modela Posted June 23, 2012 Report Share Posted June 23, 2012 I am a fan of jigs. You can usually make them quickly for repeatable events and produce professional results. One of the challenges of the Pisgah project was drilling sets of four holes at the joints. There were from one to four 3/4" bolt holes that had to be drilled through five layers of 4x material (18") using a 13/16 bridge auger. The proposal was to drill them individually but I knew that with my drilling the likelihood of them coming out straight was pretty unlikely. I proposed making a jig. My fellow workers thought it was a waste of time and the idea was met with some resistance. It was Friday afternoon and no work had begun so I decided to build the jigs on my own that weekend. The Jig is made of three layers of 3/4" plywood laminated together. You can see four 1" x 6" black pipe nipples sticking up. These are anchored from below to inset pipe flanges that bolted from the back side. This meant that I had to re-tap the tapered threads from the back side of the flange so that the pipe nipples could stick up through the jig. As a bearing Ifound that 3/4" PVC pipe would just drive tightly into the 1" black nipple. This meant the auger bit as guided by the close fitting plastic. (see picture where I am drilling the first hole). The nipple shortened up the depth the auger went in to about 12" deep. We could drill all the holes, remove the jig and bore through the rest of the way. With 12" of straight hole the rest went right through. It amazed me how accurate the holes came out. Some of the joints were only 10 1/2" thick and we could bore through completely using the jig. In addition I made a 1/2", 4 bolt jig for the upper sections of the bridge. Jim By the way, the critics who thought the jig was a waste of time changed their mind after working with it a while. 1 Quote Link to comment Share on other sites More sharing options...
Dave H Posted June 24, 2012 Report Share Posted June 24, 2012 Nice jig, being a heavy construction carpenter I've found that whatever time is spent building a jig it's more than made up for on the back end, also the accuracey, and repeatability is hard to argue with. Thanks for shareing. Dave 1 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.