What type of bit is best?

[bob buttons]

i plan on doing a roughing pass then a finishing pass with a separate bit. as for the roughing part of the job i would like the bit to be able to cut as fast as possible leaving a clean channel without any "v" or tapered edge. 1/8 and 3/16 diamters are what i plan on hoggin out on the rough pass. thanks!

[Wdyasq@yahoo.com]

Bob,

If you are asking a question, the material you are cutting and a depth would be a great help to anyone caring to respond

Ron Brown - wdyasq@yahoo.com (mailto:wdyasq@yahoo.com)

If Stupidity got us into this mess,
then why can't it get us out? - Will Rogers

[ramdesgn@ionet.net]

Bob,

I make a rough pass then offset about .03" to .05" into the material for a final "shave". That minimizes any sanding to be done after the part is finished. I do this with the same bit eliminating the need to change bits.

Dick McGuire, ramdesign@ionet.net (mailto:ramdesign@ionet.net)

[David Fisk]

Great idea Bob! That's nice and simple. I think I'll try that on my puzzles.

[pwhill@infogen.net.nz]

Hi
I have recently purchased a Shopbot and am planning to make 3D wood relief carvings - faces, lizards etc out of medium to soft natural timbers.
I need to decide on the best cutters (I have been experimenting with some cheapies so far). I think I need a cutter for roughing - probably 1/2" straight (1/2" shaft and 3+1/2" long to take account of my modified dust skirt) and one for finishing where I thought I would like a 1/2" shaft, tapered to a 1/8" diameter cutter but with a flat bottom and 1/32" radiused corners. I would need it to be 3+1/2" long. I decided on the flat bottom so I can have about 0.05" stepover between cuts and not show ridging - at least on the flatish parts of the carving. I would value others thoughts on such a cutter and where I might find one. Since I am a newbie to much of this I would also like any recommendations on no of flutes, spiral or straight, solid carbide or carbide inserts and even possible coatings.

Regards
Peter Hill

[windsor@muskoka.com]

I've been doing a lot of 3d stuff lately and use ball end mills . a .050 stepover will show ridges . I sometimes go as small as a.008 stepover ( takes a long time to cut though ). --- One source I found was http://wttool.com

[windsor@muskoka.com]

I've been doing a lot of 3d stuff lately and use ball end mills . a .050 stepover will show ridges . I sometimes go as small as a.008 stepover ( takes a long time to cut though ). --- One source I found was http://wttool.com I use Rhino for design , and visualmill for creating the toolpaths , and can customize all of the different cutters in Visualmill http://www.mecsoft.com

[jkforney]

Try conicaltool.com. They make tapered bits. All sorts of degree tapers and they will make the tip round over. I have a one degree 1/32 bit that I use for light carving, especially text. It has a cutting length of .75. I also have a 3/32 with a cutting length of 1.5. The taper makes them very strong and the size gives me the detail I want.

Mike makes a very good point about the step over determining the finish. Also, if you have a small bit, remember that most of the stress at small stepovers is in the initial pass. Often I will start a larger bit for the first pass, especially if it is a flat. I use the Art Cam products and I can see any other full depth plunges and plan accordingly.


John Forney

[jay_mack1@hotmail.com]

Its a Chilly Saturday here, but that is just the weather. The garage is nice and warm with wood heat.

I've been doing a 3D relief cut plaque. Its 3/4" red oak glued up. I'm running a Porter Cable 3 1/2 Hp, 1/8" Spiral Downcut at 21,000 rpms. I'm getting little fuzzies on the outsides of the cuts.

Am I running the router bit too fast?
Or do I need to slow the shopbot down?

What woods make good plaques?
What is harder that Oak?

[kerrazy]

What feed and spped rate are you curently using?
Also could your bit be dull?
Dale

[jay_mack1@hotmail.com]

Dale,

Looking at part wizard the bit should have been running at 1 inch per second.

Jay

[jay_mack1@hotmail.com]

I could need a new bit, I haven't found anywhere that they are locally available.

What woods make good plaques?
What is harder that Oak? Finer grained?

[bjwat@comcast.net]

Jay,
You don't want to use oak to carve 3D right off the bat...You will spend a ton of money in bits! (most of them broken) Get some pink foam to start off with...It is VERY forgiving and gives nice detail. I used it exclusively for a few months before I really understood feeds and speeds.

Generally you want to cut chips...no dust. You can get close to optimum speed and RPM by both looking at the chip size and listening to see if the router is laboring or not. Generally, you want the biggest chip that gives the nicest cut. Always test your feed speed and rpm on scrap before jumping in to do a carving.

