# How to cut HDPE sheets



## angel619392 (Jan 10, 2020)

Ok so its my first post on the forum....And I do know its a wood forum but when I googled this question this forum popped up so I thought I would ask my question here. I want to learn how to route HDPE sheets with a router as well to cut out basic shapes like squares out of 1/4 inch HDPE sheets of 4' x 8' material max 3/8 inch material...

So im just confused because I hear about deep feeding when cutting, cooling when cutting, certain rpms to it does not melt so im overwhelmed...

I just want an answer to these 2 questions

1. Then I want to know about cutting HDPE with routers like what drill bits do I need I keep seeing "O" flute and ball nose which I have no idea what it is... So ill be making basic square cuts in the middle of a sheet of HDPE so what type of bits and strategies/tips do you know..

2. Do I need to cool off hdpe while cutting? How can I do that? 

Thank you guys in advance!


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## PhilBa (Sep 25, 2014)

I wouldn't recommend using a router to cut large HDPE sheets. A table saw is a much better idea. A negative rake blade is recommended. Regular wood blades with a positive rake will bite too deeply though I have to admit using an 80T plywood blade on 1/2" HDPE. It left a moderately rough edge.

For edging, profiling, general machining in a CNC machine, an O flute - a single flute bit - is recommended for any plastics. Fast feed and low router speed are the best strategy but the bit vendor will give you more detail. For hand routing, I would try to mimic the recommended feed and speed for CNC. Too fast router speed and too slow a feed will cause heat build up. I'm not sure you absolutely need cooling. Getting the optimal chip load will carry away a lot of the heat. Try a test piece.


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## Ziegler WoodWork & Spec. (Jan 9, 2019)

Good morning,

I'm not claiming to be any expert on the cutting of the HDPE and have not cut lots but in my experience with it I have used both methods to cut it. Cutting it down to size I do also recommend the table saw. Yes negative hook blades may be best but I do tend to just put a good sharp blade on and cut it down. I have a veneer and plywood blade from Freud that has an extreme ATB tooth design that does a very clean job. (ATB= alternating tooth bevel) But any good blade and some care works. 

As for cutting out the centers of your HDPE try a good spiral up cut bit from Freud and make a couple passes. (Yes this stuff can grab) Are you using templates or follow with guide bushings or ??? "Make sure the bit is designed for plunge application as well." 
Heating is most generally caused by the chip load that is designed in to the bits themselves, and if you go to slow or to fast can cause heating up. As you route you can usually hear in your router's performance if your pushing it to hard. I would suggest testing and learning what speed works the best. RPM can also be adjusted if your router has the power to dial down a bit. 

Also for profile cutting make sure your bits have enough shear built into them again I use 90 percent of Freud bits in all I do if I am running it on a router table or hand held router with part clamped down. Speed and RPMs again have a factor in the heating up. I typically don't have these problems so doubt you will either. Test and experiment and see what seems to work for you. 
Best advice would be to run as much of this material on a router table for the safest and best control however. 
I hope some of this helps and there may be other's give you some advice as well. 

Kind regards, 

Tim of ZWW&S


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## Stick486 (Jan 4, 2013)

Table saw..
High tooth count (80+), negative rake (-3 ~ -5°) MTCG, TCG, ATB, H-ATB, ATB-R OR H-ATB-R grind/hook angle..

*Listed by preference:*
MTCG - MODIFIED TRIPLE CHIP GRIND
TCG - TRIPLE CHIP GRIND
ATB - ALTERNATE TOP BEVEL
H-ATB - HIGH ALTERNATE TOP BEVEL
ATB-R - ALTERNATE TOP BEVEL w/ RAKER
H-ATB-R - HIGH ALTERNATE TOP BEVEL w/ RAKER

.


