Bit Recommendations for hardwood

[dminnery]

Hi All,
I'm looking for help on styles and brands of bits for profiling 3/4" maple.
I need very smooth finishes, 1/4" cutting diameter.

I tried an Onsrud bit, solid carbide 2 flute upcut but had poor results. I had better results with a 3 flute endmill someone gave me, though I'm baffled why the Onsrud was so poor. In any case, I want a few that I can try out and see what's going to give the best results. I'm interested in value, not necessarily the cost of the bit. I'll be using these 5-6 hours a day, 6 days a week.

I've been curious about single flutes as well, but fear if the 2 flute onsrud was bogging and vibrating, a single flute may just be worse.

FWIW, I'm using a Romaxx CNC with a 2hp porter cable router.
thanks in advance!
David

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[ger21]

What exactly was poor about the results you got?

What feedrate, rpm, and depth of cut were you using? Climb cut or conventional cut?

How you use a bit is just as important in the choice of bit.

[dminnery]

Hi Gerry,
I posted about some of the problems I had several weeks back, and I think you replied!

I was just using a brand new 52-910 Onsrud in cherry, .2" dept, feedrate 100, had to bring rpms to 23k to minimize vibrations. Still, I had a ridiculous amount of vibration, based on the cut the bit made, it was about 1/8" on either side. I think I was using conventional tonight, but climb produced the same results in the past. I think those choices may be involved in the fine tuning of getting a finish quality I need.

It's actually a bit scary to watch. I slowed it down to .1" depth, but I need to run this machine faster to suit my production needs, so I'm looking at bit options.

The machine is about 2 months old and I just got it back today to fix this exact problem. It's actually better and sounds a whole lot healthier, but I'm trying to find a different bit that will suit my needs.

I have no problem cutting baltic birch with a compression bit at .25" depth and 225 feedrate at 14k rpm. But I have yet to get acceptable results with hardwood.

any thoughts?

[ger21]

Still, I had a ridiculous amount of vibration, based on the cut the bit made, it was about 1/8" on either side

To me that really sounds like a machine rigidity issue. Is the bit really sharp? Cherry is really soft, and should cut easily with a sharp bit.

Have you tried the compression bit with the maple? Cutting maple should be very similar to baltic birch.

[dminnery]

The bit tonight was brand new.
I did try the compression on maple and it cut great, but the profile was not so great. I need a perfectly smooth profile. Maybe I'll try that again with a brand new compression, also a big price difference from $18 to $44.

Romaxx just paid to have the machine shipped round trip from me (seattle) to michigan so they could fix it. I know Ron spent time and money to fix this, perhaps this is the best this machine can be. Serves me right for not seeing it in action first. Seriously getting knots in my stomach with the time and money I've wasted and am wasting while I'm trying to getting this thing productive.

I have the bigger model and a friend has the smaller model and he is able to run that same bit at .25" depth, 100 feedrate. That baffles me, even if it's a little larger I can understand some more flex but not that much of a difference.

He recommended a 3 flute endmill, which he gave to me. Everyone I've talked to recommends that 910 onsrud, but it's not doing the job. I'm frustrated, but need a solution.

[ger21]

You might want to try a downcut, but you'll need to take shallower cuts.

A 3 flute Onsrud or Vortex should cut better, but if the machine is flexing that much, it may not help much. You might also try a low helix from Vortex

[louieatienza]

Onsrud recommends a chipload of .006"-.008" for that particular bit; at 20kRPM that would mean 240-360IPM at .25"doc.

I still would try a 65-023 single edge Super-"O" flute bit. It actually has a lower chipload than the 52-910 in hardwood (.004"-.006") which might help you. I just used it recently to cut neck blanks in birdseye and curly maple with no tear out and clean edges; it's worth a try. I didn't even have the dust collection on. I was cutting 1" D2S which is about 7/8" finished.

[dminnery]

thanks guys, this gives me a few things to test out.

