Help me finish this...

[steve_g]

Recently I was challenged to try to create a document/lesson on router bits. This challenge was precipitated by questions asked on the forum by both newbies and more experienced users. I, and I'm sure others assume people know what we know, so when we give an answer to a question we cause more confusion.

When I answer a question, It's based on my circle of experience... recently, an answer I gave on the forum was kindly corrected by another with more experience. This is what I hope to achieve with this document/lesson. I'm putting it out for peer review and correction.

It is my hope that this can be a resource for educators, hobbyists, and professionals alike. I intend that no previous knowledge is assumed, and if a topic is not thoroughly covered, direction to more information can be given. To the experienced professional... what knowledge would you like to assume a new hire has? Help me document it here.

Your suggestions are welcome both on the forum and by PM. And please, let me know if you don't wish to have your name included in the list of contributors.

Steve
EDIT:
Please go to later posts in this thread to get updated versions of this document. SG

[myxpykalix]

one of these terms i have seen used I wasn't familiar with so i just learned something

And who says you can't teach an old dog new tricks?:rolleyes::D

[chiloquinruss]

I like the scope of the project and I think you have really good start. The biggest problem I had when I first got my Bot and therefore my first set of router bits was actually pretty simple. I had computer skills with NO wood skills. ALL of the router / bit terminology ASSUMES a knowledge of wood or substrates in general. I had no idea what the heck they were trying to tell me! :) What would have been very beneficial would have been a simple photographic comparison showing three things:

1. a picture of a router bit, with brief text about it's intended use
2. a picture showing a GOOD cut, and
3. a picture of an abnormal cut, with brief text about the probable causes
This chart would show lots of different kinds of bits, vbits, ball nose, tapered, 2 flute, etc,. Not more than 1 or 2 of each basic type. This would be followed by your much more technical description and further explanations of cause and effect.

If you follow the threads on here we get tons of wordy problems posted regarding fuzzies, burns, broken bits, how do I . . . .etc, followed by a battery of knowledgeable replies asking for an example pix! Once the BAD / problem pix is posted there are a ton of really good solutions, such as speeds, bits, feeds, etc. So the photo chart would be my wish list. A couple of years later there are still a ton of substrates and bits I have not tried. Russ

[steve_g]

Thanks to all who gave input both on and off the forum! A general consensus would seem to be 'add many illustrations!" This is not surprising as those of us who like working with our hands tend to be visual learners...

I will not search the forum for photos and risk using someone's image without their permission, however... if you have something you think may be pertinent and are willing to let me use them... please attach them here or send them to stevedotglasselatsgmfgdotcom. Just to be perfectly clear... there is no intent to make a document that will ever be any thing but free to those who want to download it.

Thanks again for encouragement and ideas...
Stay tuned for version 2

Steve

[penman]

Hi Steve,

I find the document you are providing interesting,and would like to commend you for going to the effort and trouble and I am sure many new user's will find it very helpful.

Once again, well done.

Cheers and regards,

Roger.

[steve_g]

Well... here it is Version 2.0 In an attempt to assume no previous knowledge, I've included more definitions and many illustrations. I have attempted to make it an interesting read... my wife says I failed... but she has no interest in the topic. Keeping the document "Basic" yet accurate is difficult.

I'm still open to suggestions and illustrations and please check me for accuracy. The document is to large to post anywhere on the forum so the link is to my Google Doc.s account. Some of the illustrations do not display correctly unless you download the PDF to your own computer.

I figure at least one more document revision will be necessary, I'm lacking especially in the areas that refer to metric tool sizes.

Thanks again to all who offered support, suggestions and criticism.

Steve G

https://docs.google.com/open?id=0B8GtiBWUjRyRbXFGUWg4dU1RekcxTHBEbmtBZk1mU Q

[Rick W]

Wow, very cool Steve. I learned a lot. Thanks!

Rik

[michael_schwartz]

Looks like that is going to be a useful resource for many users. You have done a great job.

I would mention the aftermarket collets available for standard routers, and how they give you some of the benefits of an ER style spindle collet. I have a set of the precisebits collets and I don't know what I would do without them.

I may have missed something, but I would suggest that the section on chip load could be improved by mentioning the visual, and audible, indicators of a chip load that is too light. (dust, smoke, screaming bit, etc...) I would also mention something about how the bit at least for most applications I am aware of should never be too hot to touch.

The more practical considerations the better. It amazes me how many woodworkers are not aware of the concept of chip load, and this was something I was not aware of myself until I started working with CNC equipment. I have taught, and demonstrated to quite a few experienced woodworkers that the reason why their bit was smoking, and producing dust was not that it was dull, but that they were cutting way to slow with it.