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## roxanne562001 (Feb 5, 2012)

Welcome to the forum


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## Herb Stoops (Aug 28, 2012)

Welcome to the form N/a, I have cut HDPE ,(Starboard) for my boat and used the same power tools as for wood cutting. Regular router bits cut it fine and so do saw blades,and drill bits. Screws do not hold very well, and neither does calking. Cutting makes a big mess, white sawdust and chips everywhere. The material I used was 1/2" thick and 1" thick. The tablesaw blade was a 10" X 60 tooth carbide blade, regular straight and 1/4 round carbide router bits. I used the router table, freehand w/ templates and a straight carbide bit with a pilot bearing. Laid the full sheet on a sawhorse and broke it down with a skillsaw. It is heavy and full sheets are hard to handle alone. Never needed any cooling, drills with regular drill bits,cuts like butter.
Herb


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## DesertRatTom (Jul 3, 2012)

Lots of specialized terminology so far. Rake is pretty important. Here is a diagram that explains rake. I have cut this stuff on my table saw (table saw zero clearance inserts), and it is pretty messy. Just don't let it linger on the blade, keep it moving forward into the blade, but don't push it too hard. Haven't used a router on it, but if I were going to, I'd use an up spiral bit. This bit is ground so it lifts the chips up and out of the cut. Other types of bits might quickly wind up with the plastic melted onto the flutes (cutting edges) and be all but impossible to remove. Same would apply to a saw blade. The negative rake is something you have to double check on any blade you are considering. It is not always obvious just looking at it. 

More teeth on an 8 inch saw blade makes for a smoother cut. At any given speed, more blades will mean smaller spaces between each tooth's cut, thus smother. The illustration also reveals the difference between crosscut (across the grain) vs. rip (with the grain). The large gaps (gullets) between the rip blade's teeth, let it carry off very large amounts of sawdust or waste. Crosscuts produce less sawdust per inch. 

Tooth shape matters. Flat top teeth make for a flat bottom groove when you don't cut all the way through. This is very useful if you are cutting a groove in your workpiece into which something will be fitted. The smooth bottom makes for a stronger glue joint. But if you're using it for a through cut, the raked, or top at an angle tooth makes for a very clean slice through the wood or other material. Through cut just means cutting all the way through a piece (cutting it shorter for example).

I've also attached a short pdf on saw blades that lays out the big facts on sawblades.

Hope this is helpful. There were a lot of tech terms flying around the responses.


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## angel619392 (Jan 10, 2020)

Wow thank you all for your replies. I am basically building a cage for an animal so id literally just cut a 4' x 8' sheet into 4 x 2 sheets with a circular saw(Dewalt 60v 7 1/4 inch) and then I would use the hand router to cut out a square through the material for example if i had a 4' x 4' square piece then I would make a 3' x 3' square cutout through the hdpe out that 4 x 4 piece.

So I called some plastic company that are local to me. They told me for the circular saw to use a saw blade with 40-60 teeth and bigger flute to allow air through so the plastic does not melt..... As for the router he could not offer much advice...


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## angel619392 (Jan 10, 2020)

PhilBa said:


> I wouldn't recommend using a router to cut large HDPE sheets. A table saw is a much better idea. A negative rake blade is recommended. Regular wood blades with a positive rake will bite too deeply though I have to admit using an 80T plywood blade on 1/2" HDPE. It left a moderately rough edge.
> 
> For edging, profiling, general machining in a CNC machine, an O flute - a single flute bit - is recommended for any plastics. Fast feed and low router speed are the best strategy but the bit vendor will give you more detail. For hand routing, I would try to mimic the recommended feed and speed for CNC. Too fast router speed and too slow a feed will cause heat build up. I'm not sure you absolutely need cooling. Getting the optimal chip load will carry away a lot of the heat. Try a test piece.


HI appreciate the reply. I have an example of what I would be doing with this HDPE and router.. Picture a 4' x 4' square piece of HDPE and then I wanted to cut a 3' x 3' square through the 4 x 4 piece so its empty inside(would hold glass piece with hinges) What type of hand router would you ideally use (plunge or basic hand router) Type of bit? 

And then the rest is just dependent on the feed speed and the rpm of the router to avoid melting. stalling etc.... Thats how I figure out the chip load??
Thanks again bro for the response...


