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http://www.amanatool.com/bits-fv/ns-100.html
http://www.toolstoday.com/p-5124-plunge-type-routing-body-for-12-shank.aspx?variantids=6353,0
I've had a problem in the past using core box router bits otherwise known as ball nose or round nose.
They would tear at the centerline of the cut especially in spruce but also in the harder maple.
I believe it was Bob Garish who recommended the Amana Nova System a year or two ago.
I've been running the first set of inserts now on at least a dozen archtop plates and show no signs of wear.
I'm getting an incredibly clean cut even at the center of the cut where the surface speed is zero.
The inserts have an extremely sharp cutting edge due to the relief on the backside.
The carbide must be good quality and super hard to retain that sharp cutting edge for this long.
The cost savings is tremendous over using standard carbide bits.
Thanks Bob!
Nelson

I remember seeing and talking about it, so maybe it was me...but I can't be sure so I won't take credit!

The price is definitely right on these things. A 1" carbide ball is $150-400 depending on the quality and cut length, VS $25 a pop from these guys! I use a really beautiful one with a 4" cut length for carving some necks...there'd be some serious tears if I chipped it...but for shallower parts like arched plates these things are the bees knees.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

So Nelson, from Bob's advice on your good recommendation, I just order these with the 1" core cutters. I am hoping that they will be good for doing things like radius dishes!

Thanks for highlighting these and passing it on....it's cool how things come 'round, you thought Bob said they were great and then Bob says that you say they were great and...well you get the idea!

Shane

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Canada

The MDF (if that's what you're using) for radius dishes should be a good test for the carbide.
Hope you have good dust collection for MDF, Shane.
What kind of tool path does a guy use for a radius dish, just regular parallel passes?
Would be cool to cut with a helical toolpath but not sure how that would be programmed.
Nelson

The Amana cutters have a real different but effective way of holding the inserts.
The two inserts overlap each other at the center and I think that's why they do such good job of cutting clear to center.

Hey Nelson,

I double laminate the mdf so it is 1.5" thick. I just finished doing 9 dishes on the cnc using a 1/2" ball end solid carbide aluminum burr with a 1/4" shaft (that was all that was avaibale but I have a bunch of different ones coming including the Amana). I just ran parallel "zigzag" paths. The radius on these dishes ranged from 30' to 12'. The first 8 I did with a .040 stepover at 200 ipm, the last one I did with .030 stepover at 300 ipm and is was 8 minutes faster and WAY smoother (not that the others weren't pretty good anyways, 2 minutes of sanding with 120 grit). Mike Turner (turmite) had Joakim of MadCAM add the ability to do a curved tool path but for now it would only be able to start in the middle of the dish and I would prefer it to be able start at an outside edge OR in the middle. The 12' dish is about a 1/2" deep in the middle. Anyway, I don't think that the zigzag method was so bad, the dishes came out very nice and way less mess than when I was doing them with my motorized rim sander and a router. I am quite happy! Now Mike is helping me do some bridge designs and tool paths.

Shane

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Canada

Shane did you get my email about roughing a small area in the middle of the dish? Joakim also emailed me a work around that will allow you to start the spiral on the outside.....

I had to take my wife back to the Dr today and am tired. Call me about 10am your time tomorrow if you have the chance and I will try to talk you through it.

Mike

ps I picked up a 7" wide 8ft long piece of 3/4 Holly today in addition to some of the most beautiful Shedua I have ever laid my eyes on......can you say fret boards???

Shane, since you are doing dishes commercially, you might want to consider a custom ground cutter.
You could get something like a 1/2" shank, 1" dia. with a 10ft (or what ever, something large) radius on the end. This would allow you to increase your step over by a lot thus reducing your cutting time.
In the past I've purchased custom ground 1/2" shank microgain carbide cutters in the $75 range.
Just food for thought.

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Jim Watts
http://jameswattsguitars.com

Sounds great Mike! I will call. I just ordered some cutters today for doing fret slots, .023 and .025. I am not sure which size I will want to match my fret wire so I ordered two of each and we will see which works best, maybe .023 for rosewoods and .025 for ebony, ziricote and the like.....or maybe not!

I will talk to you Tomorrow Mike.

Thanks

Shane

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Canada

Sounds like an elegantly simple idea, Jim.

Thanks Jim, that is worth a thought. But unless the cutter was the radius of each dish specifically wouldn't you still get a 'wavey' surface with a larger stepover? Maybe it would be so small that it wouldn't matter. Also, I suppose I should clarify that I only really get orders for a couple of these each month on average (it usually goes in waves, nothing for a few months and then 10 in 2 weeks). The beauty of the cnc machine is that it only takes about 5 minutes on the computer to draw and post process for a custom radius. With my old system it was ordering a new set of curves from a friend with AutoCAD and then an hour in the shop making a new sled. I really don't mind the 50 or so minute process time it takes now as I can even do these in the evenings while I am answering e-mails and stuff. Also, I am thinking of even going down to .020 stepover with a 400 ipm tool pass which should make it smoother yet with the same amount of process time. I just need to see how well the machine will do it. I have a 'zero' flute cutter coming that has a low radius curve. It was expensive ($130 or so) but is supposed to work well for operations like this. I will try it and see how it works.

Thanks for the suggestion, any ideas where to get these made should I go that rout?

Shane

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Canada

Shane as a example, if took a 1 dia. ball cutter (.5 Rad) and stepped over .045 on a flat plane you would end up with a scallop height of .0005, pretty small. If you used a 1 inch dia. with a 10ft (120" Rad) you could step over .693 and end up with the same scallop height of .0005.

Custom cutter grinders are abundant, probably even someone fairly local to to you. However I've used both BC Tool http://www.bctoolandcutter.com and RobbJack http://www.robbjack.com before for custom cutters.

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Jim Watts
http://jameswattsguitars.com