CLAIMS

1.

A shanked fixing device for fixing together a first member and a second member, the second member having a body portion for receiving said shank of said device in a bore of the body portion, said body portion being composed of timber end or side grain or comprising friable masonry material, the fixing device comprising the shank and an optional head and the shank of the fixing device being configured with a bore wall engagement configuration wherein helically extending first, second and third parallel threads are upstanding from a helically extending land to define by said threads first and second helically extending grooves laterally contained in the case of the first groove by the second thread and the first thread and in the case of the second groove by the second thread and the third thread, the second thread being arranged and sized so as in use of the fixing device more deeply to penetrate the wall of the bore in the body portion of the second member than either of said first and third threads.

2.

A shanked fixing device for fixing together a first member and a second member, the second member having a body portion for receiving said shank of said device in a bore of the body portion, and said body portion being composed of timber end or side grain or comprising friable masonry material, the fixing device comprising the shank and an optional head and the shank of the fixing device being configured with a helical bore wall engagement configuration and a helical land, said helical bore wall engagement configuration comprising a first helical thread upstanding from the land circumference of the shank, a second helical thread upstanding from the land circumference of the shank and spaced from and parallel to said first helical thread, said second helical thread having an apical circumference greater than that of said first helical thread, a first helical groove defined between said first and second helical threads, a third helical thread upstanding. from the land circumference of the shank and spaced from and parallel to said second helical thread, said third helical thread having an apical circumference less than that of said second helical thread, and a second helical groove defined between said second and third helical threads.

3.	A fixing device as claimed in Claim 2 wherein the third helical thread has an apical circumference substantially equal to that of the first helical thread.

4.	A fixing device as claimed in any one of Claims 1 to 3 wherein the threads have a helix angle of from 30° to 55°.

5.	A fixing device as claimed in Claim 4 wherein the threads have a helix angle of from 35° to 50°.

6.	A fixing device as claimed in Claim 4 wherein the threads have a helix angle of from 30° to 45°.

7.	A fixing device as claimed in Claim 5 wherein the threads have a helix angle of from 37° to 45°.

8.	A fixing device as claimed in any one of Claims 1 to 4 wherein the helix angle of the threads is from 37° to 55°.

9.	A fixing device as claimed in any one of Claims 1 to 3 wherein the helix angle of the threads is approximately 37°.

10.	A fixing device as claimed in any preceding claim wherein the thread angle of the threads is, each independently, from 30° to 70°.

11.	A fixing device as claimed in Claim 10 wherein the thread angle of the threads is, each independently, from 30° to 60°.

12.	A fixing device as claimed in Claim 10 wherein the thread angle of the threads is, each independently, from 35° to 70°.

13.	A fixing device as claimed in Claims 10 to 12 wherein the thread angle of the threads is, each independently, from 35° to 50°.

14.	A fixing device as claimed in any one of Claims 10 to 13 wherein the thread angle of the threads is, each independently, from 37° to 45°.

15.	A fixing device as claimed in any preceding claim wherein the thread angle of the threads is about 40°.

16.

A fixing device as claimed in any preceding claim wherein the first thread, in use of the fixing device in a bore equal in diameter to the diameter of the shank land, penetrates the bore wall in the body portion of the second member such that a first channel is formed helically therein and such that the sopenetrated bore has a diameter in helical crosssection through the first channel equal to F in the equation below, wherein the second thread in use penetrates the bore wall in the body portion of the second member such that a second channel is formed helically therein and such that the sopenetrated bore has a diameter in helical crosssection through the second channel equal to E in the following equation and wherein. the third thread in use penetrates the bore wall in the body portion of the second member such a third channel is formed helically therein and such that the third channel has a diameter in helical crosssection through the third channel which is equal to or greater than F but less than E: E = F + K, wherein E and F are as defined above and K, is a constant having a value of from F x 8 to F x Is 100 100.

17.	A fixing device as claimed in Claim 16 wherein K, has a value of from FxtoFxi3.

18.	100 18. A fixing device as claimed in Claim 16 wherein E has a value which is about 10% greater than that of F.

