Feed,Speed and DOC suggestions when profile cutting maple.

Feed,Speed and DOC suggestions when profile cutting maple.

Postby sparky957 » Sat Feb 01, 2014 2:35 pm

I am using a CMT 1/4" downcut spiral (192.008.11) to profile cut some pieces from 1 1/2" thick maple. I looked at many feed and speed charts but when I follow the recommended formulas the quality of the finish seems to suffer. I was wondering if the calculated rates are for full on profile cutting or if they are for side cutting only. Presently I am running at about 60 IPM and taking a .200 depth of cut at 14000 rpm. Beyond this the tool deflection is excessive. Even at these settings the noise is extreme. I was wondering which is the better way to decrease the noise without overheating the bit, decrease the doc and increase the feedrate or reduce the feedrate and spindle speed. I realize there are different approaches to acheive the same result. Just looking for ideas how others are doing it.

Thx Art
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Re: Feed,Speed and DOC suggestions when profile cutting mapl

Postby Adrian » Sat Feb 01, 2014 8:06 pm

Which chipload charts are you using? At your settings your chipload is running at 0.002" which is way too low for hardwood.

The noise is your best indicator. A spiral bit will scream if it's not getting fed enough material. You need to up the feed rate or lower the RPM until it's quiet(er) on the straight bits where the tool is running at optimal speed.

When you say tool deflection do you mean the actual CMT bit or the machine itself? You shouldn't be getting noticeable deflection on the bit presuming it's been properly fitted.
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Re: Feed,Speed and DOC suggestions when profile cutting mapl

Postby sparky957 » Sun Feb 02, 2014 1:32 pm

Thanks for your help. I didn't mean to imply that the rates I was cutting at were correct I was trying to find out if there was any other way to stop the noise. I believe it was just a poor choice of bit for the job on my machine. If I increase the load any more the quality of the cut begins to suffer. Example noticable steps in the cut at each pass down. I use the download spiral regularly for pocketing in maple with no problems. It is ramped into the material and then cuts at a 40% stepover with no screaming. I find it hard to get through my head how the chipload is the same when you are edge cutting a pocket at 40% width or pushing through a full width profile cutout. Anyway the way i solved my problem was to try a different style of bit. Switched to a two flute straight bit and there were nice chips flying and no screaming. Just to add both bits were brand new so it was not a dull bit issue.

Thx Art
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Re: Feed,Speed and DOC suggestions when profile cutting mapl

Postby Adrian » Sun Feb 02, 2014 1:39 pm

A lot does depend on what your machine is capable of. I cut beech and oak at 240ipm @14k rpm with 1/4" doc using a down spiral bit and get excellent results. With a straight edge bit I can't get anywhere near those speeds with good quality.

It's all a learning curve about what your machine is capable of and what works for you. Looks like you've found the right combo.
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Re: Feed,Speed and DOC suggestions when profile cutting mapl

Postby Strat » Sun Feb 02, 2014 7:31 pm

I come from a Tool & Die cnc machinist background, so I have a lot of different cutters to try. What I tried, and some success with on my machine, is a Hog mill to rough with. You have to play around with it to dial it in on your machine. I leave about .015 for a finish cut. I wound not use this on softer wood.
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