Hi Brian, After my post the other day I talked to one of the engineers and asked him to explain things a little more clearly for me. He said that when you plasma cut material the thickness like our WAFS that the HEAT AFFECTED ZONE is less than 1/16 of an inch around the edges. Yes the edges are hardened slightly as you stated. He said that it should not matter on parts like ours but that if a guy was worried about it that you could take a torch if you have one and heat the parts up to where they were just turning blue which would be in the 600 to 800 degree range for about 10 seconds and then just let air cool and they would be fine or bring up to the same temp in an oven as you have said you have done. Their holes are typically punched with hydraulic presses. The same people made my WAFS. Larry H.
Brian Kraut <brian.kr...@engalt.com> wrote: I am not a structural or materials engineer. I design electronics. I would think that engineers working for an aircraft manufacturing company would know more about it than I do, BUT it sounds a little fishy to me. They may be doing the equivalent of shot peening, but as far as I know that is only a stress relieving treatment and will not change the hardness and therefore the brittleness of the metal. Of course a lot of what is acceptable and what is not depends on the safey factor that is designed into the part to begin with. There are also different methods of plasma cutting using oxygen or nitrogen and they do not each leave the same edge on the part. It all boils down to my stock answer. If you don't know for sure that it is O.K. then use a method that you know is O.K. Brian Kraut Engineering Alternatives, Inc. www.engalt.com -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of Larry H. Sent: Wednesday, August 23, 2006 12:15 AM To: KRnet Subject: KR> WAF Plasma cutting Brian, I know someone who is making all of the 4130 fittings which includes wing attach for an aircraft mfg company. All of the parts are being plasma cut by computer and then the parts are being tumbled to deburr. The tumbling process is the normalizing effect. Their engineers think the parts are fine. What do you think about this practice? Larry H. Brian Kraut wrote: Absolutely not. Plasma cutting leaves a very hard edge. I have had several 4130 parts plasma cut including my lower gear attach fittings for the KR and the seatbelt attach fittings and canopy latch parts for the Stang. I did some finish machining on some of the parts and the edges were hard as rocks and needed carbide tools to cut them. Hard edges mean brittle edges. Brittle edges mean the high liklihood of cracks starting. The parts I have plasma cut are sent to a heat treater to be normalized when done, but if you are not getting that done don't do it for structural parts. Same applies for laser cutting. Water jet is O.K. Another problem with plasma and water jet depending on the thickness is that they both cut with a taper and sometimes also a slightly rough edge. If you do water jet and have the bolt holes cut you want to have them done undersized and ream them to finish the holes. Brian Kraut Engineering Alternatives, Inc. www.engalt.com -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of Chris Johnston Sent: Tuesday, August 22, 2006 6:56 AM To: KRnet Subject: KR> WAF Plasma cutting Can you plasma cut the wafs without affecting the metal?????? Are the tailplane hinge ply backup plates glued in place or just held on by the nuts and aluminium backup plates? The plans state the inner hinges have two bolts, does this mean the outer hinges have only one bolt per hinge half? Can you use two bolts on the outer tailplane and elevator hinge without weakening the spars too much? Chris Johnston North Richmond NSW Australia _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html --------------------------------- All-new Yahoo! Mail - Fire up a more powerful email and get things done faster.
