You ill get the up/down lines you have, that is the nature of a mill.

I note that you have an island in the middle. If you did not have that island you could skim the top with a fly cutter or if you have a face mill wider than the part use that.

Are there ridges between the lines? If so your mill might not be trammed, if it isn't I did a video of tramming my Naerok mill.

Check the tran and nod as the ridges are often due to the cutter leaning sideways. Lock evey way that is not moving but I suspect it is about a sgood as you will get with that combi machine.

Also half the speed if that was with a HSS cutter you may not blunt it as fast then. You want a speed of no more that 30m/min, at 2000rpm you were doing 62m/min (200ft/min)

The quill lock is the important thing. Other locks other than the one you are moving can help in some circumstances (stopping sideways drift) but if there are no ridges, that is what a milled finish looks like, though I can't comment on how rough it is without holding it.

Unless working with toolroom quality equipment, you must accept that often the results you get with hobby machines will often be only 'adequate' . You are probably doing all the right things anyway – sharp tools , suitable speed / feed etc etc and you still won't get that 'mirror' like finish we would all like.

The roughness you feel with your fingernail can be caused by many things ( such as suggested above ) or the material itself – some steels simply will not finish well no matter what!

As for ridges, this is normally as a result of the cutting face not being absolutely level and every pass on the Y axis creates a sort of slightly angled path with each adjacent cut creating a minute step. See diagram below (Obviously VERY exaggerated ) of a work section to try and show the principle. This is normally a result of the head to table alignment. Hope that clarifies things a bit.

regards Mike

Jason beat me to it !

Edited By Mike Hurley on 20/09/2023 10:16:54

Jason and Mike, you have forgotten the other issue you can get with inadequate tram, where the tool cuts at 90 degrees to the one implied in your diagrams where you get a dip in the middle.

In any case, here is a link of me checking and adjusting the tram on my Naerok mill:

Naerok Round Column Mill Drill Initial setup and first cut

It's an old school trick that should work, although I haven't tried it. The modern equivalent is a cutter with a radius (less than 1mm) ground on the corners. These cutters are expensive, circa £45 for a 10mm diameter one. I reserve them for final cuts when I need a good finish and a flat surface. I used one to finish the valve chest faces on my traction engine cylinders. This shows the sort of finish that can be achieved:

The part is a heat spreader, in copper, for an experimental high power inverter using silicon carbide power devices.

Andrew

Thanks for the buying tip, I had not checked if APT did anything other than inserts Jason.

Thanks, I’ll try that. I inherited lots of Clarkson cutters with my TS mill, many with chipped edges so might as well grind them off and use for facing.

If you still have enough material left Justin, you could still fly cut that surface even with the raised area just by working to known coordinates from each part edge and using the hand wheel divisions. Trying to sand and polish all that out is going to take a very long time.

I consider end mills as a material removal tool much like a drill is. For larger and flat areas and whenever possible before I bought my face mills, I'd then use a fly cutter as that's what they were always intended for as a tool to remove tool marks while roughing the part out. But I should also mention they are certainly not intended for nor should they ever be used to make large depths of cut. Yes the tool itself can do so, our mill spindle bearings and splines will get damaged after enough of that. Decent face mills can do both roughing and finishing. And the difference between them and a fly cutter, as long as you have at least 2 cutting teeth removing material at the same time during the full rotation, the cutting forces are then loaded against one side of the spindle splines. So they can take those larger depths of cut to the limits of what your mill can do. Just like a two tooth slot mill, it's still a good practice to slow a face mills entry and exit points at each end of the part. But it's the intermittent cutting loads a single tooth cutter produces that starts hammering those spindle splines and bearings to an early death. Watch any Youtube video where there taking large depths of cut with a fly cutter and you can plainly hear that high speed hammering effect if you know what to listen for.

I've set my mill up with a fair amount of tooling to also precision machine hardwoods to closely match metal parts when I need that option. As a test, I spent an extra hour or so one day and got the head on my BP clone trammed in to within .0001" over a 9" circle. Very time consuming, tough and frustrating to accomplish. I then used what's really a 3 tooth 3" diameter face mill for wood. Mine were sold by Wagner in the U.S. at one time and called a Safe T Planer that was originally designed for drill press use. There light years better on a mill and the wood locked in a vise. I made one clean up cut and then a fine finishing pass of .005" depth. Even with that light depth of cut on wood with a Bridgeport clone in almost brand new condition and properly adjusted, there was still clear evidence of the tool taking probably a couple of 10ths off the back side of it's rotation. It's the stack up up all the tiny deflections and clearances within the whole assembly that prevent a clean cut with no back cutting. And the harder the material your cutting and duller the tool, the deeper those back cuts will be. Yes tilting the head a tiny amount can eliminate those back cutting swirls or even slight grooves if chip gets between a tooth and the part face. But your part faces then aren't flat, there slightly dished. That may or may not matter in some cases. While I still get some of that back cutting with my face mills, most times it's happening on a much less used and sharper portion of the cutting tips. If I speed the rotation up a bit and slow the feed rate for those light finishing cuts to dimension. Most times those face mills will still provide a more than acceptable surface finish. I even use my fly cutters sometimes, the sanding and polishing hours they've saved trying to remove any minor tool marks still make them a worth while tool to have.

Its a collet chuck, popular from China before ER became the main choice. Uses a similar style collet I use done when I first got my X3 without problem and do still use it on the odd occasion as the nut is smaller dia.

Nothing wrong with stoning HSS lathe tools because they are easily reground, at least by experienced operators with a good eye. And stoning twist-drills for a special purpose is respectable too. But the idea of stoning a milling cutter upsets me! To my mind the sharp corner edges of a milling cutter are its most precious asset, to be cosseted as long as possible. When they're damaged the cutter loses much of it's utility, and needs to be replaced or sharpened, both a bit painful!

If finish on a large scale was important, I'd prefer Andrew's approach – buy a cutter designed for the job.

Of course being an amateur, I buy inexpensive cutters, use them for roughing out everything from squishy Aluminium to chilled cast-iron, then expect them to produce a mirror finish from fine cuts, and I'm certain they're rubbish unless they last at least 30 years. My mill's not very rigid either!

My first question is, how bad is the problem and does it need to be fixed. Andrew Skinner's photo is visually flawed, but could be acceptably flat (mostly).

Flatness can be established by shining a light on the back of a straight-edge and looking for light escaping between the work and the edge. Also possible to detect tiny ridges by feel – fingertips and nails are remarkably sensitive to surfaces.

Milling cutters almost always leave characteristic marks. They're obvious in Andrew J's excellent copper plate example, which is probably very flat and has classy finish with strong mirror effect. The example is as good as can be expected from a well-adjusted stiff milling machine, set up correctly with an appropriate cutter, and driven by a skilled operator.

The remaining milling marks are unavoidably tiny. If a better finish is needed, change technique. Usually polishing with a succession of ever finer emery paper, and then buffing.

When milling I try cut in parallel straight lines because changing course leaves deep marks. Also use the largest diameter cutter available. Fly-cutters generally produce a better finish than other types but are slow. And an HSS fly-cutter can be stoned without upsetting me!

Dave