facing plastic rod

[Martin ConnellyParticipant @martinconnelly55370]

Lug lord, one of the advantages of the 6mm diameter button inserts mentioned earlier is that they have quite a high positive rake which helps when cutting plastics and also worked quite well on some 316L stainless as I was working with recently. The problem with fast removal rates on plastic is that unlike metal it does not transfer heat into the material the way metals do. If the heat is not removed with the swarf then the surface of the plastic material heats up rapidly. I was cutting the nylon pulleys (photo in the earlier post) with a depth of cut of 0.5mm and a tool travelling at 100mm/minute. I think the RPM was about 500. The largest diameter on the pulleys is 85mm. If you are moving the tool slower than this with a higher RPM then you will get local heating which will result in molten plastic at the cutting point.

Martin C

[Russell EberhardtParticipant @russelleberhardt48058]

All the variants of polyethylene have a very low melting point so are difficult to machine. All cutting produces heat so you need to use a very sharp tool and a low speed to minimise it. Possibly a flood coolant as well.

Russell

[Ian S CParticipant @iansc]

Air is probably the best for cooling. My experience is mainly in Nylon, a good sharp HSS tool, and not too fast, and clear the cuttings away as you go or it gets all tangled.

Ian S C

[Nigel RiceParticipant @nigelrice73086]

My preference for all plastics is zero or negative rake on the tool – this will certainly prevent digging in and pulling the work from the chuck.

In order to prevent the continuous ribbons of swarf from tangling, I've never found a way of breaking this with the tool, I used high speeds and threw the swarf as a continuous ribbon into the air and clear of work and machine.

Nigel

[lug lordParticipant @luglord]

Posted by JasonB on 28/11/2017 07:27:40:

Luglord, how much material do you have sticking out of the chuck and what sort of dia are you working on, that pic of the white plastic being machined may have too much projection.

i make bushes about an inch long uhwmpe 28mm OD – 25mm OD I kind of had a thought today as i have wastage each time i make a bush so in the future i am going to try cutting just over an inch long and facing off with only a very small amount sticking out of the chuck then drill a hole all the way through and turn it down on an 8mm rod as i drill an 8mm hole using the rod as a mandrel.

with uhwmpe too much coming out of the chuck is always a risky process facing off .

I have best results using the aluminium insert on the facing tool i have but just experimenting grinding different tools its tricky as some experts on plastic machining say zero rake angles then some say plenty of rake .

As mentioned earlier i do know the difference between left and right tools i always use a right hand facing tool I think there was some confusion on how i face a part off

[lug lordParticipant @luglord]

[lug lordParticipant @luglord]

Posted by lug lord on 28/11/2017 19:27:56:

this is how i have always faced plastic off with the carriage locked so no movement

[JasonBModerator @jasonb]

For the one in the drawing above to work as a facing tool it needs the top rake in the opposite direction to the R/H Turning tool you opened the thread with.

The carbide tips have rake in both directions that is why you have had good results using the insert in a R/H holder.

Edited By JasonB on 28/11/2017 19:32:55

[lug lordParticipant @luglord]

Posted by JasonB on 28/11/2017 19:31:28:

For the one in the drawing above to work as a facing tool it needs the top rake in the opposite direction to the R/H Turning tool you opened the thread with.

The carbide tips have rake in both directions that is why you have had good results using the insert in a R/H holder.

Edited By JasonB on 28/11/2017 19:32:55

Ahhhhh now i get it

[lug lordParticipant @luglord]

[lug lordParticipant @luglord]

after a re grind using an eclipse 5/16 hss finally it works a treat now

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