Router bit selection

[ramdesgn@juno.com]

THREAD FROM ARCHIVE
-----------------------------------------------------

From: Colby Date: 27 Jan 1999

What type of router bits are being used to cut hard woods and plywoods on ShopBot tools. What type of speeds and depths per pass are you typically using. We have had our machine for quite some time now but can't seem to get the tooling down right. We need very precise clean cuts and I have heard three basic arguments for the best bits: 1) 1/4" high speed steel double flute straight bits 2) 1/4" spiral upcut solid carbide 3) 1/2" carbide-tipped double flute straight. Which do I believe?


From: David Fisk Date: 27 Jan 1999

For a while I was going crazy cutting homemade Ash plywood. I used a 1/4 solid carbide up cut three spiral blade finishing bit from consrud. I cut at about .5 ips. I made one pass 5/8" deep into the 3/4" ash the last pass was only 1/8 and it left some tabs for me to cut the parts out latter. The parts came out very smooth, but the bit cost about $60.00.


From: Dick M Date: 27 Jan 1999

To get away from the high cost of spiral bits I use reground, two flute, end mills from the aircraft industry.(trash to treasure) They work great. They are of high speed steel in 3/8" and 1/2" dia with flute 1-1/2+" long. They do have a 1/32" radius corner on the plunge end, but using a bearing flush bit, that tip left on the material can be removed. I do offer these at $4.oo each with postage paid on the first order.
ramdesgn@juno.com (mailto:ramdesgn@juno.com)

[arthur_ross]

There is a company called hyatts at http:/www.hyatts.com that stocks a variety of router bits, including a wide flat bit for "surfacing" the sacrifical boards used for signmaking. Haven't ordered any yet, so I don't know about their service.

Arthur

[-rgbrown@itexas.net]

I have had good luck with Woodline of Arizona bits. They have a 1/4" spiral bit USA made for $12.

Ron B. -rgbrown@itexas.net (mailto:-rgbrown@itexas.net)

[rlbeal]

Does anybody have any idea where i could get really big bits for carving foam. Maybe rasp bits or some other abraisive cutter? (2"+ in dia)

Robert Beal

[rgbrown@itexas.net]

Robert,

Woodline of Arizona 800-472-6950 has some 2" flat bottom bits and even larger piloted bits. I found almost all 'rasp' type cutting tools didn't have any room for the waste to clear.

Good luck,
Ron B rgbrown@itexas.net (mailto:rgbrown@itexas.net)

[rlbeal]

Ron,
Thanks, I'll check them out. It sounds like you have some experience cutting foam, what do you use?
Robert

[joa]

What did you all use when "flattening" the table? The largest bit I could find was 3/4". Any alternatives out there that are reasonably priced?

Thanks!

[giggalo]

I used a 1" only one I could find but there has to be 1 bigger?

Ron

[Chandler@n-link.com]

Joa,
Are you flattening the whole table or just the 2x4 under the plywood? I also used a 1", but only did the 2x4. Only took a few minutes. I then screwed the plywood down to them.
Since I did all the work on my Z axis, I put a dial indicator on a 8" bar in the router and "trammed" it to get the router verticle. The whole thing worked out to be within 0.004. Not too bad for a wood table.
Have fun!

[studio@renc.igs.net]

I don't think you would want to use a bit much bigger than 1" because it would put alot of force on your router.

Just a thought,


Richard

[joa]

Thanks for the tips guys. I'm going to do the whole table top (eventually) since I have a steel table.

I broke down and bought a nice 1" carbide "Viper" from Home Depot for $23. It shouldn't burn up like those cheap Black and Decker high speed steel ones!

[bruce_clark]

Joa,

I spend the "time" to get my steel table almost
completely level (took quite a few hours) but now
I can put a MDF board on the top and get a GOOD
smooth top that is _almost_ perfectly level (good
enought for what I am using it for) and when I put
enough cuts into it, I can unbolt that top and buy
a new board and have a "perfect" top again.

Bruce Clark
bwclark@centuryinter.net (mailto:bwclark@centuryinter.net)

[studio@renc.igs.net]

Once you have bolted your board on, take the 1" flat bit and plane 1/16"- 1/8" off The whole top surface. This will be really good. Be sure your wheel are always going in the exact same spot along the strut, or it will change the depth.

Richard

[seaside@esva.net]

Joa,

Even if you get your table and top absolutely flat, moisture and temperature will make the table surface move around a little, especially along the edges where moisture is absorbed. For most jobs a couple of hundredths of an inch don't matter, but for things like cutting scarf joints and very detailed 3-d signs your top needs to be really true.

