Lap joint

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Lap joints can be used in wood, plastic, or metal.[1] A half lap joint or a halving joint is a technique of joining two pieces of material together by overlapping them.[2] A lap may be a full lap or half lap. In a full lap, no material is removed from either of the members to be joined, resulting in a joint which is the combined thickness of the two members.[3] In a half lap joint, material is removed from each of the members so that the resulting joint is the thickness of the thickest member.[4] Most commonly in half lap joints, the members are of the same thickness and half the thickness of each is removed.[5]

Half laps[edit]

Left to right: Half lap, mitred half lap, cross lap and dovetail lap

Half lap joints are used extensively in traditional timber framing, construction and cabinetry for framing.[6] They are quick and easy to make and provide reasonable strength through good long grain to long grain gluing surface.[7] The shoulders provide some resistance to racking (diagonal distortion). They may be reinforced with dowels or mechanical fasteners to resist twisting.[8]

Applications[edit]

Table

End lap[edit]

Also known simply as a 'pull lap', it is the basic form of the lap joint and is used when joining members end to end either parallel or at right angles.[9] When the joint forms a corner, as in a rectangular frame, the joint is often called a corner lap. This is the most common form of end lap and is used most in framing.

For a half lap in which the members are parallel, the joint may be known as a half lap splice.[10] This is a splice joint and is an alternative to scarfing when joining shorter members end to end.

Both members in an end lap have one shoulder and one cheek each.

Use for:

Cross lap[edit]

The main difference between this and the basic half lap is that the joint occurs in the middle of one or both members, rather than at the end.[11] The two members are at right angles to each other and one member may terminate at the joint, or it may carry on beyond it.[12] When one of the members terminates at the shin , it is often referred to as a Tee lap or middle lap.[13] In a cross lap where both members continue beyond the joint, each member has two shoulders and one cheek.[14]

Use for:

Dovetail lap[edit]

This is a lap in which the housing has been cut at an angle which resists withdrawal of the stem from the cross-piece.[15]

Use for:

Mitred half lap[edit]

This is a variation of the end lap which shows a mitre on the face of the finished work.[16]

The mitred half lap is the weakest version of the joint because of the reduced gluing surface.[17]

Use for:

See also[edit]

References[edit]

  1. ^ "Lap Joint". corrosionpedia. Retrieved 10 January 2015. 
  2. ^ "lap joint". Memidex. Retrieved 10 January 2015. 
  3. ^ "joinery". New To Woodworking. Retrieved 10 January 2015. 
  4. ^ "joinery". New To Woodworking. Retrieved 10 January 2015. 
  5. ^ "joinery". New To Woodworking. Retrieved 10 January 2015. 
  6. ^ mathegenius. "Frames joint". WordPress. Retrieved 10 January 2015. 
  7. ^ "Furniture Joinery". www.OnlineDesignTeacher.com. Retrieved 10 January 2015. 
  8. ^ "Half Lap Joints". Wikispaces. Retrieved 10 January 2015. 
  9. ^ mathegenius. "Frames joint". WordPress. Retrieved 10 January 2015. 
  10. ^ mathegenius. "Frames joint". WordPress. Retrieved 10 January 2015. 
  11. ^ mathegenius. "Frames joint". WordPress. Retrieved 10 January 2015. 
  12. ^ Sunil, Kumar Ojha. "Carpentry Shop". Slideshare. Retrieved 10 January 2015. 
  13. ^ mathegenius. "Frames joint". WordPress. Retrieved 10 January 2015. 
  14. ^ mathegenius. "Frames joint". WordPress. Retrieved 10 January 2015. 
  15. ^ "Half Lap Joints". Wikispaces. Retrieved 10 January 2015. 
  16. ^ akinyi, aroha. "Basic Woodworking Joints ¦ Autonopedia". Bundlr. Retrieved 10 January 2015. 
  17. ^ mathegenius. "Frames joint". WordPress. Retrieved 10 January 2015. 

External links[edit]