Just thought that I'd share my experiences with you guys.
I have a plan to make some rather strange shape oil cooler fittings out of aluminium. This includes on 9/16 UN 18 TPI (JIC -06) external thread fitting.
I've not done any thread milling before so I thought, seeing as I'm on holiday, I'd have a play.
A quick search through my handbook showed me the thread spec, so I ground up a spare M12 tap, leaving just one tooth remaining.
The thread milling in Solidcam seems pretty straight forward, so I just filled in the blanks, generated the toolpath, checked it a few times in my code editor and ran it on the machine. The SC threading table has this thread in it so no real worries there.
Oh yeah, fantastic. I'd set up to use compensation so that I could tickle the size if needed, but thankfully it was pretty well perfect right off the bat. I checked it with the female fitting that will be used and it was a very nice fit.....well chuffed.
So I couldn't leave it at that.
Some of my parts have a 22mm, 24mm and 33mm x 1mm pitch internal thread in then. Normally I get my local machine shop to do the first roughing, including the thread, then I cut the rest.
So....out with a spare M10x1 straight fluted tap, and ground off three of the four flutes, and then ground off the chamfer at the bottom so I was at full diameter thread. I ground away until I had 15 threads remaining.
I then messed around again with the thread milling and cut the 12mm deep M24 thread I wanted with a couple of revolutions. I used the roughing and finishing option and it works a treat.
Probably most of you are thinking, so what's the big deal? Well, I've never done it before and don't have the proper tools, but when you're a cheapo like me you have to make do with what you have on hand and it worked out great.
A couple of people have asked me about using taps for threadmilling. Is it the right way or the wrong way.
Well, I can't really answer that properly I'm afraid, but I can say that it's almost there.
Looking closely at the 9/16 thread it ain't perfect and wouldn't pass NASA checks but as a first attempt I'm quite happy.
Grinding a little extra clearance would be a good thing.
I took a couple a couple of rough cuts and a finish cut.