19.

A fixing device as claimed in any preceding claim wherein the first thread, in use of the fixing device in a bore equal in diameter to the diameter of the shank land, penetrates the bore wall in the body portion of the second member such that a channel is formed helically therein and such that the so penetrated bore has a diameter in helical crosssection through the channel equal to F in the following equation: F = C + K2 wherein F is as defined above, C is shank land diameter and K2 is a constant having a value of C x 10 to C x 30 100 100.

20.	A fixing device as claimed in Claim 19 wherein K2 has a value of from CxtoCx2.

21.	100 21. A fixing device as claimed in Claim 20 wherein K2 has a value of from Cx 20 toCx 25 100 100 22.

22.	A fixing device as claimed in Claim 19 wherein F has a value which is about 20% greater than that of C.

23.	A fixing device as claimed in Claim 19 wherein F has a value which is about 25% greater than that of C.

24.

A fixing device as claimed in any one of Claims 1 to 18 wherein the first thread, in use of the fixing device in a bore equal in diameter to the diameter of the shank land, penetrates the bore wall in the body portion of the second member such that a channel is formed helically therein and such that the so penetrated bore has a diameter in helical crosssection through the channel equal to F in the following equation: wherein F is as defined above, C is shank land diameter and K3 is a constant having a value of from 25 to 30.

25.	A fixing device as claimed in Claim 24 wherein K3 has a value of 26 to 28.

26.	A fixing device as claimed in Claim 25 wherein K3 has a value of 28.

27.

A fixing device as claimed in any preceding claim wherein the spacing of the first and third threads measured as the distance between the apices thereof in a single turn of the bore wall engagement configuration is from 25% to 40% of the spacing between the turns of the second thread measured between the apices thereof.

28.	A fixing device as claimed in Claim 27 wherein the spacing between the first and third threads is from 28% to 35% of the spacing between the turns of the second thread, all measurements of spacing being on the basis set forth in Claim 27.

29.	A fixing device as claimed in Claim 27 wherein the spacing between the first and third threads is from 28% to 33% of the spacing between the turns of the second thread, all measurements of spacing being on the basis set forth in Claim 27.

30.	A fixing device as claimed in Claim 27 wherein the spacing between the first and third threads is about 30% of the spacing between the turns of the second thread, all measurements of spacing being on the basis set forth in Claim 27.

31.	A fixing device as claimed in any preceding claim wherein one or both of the first and second grooves of the bore wall engagement configuration has its floor depressed relative to the shank land.

32.

A fixing device as claimed in any preceding claim wherein one or both of the first and second grooves of the bore wall engagement configuration has its floor sufficiently depressed relative to the apex of the adjacent one of the first and third threads that the diameter of the shank in helical crosssection through the floor of said groove is less than the diameter of the shank in helical cross section through the apex of said thread by a margin of 25% to 45% relative to the latter.

33.

A fixing device as claimed in Claim 32 wherein one or both of the first and second grooves of the bore watl engagement configuration has its floor sufficiently depressed relative to the apex of the adjacent one of the first and third threads that the diameter of the shank in helical crosssection through the floor of said groove is less than the diameter of the shank in helical cross section through the apex of said thread by a margin of 27% to 40% relative to the latter.

34.

A fixing device as claimed in Claim 32 wherein one or both of the first and second grooves of the bore wall engagement configuration has its floor sufficiently depressed relative to the apex of the adjacent one of the first and third threads that the diameter of the shank in helical crosssection through the floor of said groove is less than the diameter of the shank in helical cross section through the apex of said thread by a margin of 30% to 38% relative to the latter.

35.

A fixing device as claimed in Claim 32 wherein one or both of the first and second grooves of the bore wall engagement configuration has its floor sufficiently depressed relative to the apex of the adjacent one of the first and third threads that the diameter of the shank in helical crosssection through the floor of said groove is less than the diameter of the shank in helical cross section through the apex of said thread by a margin of 32% to 37% relative to the latter.

36.