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## PhilBa (Sep 25, 2014)

angel619392 said:


> HI appreciate the reply. I have an example of what I would be doing with this HDPE and router.. Picture a 4' x 4' square piece of HDPE and then I wanted to cut a 3' x 3' square through the 4 x 4 piece so its empty inside(would hold glass piece with hinges) What type of hand router would you ideally use (plunge or basic hand router) Type of bit?
> 
> And then the rest is just dependent on the feed speed and the rpm of the router to avoid melting. stalling etc.... Thats how I figure out the chip load??
> Thanks again bro for the response...


Hmmm, I'd be temped to use a jig saw (or plunge/ track saw) to rough out the inside square and then edge trim it with a router. Doesn't matter what kind. Slowest speed on the router and feed it as fast as you can with it not feeling forced.

If you use a router to cut out the inside square, I'd worry that by making contact on at least 1/2 of the bit circumference, you will get a lot of heat buildup. If you have to do it that way, I'd take shallow cuts, maybe 1/4" or less each pass.


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## angel619392 (Jan 10, 2020)

Ziegler WoodWork & Spec. said:


> Good morning,
> 
> I'm not claiming to be any expert on the cutting of the HDPE and have not cut lots but in my experience with it I have used both methods to cut it. Cutting it down to size I do also recommend the table saw. Yes negative hook blades may be best but I do tend to just put a good sharp blade on and cut it down. I have a veneer and plywood blade from Freud that has an extreme ATB tooth design that does a very clean job. (ATB= alternating tooth bevel) But any good blade and some care works.
> 
> ...


The local plastic sheet company I called and get my stuff from also told me ideally a table saw would be great but they said if I only have a circular saw to use less teeth(40-60) for the bigger flute on the blade and then make sure its made for plastic cutting... He said soft plastics do not need many teeth because that is what causes heat build up,...

For the router I would have a template cut out. Id really only be making square cutouts with rounded edges I tried to make a little sketch with dashes and parantheses lol but yeah that would be how id doit. Ill attach a picture of a this cage. That is the type of cut I want to make with the router the front 2 sides with the middle support beam I would make a template for that out of wood then put the HDPE under the wood template and cut it.
What type of bit should I use.. You mentioned spiral bits but I hear o flutes and all these weird router bits im confused lol.
___________
| _ _ _ |
| ( ) |
| | | |
| (______) |
|_______ ___|


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## angel619392 (Jan 10, 2020)

PhilBa said:


> Hmmm, I'd be temped to use a jig saw (or plunge/ track saw) to rough out the inside square and then edge trim it with a router. Doesn't matter what kind. Slowest speed on the router and feed it as fast as you can with it not feeling forced.
> 
> If you use a router to cut out the inside square, I'd worry that by making contact on at least 1/2 of the bit circumference, you will get a lot of heat buildup. If you have to do it that way, I'd take shallow cuts, maybe 1/4" or less each pass.


THat is what one plastic company suggested to bro. They said use a jigsaw to cut most the meat off then use the router to clean it off.... LIke the jigsaw align it about 1/8 inch off the line you make for your cut then come back and use the router to clean it all up for the rest. But that track saw looks cool too tbh .. The router or tool id use would make a cut that leaves me with how the front of this cage looks like. See how its cut out and only the edges are left on and the middle support beam.. That would be exactly what id make..


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## angel619392 (Jan 10, 2020)

Stick486 said:


> Table saw..
> High tooth count (80+), negative rake (-3 ~ -5°) MTCG, TCG, ATB, H-ATB, ATB-R OR H-ATB-R grind/hook angle..
> 
> *Listed by preference:*
> ...


I honestly do not know so ill just put this question here.... Would more teeth cause less airflow along the teeth so more heat buildup for my dewalt cordless 5800 rpm circular saw???? Some guy at a plastic company told me to get 40-60 teeth carbide blade for plastic and this would allow airflow along the teeth and since HDPE is soft plastic the fine finish after the cut wont be bad because its a soft plastic so he said I could just use a knife to cut off the few inconsistencies but what do you think??


