Hi all,
I’ve been working on some catch-all trays and I’m getting what seems like a lot of tear out when using a bowl and tray bit. The bit is an inexpensive one but its brand new so I wouldn’t think it’s too dull.
I’ve attached 2 photos. The first is walnut with the feeds and speeds from the bit manufacturer. The second photo is pine with things slowed way down.
Is this normal and I just need to sand or should I make more adjustments to try and get better results?
Thanks!
Lots of tearout and fuzz even in your letters
What bits?
What’s your speed and ipm?
A note, just because a bit is new doesn’t mean it’s sharp. Especially a cheap bit.
Pony
The bits are all Spetools from Amazon. Given that Im new I took the advice I’d read online to start with inexpensive bits.
Here’s the tool setup for the walnut:
For the Pine I did a roughing pass and a finish pass with the following settings and the same bit:
It sounds like your general view is that I should get better results from the cut itself and have less sanding.
Are you climb or conventional milling? Maybe try the opposite.
I dont use my bowl bits much but I wouldn’t expect the best cut ever from them just due to the design. Does the walnut have burn marks or is that just a shadow?
I don’t know you or your machine, but try this.
Take a piece of scrap and cut into it, even just a straight line will work, 5-6" long.
Make a row of 5 lines, each one deeper, but start with a depth of .05, and your speed 60 ipm.
See how it cuts.
After you have done that, try it again & again with faster speeds, increasing by 20 ipm each time.
See how it cuts.
Same thing again, but now also increase your depth of cut.
See how it cuts.
You will soon realize that there is a ‘window’ of feeds and speeds where your cuts are almost perfect.
Also, when I do cutting, I hog out the majority of wood with a straight bit first, then finish with the final bit.
And my final cut is usually less than .05 deep.
You will also find that cutting with the grain is completely different than cutting across the grain.
And if you have never used a hand held router, try it. If you learn to get good results with it, you’ll get EXCELLENT results with a CNC.
Forgive an old man for saying this, but I’m old school, if you learn how to do something manually, you can then run a machine MUCH better than anyone who hasn’t.
Pony
@Pony - Thanks for the feedback. I’ll try that later today and post some results.
FWIW - I have an X-50 Journeymen with a Makita router. I’ve used a handheld (mostly trim router) plenty of times but never with someone to help me correct my technique and my results usually look like the photos above.
@Echd - You asked about burning and yes there is some on the walnut which also surprised me.
+1 on reviewing your direction of cut. I’ve found that climb cutting is best for roughing, with less tendency to chip the wood. But I was milling some stringy red oak recently, also climb-cutting on the final passes, and it created fuzz that looked a lot worse than yours.
After thinking about it, It struck me that the climb cuts I was using for finishing passes would “eject” unsevered wood fibers to the rear of the cutter path, leaving the bit with no further opportunity to sever them.
With a conventional cut, however, the fibers will be pushed forward, giving the cutting flutes additional opportunities to sever them as the bit advances along the toolpath. So I changed my climb-cutting passes to leave 0.010" of stock, and added conventional-cutting finishing passes. That totally eliminated the surface fuzz on that red oak.
I wanted to post results from @Pony’s suggested test. Here they are (I realize that the five cuts to the right are with the grain and not across it 
):
Although I’d be happiest with the results from the 100ipm/0.15 cut I still got a lot of tearing.
As for the direction of cut - I’m using Carbide Create and it looks like it’s not a configurable setting in the software.
Thanks for the input all. I think the next step for me is more research and trial/error.
Good for you! Nice testing!
If you have a good sharpening shop around you, have that bit sharpened and see if that changes your results. It usually costs about $15 around here.
Or buy a higher quality bit, such as one from IDC and try it.
Pony
Just for completeness - I purchased a better bit from Amana Tools for and re-ran my pine hexagon cut.
Here’s a picture comparing the $60 Amana bit (bottom) to the $25 Spetool bit (top):
There is a noticeable difference in cut quality!
There sure is, thanks for posting this, going to invest in a better bowl bit for sure.
Pat
Has to do with grain direction. I create 2 tool paths, move toolpath from affected area for one. Use first toolpath with opposite cut direction. Also helps to reduce cut depth.
Hope this helps.