[dminnery]

After many hours and shipping this back to Romaxx for repair I have come to some conclusions.
I tried single, double and triple flutes, upcut, downcut and compression bits. Mind you these were all onsrud bits, so I was trying some of the best available.
The biggest improvement was putting an after market collect on the porter cable router.

In the end this is the best I can get with this machine. Using an Onsrud bit (52-910) I can cut.1" depth at 23k rpm, with a feedrate of 40. I tried a final pass at full depth 3/4" offset .02" to get a smoother profile but it's not that much better. There is just too much deflection in the machine. I still have to go over my profile with sandpaper by hand to get an acceptable result.
Perhaps with his smaller machine the deflection is less with less of a span on the axis, it may produce better results.
This machine hit a price point that fit my budget, so maybe my expectations were too high. The weak point is the V groove bearings, I think they just have too much slop. In the long run I expect to go through a lot more bits running at this high rpm and low feedrate.

The customer service has been very good, but if the machine design was different I may not have needed as much service. Perhaps this is the compromise with a machine in this price range.

[louieatienza]

Sorry to hear about your experience... I have also heard a lot of good things about Romaxx machines. There are folks who have built a Joe's Hybrid, with v-bearings, and had similar experiences. It could also be that, with a combination of the belt drive, though there are many successful machines with both. Also keep in mind that with belts, your mechanical resolution is going to be dependant on the diameter of your pinion (excluding micro-stepping) and it is possible you're seeing that in the curves of your workpiece, although unlikely. Nevertheless, my best guess is that the load of the tool cutting is far less than the rated load of one v-bearing, and you have at leat 4 on each axis...

Your chipload isn't even .001" which is perplexing to me, since it doesn't take a lot of power to cut wood, even maple, with these smaller bits. It's hard to say, without looking at the actual cut quality on your work, and a video maybe, to see what exactly is going on. I have some flex in my machine, but still can produce cuts that require little sanding. Unless you have a heavy commercial machine, making parts that require absolutely no sanding is not trivial.

Some other things you can try would be to bolt the machine down to your workbench; this should give it some added mass. It may sound counter-intuitive, but try climb-cutting your profile; that would be clockwise for an outside contour. Yet another thing would be to simply use a larger diameter bit; you can leave .02" or so and clean it up with the smaller bit, taking .2" or so to decrease the load on the bit. Lastly, you can try another router; you could just have a lemon...

[louieatienza]

I have to actually cut some maple parts out tomorrow, so I'll make a mote of my settings (and maybe a video) and get back to you here... But, IIRC, I used a single Super-"O" flute 1/4" at .2"doc at 18krpm and 72ipm, using a spiral contour ramp-down strategy, which is about .004" chipload.

[dminnery]

Thanks Louie,
This is the third router I've tried, so it's not that. I also replaced the computer per romaxx. The machine is actually heavy and quite stable. The problem is pronounced and you can actually see the router shaking if the feedrate is too high or the rpm is too low.
I'll try climb cutting again and maybe finish with a final pass at .02" offset.
I've done that before but not since I got it back from Romaxx.

I've been in touch with another WD owner who has had the same experience, he's also been in touch with a few others.
To be honest every time I run this machine I'm afraid to walk away from it.

Regarding a lemon, yes I thought the same thing. Ron rebuilt much of it, ran some tests and said it was as good as any he's made.

I bought this largely based on the great reviews, perhaps the HS is better and more stout. I can't afford much more at this point, but an upgrade is in my future.

[dminnery]

Here is another test I ran at Louie's suggestion. A picture is worth a thousand words, so here they are.
I tried four bits, all 1/4" solid carbide onsrud: single flute upcut, double flute upcut, triple flute upcut, and a compression bit.
All cuts were at 80ipm, 20k rpm, porter cable router 892, 2.25 hp, with a precision collet.
I tried cutting straight lines on the Y axis, single passes at .05", .1", .15" and .2"
I also cut 3 circles, single pass at .1", .15" and .2"
You can see where most of the deeper circle cuts reflect a lot of vibration where the router is physically vibrating.
The machine is sloppy, no doubt. could use some help.
Dust collection is very good, so that is not causing the issue.

