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| Boring an Al Alloy casting |
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| Jasonb:
Any chance you have got sand inclusions, I had it once on a bronze cyl casting, tool would cut for a while then as it hit a bit of sand/dross lost its edge and got pushed off the work. J |
| sparky961:
There are lots of things that come to mind, but I was also thinking along the lines of sand inclusions. I'm not sure what the tools you're using are made of, as I think you've referenced brand names. Ordinarily, HSS works great on aluminum of any sort I've machined, but in this case carbide might be the tool of choice. I've done some aluminum casting and found that my castings machine more like cast iron than something tougher like 6061. Getting through the skin and any sand inclusions can do a real number on an HSS tool though. As far as porosity, I do find many bubbles near the surface but not too many getting deeper down. I don't find they usually interfere with the machining. To each their own, but I haven't found a lubricant that is worth using on aluminum. I machine dry with plenty of success and great tool life for hobby needs. Some pictures of your troubles would go a long way to help people understand what's happening and help out. -Sparky |
| Jonny:
Bill i assume its a smallish hole you are trying to bore out if using a 10mm dia bar. There are lots of rubbish HSS about that wont hold an edge i only buy the high content cobalt ones around 8%. What i suspect is the hss bar or movement in the machine ie far from rigid and did have the same in an ML7 until scrapped. Of course the casting could be another form of alloy but everything i have ever come across has been easier than 6082 T6 and much like machining chinese castings. The Suttons drills are poor, very poor not a great deal harder than MS keep the heat out. Dormer, Titex you wont go wrong as what used to be exceptional brands years ago are no more, same with saw blades. |
| bp:
I've found out that the castings were/are heat treated LM25. The opinion of the supplier was that my difficulties have been caused by the inclusions from the dregs of the pour. He is generously providing two new castings......hopefully from an earlier part of the pour!! Interesting what you say about Sutton drills, as I have found that they are generally the best that I can easily get up here in 'Straya. I'll have to have a look around for some Dormer and/or Titex. cheers Bill Pudney |
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