[dlcw]

I will start reading through it this weekend Steve and provide any feedback next week.

Thank you, so much, for making the effort to put this very valuable document together. Being able to steer people to your document to "Read this first" then ask questions will help people get much better educated.

Great Job!!! :D

[chiloquinruss]

Another thing I have started doing more of lately is since I can't get really good wood most of what I cut leaves my bits really gooped up. If I don't clean them up when I finish a job it won't cut very good on the next job. So I got a bag of those brass wire brushes from HF and they do a good job of getting the sap / glue etc, out of the bit. And amen on the comment about keeping the collet clean as well.

Great job and the illustrations are terrific. I also learned alot. In my past life in the computer biz when doing documentation we used a lot of icons for special notice. I.E. where you have a warning make a warning icon to highlight that so the reader begins to look for those warnings or hints or links or whatever.

Keep it up you are doing super! Russ

BTW do you need any pix of broken bits? :)

[michael_schwartz]

Another thing I have started doing more of lately is since I can't get really good wood most of what I cut leaves my bits really gooped up. If I don't clean them up when I finish a job it won't cut very good on the next job.

Have you tried the boeshield blade, and bit cleaner?
http://www.amazon.com/BOESHIELD-BLADE-BIT-8-OZ/dp/B001N9YLWK

I spray a little on and clean it off with a tooth brush. No need to let it soak in for long. 8 FL OZ. isn't much but it lasts for a long time, and I use it to clean my tablesaw blades after every project.

I used to use the product sold by CMT but I find I had to use a lot more and let it soak in for a lot longer.

[steve_g]

OK... lots of down loads almost no comments. That can be seen as good or bad. Either we are getting close to a finished document, or so far away that no one knows where to start to make it right.

Here is a list on items that I see on the to do list...

Ver. 3:

new intro (Less personal, more about what's to come)
add icons to "caution" items
more tips
more links
clean up some drawings

Are there more things that need defining? OK... some of you that have looked at Ver.2 are new to this... What did you still have questions about?

add "rougher" bits? I ordered my first ones last night when I found them on eBay cheap. I don't have a compelling reason to try them, just curious... those of you who have used them tell me why.

Do we need a poster type "chart" that summarizes all?

Metric tool sizes? I have zero experience here and have received that same amount of feedback... don't some of you cabinet guys use metric bits on some of the Euro style cabinets?

Collet options and bushings, Do the more experienced users out there use bushings for say... 1/8" bits (1/4 X 1/8 bushing) or 3/8" bits (1/2" X 3/8" bushings). for some reason I have negative feelings toward bushings, but I don't know why. Give me your feelings.

Russ: broken bit photos... yes if you have a story to go with them...

lurkers, timid, famous/infamous, and others wishing to protect their Identity... please email your impressions directly to me at steve dot glassel at sgmfg dot com. (the cryptic method of giving an email address helps prevent automated scavenging of addresses by companies wanting to sell you certain medications)

File type: I actually created the PDF from a Power Point file... Power Point handles the insertion of graphs and photos better than Word. I was also thinking that video clips, sounds and transitions would help make this an attention grabbing classroom tool. If the PP file would be useful to you... email me.

Steve

[danhamm]

Steve its guys like you that make "shopbot" a prosporous company..I think this will be a very good resource for those just starting out.

There seems to be 3 or 4 main areas of endevor the Cabinet cnc'ers the Sign folks and the 3d relief'ers and general do it alls, probably down the updates you will flesh out the bits for those areas

The form tool bits, I always called round overs were the bits I used most when first starting out...we didnt have V-carve or partworks and so followed the lines...also flat bottom round overs.

Setting up the bit parameters in your tool path chart, I think is critical for the shapes and variants of the many designs, such as flat bottomed V-bits or tapered carving bits..any way have fun with your project...

[dana_swift]

Steve: Correction I suggest- you have a "ball nose" bit labeled as a ball end. I have seen the ball-end designation misused a few other places also, but its a "ball nose".

A Ball end bit has a ball on the end and allows undercutting. A ball nose does not.

Here is a ball end bit:

http://www.amazon.com/Amana-Tool-45960-2-Flute-Carbide/dp/B000P4JSEU/ref=sr_1_1?ie=UTF8&qid=1330974413&sr=8-1Hope that helps keep the confusion down..

D

[genek]

You may want to say what each style of bit is normally used for... And maybe show some examples.

