Bob_Nor Posted January 1, 2013 Share Posted January 1, 2013 Hello together and a happy new year! this is my first post here after learning a lot by reading the posts in this forum. I now have a task where I could do with some help. A while ago I have bought cheaply a handheld bandsaw made by Rockwell. Unfortunately the frame is slightly twisted an the band is not tracking properly. The frame has flat reference areas with which proper alignment can be checked and with which the frame could be clamped to a ridgid surcface for straightening. I am not new to metal working and have bent (and occasionally broken) quite a few parts. Since the frame is from cast aluminium, I am not shure whether to straighten the frame cold or in heated condition. How much heat would be enough to reduce the brittleness of the cast aluminium? Does someone have experience with tasks like this? Have you successfully bent similar parts in cold condition? Here is a picture where you can see the slight twist: http://i1249.photobucket.com/albums/hh505/bob_nor/DSC04196klein2.jpg It would be nice if someone could offer me an opinion about this. Bob Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted January 1, 2013 Share Posted January 1, 2013 That material is hot short...Simply put, if you get it even a little too warm and move it it will crumble. When I forge aluminum I use my hickory hammer handle to determine heat. If I rub the handle across the metal and it leaves a light brown mark it needs more heat,,,if it leaves a dark brown mark it is too hot and I have to wait for temps to drop...a medium brown is right to forge,,,See how tough it is to do this in word? My brown may not be same as yours. And remember this aluminum is not cast. I have never been able to forge and aluminum casting without failure,i would try a new blade first. I see wot yoiu mean in the pic, but it may be that your blade is off by running off. I woiuld also examine to see if I couild machine anything to make it right. you may also try contacting the maker to see if the parts or replacement are availeable and cost worthy,. Quote Link to comment Share on other sites More sharing options...
macbruce Posted January 1, 2013 Share Posted January 1, 2013 No heat. If it twisted cold it will untwist cold. You might try clamping one flat end down to a table and clamping a say meter long bar across the other to use for twisting it back into shape.....It's hard to tell from one picture what your clamping options are and dissasembly will likely be nessisary. Just don't get tooo heavy handed with the clamps or you'll break the casting.....welcome aboard Quote Link to comment Share on other sites More sharing options...
Bob_Nor Posted January 1, 2013 Author Share Posted January 1, 2013 Hello Rich,The way the tracking is off fits perfectly to the way the wheels are out of alignment. So I dont think that I will get around fixing the alignment.A repalcement part won't be available here in Germany since this Rockwell saw is a true exotic here.Compared to real forging of the metal the necessary twisting of the frame is a very small deformation.For me it would be interesting to know whether it would be an advantage to lift the temperature from room temperature to 300-400 °F.Hello macbruce,my idea was to use the flat areas around the wheels as a reference an clamp these to a table or I-beam as you suggested. Then I would use a strong clamp or a bar to twist the casting. I would place the frame so I can twist a little over "well aligned" to compensate for the elastic back twist.I would be very happy it I could make this saw usable again as it would save me lots of dirt compared to the angle grinders.Bob Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted January 1, 2013 Share Posted January 1, 2013 I have a real high success welding cast aluminum with an oxy acet torch,,,,,if you can do that...It could also likely be tig welded. All of which gives you options if it breaks. I would not try and heat to twist..... Quote Link to comment Share on other sites More sharing options...
ciladog Posted January 2, 2013 Share Posted January 2, 2013 I can’t imagine a situation that would distort such a beefy casting on a small portable band saw. I guess it could happen. Perhaps it was a bad casting to begin with. I don’t think you will have much luck trying to straightening the frame. I would work on the tracking adjustment and see if you can get the blade to track. On those portable band saws the tracking is usually adjusted either with two opposing screws, one on the outside of the frame and one on the yoke inside the cover. By turning one screw in and one out you change the tilt of the wheel. Or it is spring loaded and there will be one adjusting screw on the outside of the frame. Here is a pdf of the schematic of the parts to the Rockwell (now called Porta-Cable) band saw. Part #84 is the tracking adjustment. If you post the serial number and model number we could see what parts are available. Or you could check online for parts. Porta saw.pdf Quote Link to comment Share on other sites More sharing options...
ironwolfforgeca Posted January 2, 2013 Share Posted January 2, 2013 looks like it will take some pre heat & be ok just warm to touch untwist & clamp flat &walk away also it looks Tig weldable if you have one do a small test bead to ck it out for welding Steve's Welding carefull on the heat !! heat hole frame not just small area Quote Link to comment Share on other sites More sharing options...
Charles R. Stevens Posted January 2, 2013 Share Posted January 2, 2013 Not a lot of experience with cast, I have forged a few shoes. The info I drug up indicates anneal and work cold. 800 F was the annealing temp I found. I also found more seat of your pants methods. Torch blacken then heat to burn of the black Paint with a bit of motor oil and heat until it smokes Hot enough to char pine The references stressed not to work hot, especially not more than 375 F Welding was suggested at 550F preheat. If it's a weldable alloy. hope that helps Personally I'd strip it down and start out chucking it in the oven and run it threw a self cleaning cycle. Let it cool and check, try to adjust. Re anneal as nesisary. Quote Link to comment Share on other sites More sharing options...
Bob_Nor Posted January 2, 2013 Author Share Posted January 2, 2013 Thank you for your replies and the work you spent on solving my problem. I will give it a try at room temperature. The casting is not that ridgid, it's an open box cross section. In normal use it doesn't have to withstand much load since the band tension is not very high. The saw was mounted in a heavy stand and I think it may have been dropped together with the saw. Adjusting the tracking didn't work, putting washers under the non-powered wheel allowed for the best tracking, but still not acceptable for longer use. It's good to hear that the alloy might be weldable though I don't own the necessary equipment. I will post the result of my attempt at straightening but it might take some days until I get it done. Bob Quote Link to comment Share on other sites More sharing options...
Bob_Nor Posted January 8, 2013 Author Share Posted January 8, 2013 Repair completed! I straightened the frame with two strong F-clamps. It was flexible, so I had to twist it quite a bit further and then let it spring back. Alltogether I managed to remove 90% of the twist and left the rest as it was. The tracking was already much better. Since this is about the only band saw without a system to align the tracking (other models oft this saw have), I did the rest by shimming with washers. Now the saw band tracks fine and the saw is a joy to use. Cutting speed is about the same as a strong small angle grinder with a 1mm - cutting disc, but there is much less noise, no smoke and no abrasive dirt on every surface in the workshop! Thank you all for your help! Quote Link to comment Share on other sites More sharing options...
bosox Posted January 17, 2013 Share Posted January 17, 2013 Wow! Glade to hear you were able to fix the twisted band saw frame. Mind posting pictures? Quote Link to comment Share on other sites More sharing options...
Bob_Nor Posted February 5, 2013 Author Share Posted February 5, 2013 Sorry, no pics of the straightening process. It is a Rockwell porta-band saw. If somebody had the same problem, I could bring him onto his way to a repair. Quote Link to comment Share on other sites More sharing options...
aessinus Posted February 5, 2013 Share Posted February 5, 2013 I have the same saw, except with a weld repair in the frame center. Construction guys find all sorts of high places to drop these from. Got mine for less than the price of blades & it paid for itself in labor on the first job. The really cool thing is it clamps up in the post vise. Quote Link to comment Share on other sites More sharing options...
bosox Posted February 5, 2013 Share Posted February 5, 2013 Okay, it's fine. You must be really pleased with your saw. :) Quote Link to comment Share on other sites More sharing options...
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