J 50(11/12):53-63.nDIN (1998) DIN 68140-1. Finger joints in wood. Part 1: Finger-jointed structural timber (softwood). Deutsches Institut für Normung (the German Institute for Standardization), Berlin, Germany.nFPL (1999) Wood handbook: Wood as an engineering material. Gen Tech Rep FPL-GTR-113 USDA For Serv Forest Prod Lab, Madison, WI. 463 pp.nGong M, Delahunty S, Chui YH (2009) Development of a material-efficient finger-joint profile for structural finger-joined lumber. Final Report (UNB043). Wood Science and Technology Centre, University of New Brunswick, Fredericton, New Brunswick, Canada.nJokerst RW (1980) The effect of geometry on the performance of structural finger-joints. Pages 169-180 in CFL Prins, ed. Proc Production, Marketing and Use of Finger-Jointed Sawnwood, 15-19 September 1980, Timber Committee of the UN Economic Commission for Europe. Martinus Nijhof/Dr. W. Junk Publishers, The Hauge, The Netherlands.nJokerst RW (1981) Finger-jointed wood products. Res Pap FPL-RP-382.USDA For Serv Forest Prod Lab, Madison, WI.nMohammad M (2004) Finger-joint process and products quality. Report #4016. FPInnovations-Forintek Division, St-Foy, Quebec, Canada.nNLGA (2006a) SPS 1. Special products standard for fingerjoined structural lumber. National Lumber Grades Authority, Westminster, British Columbia, Canada.nNLGA (2006b) SPS 4. Special products standard for fingerjoined flange stock lumber. National Lumber Grades Authority, Westminster, British Columbia, Canada.nPavlov VP (1955) Joining wood longitudinally with toothed tenons. Translation No. 2705 of Australian CSIRO. Translated from. Derev Prom 3(10):5-8.nRaknes E (1982) The influence of production conditions on the strength of fingerjoints. Pages 154-168 in CFL Prins, ed. Proc Production, Marketing and Use of Fingerjointed Sawnwood, United Nations Economic Commission for Europe. Martinus Nijhof/Dr. W. Junk Publishers, The Hague, The Netherlands.nSelbo ML (1963) Effect of joint geometry on tensile strength of finger-joints. Forest Prod J 13(9):390-400.nStrickler MD (1980) Finger-jointed dimensioned lumber: Past, present and future. Forest Prod J 30(9):51-56.nWalford BG (2000) Effect of finger length on fingerjoint strength in radiata pine. Paper 3-5-2 in Proc 6th World Conference on Timber Engineering, University of British Columbia, Whistler, British Columbia, Canada.n






Research Contributions