But i think you are doing a good job and something that new shop botters need to learn..

[beacon14]

Excellent job, the only thing I see is the illustrations of Climb and Conventional cuts have the rotation of the bit reversed from the way it actually cuts in the machine.

[steve_g]

rotation of the bit reversed


OUCH!

But that's why I asked...

Steve

PS Did anyone like the alternate definition of "chipload"?

[steve_g]

Dana...

You are of course correct, help me here... is a core box bit a class of it own or a type of nose or ball?

Steve

[bleeth]

Core box is specific terminology to it's own shape (1/2 ball). Ball nose is a long straight cutter with a round end. Ball end is a round ball on the end of a narrower shaft. Ball nose and ball end are two terms that are sometimes used interchangeably in common usage. As long as you are consistant in your usage and make clear at the beginning with illustration which words you are using for what then there is no issue.

[myxpykalix]

I usually use core box bits when i want to hog out a wider path or a curved area say in a wide spiral. Ballnose is like when you want to carve fine details like a lithopane.

Everyone uses their own terminology but when i need a flat end tool for a toolpath it is named "endmill" in the toolpath name.

When i need a rounded over tip I call it a "ballnose"
Some people use the term "ballmill"....that would confuse me thats why they are named with totally different names to end any confusion.

[dmidkiff]

Steve,

I have a 1/4 X 1/8 bushing and it has worked fine when it was used. Don't use it much and would look for something different if I used it alot, because of getting it chucked up just right. I use a PC router and found a 3/8" collet. I think I found it at precise bits where I got the bushing.

Good job, very informative.

[steve_g]

Basic Router Bits Ver. 3.0

Lots of changes, getting close I think... I'd add more "practical tips" if someone has something to say... I think I have all the bit rotations straightened out, and the Ball end /nose issues fixed. I put a greater emphasis on chip load (now three pages worth).

Tell me what you think of:

the use of color (trying to not be boring)
Caution items in bold red (no icons)
The amount of info on a page. (too much?)
Have I gotten away from the mission? (basic router bits)
total length... will people seeking answers read the whole thing?
any thing else I've missed

Steve

Again... the graphics display better if the PDF is downloaded rather than viewed over the web.

https://docs.google.com/open?id=0B8GtiBWUjRyRSi1RWXNIWTRRbXFfQU9NanlxMDR2Z w (https://docs.google.com/open?id=0B8GtiBWUjRyRSi1RWXNIWTRRbXFfQU9NanlxMDR2Z w)

[dana_swift]

This is an excellent document!

Steve- do you mind if I give out copies? I sometimes teach people how to run the shopbot at FabLabTulsa. Your work is exactly what is needed.

Its not too basic for someone staring out. If they happen to be familiar with part of the subject material they can skip that part.

Its not too long, and not too detailed.

About the only other things I might include is references to such things as the machinery's handbook, and sites with chipload/rpm formulas and tables like:

For metals:
http://its.fvtc.edu/MachShop3/SpeedCalc/feedratecalc.htm

For non-metals:
http://www.cutter-shop.com/main.asp?sitepages=feeds_and_speeds

The tables provided on these sites are the best reference I have found so far for chip load starting points.

One other point you dont mention is depth of cut. That depends on the actual torque available to the bit at the cutting RPM. Seperating any given hardness of material requires a certain sheering force per inch of cut. The torque in the shank of the bit becomes the available sheering force at the radius. Most of us learn from listening to how hard the machine is working as to whether we can cut deeper or shallower on a material and adjust future cuts based on the experience. The worst case is a stalled bit.. followed by "bits of bit".

Steve: You have produced an excellent document without any of the above! At some point you will have to decide its "good enough" and call it done for now.

Thanks for all your efforts..

D

[chiloquinruss]

Great piece, thank you for sticking with the project to get it complete. Russ

[dlcw]

Steve,

I just read the document completely. You did a GREAT job on this! I wish there had been something like this when I first started playing with the CNC. I was always scared to push the machine because I didn't want to 'break' bits. But as you note, it turns out that going slow was the cause of overheating and 'breaking' bits. Live and learn (expensively).

I think this should be REQUIRED reading pushed by Shopbot for anyone who purchases a CNC from them. It would eliminate a lot of tech support calls for Gary though :D.

If I hire anyone (economy turn around) this will be required reading.

[steve_g]

Thanks all for the kind comments... Dana and any one else interested, I don't consider this "my" document... I'm the editor at best. It is my sincere hope that you will copy and use it in any way appropriate. I do however feel it's only right to retain the ShopBot and Forum references intact.

