# Achieving Clean Cuts



## maguru

Hi,

I can't achieve clean cuts no matter what. Not just tearout which is manageable, but the inner part of the cut. It's never clean enough to be presentable and when the cuts are intricate, they're nearly impossible to sand inside. I attach a picture as an example, that was cut with a 2-flute Yonico 31212-SC endmill. It's an 18mm finger jointed pine panel. The cuts were done in 4mm passes. I get worse results on plywood.

Any recommendations? Bits, improvements I should focus on my DIY machine, techniques for toolpaths?

Thank you


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## AlaskaGuy

What are you using to power the 2-flute Yonico 31212-SC end mill bit with?


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## CaptainKlutz

IMHO - Dump to low grade Yonico bits and your results will be better.

Switch to Whiteside you will notice a huge difference. Amama has a line of coated CNC end mill bits that also leave nice edges. The regular Amama carbide spiral bits are just so-so. Good carbide bits are never cheap.

I also buy end mills from MSC online, when they are on sale. The 2 flute are perfect for domestic woods, and the 3 flute leave wonderful finish on hardest exotic woods. The offshore brands are usually cheaper than any of the router bits sold by wood working suppliers, which helps when you need a dozen.

I own 3-4 Yonico bits, bought to test how they work, due low price. Love a good bargain. 
All of them lasted about 10-15 linear feet before the cut quality started going bad. Had burning/fuzziness on fine grain wood, and tear out on large grain. The carbide quality is horrible. Look at your edges under microscope and will see why they not cutting well. 
IME - Yonico bits are one project and trash bits. Maybe need 2-3 to complete a large project. Was able to touch up the back of profile carbide with diamond hone, and get another 10 minutes of lifetime before started burning edges again. I get better lifetime from coated HSS bits (with slower speed/feed) than I do with Yonico solid carbide when used for cutting circles with router jig. YMMV

Best Luck.


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## CWWoodworking

Yonico bits are the worst tooling I ever purchased. I tried a rabbit set and a chamfer bit. 3 bearing were locked up and what took 6-7 passes with yonico chamfer bit, takes 2 with Whiteside.

Yonico is terrible.


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## MadMark

Cut it in one pass. The bits have long carbide for deep cuts. Why would a bit have 25mm of carbide if you could only use 4mm of it?

Perhaps use a smaller cutter for the first pass and then clean up with the full diameter bit.

A little masking tape on the cutting edge..

Umm, thinking about it when you do a full with pass one side of the cutter is feeding into the wood, the other side is cutting against. If the outer radius is cut first and the inner on the 2nd pass, the 2nd pass will be into the wood instead of against. This should address your "only the inside radius is rough" issue.


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## Lazyman

I have had great luck with Yonico bits. I have several and have not gotten a stinker yet. In fact the one Whiteside bit that I purchased for my CNC is the only one that I (no longer) use on my CNC machine that gives me terrible tear out every time and from the first time that I used it. It also seems to burn more easily than my other bits. I actually had to abort a job because I was afraid it was going to start a fire. I'd call that a stinker.

A down cut bit will usually give you less tear out. Since it is slicing downward there will be very little on the top and the spoil board will minimize it on the bottom. Just be aware that it can pack the groove with dust so you may want to make lighter passes.


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## maguru

> What are you using to power the 2-flute Yonico 31212-SC end mill bit with?
> 
> - AlaskaGuy


My machine is a DIY CNC, I use a palm router, it's a chinese knockoff of Makita.



> IMHO - Dump to low grade Yonico bits and your results will be better.
> 
> Switch to Whiteside you will notice a huge difference. Amama has a line of coated CNC end mill bits that also leave nice edges. The regular Amama carbide spiral bits are just so-so. Good carbide bits are never cheap.
> - CaptainKlutz


Makes sense, but I can't afford high end bits now, and especially due to my setup, they wouldn't shine the way they should.



> Cut it in one pass. The bits have long carbide for deep cuts. Why would a bit have 25mm of carbide if you could only use 4mm of it?
> 
> - Madmark2


I thought that you souldn't make passes deeper than the tool diameter. I got that idea somewhere… but I can try what you say, sounds like my machine can't handle it, but regardless, can try on a scrap piece.



> I have had great luck with Yonico bits. I have several and have not gotten a stinker yet.
> 
> - Lazyman


That's good to hear! I have had good experience with Yonico on my regular router as well.


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## MarioF

Tearout is tamed with the use of high grade spiral bits like Onsrud, Amana, or Whiteside. Even tinkering with your machine variables like overpass percentage, deph of cut, speed, etc, there is so much you can expect from pine lumber…if you are using an underpowered motor on your cnc better go for basswood or soft maple, pine wood fibers are just too long and tough to expect all around clean cuts. Good luck.


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## Lazyman

I think you are right. Depth per pass equal to the width is a good rule of thumb for the upper limit in wood. Depending upon how solid your machine is, 1/2 might be a better limit.


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## maguru

> Tearout is tamed with the use of high grade spiral bits like Onsrud, Amana, or Whiteside. Even tinkering with your machine variables like overpass percentage, deph of cut, speed, etc, there is so much you can expect from pine lumber…if you are using an underpowered motor on your cnc better go for basswood or soft maple, pine wood fibers are just too long and tough to expect all around clean cuts. Good luck.
> 
> - Mario


Thanks for the advise. I will look into the variables and do some testing. I'm not expecting a perfect cut, just a bit better so it's presentable for certain applications.


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## RichT

I'd take a close look at your DIY CNC set up, and also that knock-off router. Using a fluted bit can create chatter. Unless your CNC is rock solid, that'll cause rough cuts. Also, if the router itself has run out, it'll exacerbate the situation.

