Turning 304 stainless

[glenn thomasParticipant @glennthomas48964]

Hi ,i'm attampting to make a stainless wheel spindle fron 304 grade stainless, could someone please advise me on speed and technique etc as i'm just ruining my cutting tools. It hasn't work hardened as i've tried several pieces. Also if i ever get it turned to size whats the best threding technique?

Thanks in advance.

[glenn thomasParticipant @glennthomas48964]

[AjohnwParticipant @ajohnw51620]

Quote from aalco

Machinability

304 has good machinability. Machining can be enhanced by using the following rules:

Cutting edges must be kept sharp. Dull edges cause excess work hardening.

Cuts should be light but deep enough to prevent work hardening by riding on the surface of the material.

Chip breakers should be employed to assist in ensuring swarf remains clear of the work

Low thermal conductivity of austenitic alloys results in heat concentrating at the cutting edges. This means coolants and lubricants are necessary and must be used in large quantities.

I've turned it without too much trouble but only from 6mm dia. I used around 400rpm and a smear of cutting oil.

John

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[Chris Evans 6Participant @chrisevans6]

I take it that it is a motorcycle wheel spindle. I am not a lover of stainless for this type of application but have made a few. (I would use EN16T). To get reasonable results try turning at around 500/650 RPM and apply a little cutting compound to the work piece. This should stop it knocking the tool about, if no better go a little slower. Screw cut to within 5 or 10 thou and run a die down with plenty of compound to ease the cutting.Lubricate the threads when fitting the nuts to prevent galling. Chris.

[Joe PageParticipant @joepage27051]

Hi, I haven't turned 304 but have turned 316L which is harder. Use only carbide inserts for turning, HHS ground tools can be used but are unforgiving, Flood with coolant, lots and lots. Don't dwell at all otherwise it hardens, so keep moving, your looking for blue chips when you've got the right speed. As for threading, carbide inserts again, set the compound at 29.5 degrees and use that to move in, don't use the cross slide. It's so it cuts the majority of the metal on one size of the tip, longer tool life and better finish. Shallow cuts, lots of oil and slow spindle speed.

Plus all of this depends on what size the shaft it, I turn everything at about 600rpm up to 100mm and it all seems good. I've found the slower you go the better finish and the longer the tips last, but it depends if your in a hurry or not. I'm assuming manual lathe or CNC?

[Involute CurveParticipant @involutecurve]

Higher than normal!! feed rate helps.

What lathe do you have?, type of cutter?

[LambtonParticipant @lambton]

Glenn,

Try using Ambersil Tufcut fluid when screw cutting, tapping or drilling stainless steel. It is also OK for turning if you take things easy. It is designed use when cutting tough metals. It is widely available from e.g. Axminster, Cromwell, RS etc.

[Martin ConnellyParticipant @martinconnelly55370]

If you look at drilling tables for stainless steel you will get maximum speeds and recommended feeds. If you are using HSS tooling these figures can be used with a workpiece in a lathe. For example a Ø25mm drill should be run at a maximum of 235rpm and this figure should be used for a Ø25mm workpiece. If using carbide tooling then higher speeds can be used but double that for HSS is probably a safe guide. The feed per rev is very important for stainless. I use about 0.2mm per rev (CNC setting makes it easy) so you will need to find something similar to this if using power feed on the lathe. Hand feeding runs the risk of dwelling and causing work hardening. If you are doing 500rpm then the feed rate works out at 100mm per minute. This is may result in manual cranking at quite a high rate so slower revs may be important for manual operations.

Depth of cut is often critical, especially when using carbide. I try to stick close to 0.2mm. You need to work out what will get to your desired diameter using steps of about 0.2mm with a regular checks as you approach your target size.

I have a 25mm paintbrush which is well soaked with high sulphur cutting oil. I keep this on the workpiece to apply a thin film of lubricant and to keep small particles of stainless away from the cutting action.

I use carbide insert tooling with 0.2mm radius tips

Martin

[Martin ConnellyParticipant @martinconnelly55370]

This is one of the parts in stainless that I made for the UK Monowheel Team's record holding Warhorse. See their facebook page for further details. (Welding by someone else)

Martin

[Ian S CParticipant @iansc]

Turning stainless steel on a……………….Super Adept.

Ian S C

[egaParticipant @ega]

Lawrence Sparey recommended ethyl tetrachloride for turning stainless steel – "used for filling certain types of fire extinguishers, and most large garages stock it".

Remembering warnings about carbon tetrachloride, I imagine that this recommendation is not to be followed today?

[CirclipParticipant @circlip]

Posted by ega on 03/12/2015 09:57:25:

Lawrence Sparey recommended ethyl tetrachloride for turning stainless steel – "used for filling certain types of fire extinguishers, and most large garages stock it".

Remembering warnings about carbon tetrachloride, I imagine that this recommendation is not to be followed today?

Not if you carnt spull or 1+1=3

Most of the "Old" concoctions and potions still work, just a case of using common sense when applying. Carbon Tet is ideal for washing the coke off the top of IC pistons and Trike is super degreasant. Oh, if you smoke over the top of Trike, it turns to Phosgene in your lungs. Errr that's an easy one, not missile tech.

A couple that need to be pointed out, DON'T play with electrics when your hands are wet and DON'T walk in front of an oncoming bus (or car).

Regards Ian.

[MuzzerParticipant @muzzer]

As for carbon tet, make up your own mind about its toxicity. It was banned for a good reason, mainly its very toxic effects on the liver. Trike (Genklene) isn't as nasty but isn't good for the ozone layer.

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