Best approach to pip removal

[Bill PhinnParticipant @billphinn90025]

When you have to remove a small pip after parting off a small (i.e. less than 1/2”) diameter part, and the pip you’re concerned with is on the back of the piece you’ve parted off, meaning the part has to be re-chucked and there is a slight increase in runout as a consequence, what is the best approach?

I ask because the forces involved in removing the pip seem very considerable at times, whether I face off the pip or advance the carriage to do so, or use a combination of both.

What type of tool is best for the job and what sort of spindle rpm? I’m doing brass mainly (e.g. knurled thumb screws), am after a very good surface finish (maybe even a slightly domed end) and I’m wondering whether this might be a job for a hand-held tool, not just to achieve the dome but to remove the pip as well.

[peak4Participant @peak4]

I can’t really speak for brass pips, but generally I’ve found that the job is very sensitive to tool height.
Also, particularly if the pip is off centre, ground carbide inserts are more sensitive to chipping, as it’s a small area of metal that’s hitting the insert at a comparatively low speed.
I tend to knock off the pip as fast an RPM as possible, and face at whatever speed seems appropriate.
Easier with a VFD driven motor of course.
Alternatively, use a fine file, and then face.

Bill

[Michael GilliganParticipant @michaelgilligan61133]

It seems like an ideal job for the hand Graver

Sorry … old age and Arthritis have made me too clumsy to demonstrate.

MichaelG.

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Edit: … You might start here:

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[JasonBModerator @jasonb]

If you want a domed end then you have two options.

1. File against the rotating work, moving the file to create the dome shape and you can just file off the pip first. Single cut lathe file will make quick work of it.

2. Requires a better grip so maybe a threaded split bush so that you can use a form tool set on ctr height it will also deal with the pip

 

For a flat end if filing off the pip is not good enough then just a sharp HSS or **GT insert with small 0.2 tip radius. Ideally hold in a split bush as you won’t get a solid grip on a threaded surface so the pip may want to ride up over the tool.

In all cases small dia brass wants a fast speed probably as fast as your lathe will go but whatever is quick to select.

The pip can be reduced if you use a parting tool with an angled end. Again what ever parting tool used needs to be sharp.

Or do it a sI do when making screws for my engines. Turn shank and thread (knurl in your case). Saw off from bar a bit over length. Hold by threaded end as appropriate and use a form tool to shape the head. Works well with batches of screws as well as singles

[DellParticipant @dell]

If I want a slight dome on a part no matter if it’s on the Pultra or the Myford I use a graver because it will also remove the pip but if the item is to be slotted then I don’t mind the pip as it shows centre of part, my hand parting tools have slight taper left & right so if I want the pip on part I use right taper or left if I don’t want pip on part.

This video may help as the end of it has a rounded end it was for a drum clock I restored.

[HollowpointParticipant @hollowpoint]

You can get such a thing as an engineering chisel, for exactly this type of thing. Cut the pip off flush with the chisel and then face the part as normal. CCGT tips and high speed give a fantastic finish.

[Michael GilliganParticipant @michaelgilligan61133]

Nice demo, Dell

… compared with all that, of course, removing a pip is a doddle !

 

MichaelG.

[Julie AnnParticipant @julieann]

Use a right hand parting tool so it doesn’t leave a pip on the work in the first place.

Julie

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