Hopefully this will be a dynamic or "living" document and be updated as necessary. I will add the links Dana supplied in 3.1, and continue to solicit photos and stories from members experiences.

Again... the PDF was produced from a power point file. The PP is available to all who can use it in that way.

One note of concern... Along with the photos and drawings I generated, I also shamelessly appropriated Images from the web. If this article will be used out side of the forum, do others feel it will be necessary to recreate our own images100%?

Steve

[beacon14]

"The speed at which a Router spins the bit is called its RPM (revolutions per minuet)."

How many times can one spin a router bit during the typical minuet?

Also, in the discussion of cut direction, I believe you have your descriptions reversed. A clockwise cut around the perimeter of an outline would produce a climb cut, while counter-clockwise would be a conventional cut. Good job on fixing the rotation diagram.

"The solution to this dilemma is to cut to each methods strength. Climb cut an object allowing .01” - .015” then make a final pass, full depth without allowance in a conventional direction. This method, called an Onion Skin strategy, will often result in the best possible finish on a part."

This makes perfect sense to me as I already understand the concept, but I could see how this would be ambiguous to a beginner. Is the allowance left on the size of the part, the depth, or both? I could see this benefiting from some clarification. (What is an 'allowance' anyway? I used to get $.50 every Sunday as my allowance.) Onion Skin refers to not cutting full depth on the 1st pass (to maintain full vacuum until all the rough cutting is complete), while allowance refers to leaving the part oversize on the 1st (typically climb-cut) pass. Either method could be used with either conventional or climb-cutting. It's the right combination of all three of these concepts that produces the best combination of part size, edge quality, bit life and hold-down success.

Overall this is an excellent document, and I plan to share it with my employees, students, and anyone else who will be running my machine. Thank you for putting in the significant effort to produce this manual. One last impression, the opening paragraph kind of gave me the feeling I was being pitched something by a snake-oil salesman, I was almost wondering if this was an introduction to something that was tailored to get me to buy something, especially when the last sentence refers to products available to buy. Not a big deal, but you did ask for feedback. I think the use of color is just right, enough to be interesting without being distracting. As for the images, unless they were copyrighted I don't think using them would be a problem, content is "appropriated" from the web and re-printed every day. Others may disagree.

Thanks again.

[steve_g]

David
Your feed back is EXACTLY the kind I was asking for... Thank you!



"The speed at which a Router spins the bit is called its RPM (revolutions per minuet)."


would "Rotate" be better?


I believe you have your descriptions reversed

Is that the perspective of the router or the product? ... really I think you're right, I changed the drawing and didn't re think the CW CCW terms.


This makes perfect sense to me as I already understand the concept

I'll clarify this as I did say "no previous knowledge assumed". My understanding was that Onion skin referred to both perimeter and depth... I will defer to your explanation as it makes perfect sense.



the opening paragraph kind of gave me the feeling I was being pitched something


Yes, me too. I was trying to be humorous. interesting and pique ones interest. I admit it fell short... Anyone else care to have a stab at an introduction?

Steve

[rcnewcomb]

I was confused by the statement, "More flutes increases the strength of the tool". Do you have a source for this information? It would seem to me that more flutes would weaken the tool.

[steve_g]

Randall,

I know... it sounded counter intuitive to me too at first. I didn't find my original source right off but it had a drawing similar to the first one I've attached. I also attached a real life photo of 2 VS. 3 flute. The 3 flute is obviously "beefier" due to shallower gullets and hence the reduced chip flow area.

What I haven't figured out, and was hoping some one would question, is multiple sources say you can cut faster with a single flute free flowing chip design than a 3 flute bit. However if you enter the data into chip load calculator it says to cut faster with the 3 flute design. Any one have some insight here?

Steve

[rcnewcomb]

The photos do help with the explanation. Thanks!

Regarding how fast you can cut as a function of the number of flutes, yes, the chip load calculator indicates the federate must be faster for more flutes.

[gsartor_1999]

Thanks for all the hard work! As a newbie the information is really helpful.

Some other questions I have had as a novice include:
Can all/any router bits be used in my CNC machine? What are the differences?
How far into the chuck should the bit go?
How tightly should the chuck be cranked down? (got mine stuck early on)
Can my bits be sharpened? Should they be?
What are some examples of "bad" cuts?

I am sure there are others. Hope you can use my feedback.
Gina

[beacon14]

Actually I was trying to point out that you spelled minute wrong.

