I am so thrilled with new type of hand tool in aluminum that I am thinking of making it out of steel. I know stainless is supposed to be hard on tools, even carbide tools. I also can't seem to find a table showing hardness of cold rolled, hot rolled, stainless, and tool steel. I need to mill slots and turn a .75" rod to .5" on one end.
If it is too difficult to do in steel, I may stick with aluminum. I found this table for steels, and it appears that some of the hot rolled steels are not as hard as 6061 aluminum. Stainless is dramatically harder than 6061 aluminum
I guess that steel is required. Several in and outs of stainless steel set screws in aluminum pretty well strips the threads, and so thoroughly that you can't retap the hole. But now I know the manufacturing steps (including the gCode for the milling part of the tool). Doing this in hot rolled steel should be relatively easy.
Stainless is tough to deal with on any level. It's tough, and it's a lousy heat conductor meaning machining it is slow and difficult. I don't know what kind of tool you're talking about, but unless you need the corrosion resistance of stainless I'd try just about any other kind of steel.
ReplyDeleteAluminum alloys tend to be soft until they are tempered. An anodized coating can be harder than steel, but not the underlying alloy, even when tempered. (That would be Hard Anodize vs standard type.)
ReplyDelete7075 is better than 6061. If you have a choice, go with it. Tempered, for most applications, of course.
BTW, anodizing can be had in any color, including clear.
just to throw it out there, for consideration, if the durability of threads in aluminum is the only issue with your tool, you could tap it for, and then insert, heli-coil inserts. they're available in stainless and inconel(!), so you could get extremely tough threads without the trouble of cutting them yourself.
ReplyDeleteWorlds of difference between machining Al and SS. Just about anything works with Al. Just about nothing works with SS. Unlikely to succeed through trial and error.
ReplyDeleteSpeeds, feeds and angles all matter. As does type of cutting fluid.
http://www.mmsonline.com/articles/read-your-chips
http://www.bssa.org.uk/topics.php?article=193
I would try an insert instead of switching to a steel component. A high strength steel threaded insert like a Keensert would probably give you more strength then you would possibly need. A Helicoil would improve the design, be something you could get at an auto-parts store, but it wouldn't be as strong.
ReplyDeleteThe ALCO Fastener site: ALCOA owns the Keensert title.
http://catalog.arconicfastenersandrings.com/category/keenserts-reg-
Helicoils are more common, just not as strong. Lots of sources for them
So drill out the hole large enough for the external size of a Keensert with 1/4"-20 interior threads? A stainless steel set screw won't push the Keensert out of its threads. I notice the second prototype I used carbon steel set screws and even repeated insertion and removal caused no problems. If turn hot rolle steel does not work out the Keensert sounds like a good idea.
ReplyDeleteKeenserts are functionally equivalent to what I use to use 3/8"-16 bolts in 1/2"-13 threaded holes.
ReplyDelete