I usually end up re-truing my top at the beginning of every week. I rarely have to take off more than .01", but that's half a step in a scarf joint.

Bill

[threehawks@earthlink.net]

AMANA manufactures a 1 1/4" dia morticing bit that cuts like crazy and is scary sharp. My table crosspieces are three layers of 1/2" marine plywood laminated together and that bit hardly makes a sound. I took .125" off and noticed no resistance to cut at 2.5 ips,and almost no noise. Call the industrial suppliers in your area and find an Amana distributor, their bits are superb,(no,I don't work for AMANA,I just use their product.)
Gerry

[mark]

Hi everyone, I have a job for a customer where I need to cut 900 pieces of acrylic plastic. I am struggling to hold the pieces which are only 1/2"x 2" tall. Also the bits I use seem to melt the plastic back together unless I route at no 1 speed on the dial. An upcut spiral clears the swarf before it remelts but it makes double sided tape useless because of its upward pull. All help appreciated.
Mark.

[joa]

I just saw a plastics web site that had real good info on routing acrylic. Bugger thing is I don't remember where I saw it. Do a search for rout* and plastic and you'll probably find it.

I just cut a bunch of ABS and the darn stuff will only cut one direction (climb cut) without terrible remelt on the piece. I've also found the feed rate to be very critical.

Joa

[bruce_clark]

Mark and Joa,

Not that I have cut a lot of ABS or acrylic, but
I have found that melting is the BIGGEST problem
with plastics. _MY_ personal experience is that
a router spins WAY to fast. I have had pretty
good luck with a speed controller.

First, my router is a PorterCable 1.5hp single
speed jobs. I got the router speed control from
Woodcraft (recommended from fellow ShopBotters)
and run my as slow as possible (just til the
router sounds like it is running "smoothly"--if
you have a speed control, you will recognize this
sound). I am guessing that this speed is
somewhere near 8Krpm (maybe a little slower, maybe
a little higher). I then set my cut speed to one
inch per second (60ipm). The bit I use is a
single straight flute mill.

When using these setting, I have had REAL good
luck with doing engraving and cutouts in
engraver's plastic (which is two color ABS). I
get real "chips" and almost NO melting of the
plastic.

Now, if you cannot run your router that slow, you
could try a spray bottle of water (misting the
plastic every few seconds/minutes). You could
also try increasing the feedrate, but if you are
doing engraving or fine detailed cutouts, upping
the feedrate will leave a rougher cut with more
jaggy lines, so really here your only solution is
to slow the RPM down.

Lastly, ALWAYS use the sharpest bit you have when
you cut plastic. Most plastics are VERY abrasive
and will eat up HSS tools very quickly (especially
nylon or any plastic that is glass fiber filled).

Most carbide tools are not the sharpest tools
(even when new) so if you are planning on cutting
at lot of plastic, you should buy a diamond hone
and give the cutting edge a quick going over. If
your tool is not cutting, it is generating heat
and carbide is the worst for generating heat.

Bruce Clark
bwclark@centuryinter.net (mailto:bwclark@centuryinter.net)

[joa]

Bruce,

Tried what you recommended and it worked great. Ran at 1 ips and 10K RPM (standard on the P/C 7518.) It cut nice. Left chips attached but they brushed right off.

Man, when the R&P SB is set up right it sure is accurate. I was cutting a huge file over a 2'
X5' area and after 2 hours of cutting and thousands and thousands of lines I went and re-cut an area and it was dead nuts.

Thanks for the advice.

Joa

[ricl_bruner@sunshine.net]

Iam cutting thru 1 inch laminated acyrilic with a 1/2 inch staight router bit by blowing compressed air on the bit. The going is slow, the whole problem is keeping the bit cool. If you keep the bit cool the plastic will not melt. The feed speed is as important as well. With a spiral bit this should work even better.

[SteeveM@home.com]

I've been cutting lots of foam and some acrylics lately, usualy gatorboard a pvc foam core laminate. I found that High speed steel bits cut much cooler and give me a good finish. The biggest problem is holding down material. If the bits start cutting into the boaard and quickly dulling the bits. speed is also extreamly crutial.
Steve Miller.

[hep]

Is anyone using "roughing" or "chipbreaker" bits in solid carbide? We're cutting 1/2" thick OSB (Oriented Strand Board) and I want to go as fast as possible. I've experimented with a High Speed Steel Roughing bit and my speeds increased three-fold. Now I'd like to switch to carbide to handle the heat better. I've seen companies that make them, but there are subtle differences in these types of bits and someone else's experiences could reduce my research time...

