Hehe. Now to teach yourself to grind a chipbreaking tool for Alloy ;) How I hate the stringy swarf produced by HE30 and the like. This is actually an area where carbides would work on your small machines. There are really nice tips made for turning Al-Alloys which are extremely positive geometry and pretty sharp.
Positive geometry is the answer for light machines. Heavy machines and negative geometry pushes the material off, and is one of the reasons they don't work on light lathes.
Wayne...
A good tool to make for this kind of mirror / almost ground looking finish is one from a round piece of HSS. Grind the end square accross, but with about 10 degrees of 'front' clearence. grind the more forward part to half the thickness, and then get you dremel/similar tool out with a grinding/cutting disk on it and make the flat into a hook by grinding a grove accross the bit you just flattened. You want to end up with a razor sharp edge, perpendicualr to the length of the bar, and at half height. I cant ascii art it, but hopefully thats clear? stack a couple of bits of mild steel bar, about 1/2 the height of the tool holder slot into the too post and drill through at the size of your tool, so you create a split tool holder for your new tool, and magically its on center height :) just lightly take a file to the inside top half to give it a small clearance so the tool will clamp. To use put tool in tool holder, set the cutting edge to about 30 degrees from horizontal, with the down side in the direction of travel, and take the lightest cut you can. The long straight cutting edge means your tool is guarenteed to touch absolutly smack on center height and the sharp edge means you can take the lightest of finishing cuts. The swarf should come of looking like spiders webs.
Its amazing how the foundrys manage to hide the correct things in 90% of the bars that I get ;) I think the other 10% were meant for someone else, so when I was looking for a cylinder, but it was actually a crank its no wonder it ended up in the scrap box...
Dave
Give us a clue on the tip boss! I've currently picked up TNMG and TCMT off eBay cheap - what am I looking for to avoid the bouffant aluminium wig that keeps appearing on my lathe?
Steve
I use the Bohlerit tips for Al-alloys. J&L sell them, they are not cheap but last a fair while on Al-Alloys.
They can also be used for machining titanium to good effect.
An axample of the type is "
As usual to make the tool chip the material you hit it hard and fast for roughing. These tips give a good finish with very light cuts too.
I have also used them for light cuts on steel, but never dry.. They can be used dry on Al-Alloys.
Wayne...
what am I looking for to avoid the bouffant aluminium wig that
I should of added you could try grinding your own chipbreaker in HHS of course. You need to grind a severe narrow trough behind the cutting edge. This serves to make the material curl so much it breaks off in short chips. The feed rate needs to be fairly high to make the swarf less flexable and more prone to breaking.
Once you get it right you'll be pleased you dont get that crap wrapped around the chuck and flailing around again!
Some stainless steels can do the same thing. Like the 316 I've been machining all day...
Wayne...
"
Thanks Wayne - the link worked fine DCGT style tips.
If you do a general search the Bohlerit on the J&L website you will see most of the tip shapes.
Wayne...
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