Slot Cutting Question

[RJS100]

I am fairly new to machining and was making a flat part that was attached to fixture plate of sorts. Everything worked out fine, but I had a small issue with the 2D contour tool path that I used to cut the part free from the .625 thick aluminum stock. I used a 3/8" endmill and took three passes with a depth of cut of about .210 deep. For some reason, at some points the endmill made a squealing sound. I stopped the feed momentarily and moved the position of the Fog Buster thinking it was not getting adequate mist lubrication. When I restarted the feed, the sound went away. I later realized when it started to squeal again that just pausing the feed and restarting it stopped the sound, so it had nothing to do with lubrication. I tried slowing down the feed rate, but it did not stop the squealing. The finished piece has a very nice surface finish with no signs of chatter.

I ran this at 4500 rpm, 12 ipm, .375" WOC and .20" DOC. This results in a chip load .00089. Do you think the squealing sound is due to chip thinning and that I need to take a more aggressive cut? Or is there something else going on here.

Best... Richard

[suntravel]

Hi Richard,

do you have a picture of the 3 flute mill you are using?

Your cutting rate is very low, it should be no problem to go with 24 ipm.

The plate under the part is very thin, this would better work on a vacuum plate, or use something at least 3/4" thick.

Uwe

[tblough]

What Uwe said. Your feedrate was too slow. 25-28 in/min for HSS 2-flt cutter.

[RJS100]

Thanks for your thoughts. Really appreciate it. The endmill I am using is a 3-flute aluminum specific endmill:

https://allindustrial.com/yg1-28584-3-8 ... -end-mill/

My reflex is to slow down the federate when something doesn't look/sound right. In reality, it looks like I needed to take a more aggressive cut. The screen shot of the G-wizard calculator show exactly what you guys are saying. With a more aggressive setting, it suggests a feed rate of about 24 ipm. That seems fast but I will surely give it a try on my next project.

Uwe, I buy my aluminum at Industrial Metal Supply that sells lots of scrap pieces of ATP5 fixture plate material for a very low cost of about $2.40/lb. (https://public.vistametals.com/products ... -plate.pdf). The fixture plate material I used for this project was .625 inches thick. I was surprised to that you thought it was too thin. My next project was to make a fixture plate with a series of threaded M6 holes. I have a piece of material that is .750 thick, but they also have .875", 1", 1.25" and 1.5" thick. I plan on making the plate about 8" wide x 17" long. How thick do you think I need to go?

Richard

[suntravel]

I thought from the pic it was 1/4".

For only clamping it at the ends, it must be stiff enough not to flex or vibrate.

YG1 endmills are top notch.

Uwe

[RJS100]

Thanks again for all our help. I guess I have to be less of a wimp and take some more aggressive cuts

[tblough]

This assumes a tight machine and spindle. Slop in either or both places will decrease the max feed. However a good rule of thumb is increase chip load to reduce chatter.

[RJS100]

Thanks Tom. I am running an 800 lb. benchtop mill that is fairly rigid for a benchtop but is still a benchtop. Looking at my some of my past jobs, the chip load was between .0015 and .002. On this particular job, the chip load was only .0008. If I had run at 18 or 19 imp, my chip load would have bumped up to .0136, so surely a more aggressive on the next round.

Richard