[saintjohnbosco@yahoo.com]

John, You might try calling the technical department at Consrud. They make cutters specifically for cnc machines and know a lot about the technical differences and what would work best for you. They are very helpfull.

[hep]

Thanks David. I tried looking up Consrud on the internet but I couldn't find them. Do you have the website or phone number? I'd appreciate it. Thank you!

[bruce_clark]

John,

The proper name is Onsrud. There webpage is:
http://www.onsrud.com/

There is a really nice bit selection page. You
enter the type of material ect. and it shows you
their recommendation. You can get there directly:
http://www.onsrud.com/new/routing/index.html

Just be aware, Onsrud are TOP of the line router
bits, so they are a little more expensive.

Bruce Clark
bwclark@centurytel.net (mailto:bwclark@centurytel.net)

[saintjohnbosco@yahoo.com]

Bruce thanks I guess I always looked at their logo and put a c on their name. I have their phone number someware, but I havn't unpacked that yet:^(

[Ron B]

Another good 'bit site':

http://www.hayestool.com

Some good advice on what works.

Ron

[hep]

Thanks Bruce, David, and Ron! I appreciate all your help...I went to both websites and I'm a lot closer to knowing what I need now...

[jebox@innet.com]

The best bits I have seen for the Shopbot are Spiral upcuts. they really cut nice compared to a straight flute because the spiral assures the cutter edge always remains in contact with the workpiece. Just watch your speed rates as they are solid carbide and will snap id pushed too hard.

[b1705@bellatlantic.net]

Jim, I also like the spiral upcuts. and I think they hold an edge longer than a straight bit will. If you keep an eye on the web site for the Price Cutter company ( www.pricecutter.com), you can get great deals on the 1/4 "ones. I just bought a half dozen at 7.49 apiece a few weeks ago...Bill P.

[woodcuts@mindspring.com]

I'm cutting 1/8" plywood with a #5 scroll saw bit. The hole that I use to push the bit through is a #60 drill bit. We're looking for something which will cut 1/8" plywood in VERY intricate detail. (To see an example of detail we're talking about, check our web site: www.woodcutdesigns.com )
Is there a router bit that will cut that small--the size of a #60 drill bit? And will this shopbot handle that kind of detailed work?

[SaintJohnBosco@yahoo.com]

The Shopbot can handle that amount of detail, but I don't know of a bit that would cut that small. I've been doing engraving with a 1/8 inch dremel bit v bit.

[Mark S.]

Look at Think and Tinker at http://www.thinktink.com/. They have some extremely fine carbide bits (down to .005!) The bits they have that are appropriate for soft materials (including wood) are listed under end mills. Hope that helps.

[seaside@esva.net]

Bill,

I don't know if these are too big for what you are doing, but Eagle American has 1/16" and 3/32" solid carbide straight bits. Their phone # is 800-872-2511.

Bill

[self@nwlink.com]

Sounds like you guys do some cool stuff, I program routers and milling machines as well as point-2-point machines as my day job. If I can help let me know.

[srwtlc]

Hi all,

I need to cut a lot of shallow recesses(1\4"-3\8") in hardwood, and because of there small irregular shape I can't sand the bottom of them at all. I'm limited to using a 1\4" diameter bit. What I would like to know is, is there a bit that will give me the best possible bottom cut while still doing a good job of cutting the edge of the recess.

Thanks,

Scott

[jerryk]

Scott,
I would use a downcut spiral carbide bit. I have been having good luck with them cutting recesses as you have described. Also the downcut spiral will leave a perfect edge.
Jerry

[davenadeau]

Hi Scott,
A few things to consider after you find the bit that gives you the best bottom cut...
During pocketing you should be able to tweak the overlap between passes to further improve your bottom cut. Reversing the direction of cut will tell you whether bottom quality with a given bit is better with conventional cutting or climb cutting. Bottom cut quality may also be related to the type of pocket toolpath applied (for example, X-parallel pocketing versus a spiral fill pattern) because of grain orientation and Z-axis being slightly tilted off of the vertical. If the quality of your bottom cut is due to an upspiral bit picking up your material then Jerry may be onto something by suggesting the downspiral bit. Your dust collector will be especially important with the downspiral bit in a blind pocket because there isn't anywhere for the chips to go.
Dave

[Gerald D]

The photos under this topic (http://www.talkshopbot.com/forum/messages/312/505.html?) may help.

It is under Let's Talk ShopBot: ShopBotter Message Board: The absolute ultimate solid carbide cutting bits for the Shopbot!!! Look!!! Posted by ABC Bird Toys Inc.

