I've just started making some of the components for my suspension, one of which is a pin that fits in the tapers in the hubs and provides a spigot to mount a spherical bearing on.
I've been turning them out of EN16T round bar, but have had some serious problems with the surface finish (its very coursely ridged, obviously turned). I've tried varying the speed of the machine, reducing the depth of cut to as small as I can go (0.05mm) and changing the tools (HSS or carbide tipped) to no avail.
Is there something I'm missing here, or do I just accept the poor surface finish?
Cheers,
Badger

I've no advice regarding EN16T as I'm just not that knowledgable but I've found having the tool tip at anything other than centre height has quite an effect on the quality of finish. But if you do much lathe work you're gonna know that yourself I suppose!

is everything completely rigid? Is the tool at proper centre height? Is the surface speed correct? how far is the tool hanging out of the holder? and are you using coolant or running it dry? Best way to get good surface finish is to run at correct height, with everything rigid, and with coolant, using a carbide tipped tool, and at a low z feed - incidentally, a lot of steels prefer a larger depth of cut, as it chips a lot better. You will find that the metal being removed from the cut will start to chip into little pieces when everything is good.

edit, incidentally, en16t should be fairly readily machinable


[Edited on 12/7/10 by hellbent345]

I remember EN 16 when i was an apprentice on the lathe etc, it was used as it was tough and a lot stronger than regular low carbon steel.
But it can be a bitch to get a good surface finish.
You definetly need a tipped tool,HSS will get eaten alive !!!!!!!!!

What lathe are you using?

Needs to be fairly slow speed and feed on a hobby type lathe.

I can't remember the make of the lathe I'm using, but it's quite a large model, bigger than most hobby ones (it's on a uni campus).
The centre height is as close as I can get it, with the tool held very short and the piece chucked on one end and held with a centre on the other.
I was thinking about increasing the depth of cut, the most I took off in one go was 1mm and that was about the limit. Surface finish was still poor.
I've been using coolant on all cuts, would that make much difference?
I'll have to play around with feed rate a bit, but am not very familiar with the machine. As a guide should I look at increasing or decreasing the feed rate to begin with?

Use a tool with disposable inserts. This will ensure that you have the correct cutting angles. The next step to getting a smooth finishing cut is to lower the feed rate and possibly using a cutting oil.

A good picture would help but if the finish is a nice and regular (like a really fine thread) I would half the feed and go from there.

If it is not regular - are you burning out the tool or is the machine really sloppy?

Whatever you do, cutting oil would help you.

hi, try upping the speed lower the feed small finish cut less than .1mm or a couple of thou.
try with and without coolant also some tips are just for roughing and some will be ok for finish
you can try hss gives a better finish on some steels if your grinding your own hss grind all the clearance angles the take off the very sharp bit that would do the cutting ((similar to putting a chamfer on it)only about 10 thou though) a really sharp point will not give the best finish.
hope this helps Ray

OK, cheers for the advice guys! Will try to put this into practice next time I'm there.