Don't knock it, a good finish is a good finish no matter how it was obtained.

I suspect part of the issue may be that the tailstock centre allowed the pipe to flex slightly compared to the chuck end. Schedule 80 refers to the pipe size but not the material. I'd guess it's a low carbon steel and hence might be sticky. The key to machining sticky steels with inserts is high surface speed, as discovered.

Andrew

Pays to play with speed and feed to be sure. Pipe can be tricky material to machine. Welded seam down the length adds to its woes.

Some materials are difficult to get a good finish on. Sometimes having the surface shiny may actually be a worse actual surface finish than one that looks dull but has no tearing. In general , a depth of cut of 1/4 the radius of the tool ,and a feedrate of 1/4 to 1/8 feedrate. So with a 0.4 radius tool, a 0.1mm depth of cut (0.2mm diameter) and a feed rate of 0.1mm to 0.05mm per rev .Sometimes an oil can help improve the surface finish, sometimes a soluble coolant can help as well.

I had a bit of tube "ringing " . Deafening it was. Stuffed it full of rag., end of problem. Nice finish too.

Personally, I'd be pleased with that, well done!

The multi-thread problem at the tail-stock end is likely due to movement; it doesn't take much to spoil things. Maybe a steady would have helped.

However increasing speed and depth of cut is often a very good idea with carbide. There's some combination of tool-shape, surface cutting speed and feed-rate that works best with the material being cut. There's no guarantee in a limited home workshop that all four can be satisfied at the same time. HSS may be easier because it works well at slower speeds than carbide, but grinding the tool is your problem!

With one exception, I've always found steel pipe difficult. Sticky and often gritty as well, yuk. Looking up Schedule 80 pipe on The Engineering ToolBox I see ' intended for mechanical and pressure applications. Can be used in steam, water, gas and air lines. Suitable for welding and forming like coiling, bending and flanging.' So, in choosing suitable steel for making Schedule 80 pipe, machinability isn't a consideration at all; they don't formulate it to be precision machined.

Certainly not impossible to turn nasty steel pipe in a lathe, but finding the sweet spot may be a right fiddle. Provided the finish was OK I'd put up with unbroken blue stringy swarf, but increasing speed again above 1500 rpm would probably spray chips. Like as not though, increasing speed would spoil the finish, making it necessary to repeat the fiddling stage again.

I find carbide insert catalogues difficult to navigate. What I need is an index that goes straight to the point: 'For sticky mild steel as used in Schedule 80 pipe, select Insert XYZ'. They don't do that! Instead, giant tables full of information I don't understand. If the professionals don't know what to buy, insert makers offer a service where you tell them what you need to do, and their expert makes a recommendation. Unfortunately this is for big spenders only, not the chap with a lathe in his shed who buys inserts off ebay. For ordinary purposes the simplified range of inserts sold by ArcEuro and the other Hobby Suppliers are suitable for machinable metals, but they're unlikely to be ideal for tricky materials like pipe.

Congratulations! Effective result achieved in tricky circumstances, I'd be smug for at least week.

Dave

The only time I've seen frizzy blue swarf like that shown was when turning hardened silver steel with a CBN insert. The turning was done at high speed, shallow DOC and a high feedrate. The swarf was also very brittle.

Andrew

I’m looking at the tailstock extension. Something I keep to the bare minimum, whenever possible. Every little helps….