The WM290 has a 5MT spindle bore, and presumably comes with a 5 MT to 3 MT sleeve?

If so, would it not be better be better to buy a 3MT Shell Mill Arbor, to minimise the number of parts between the spindle and the cutter, to minimise the risk of run out. One possible supplier of such a fitting is Arc Euro, with a M12 drawbar thread, and probably RDG or other suppliers would also be able to offer one.

I hope that you were not contemplating fitting the hexagon block into the 3 jaw chuck! That would probably give you a much greater run out!

Howard (aka Fat Fingers )

Edited By Howard Lewis on 14/01/2020 19:56:59

What I would suggest for your lathe setup is a two point fly cutter. Make an arbor which you can hold in your chuck with a thick disc attached. Couple of 6mm holes in the face side of the perimeter with one at a slightly smaller radius than the other with a couple of tapped holes suitably placed in the perimeter to hold a couple of round cutters. Form the cutters in the usual way and arrange that the innermost cutter is slightly proud of the other. You then have a tool that you can stick in the chuck in seconds and will take a rough cut with the outer cutter and a smoothing cut with the inner. George Thomas did it with a bar holder in the four jaw but you said you didn't like taking your chuck off.

regards Martin

Way too much overhang, as Andrew pointed out. I would look at cutting off the tapered section all together and grip the cutter by the larger-diameter parallel section on the end in the three-jaw chuck. The closer you can get the cutting tips of the inserts to the headstock spindle bearing, the more successful your cutter will be. IE less chatter.

Not sure I would totally agree with that Hopper.

Although the machine will dictate the depth and width of cut to some extent the indexable heads can be fed faster than a fly cutter for the same given cut as there are more cutting edges, the one in the photo will be able to be fed 4 times faster than a single point flycutter while still giving the same chip load.

Added to that being carbide tipped they can be run faster than a typical HSS flycutter toolbit so that can be multiplied by the number of teeth and you can soon be looking at feeding 10 times faster. There is the added bonus on hobby machines that the faster rotational speed also puts the motor into a better torque band so increasing what can be cut and there is no worry about keeping things balanced like you may have to do with a fly cutter

This does depend on having all the cutters cutting which depending on the accuracy of the OP's 3-jaw may not be the case as is the poor fit on some of the very cheap heads on the arbor

Edited By JasonB on 16/01/2020 07:46:46

Jason has said it!

The feed per tooth will reduce, if the feed rate is reduced, for the same cutter rotation speed.

Feed per tooth is determined by the type of cutter in use, and the material that it is cutting. This, combined with the speed of rotation, will give a MAXIMUM feed rate, i.e. ,the speed at which the cutter traverses the workpiece.

With a feed per tooth of 0.002", a single tooth flycutter operating at 100 rpm will travel at 0.2 inches per minute relative to the work.

An inserted tooth cutter with 20 teeth will travel at 4 inches per minute, all other things being equal. They won't be, in that a 20 tooth cutter will, be larger, and so likely to rotate at lower rpm, for the same cutting speed. So the actual rate of travel is likely to be less than 4" / min..

But it will remove metal a lot faster than the flycutter, and need more power to do it.

If the 6 inch vertical slide is made of parts with the same section as the 4 inch, it is likely be more flexible.

Hopefully, being taller, it will be made of thicker section components. IF in proportion, (say 0.1 is increased to 0.15 ) the individual parts will be 3.375 times as stiff, but being half as large again, the stiffness, overall is only likely to be 2.25 times that of the 4 inch one. Having said that, a doubling of stiffness is to be most beneficial!

Blunt cutters have nothing to recommend them, in my view. A sharp cutter, properly aligned, requires less power, and cuts more cleanly, with less tearing.

Howard

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Dave think of it like threading as you alter the tpi (distance between cuts) the thread becomes finer or coarser. Time between cuts will not alter things if each cut is kept the same (loading)

I can run an insert cutter at 2000rpm (limit of my spindle speed) and feed at 4-500mm per min and get as good a finish as a flycutter run at 1000 rpm but have to feed at something like 75-100mm/min.

I have found the insert cutters run smoother on teh X3 as there is more tooth engagement, with a flycutter I do sometimes get gear noise as the load goes on and off. I have found that poor quality blunt inserts will make the machine vibrate but not so with reasonable and high cost ones.

Look at the rate that the handle is going at in some of these clips, your arm would drop off trying to keep up.

One thought, if you have a wobbly set up with plenty of overhang, then the more inserts on your cutter, the more expensive it is when they all get chipped.

I agree with Howard about multiple tooth engagement.

In the early days when milling tools were seen as 'rotary files' they had vastly more teeth, which possibly helped with spindly setups and questionable alignment.

Neil

That's my issue really; a single point cutter can be set to whatever tpi is wanted, which can be extremely fine. To get a good finish, the feed-rate has to be reduced, which means less metal is removed in a given time. Adding a second cutter allows the feed rate to be doubled. Metal is removed faster but it doesn't alter the quality of the finish.

The tpi analogy doesn't quite hold water because it assume the tool cuts a clean groove. I'm not sure it does, rather metal is sheared off in front of the point, and – maybe – the tool smooths the finish by polishing the rough surface left behind:

The picture illustrates 'Built Up Edge' causing rings on the the work. Could this be what's causing Andrew Johnston's recent woe in EN1A?

Lathe tools intended for finishing are often shaped with rounded rather than sharp edges, isn't that because they polish rather than groove the work? And as a final obsevation, lathes produce excellent finishes with single point cutters: they don't need multiple teeth to get top results.

Got to admit I'm hypothesising. I think some of the facts support what I'm saying but I wouldn't bet the farm on any of it! But my proposition remains that multiple-teeth are there only to increase metal removal rates, and they don't produce a better finish than a single point tool at the same effective feed rate.

My case rests, and I ask for 27 other offences to be taken into consideration!

Dave

Absolutely, the cutting process is shearing, not slicing. I think the tool bit may well burnish the material as it passes, particularly for insert tooling. That may explain why insert tooling sometimes works better at higher speeds. The shear zone is much hotter at higher speeds, so the material is softer and more easily burnished.

Interesting idea about BUE on my EN1A. But I'm not convinced. The tool on the hydraulic copy unit is actually upside down. During roughing the swarf fell away in a steady stream of small blue chips. When finishing the swarf had more of a tendency to produce strings, but again no evidence of BUE. This morning I've used the same holder and insert in the normal toolpost to clean up a nut I welded on to my M16 drawbar yesterday. The insert looks clean and in remarkably good shape given the duty of producing a bucket load of swarf. I've also just cleaned the lathe and it really was a bucket full of swarf!

Andrew