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## angel619392 (Jan 10, 2020)

Herb Stoops said:


> Welcome to the form N/a, I have cut HDPE ,(Starboard) for my boat and used the same power tools as for wood cutting. Regular router bits cut it fine and so do saw blades,and drill bits. Screws do not hold very well, and neither does calking. Cutting makes a big mess, white sawdust and chips everywhere. The material I used was 1/2" thick and 1" thick. The tablesaw blade was a 10" X 60 tooth carbide blade, regular straight and 1/4 round carbide router bits. I used the router table, freehand w/ templates and a straight carbide bit with a pilot bearing. Laid the full sheet on a sawhorse and broke it down with a skillsaw. It is heavy and full sheets are hard to handle alone. Never needed any cooling, drills with regular drill bits,cuts like butter.
> Herb


Man thank you, you made it very simple for me to understand and so did another user I cannot remember his name but he suggested a track saw and then I thought of using a track and the router attachment for the tracksaw to make the straight cuts i need for the router... with that 60 tooth carbide blade did it leave a relatively smooth finish on the edges after the cut?? I assumed you probably were able to easily smooth it out with a file or knife huh?? And ok thank you for the info on the router bits...


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## angel619392 (Jan 10, 2020)

DesertRatTom said:


> Lots of specialized terminology so far. Rake is pretty important. Here is a diagram that explains rake. I have cut this stuff on my table saw (table saw zero clearance inserts), and it is pretty messy. Just don't let it linger on the blade, keep it moving forward into the blade, but don't push it too hard. Haven't used a router on it, but if I were going to, I'd use an up spiral bit. This bit is ground so it lifts the chips up and out of the cut. Other types of bits might quickly wind up with the plastic melted onto the flutes (cutting edges) and be all but impossible to remove. Same would apply to a saw blade. The negative rake is something you have to double check on any blade you are considering. It is not always obvious just looking at it.
> 
> More teeth on an 8 inch saw blade makes for a smoother cut. At any given speed, more blades will mean smaller spaces between each tooth's cut, thus smother. The illustration also reveals the difference between crosscut (across the grain) vs. rip (with the grain). The large gaps (gullets) between the rip blade's teeth, let it carry off very large amounts of sawdust or waste. Crosscuts produce less sawdust per inch.
> 
> ...


Thank you bro appreciate the help


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## Herb Stoops (Aug 28, 2012)

Don't worry about heat buildup or sticking to the cutter, there is none. That only happened to me on Plexiglass which is an entirely different animal. I ran all my tools at normal speeds for wood, used straight cutters on carbide,rough cut the large openings 1/8"-1/4" undersize and finish cut with the router. Standard size router works best.
What are you going to use to join the corners together, glue doesn't work, screws are marginal holding, I used "L" clips or metal angles,(aluminum)and thru bolted with small machine screws and nuts. Best is SS they won't rust. They do use a a full fillet weld with a filler rod and a hot wire or hot air welding gun. 

If you are using clear plexiglass for the openings you may experience cracking from drilling and heat melting build up on your cutters, that is a different type of material.
Herb
EDit: I just reread your post, you might be able to use silicone to hold the glass in and be sure to thru bolt the hinges for the best results. From the picture, it looks like the sides and bottom have a welded joint..


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## Stick486 (Jan 4, 2013)

angel619392 said:


> I honestly do not know so ill just put this question here.... Would more teeth cause less airflow along the teeth so more heat buildup for my dewalt cordless 5800 rpm circular saw???? Some guy at a plastic company told me to get 40-60 teeth carbide blade for plastic and this would allow airflow along the teeth and since HDPE is soft plastic the fine finish after the cut wont be bad because its a soft plastic so he said I could just use a knife to cut off the few inconsistencies but what do you think??


these blades are for a table saw...
The plastic company is correct for a circular saw...

think of how much spacing there is between each individual tooth on your CS smaller diameter blade at 40T and the 10'' TS blade at 80T... they're about the same...


