facing plastic rod

i made up a hss facing tool i put very sharp angles and a point on the tool but when facing it had a tendency to dig right in and pull the part out of the chuck .

would i be better rounding the tip on the point,

I can face it off no problem using a aluminium tippped facing tool but was just plating around grinding my own tools hhs 5/16" on a myford super 7 ill put a pic on of the tool in a bit

Edited By lug lord on 24/11/2017 13:14:32

i mainly turn down uhmwpe its not the best to work with not very forgiving

That looks to be completely the opposite geometry to what you need.

I would call that a right hand tool and they are used for cutting from the right towards the left so ideal for reducing the diameter of a cylinder cutting from end towards the headstock..

You need what is called a left hand tool which will be the mirror image and the tool is mounted with it's length along the lathe axis and used from the outer dia to the ctr or left to right as you look at the end of the stock

J

PS This is not as it is described in a certain editors beginners guide

I put the tool in at an angle so there is a clearance on the end of the plastic piece in the chuck I am pretty sure its a right hand tool i need i been doing this job facing plastic for over 2 years now i just think maybe my tool is too sharp on the angles .

cutting from the right to the left is what i do

You haven't got much rake in the direction of cutting when facing with this tool. I use a tangential tool for plastic, rake both ways. Horrible stuf to machine tho' very easy to get entangled in long ribbons of quite tough swarf

oh i thought i put fairly extreme slopes on the tool with this plastic you know if it wrong for sure it goes wrong badly.

by rake do you mean the slope on the top needs more of an angle

From the photo it looks like you've got plenty of rake for turning towards the headstock but for facing it needs to slope back towards the operator as well. Or as Jason says use a facing tool which is a mirror image of what you've got but mounted with the axis of the tool parallel to the spindle.

However the photo might lie!

When facing, you start from the outside and work towards the centre, so your tool is traveling from left to right. So you need a left hand tool like Jason said. And yes, it needs a greater slope on the top surface (rake) for cutting plastic.

i do it like in the pic work from the outside to the centre this seems to work better now i put a nose on the tool instead of a sharp point

I turn quite a few pens with plastic barrels on my lathe (about 300 now). I get a perfectly adequate finish with carbide insert tooling designed for steel on Nylon, Delrin, acrylics and polyester resins. PTFE gets a bit hot and melts at the contact point.

I get the best finish with a 6mm dia finishing carbide insert.

Regards

Richard.

Look at what Threadexpress gets up to on Youtube. He does a lot of work with Delrin and gets a great finish. You can probably take a look at his tooling there, although I don't recall him appearing to need anything special.

Murray

I must be unusual as i often face from the centre outwards particularly if there a hole in the end,in that case the tool pictured would work.

Edited By mark smith 20 on 24/11/2017 16:08:20

the tool above is the one i use with great results with an aluminium insert very sharp but i like to try and grind my own as i am a messer with things

Richard, I made some nylon pulleys last week with a 6mm button insert, lovely finish. Duncan, I set up a vacuum cleaner to suck the ribbon of swarf away as it came off the tool.

Martin C

ps Pulley fits over 1.25" diameter tube. 

Edited By Martin Connelly on 24/11/2017 22:15:03

It depends what plastic but assuming Delrin or Nylon, the tipped tool for aluminium above is what I use too. Delrin is a little more forgiving of rake angles than Nylon but both should be OK if you add a small radius to the tip of the tool.

I use a neutral tipped quality parting tool and turn with it

Jason comments: PS This is not as it is described in a certain editors beginners guide

Perhaps it was an uncertain editor, then?

Tim

Just one who knows not his left from his right

In this case I can blame my subby (who will remain nameless) as I got it checked for me

Edited By Neil Wyatt on 27/11/2017 09:36:55