Cutting plastic on Sherline lathe

Hi, I may need to machine up some small (6mm) plastic tubing on my Sherline Lathe. Is there any thing I should know as far as cutters etc is concerned or will standard HSS cutters suffice.

Chris

Chris, HSS are usually OK on most plastics, I do grind with plenty of rake on all edges as for aluminium, some plastics will deform or even melt if the speeds are too high so experiment to find speed and rate of cut to suit the material. A jet of air may be enough to keep the job cool to prevent deforming.

Emgee

As said nice sharp HSS works well on most plastics, i also like using **gt inserts on my Sherline for plastic as well as HSS.

Thanks Guys

Just to underline that - as sharp as possible and expect it to blunt surprisingly quickly if HSS.

Neil

You said 6mm plastic tubing. This is not going to, be particularly rigid (Probably, it will deform badly when you clamp it in the chuck, tightly enough grip it to turn it )may i suggest putting a rod down the tube;sacrificial, if need be; to stiffen it for the work?

Howard

Thanks Howard, I believe that different plastics have different machining characteristics. As yet bplastic is plastic, luckily I have a local supplier and will ask for advice as to suitability.

Chjris

I think Howard's stiffening rod is the best method, hopefully something that just slides in with the minimum of clearance. It could have a tiny centre in the end for tailstock support. Or a larger diameter at the tailstock end and the shank made to fit in the tube. The tube clamped in the chuck jaws with the rod inside it would be much more secure. A number of tests would have to be carried out to find the optimum cutters, and a fine diamond hand lap to get the sharpest edge on the hss.                                                                                                                                                  As already mentioned, the carbide inserts for aluminium are very sharp, and may be suitable.

Edited By old mart on 19/11/2019 20:06:25

It would help greatly if we knew what type of 'plastic' the material is. Since you are calling it 'tube' and have sort of confirmed its soft material (by positively acknowledging Howard's stiffening thoughts) then possible contenders for 6mm (OD or ID?) tube might be Nylon, PTFE, PFA, PVC or something harder like Polycarbonate.

I presume that whatever you are making needs to have a large length to diameter ratio and that the tube has to pass through the headstock spindle? I can think if no other reason for not using solid material and drilling a hole through.

Am I correct in assuming that you are wanting to make a large quantity of whatever the item? Why otherwise would you need to a number of tests to find the optimum cutter?

Obviously the replies, or some of them may have helped you but by providing more detail with your initial question the help offered will be much more focussed.

Ian P