As mentioned above, a name brand spiral bit will give you better results right away.


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## maguru

> I d take a close look at your DIY CNC set up, and also that knock-off router. Using a fluted bit can create chatter. Unless your CNC is rock solid, that ll cause rough cuts. Also, if the router itself has run out, it ll exacerbate the situation.
> 
> As mentioned above, a name brand spiral bit will give you better results right away.
> 
> - Rich


I think that the wobble of my machine is unacceptable. I thought that it was small, but I'm not an engineer so what's small to me, it's actually huge. I'll have to completely rework the structure and will try to upgrade to a spindle. My router has no speed control and I need a palm router anyway so I might as well use that one lol.

Thanks everybody, really appreciate all the time you took to reply!


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## oldnovice

In my opinion, if you want both the outer track and the inner track to be clean use a smaller bit, increase the number of passes, leave a little on your first complete through cut and make a clean up cut.

Also pay attention to climb and conventional cuts as it does make a difference! 
On a router table you pass the wood into the cutter, that is a conventional cut.
On a CNC you can move the cutter into the wood, conventional, or move the cutter in the opposite, climb cut. This does make a difference on the cleanliness of the cut.

Use a downcut cutter for the first 1/16" and then switch to an upcut or straight flute bit.

Or, get some better cutters, Whiteside, Onrud, or Amana.

I have tried all of the above and it does take some "tinkering" to find out what provides the best results, after all most of us are still novices when it comes to *perfect* CNC results.


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## therealSteveN

> In my opinion, if you want both the outer track and the inner track to be clean use a smaller bit, increase the number of passes, leave a little on your first complete through cut and make a clean up cut.
> 
> - oldnovice


Even with a dodgy bit, and set up, taking skim passes is stressing the set up less, and would be a better way to go. Clean edges on plywood and interior cuts with a router can be trickier than solid wood, glue, and crossing layers, allow for a lot of bumps in the road.

The small passes to get close, and a final skim pass to get a clean edge has worked for routers since the early years.


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## maguru

> In my opinion, if you want both the outer track and the inner track to be clean use a smaller bit, increase the number of passes, leave a little on your first complete through cut and make a clean up cut.
> 
> Also pay attention to climb and conventional cuts as it does make a difference!
> On a router table you pass the wood into the cutter, that is a conventional cut.
> On a CNC you can move the cutter into the wood, conventional, or move the cutter in the opposite, climb cut. This does make a difference on the cleanliness of the cut.
> 
> Use a downcut cutter for the first 1/16" and then switch to an upcut or straight flute bit.
> 
> Or, get some better cutters, Whiteside, Onrud, or Amana.
> 
> I have tried all of the above and it does take some "tinkering" to find out what provides the best results, after all most of us are still novices when it comes to *perfect* CNC results.
> 
> - oldnovice


Lots of info to process, thank you so much will read about that.



> The small passes to get close, and a final skim pass to get a clean edge has worked for routers since the early years.
> 
> - therealSteveN


Will deffinitely try that ASAP. One downside is that the worktime would be a lot longer than one pass, but if the result is much better I will consider it.

Thank you


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## maguru

The cuts improved considerably after some trial and error:
Instead of Pocket, I used the Adaptive Clearing toolpath on Fusion360.
For the slots, I changed from 2D contour to Slots.
I took into consideration the grain direction.
And on my machine (grbl) I increased both the speeds and the acceleration.

All of that resulted in very satisfactory cuts and I'm very happy.

Thanks everybody for the tips.


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## mghood

It sounds to me that you are underpowered using a palm router. I think that you should back off the depth of cut and don't use a bit over 1/4" wide. I have had the best luck with spiral endmills. It's my opinion that if you buy better cutters they will cut better and last longer.

mghood


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## finns

I would suggest using compression bits for plywood. A 1/4" bit should be able to handle your project just fine.


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## oldnovice

Lately I have been cutting a lot plywood, I mean a lot of plywood, and found that the Onsrud up-cut bit (52-910) with 8 passes in 3/4" plywood worked the best. The resulting cut had some fuzz on the top surface but the inside cuts were very clean and the fuzz was easy to sand off.

I used that bit because I didn't want to change bits between passes as I said, I was cutting a lot of plywood.


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## Blindhog

Pretty interesting video explaining different router bit types and applications.

Router Bits


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## oldnovice

I have stopped buying straight router bits as I find the upcut and downcut work so much better and are much quieter.
A little more expensive but, in my opinion, worth it.

I have not tried a compression bit as yet, but I will surely get one!


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## Ger21

A bit late, but this is most certainly a machine rigidity issue. Any flex in the machine at all will lead to poor quality cuts.


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## oldnovice

I have to agree with *maguru* on all of his points. Better bits, spiral bit up/down bits, feeds and speeds will help greatly.


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## tvrgeek

> I d take a close look at your DIY CNC set up, and also that knock-off router. Using a fluted bit can create chatter. Unless your CNC is rock solid, that ll cause rough cuts. Also, if the router itself has run out, it ll exacerbate the situation.
> 
> As mentioned above, a name brand spiral bit will give you better results right away.
> 
> - Rich
> 
> I think that the wobble of my machine is unacceptable. I thought that it was small, but I m not an engineer so what s small to me, it s actually huge. I ll have to completely rework the structure and will try to upgrade to a spindle. My router has no speed control and I need a palm router anyway so I might as well use that one lol.
> 
> Thanks everybody, really appreciate all the time you took to reply!
> 
> - maguru


Yes, in woodworking massively strong and just plain massive are your friends. So are good bits.


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