While the chipload would indicate that the 3-flute bit should be run at a faster speed, one might not have the power in either their spindle or motors to push the 3-flute bit through the material as fast as it wants to be pushed. I use single-flute 1/4" compression bits instead of 2-flute bits for this reason. I can push the 1/4" bit faster than I can push the 2-flute bit, only because the 2-flute bit starts to bog down with my 2.2HP spindle if I try to push it too fast.

[steve_g]

Actually I was trying to point out that you spelled minute wrong.


Ha!... Now that's funny... or sad, a perfect example of the failure of the "look - see" reading method of the 50's! Spell check missed it because it's a word.

So the answer to your question... It appears that minuets range from 2-4 minutes long, average say 3... with a RPM of 10-20K average 15,000 that makes it 45,000 times...

All kidding aside... I appreciate feed back, even spelling error feedback. Since I hope this article can be used in many situations including classrooms, the perception of ignorance is not acceptable!

Thanks

Steve

[steve_g]

Gina:



Can all/any router bits be used in my CNC machine? What are the differences?

Some things I didn't go into in the BASIC information about router bits are Rake angle and Relief angles. These and other factors determine a bits suitability for a particular purpose. When you buy a generic router bit these sharpening angles are a compromise of what the manufacture thinks the bit might be used for. Sure... you can use any bit in your router but your results may be disappointing. When you buy from a trusted source you buy a bit for a particular type of job, Hardwoods, composites, plastics and the list goes on...

If others want to jump in here, I'll add a consensus paragraph to the article


How far into the chuck should the bit go?

Does page 6 of the current document answer this question for you?



How tightly should the chuck be cranked down?

I don't know if there is a Ft/lb answer here. My experience is if the bit slips it wasn't tight enough. I'm told that when people call SB tech support reporting missing steps on the Z axis... 90% of the time it's the bit slipping in the collet.


Can my bits be sharpened? Should they be?

At least one manufacture has stated that if a bit has .1" of carbide remaining, it's sharpen-able. Problems I see... Can you find a reliable service? by the time you pay for the service and shipping you have a lot of money invested in a bit that may not be its full design diameter. When a bit is under size you either have to define a new bit or program a path offset, you'll have to keep track of bits and actual sizes also. I know one company that amasses a large number of dull bits, has them all sharpened to the same CED and lives with two sizes of bits. Myself... I have my large V-bits sharpened after I have accumulated several. A sharpened V-bit that's Z-zeroed needs no compensation.


What are some examples of "bad" cuts?

A bad cut is one that you are unhappy with. If you are trying to do a glue up with no additional post cut work, you'll want a lot smoother cut than one that's going to be hid in a dado. In some future revision I hope to show poor cuts and what was done to make them better.

Steve

[steve_g]

Getting close to releasing version 3.2 , still two unresolved issues... One issue is that some sources say you can cut faster with a single flute but with poorer quality than say a 3 flute bit. No chip load charts support this, but people in the trenches say you have to slow down the feed speed of a three flute due to torque/Horse power issues. If that is true... you are actually changing the chip load for a three flute bit? Is this going to damage the bit if you don't have the HP to run at full chip load?

The second is similar to the first. As per the Onsrud chip load recommendations... I have suggested that when cutting 2X or 3X the bit diameter you need to reduce the feed speed by 25% and 50%. Other manufacturers make no mention of this, nor does the SB3 chip load calculator... As long as the router bit is maintaining RPM and not breaking, isn't chip load being meet without the reduction in speed?

Another interesting caveat I've come across is the statement by at least one manufacturer... "chip load calculations fail for bits 1/8" and less" WHAT? A lot of us do much of our cutting with 1/8" bits. Does that mean we're just on our own? Watch those bit temperatures... Let me know if your experience is that chip loads fail for smaller bits!

Steve

[geneb]

Steve, another pointer I've found in the forum is on how the bit sounds when it's cutting.
The quote went something along the lines of, "If the bit is screaming, it's hungry! Feed it more! (increase the movement speed a bit) It's as if the bit is yelling for more food. I know, silly, but it made perfect sense to me. :)

g.

[steve_g]

another pointer I've found in the forum is on how the bit sounds when it's cutting
Page 20 current document


Just like a baby… Feed a screaming bit. Usually a bit that’s “screaming” wants a greater chip load.

[geneb]

*sheepish grin*

Nevermind.

:D
g.

[steve_g]

An update is available but I decided to make a new thread as apparently some people are unaware of how to go deeper into a thread. I am still seeing some folks downloading the first version of this document...

Steve

http://www.talkshopbot.com/forum/showthread.php?t=15176