[David Fisk]

What are the advantages of using low helix spiral bits?

[Gerald D]

What is a "low helix" spiral bit?

[David Fisk]

They have a gradual spiral, up or down, compared to the tight spirlal of regular spiral router bits.

[Gerald D]

For a vertically mounted bit, do you mean that the cutting edge is nearer to the vertical line than with Belin/Onsurd bits?

[sheldon@dingwallguitars.com]

I'm kind of curious about the really high helix milling bits. I think they are designed for aluminum.

[David Fisk]

The Bits I was looking at were from Vortex Tool Company. They are simular looking to the finishing bits by Onsrud. I contacted both Onsrud and Vortex and from what I can gather the low helix reduces the up/down presure on the chips. So it should help reduce the amount of top or bottom tear out. I ordered a 3 edge low helix finishing bit. What I'm really after is an edge that dosn't need any sanding. I'm cutting baltic birch plywood. Both companies recomended a compression bit so I ordered one of those as well. I've tried straight bits and they are great for eliminating surface tear-out but they don't leave a perfect sanding free edge. I was told by Onsrud that straight bits are not as smooth b/c of the chopping action verses the smooth shearing action of spiral types. So my guess is that the low helix are sort of a cross between the straight bits and the regular spiral bits.

[gerald_d]

Hi David, if you are cutting right through the ply in one pass, a spiral bit gives you a nice edge on one side and a bit of a mess on the other. A straight bit gives two equal edges, slightly frayed. The in-between "low-helix" will probably still leave you with two edges that need sanding (one more than the other).

The (expensive) compression bit is the solution if you have to cut right through in one pass. Otherwise use a down-spiral for cutting half-way through and then an up-spiral for going right through. (Down-spirals into blind grooves are normally no problem.)

Quite frankly, I can't really see a need for a "low-helix" bit unless it is the same price as a straight, can be re-sharpened at the same price as straight, but gives the cut qualities of spiral. If it can do all of these things and leave two sanding-free edges, that is the Utopia that has been eluding us all!

[gerald_d]

Just to give the full picture, the most practical solution is often to down-cut onto a spoil board. This gives a good top edge and a bottom edge needing only light sanding.

[sheldon@dingwallguitars.com]

Does anyone have experience machining printed circuit board? I'm looking for small diameter (1/32" or so) cutters that are specific to this purpose.

[edcoleman]

Sheldon:

I haven't machined any PCB's but you can find bits at the site:

http://www.thinktink.com/

that are for this purpose

[gerald_d]

Sheldon, the copper on printed circuit boards would come unstuck from the insulating backing if you are trying to machine fine tracks. Drilling the PCB with a SB should be good, but the traditional etching (acid bath) methods are probably the best for removing excess copper.

[flyboy]

I've seen a guy route out his prototype PCBs. He's the owner of Maxnc. They make little CNC mills. I bought one since they are down the street from me and when was there I remember him showing me the circuit boards. They were pretty small and had fine lines. I don't know how he achieved it but it is possible. Probably just small, sharp bits.

[sheldon@dingwallguitars.com]

Thanks for the tip Ed. I called Ron at Think & Tinker(yeah, the name's a little weird) and was very impressed with his understanding of what I am trying to do.

I recommend anyone interested in inlays or PCB board work to check them out.

Gerald, that's a good point to consider. My needs on this application are pretty crude so "mechanical etching" should work OK and save a lot of steps.

[kaaboom_99]

I also am interested in circuit board milling. I was to have a partner in this businesswho decided to go out on his own. He bought a custom made cnc complete with a special head and paid $4000 US for a bed that is 12" x 12". My application doesn't require the tolerance of some of these machines. But with the prt96, I can now machine virtually anything for a little more that my friend paid for his dedicated machine. I have seen router bits and endmills down to the 0.004" range. The only thing you need to watch out for is that you are machining trace isolation, not the trace itself. I just ordered my Bot today (now the 3 week wait for delivery) and look forward to using it for PCB's and a whole host of other ventures. I hope to see more discussion on PCB's here in the future.

[danhamm@abccom.bc.ca]

I must be missing something?...Why would you want to engrave pcb's..you can buy and resistive pen for under $2 bucks, a jug of etching acid or muriatic acid full stength for $10.00 and it will do quite a few boards..if you want to get fancy and fast you go for photo sensitive resist material you can use a laser printer to put the schematic on with.

[sheldon@dingwallguitars.com]

I can't speak for the prototype electronics industry, but in our case the part we are making has only 4 large traces.

For an extra 10 seconds of machine time the entire part can be done in one setup.