Work hardening 304

--Having a little problem with same. I'm trying to bore 2-3/4" dia holes thru 2-1/2" thick 304 stainless; gotta do 4 parts. I managed to get the pilot holes up to about .875" with available drillbits, then I switched to a boring head and, moving in increments of 0.1" on diameter I got the holes enlarged to about 1.2" but then suddenly it got reeeeal hard to cut, even with a carbide tipped boring bar. Shallower cuts seem my only option but at this rate it'll be winter B4 I get the holes finished! I'm going to go see a pal with a honkin' big lathe who can speed things up a little bit and that will solve the predicament. --But I'm thinking *next* time I'll want to do something different like use an endmill and a rotary table to hog out that kind of material, then do a cleanup pass on my wimpy little lathe. I'm curious to know what others have done in similar situations. Any ideas?

Reply to
steamer
Loading thread data ...

All stainless will work harden. Some alloys more than others. (304 is easy) The general rule is to use a fast feed, low RPM and a broad nose on the tool. Of course this assumes the lathe is stiff enough to handle the increased load. Small lathes makes these jobs very difficult. My suggestion is to use M42 cobalt tools (8% Cobalt) and more tool relief angle to reduce tool drag. Carbide cannot support the amount of relief required. Normal HSS isn't hard enough and all tools must be SHARP. Please also consider using a cool mister. Anything to resist temperature rise also helps. Steve

Reply to
Steve Lusardi

snipped-for-privacy@news.sonic.net...

y) The general rule is to use a fast feed, low RPM and a

to handle the increased load. Small lathes makes these

and more tool relief angle to reduce tool drag. Carbide

h and all tools must be SHARP. Please also consider using

Not tried boring stainless myself but I was chatting to my dad yesterday about pillar drills and he said that when he was drilling stainless they had to up the motor size as stainless needs something like 50% more feed pressure than free machining steel or the drill rubs and burns out in no time at all - even if you have re-ground it to around 130=BA angle etc - and of course the higher feed pressure translates into more motor power required.

Druid

Reply to
Druid

general rule is to use a fast feed, low RPM and a

handle the increased load. Small lathes makes these

--Yeah; a proper tool would probably help a lot. I'm using a stock boring tool with a brazed on carbide that's pretty square-ish, so to speak. will try grinding in a wee bit more relief angle.

--Am using one; running it rich too. Mobil synthetic lube seems to work pretty well.

Reply to
steamer

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.