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## angel619392 (Jan 10, 2020)

Herb Stoops said:


> Don't worry about heat buildup or sticking to the cutter, there is none. That only happened to me on Plexiglass which is an entirely different animal. I ran all my tools at normal speeds for wood, used straight cutters on carbide,rough cut the large openings 1/8"-1/4" undersize and finish cut with the router. Standard size router works best.
> What are you going to use to join the corners together, glue doesn't work, screws are marginal holding, I used "L" clips or metal angles,(aluminum)and thru bolted with small machine screws and nuts. Best is SS they won't rust. They do use a a full fillet weld with a filler rod and a hot wire or hot air welding gun.
> 
> If you are using clear plexiglass for the openings you may experience cracking from drilling and heat melting build up on your cutters, that is a different type of material.
> ...


HMmm see I would think that the screws would hold them in tight good but it sounds like thats not the case I may have to use some brackets or metal angles like you mentioned but preferably I would like to use some screws and caulking to seal any water or feces from seeping through the cage .... I heard HDPE is a pain in the ass for anything to adhere but I was told that acrylic silicone/caulking will stick to hdpe.


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## Herb Stoops (Aug 28, 2012)

... I heard HDPE is a pain in the ass for anything to adhere but I was told that acrylic silicone/caulking will stick to hdpe.[/QUOTE]

I didn't try that type of calk, I tried screws and predrilled the holes. They held a little,but stripped out the threads, and at the corners cracked and broke diagonally across to the side. I was not confident with the screws,and especially on a power boat with the vibration and twisting, and torquing. 
You might mock-up a sample and put it through some paces to see it it will holds up stuck together with caulk. 

Just as a suggestion, have you considered MDO plywood? it would work a lot better and is a LOT cheaper. It is 100% waterproof, Get the sheets with melamine coating both sides. We used it for years for architectural concrete forms and I use it for all my shop cabinets. You get it at the lumber yard in 4X8 sheets, 1/2" or 3/4" and it works just like regular plywood and holds fastners the same too. It paints beautifully,the commercial sign companies use it for signs,works with woodworking tools and nail/screws. Please look into it, you won't be sorry. It comes in one face or 2 face overlay, I recommend 2 face. If the HD doesn't have 2 face call the lumberyards.
https://www.homedepot.com/p/1-2-in-x-4-ft-x-8-ft-G1S-Fir-MDO-Board-123583/206460868

Herb


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## Herb Stoops (Aug 28, 2012)

https://www.performancepanels.com/enhanced-faces-overlaid-coated-hdo

HDO is even better(High Density Overlay). It is almost bullet proof.
HErb


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## angel619392 (Jan 10, 2020)

Stick486 said:


> these blades are for a table saw...
> The plastic company is correct for a circular saw...
> 
> think of how much spacing there is between each individual tooth on your CS smaller diameter blade at 40T and the 10'' TS blade at 80T... they're about the same...


HMM that makes sense and I do not know how I overlooked this lol .Thank you..


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## angel619392 (Jan 10, 2020)

Herb Stoops said:


> ... I heard HDPE is a pain in the ass for anything to adhere but I was told that acrylic silicone/caulking will stick to hdpe.


I didn't try that type of calk, I tried screws and predrilled the holes. They held a little,but stripped out the threads, and at the corners cracked and broke diagonally across to the side. I was not confident with the screws,and especially on a power boat with the vibration and twisting, and torquing. 
You might mock-up a sample and put it through some paces to see it it will holds up stuck together with caulk. 