The last photo is a closeup of the compression bit test.

[louieatienza]

Here is another test I ran at Louie's suggestion. A picture is worth a thousand words, so here they are.
I tried four bits, all 1/4" solid carbide onsrud: single flute upcut, double flute upcut, triple flute upcut, and a compression bit.
All cuts were at 80ipm, 20k rpm, porter cable router 892, 2.25 hp, with a precision collet.
I tried cutting straight lines on the Y axis, single passes at .05", .1", .15" and .2"
I also cut 3 circles, single pass at .1", .15" and .2"
You can see where most of the deeper circle cuts reflect a lot of vibration where the router is physically vibrating.
The machine is sloppy, no doubt. could use some help.
Dust collection is very good, so that is not causing the issue.

The last photo is a closeup of the compression bit test.

Great experiments! From here, the single flute and 3-flute at .15" look pretty good. But if you're still getting vibrations (hard to tell from the pic) you can go to like .125". Then start increaing the speed.

The compression is a tough call, because you may not see the benefits unless you're cutting deeper than the upcut section, which is about 9/16" on Onsrud's typical 1/4" single edge compression spiral. Their 1/4" single edge mortise compression spiral has a .175" upcut section, so even them you still have to be at least I'd say .2" doc to get any advavntage from the MC spiral.

Onsrud also makes a 3-flute low-helix bit that might help also, p/n 60-241... but even with a little bit of "slop", the trick is to have your cutting force at the bit just less than the force needed to deflect the machine

[dminnery]

Thanks Louie,
I included the detail of the compression because it's actually the most robust cutter, however you can still see chatter marks clearly at .1" depth.
In my testing I've tried a final profile at .02" and .03" offset, passing at full depth 5/8" and tried with 2 passes. These finish passes actually make little to no difference, which is frustrating.

Appreciated your help. This machine fit my budget but I'm looking forward to getting something more accurate, I thought I wouldn't have so much hand sanding to do...oh well.

[louieatienza]

I would also rotate the job 90 degrees and try the test again, and see if you get the same chatter. IIRC the Romaxx has rather tall gantry legs, but may be not the thickest. You can try c-clamping bar stock to one leg and see if that improves ridgidity. Also, if you can, you can try adding a little more peload to the v-bearings...

[louieatienza]

Thanks Louie,
I included the detail of the compression because it's actually the most robust cutter, however you can still see chatter marks clearly at .1" depth.
In my testing I've tried a final profile at .02" and .03" offset, passing at full depth 5/8" and tried with 2 passes. These finish passes actually make little to no difference, which is frustrating.

Appreciated your help. This machine fit my budget but I'm looking forward to getting something more accurate, I thought I wouldn't have so much hand sanding to do...oh well.

Ridgid makes a really nice oscillating spindle sander for $249....

[dminnery]

I have that sander, it's been a workhorse!
But I just want to push a button Louie, I'm sick of being covered in dust!

[dminnery]

I would also rotate the job 90 degrees and try the test again, and see if you get the same chatter. IIRC the Romaxx has rather tall gantry legs, but may be not the thickest. You can try c-clamping bar stock to one leg and see if that improves ridgidity. Also, if you can, you can try adding a little more peload to the v-bearings...

Can you explain the preload to bearings?

[louieatienza]

Usually with v-bearings, two bearings are set on concentric bushings, and tow on eccentric bushings. This allows the clearance to be adjusted. The friction on v-bearings/rails is very low, so you could probably run the bearings slightly snug and not bind them....

As for just push a button, there will always be some post-process afterward; we're not cutting a pice of metal here!