Rough finish.

I fu**King cracked it!!!
OK here's what I did first ensure the tool is a smidge below center like 0.1mm then I sharpened my tools again increased the angle on the front so it was Not tearing now that improved it a bit but what really killed it was dousing it in oil whilst actually turning it and reducing the speed down to more slower than seemed right. After that the cut sounds different if that makes sense...
 
You cannot expect to get a smooth finish when contouring an irregularly shaped cut such as you show, a pointed tool will remove metal in the quickest fashion, but to achieve a decent finish on a contour, you need to use a round nosed tool with back and side rake, moving both feed directions slowly, also use of a cutting oil is necessary to avoid tearing. To test tools and procedures for finish cutting, you should be taking straight cuts, not contours. In our high school machine shop, we used a round nose tool, taking light cuts for finishing, using cutting oil for lubrication, then using (possibly) a file, then emery cloth.
If, when filing a part on the lathe, to avoid pinning of the file teeth, one can rub chalk onto the face of the file, and frequent cleaning of the file teeth is necessary to avoid loading up of the teeth and subsequent pinning; use a file card ( a flat brush with short stiff teeth on one side and bristle brush on the other side) every machine shop should have one, not just for lathe filing, but for keeping all your files clean so that they do not gouge up any and all filing work.
 
I was testing on straight cuts to begin with just so many passes ended up contoured if that makes sense...
 
Also using a emery cloth and file seemed like cheating... I think it was mainly the oil I was missing and tearing was what it was doing... I applied oil and it was great afterwards
 
vimes1984 said:
Also using a emery cloth and file seemed like cheating... I think it was mainly the oil I was missing and tearing was what it was doing... I applied oil and it was great afterwards
Click to expand...
Flood coolant is almost essential if a nice surface finish is required.
This is 1045 CR turned at 400 SFM (6 1/2" diameter at 250 Rpms) .020" /.5MM doc and a feed rate of .008" /.200MM per revolution using a common triangular carbide insert tool with a 1/64" /.25MM nose radius.
The surface finish was excellent considering the material
 
vimes1984 said:
Ye sit's mild steel, this is so confusing I've read somewhere that a touch above center is good and a touch below is bad :D
of the joys :D
Click to expand...


Never want to be above center when turning OD . Slightly below won't hurt . When boring , it's the opposite . Slightly above and not below . ;)
 
Been a lot of discussion on this topic lately . A easy was to take the guesswork out of being on center ........... Take a piece of round stock and drill a 1/4" hole thru it , drill and tap 2 holes in it and put a 1/4" rod thru it . Set up a turning tool and find dead nuts center taking face cuts and adjusting . When you're there , set that little piece you just made on your tool tip and set it to a piece of flat stock across your ways or carriage etc . Lock it up and keep it on the lathe forever or until you can afford a height gage . It's an easy tooling aid .
 
Using Emery, Files, is not cheating. Any method that achieves the result you want, is the correct method for you. Emery cloth is not made, just to sell to the likes of us,. not enough business. It is made for "Professional Engineers" who use it all the time.
You will find, that some ALL METALS, Brasses, steel, aluminium, are like women. Some are easy to manipulate, ie, turn or polish, others will reject every advance you make. Turning copper is something else again.
Sharp tool bits, is the key. Even burnish the cutting edge of your bit, on some emery paper. Back the paper with something flat and rigid, and rub the tool face carefully against it
Your wife or girlfriend has some handy tools also. Their finger nail polish board, does a nice job honing HSS edges. Nail polish, Lacquer, makes an excellent coating for electronic circuit boards, waterproofing! Scissors cut tin plate, flour sieves are good for moulding sand, and their knickers feel nice worn under your strides.
Kidding, sort of, about the last bit, but the other stuff is f'real.

You ask, am I still married. No, for some reason.
 
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