Breaking end mills

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CosmosK
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Re: Breaking end mills

Post by CosmosK »

runout is the wobble in then spinning thing. Each spinning element will have some: spindle, collet, end mill. You need and indicator to measure. Hopefully, it's under a thou, better under 5/10ths. To me, I've never got "chips" cutting MDF. It always seems to turn to dust.
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CosmosK
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Re: Breaking end mills

Post by CosmosK »

Bradya wrote:I've also looked on the onsrud site for chip load calculations. It says with the 1/4in bit in mdf at 1800 rpm it should run from 216 ipm to 288 ipm. At 12000 rpm it says run at 144 to 188. Do you guys go off of these? The bit could be getting too hot? But it has starting breaking faster, not even getting hot. It's more of a powder/dust than chips or shavings. Is that bad? When it was working I was cutting at 12000 rpm and 100 ipm full depth. I'm using Mach 3 and when I override the ipm and spindle speed it doesn't seem to effect or sound different. Should it be pretty noticeable?
Note, Onsrud is probably going to tell you the max numbers you can run their bits at. Whether or not the rest of your machine can support that is another thing entirely. You could probably cut those numbers in half if you wanted to be conservative.
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Leo
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Re: Breaking end mills

Post by Leo »

Roundness and runout are two different things

Roundness is exactly that - how round something is.

Runout - is not roundness.

Something can be perfectly round, and still get really bad runout.

If your spindle has perfect roundness and your collet has perfect roundness and your cutter has perfect roundness - you can still get bad runout.

WHY????

1) Inside the spindle can be impacted with packed on dust and displaced unevenly inside the tapered portion of the spindle - that can cause rounout
2) The collet could be cracked, rusted, worn, and impacted with packed on dust and unevenly distributed on the inside and/or outside
3) The tool shank could also be worn, damaged, impacted, rusted.
4) The collet nut could be damaged, cracked rusted or dirty.
5) The spindle bearings could be worn, damaged, loose

It is NOT likely that the tool shank, or spindle is out of round.
It is very likely that the inside of the spindle needs to be cleaned.

I would get inside the spindle and be absolutely the taper is CLEAN, and free of impacted dust. That is NOT an easy thing to do.

Use a new collet and collet nut.

Rounout should be checked on a solid diameter, like a ground rod. You CAN place the indicator tip on the SHANK of the tool.
You can check the inside of the spindle taper seperately, but the real deal is the entire setup with collet and nut in place
If you still have runout - then check spindle bearings.

My experience with this stuff is purely professional, as an engineer, working in the metal cutting industry with a multitude of machines and processes for about 40 years. I work to within 10 millionths of an inch and grind roundness every day. I make master gages.
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martin54
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Re: Breaking end mills

Post by martin54 »

Can't really add much to what has already been said other than are you using Osrund Bits? If you are not then you can't really go by there figures especially if you are using cheap as chips ebay bits :lol: :lol:
Even if you are using Osrund bits then as has already been said the figures they give are really only a guideline, lots of other factors come into play depending on the machine you have & how rigid it is. It is always best to run your own tests to determine what are the optimal feed & speed settings for your machine.

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