brianc Posted February 5, 2014 Share Posted February 5, 2014 I'm trying to form a rectangular tenon to join two pieces of 5/16". The tenon is 3" long. I'm not sure how much to leave beyond the mating surface to form the tenon. My initial guess was 5/16" or one material thickness, but I dont know if there is any rule of thumb. I am going for a finished pyramidal shape once it is formed over. I am going to try a sample piece this weekend but thought I would see if anyone had any tips to pass along. Thanks Brian Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 5, 2014 Share Posted February 5, 2014 Look at the volume of the finished piece and calculate the volume of the original stock needed to produce that (volume = volume + forging losses) Now if you are more of a hands on type---take a piece of scrap of the correct thickness, measure it, forge the needed piece and re-measure to the transition giving you the how much was used. Quote Link to comment Share on other sites More sharing options...
divermike Posted February 5, 2014 Share Posted February 5, 2014 I would start at 1.5 aprox, and go from there. Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 5, 2014 Share Posted February 5, 2014 Yeah, 1.5 x the material thickness is the general rule of thumb. Of course having a little extra is (I think) better than too little, it's easier to remove metal than add some. Heck, I think I'd just figure on extra and hot rasp dress the head. Let us know how it goes please and don't forget we LOVE pics. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
anvil Posted February 27, 2014 Share Posted February 27, 2014 sgreed, 1-1/2 the thickness is the rule of thumb for a structural rivit head. however for a custom shape, a test piece will answer your question Quote Link to comment Share on other sites More sharing options...
anvil Posted February 27, 2014 Share Posted February 27, 2014 I meant to add to the above, there is a wonderful example of forging a rectangular tenon in one of the cosira books. I believe the series is free to download on line. google is your friend. Quote Link to comment Share on other sites More sharing options...
lupiphile Posted March 1, 2014 Share Posted March 1, 2014 There is a rule of thumb here. No matter the widest dimension, you're looking for 1.5-2 times the thinner dimention for a dome-ish or simply faceted rivet head. To use an extreme illustration, I was recently making a test picket with a horizontal element riveted to the side and thus made a 3.5" x .125" tenon. In that instance I added a quarter inch (.25", to keep things decimal-y) to the width of the material i was going through to get my proper length for my rivet head. Hope this is some help, Take care, Matt Quote Link to comment Share on other sites More sharing options...
anvil Posted March 1, 2014 Share Posted March 1, 2014 Lol, we all forgot. the rule is thickness of material you are going thru + 1-1/2 x thickness of rivit material. Quote Link to comment Share on other sites More sharing options...
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