Whistling Cutter

This topic has 9 replies, 6 voices, and was last updated 16 February 2012 at 15:27 by colin hawes.

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15 February 2012 at 17:00 #5957
David Parsons 3
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@davidparsons3
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15 February 2012 at 17:00 #84833
David Parsons 3
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@davidparsons3
I’m trying to mill some gauge plate steel on my VME Myford mill. I’m using a fairly new 10mm HSS endmill, but everytime I apply even the slighest sideways movement to the table the cutter starts whistling.

What’s the problem? Is the cutter blunt already?

The cut is 5mm deep, I’m using plenty of coolant, everything’s locked down properly. It only takes the slightest of pressure on the table and the noise just seems to get louder and louder until I let off.

Many thanks.
15 February 2012 at 17:14 #84835
Anonymous
Two things; first while a depth of cut of half the cutter diameter is a good rule of thumb, it is prehaps a little ambitious for gauge plate, assuming a full width cut. Reduce to 2.5mm.

Second and possibly more important you must keep a positive feedrate going with gauge plate; at least 1-2 thou per tooth. If you let a HSS cutter rub, even briefly, it’s bye-bye cutter. Been there, done that; I now use carbide cutters for gauge plate.

One other thought; what surface speed are you cutting at? For oil hardening steels you should be below 50fpm, and probably much lower, say 25fpm?

Regards,

Andrew

Edited By Andrew Johnston on 15/02/2012 17:15:04
15 February 2012 at 18:46 #84839
Jon
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@jon
Decent cutters or the disposable FC3 work well on guage (o1) plate.

May have been too quick a speed originally wearing the edge off the cutter. Above info good and worth checking.

I would learn to get a feel for whats happening, if it dont cut no good forcing it.

Having learnt that its quite easy patterning completed parts from 8mm thick guage plate with a 6mm dia FC3 and high content cobalt hss cutters.
15 February 2012 at 18:49 #84841
David Parsons 3
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@davidparsons3
Thanks for the responses.

I would find it hard to imagine that the cutter is now blunt, it’s seen very little use, and I certainly didn’t persist with that whistling cut.

It wasn’t on the end of the plate and so therefore can only be the depth of cut, unless of course something funny happened to the entire plate.

I will try a 2.5mm cut and see if this resolves the problem. Failing that a carbide cutter will be purchased.

Question though…
What is the physics behind a whistling cut? Is it the endmill rubbing against the work without taking an actual cut?

Many kind thanks indeed.
15 February 2012 at 18:51 #84842
nigel jones 5
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@nigeljones5
mine does the same thing if the cutter is turning too fast. I slowed it right down and had much better results, but not before ruining several new cutters!
15 February 2012 at 19:38 #84848
Jon
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@jon
I think your definition of whistling needs to be addressed first but think it will be very hard to distinguish verbally.

I have several brand new expensive cutters that will screech mainly because i cant generate the speed required to run them.

It could also be the actual cutter or machine flexing and in turn ringing.

A blunt cutter can screech as well and more force required to get it to cut. Another + for getting the feel of whats happening.

What cutter and speed are you using?

Try a smaller cutter with less depth of cut, see if its any better. Or even starts ok then goes off.
15 February 2012 at 20:34 #84851
Anonymous
David: The simple answer is that something (cutter, part, machine) is vibrating at a frequency which happens to be in the audible range. Now as to what causes it; that’s more difficult. However, empirically I find that too low a feedrate often causes vibration or squealing, as the cutter is cutting, rubbing, cutting, which excites the cutter and causes it to vibrate.

Regards,

Andrew
15 February 2012 at 22:22 #84871
MICHAEL WILLIAMS
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@michaelwilliams41215
Tell me what the cutter marks look like where the cutter touches against the workpiece when the ‘whistling’ occurs . Describe it yourself but note in particular :

(1) Ordinary clean cutter marks , burnished surface , whirl marks , vertical stripes , horizontal bands , moire patterns , random digs or scrapes .

(2) Clean cut half cylinder , similar but tapered top to bottom , either with/out a bright bit where corner at end of cutter goes .

(3) Lead in to cutter marks (ie the edges of the cut) sharply defined , burred over , ragged , wider apart than they ought to be .

(4) Any signs of heat colouration .

MW
16 February 2012 at 15:27 #84926
colin hawes
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@colinhawes85982
Slower speed , less cutting depth, coolant and heavy-ish feedrate gives best results when using HSS cutters on tool steels. As Andrew says, allowing the cutter to run on the work without a good feed rate can quickly blunt it. The cutter must be kept sharp.Wear on it's diameter is fatal on toolsteel. HSS is perfectly satisfactory on toolsteel if these guidelines are followed Colin.
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