Just as a suggestion, have you considered MDO plywood? it would work a lot better and is a LOT cheaper. It is 100% waterproof, Get the sheets with melamine coating both sides. We used it for years for architectural concrete forms and I use it for all my shop cabinets. You get it at the lumber yard in 4X8 sheets, 1/2" or 3/4" and it works just like regular plywood and holds fastners the same too. It paints beautifully,the commercial sign companies use it for signs,works with woodworking tools and nail/screws. Please look into it, you won't be sorry. It comes in one face or 2 face overlay, I recommend 2 face. If the HD doesn't have 2 face call the lumberyards.
https://www.homedepot.com/p/1-2-in-x-4-ft-x-8-ft-G1S-Fir-MDO-Board-123583/206460868

Herb[/QUOTE]

Thanks for the suggestion and I work at a lumber yard here in california Ill see if we have it tomorrow I work at a dixieline here in california


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## Stick486 (Jan 4, 2013)

Herb Stoops said:


> ... I heard HDPE is a pain in the ass for anything to adhere but I was told that acrylic silicone/caulking will stick to hdpe....
> 
> I didn't try that type of caulk, I tried screws and predrilled the holes. They held a little,but stripped out the threads, and at the corners cracked and broke diagonally across to the side. I was not confident with the screws,and especially on a power boat with the vibration and twisting, and torquing.
> You might mock-up a sample and put it through some paces to see it it will holds up stuck together with caulk.
> ...


it beds well w/ most any caulk except pure silicone.. the active chemicals in silicone ''eat'' the plastic drying it out making it become brittle...
siliconized caulk is a different animal...
I like the urethanes, butyl rubber and my all time #1 preferred favorite for this, Vulkem... 

thicker HDPE accepts tapped threads well.. use nylon fasteners w/ locktite and you'll have something...
on a boat.. all bets are off...

a bedded containment frame is the real way to go; that's the ticket... 
use architectural style Z bar or U channel...
anodized aluminum is the choice material here...

note:
treat the stuff as nick sensitive..
RO the edges/shoulders super smooth and make any cuts baby butt smooth..


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## Herb Stoops (Aug 28, 2012)

Thanks for the suggestion and I work at a lumber yard here in california Ill see if we have it tomorrow I work at a dixieline here in california[/QUOTE]

That is great maybe you can get a discount on it too.
Herb


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## Larry42 (Aug 11, 2014)

We've cut a lot of UHMW and Star board. You're over thinking it. As a few have said you want to keep moving fast enough so that heat doesn't fuse the plastic. It doesn't have to be super fast, just don't go real slow. These plastics don't generate a lot of heat. What will generate the heat is if there is not enough gullet space for the feed rate and not enough feed rate to make sufficiently large chips to carry away whatever heat is being generated. Shouldn't be a problem with 1/4" material. They cut very easily. They do make a mess, static electric charge makes the fluff stick to everything in the shop. 1/4" won't tax just about any saw or router. Most plastics will produce a better looking edge with an O flute but certainly not required. Most any sharp saw blade will work on 1/4", just keep the feed going. 
We make tool boards for the railroad. 2 & 3" UHMWPE (UltraHighMolecularWeightPolyEthelene) Our beam saw only has 15hp so it has to make two passes on the 3" stuff. The reason is, the dedicated plastic cutting blades in this size are pretty pricy and we will only be cutting 10 or 20 sheets per job. Our router has 12hp and we pocket with a 3/4" up spiral 2 flute, engrave with a 1/4" ball nose. Feed rate 600ipm. The chips are big and flaky and fly everywhere. The dust hood only gets about 1/2 of them, the rest we shovel up into 55 gallon barrels. We use 3/4" Starboard to make cat displays for a chain of pet stores, stainless steel screws with deep, wide threads. Drilling is done on the router with the usual boring bits that have cylindrical tips the same as are used for melamine board. UHMW is very slick. Keep your scraps for making guides. We have made sled runners for Arctic expeditions, conveyor guides for food processing equipment and for a brick making plant, & cutting boards for grocery stores with the stuff.


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## Gaffboat (Mar 11, 2012)

An ‘O’ flute router bit is a single flute design that dissipates heat while cutting to prevent melting, and are designed for CNC machining of plastics, although they work equally well in wood.


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## Herb Stoops (Aug 28, 2012)

I had a drill bit like that once, just wouldn't stay on center wanted to walk all over the place.
HErb


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