If you have to carve something in wood I recommend Poplar, Basswood or Honduras Mahogany. 3D carving in oak is very tricky and requires you to run at a very slow speed with a low stepover to eliminate lines and tool walking.

The fuzzies are a lot of times unavoidable. It depends on the wood.

-Brady

[jkforney]

Stickman
Harder than oak and finer grained. Maple comes to mind.

John Forney

[jamesgilliam]

Jay,

Brady is right about poplar for making plaques. I started out using it, then moved into agathis, which has varied grain and is easy to work with. I have also had some good results cutting cypress. If you want to see some of the work I've done look at our website. www.jgremembrances.com Most of the plaques pictured there are in agathis, and a few of the earlier ones are in poplar. Some of the pictures are missing, but you can get an idea of what we are doing. Jo-Anne just has not had the time to update it in a while. As far as fuzzies, a quick pass of a palm sander with 120 grit paper does away with them. I have been doing the v-carving of the graphics and text with a 60 degree V-bit, and the straight line borders with a 1/16" end mill. Running both at 19,000rpm and around .5in/sec on the feed rate. Hope this helps.

James

[gbatten]

James,

Agathis is new to me. Is it a domestic wood? Is it expensive? Where do you get it? I am using poplar for plaques also and would be interested in knowing more about alternative woods. I usually get a fuzzy spot on the edge of my poplar plaques depending upon how the grain runs. Sanding helps but does not completely fix the problem.

Gene

[jamesgilliam]

Gene,

Agathis is an import, from the South Pacific, mainly Australia, New Zeeland, and Indonesia. Getting mine from Hogan Hardwoods in Houston, but am now going to cypress for a try. Getting it direct from the mill at 1/3 the cost of the agathis. Only real advantage to the agathis was it was already planed and edged, and I will have to do this myself on the cypress, but for the price I think I can haul a few extra bags out to the curb once a week.

James

[sheldon@dingwallguitars.com]

Any suggestions for a bit to cut soft plastic? I need to cut .090" vinyl sheet. I've tried an up-cut spiral, but vinyl produces strands that get tangled on the bit. I've tried a straight cutter, which works better, but the chips get stuck in the groove.

[kerrazy]

onsrud, has a great site at http://www.plasticsmachining.com/

I am sure you will find exactly what you need there.
Dale

[gerald_d]

Dale, I havn't had much luck from that site, probably because our routers and tables are not up to full professional standards, and because their cutters are not available here. I think that I speak on behalf of Sheldon when I say that we are very interested to hear firsthand recommendations from ShopBotters who have already cut thin vinyl sheet successfully.

Our limited experience told us to drop the spindle speeds, increase the feed speed and blast a jet of air directly at the cutting area - this was more important than the actual type of bit?

[sheldon@dingwallguitars.com]

"Our limited experience told us to drop the spindle speeds, increase the feed speed"

That was my logic too, but I had better results with lowering the feed and speeding up the router.

I'm going to try doing a hogging pass and a cleanup pass today.

Thanks for the link Dale, I'll take a look.

[gerald_d]

Our results were also all over the show, depending more on the weather I think??? (Actually more to do with the client not having the foggiest idea what type of plastic he had brought to us)

Oh, something I forgot, once we had good results with a down-spiral into a mdf spoilboard, cutting more mdf than plastic. Seems the mdf chips mixed with the plastic helped to stop the plastic from binding back into the groove....

[kerrazy]

Here is a trick I did with cast acrylic, CUt speed of 1.25, rpm, of 13000, and i did an offset cut .o1 larder than the piece I needed, almost all the way through, then I did a finish pass at exactly the dimension I wanted all the way through, less material to remove and it gave a very clean cut.
Dale

[gerald_d]

Dale, what size bit was that? With thicker plastic and around 1/4" bits, we can normally find speeds and feeds that work. But, with 1/8" and smaller bits we have the problems.

[kerrazy]

i used a 1/8 Upcut Spiral O -flute, Onsrud Part # 63-712, For Extruded or soft plastics I would suggest the 63-750 seriesin particular the 63-760 which is an 1/8 inch upcut SPiral o-flute.
By the way the acrylic was 3/8 thick
Dale

[bleeth]

Check out www.bitsbits.com (http://www.bitsbits.com) for a great selection of cnc carving and engraving bits made to very precise tolerances. You can pull off some lovely line art engraving with 30 degree bits with a slightly flattened bottom. Also Scott from Onsrud told me they are close to releasing their own line of engraving bits soon. A great source for their and whiteside bits is ballew tools also.
Both of these outfits cater to pro grade buyers.
Dave