A fixing device as claimed in Claim 32 wherein one or both of the first and second grooves of the bore wall engagement configuration has its floor sufficiently depressed relative to the apex of the adjacent one of the first and third threads that the diameter of the shank in helical crosssection through the floor of said groove is less than the diameter of the shank in helical cross section through the apex of said thread by a margin of approximately one third relative to the latter.

37.	A fixing device as claimed in any preceding claim wherein the apices of said threads are flattened.

38.	A fixing device substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

39.

A fixing method which comprises turning into a bore in a substrate a fixing device as claimed in any preceding claim, the bore having a diameter less than the diameter of the fixing device shank in helical crosssection through the apex of the one of the threads having the smallest diameter, the substrate being a substrate of a member to which another member is to be fixed by use of the fixing device and the substrate being composed of timber, plastics or comprising friable masonry material.

40.	A method as claimed in Claim 39 wherein the friable masonry material is autoclave aerated concrete, a cured plaster or render coat, plasterboard or soft red brick.

41.	A method as claimed in Claim 39 or Claim 40 wherein the friable masonry material is masonry material having a crush resistance of less than 5NM.

42.	A method as claimed in Claim 41 wherein the friable masonry material is masonry material having a crush resistance of less than or equal to 3.5NM.

43.	A method as claimed in Claim 41 or Claim 42 wherein the friable masonry material is cementitious or clinkerbased.

44.	A method as claimed in Claim 39 wherein the timber substrate is timber end grain.

45.	A method as claimed in Claim 44 wherein the fixing device is turned into the bore in the substrate by application of axial force.

46.	A method as claimed in Claim 45 wherein the application of axial force is application of intermittent dynamic force along the axis of the shank of the fixing device.

47.	A method as claimed in Claim 42 wherein the axial force is a percussive force applied by hammering.

48.	A method as claimed in any one of Claims 39 to 47 wherein the diameter of the fixing device in helical crosssection through the apex of the second thread is equal to 115% to 145% of the nominal diameter of the bore in the substrate.

49.	A method as claimed in any one of Claims 39 to 48 wherein the diameter of the fixing device in helical crosssection through the apex of the second thread is equal to 120% to 135% of the nominal diameter of the bore in the substrate.

50.	A method as claimed in any one of Claims 39 to 49 wherein the diameter of the fixing device in helical crosssection through the apex of the second thread is equal to 125% to 130% of the nominal diameter of the bore in the substrate.

51.

A method as claimed in any one of claims 39 to 50 wherein the pitch between the first and third threads in each turn of the bore wall engagement configuration is from 40% to 90% of the nominal diameter of the bore, the diameter of the land of the fixing device shank corresponding to the nominal diameter of the bore less minimal clearance.

52.

A method as claimed in any one of claims 39 to 51 wherein the pitch between the first and third threads in each turn of the bore wall engagement configuration is from 50% to 80% of the nominal diameter of the bore, the diameter of the land of the fixing device shank corresponding to the nominal diameter of the bore less minimal clearance.

53.

A method as claimed in any one of claims 39 to 52 wherein the pitch between the first and third threads in each turn of the bore wall engagement configuration is from 60% to 70% of the nominal diameter of the bore, the diameter of the land of the fixing device shank corresponding to the nominal diameter of the bore less minimal clearance.

54.

A method as claimed in any one of Claims 39 to 52 wherein the diameter of shank of the fixing device in helical crosssection through the apex of the first thread and the diameter of said shank in helical crosssection through the shank land are such that the material of the wall of the bore is penetrated by said first thread to a depth equal to at least 5% of nominal bore diameter.

55.

A method as claimed in Claim 54 wherein the diameter of shank of the fixing device in helical crosssection through the apex of the first thread and the diameter of said shank in helical crosssection through the shank land are such that the material of the wall of the bore is penetrated by said first thread to a depth equal to at least 10% of nominal bore diameter.

56.	A method as claimed in any one of Claims 39 to 55 wherein the second thread is disposed midway between said first and third threads.

57.	A method substantially as hereinbefore described with reference to the accompanying drawings.