Q: Knife-Edge Blades

lothian

New User
lothian
Does a 10" knife-edge blade exist?

I need to size down a fair amount of foam core and cardboard accurately. As I slog about using a straight-edge and utility knife at my workbench, I sense my table saw over there sniggering at me. It occurs to me that a 10" knife edge would be splentastic for this chore, yet the interweb reveals nada.

Maybe I stumbled onto a patent-able idea; or just lost the Google Keyword Search Game yet again.

Anyone heard of such a blade?
 

Mike Davis

Mike
Corporate Member
I have seen something similar for the bandsaw which may be a better machine for that use.
They are usually simi serrated sort of a wavy edge and razor sharp.

Usually card stock is cut on a guillotine. Look for board shear or paper guillotine.
 

lothian

New User
lothian
Right. And knife blades exist for the jigsaw, of course. But I'm specifically looking for a straight-cut blade for a table saw.
 

Mike Davis

Mike
Corporate Member
I think it would be impractical due the the thin thickness needed to prevent curling the cardboard as the knife passes through.
A knife does not remove material as a saw blade does. The material is pushed aside when cut, that is why razor blades for mat knives are very thin.
The thin blades work well under tension on a band saw but a table saw would need a thicker blade that may not play well with cardboard and foam core.
 

lothian

New User
lothian
That occurred to me also. Additionally, the typical RPM of a table saw would subject a (presumably) thin knife blade to significant forces. A meat cutter, by comparison, has a lower RPM; and unlike a table saw, that RPM is operator variable.

hmmph...
If this old worn-out 24T blade was just...

...to the grinder!
 

JimD

Jim
Senior User
Do you have an electric knife? Like I use to carve the Thanksgiving turkey? They work great on foam.
 

lothian

New User
lothian
Buried deep in my blade cabinet I discovered a 10" 180T blade! ...guess I got the thing on sale.

I'm gonna give that blade a shot, maybe with some 5mm backer under the foam-core and cardboard in hopes of lessening tear-out--though it'll probably just make things unwieldy.
 

awldune

Sam
User
FWIW, I have cut "blueboard" polystyrene sheets with a regular TS blade and it worked fine aside from making a huge mess and gumming up the blade. You will probably want to clean your blade after.
 

Gofor

Mark
Corporate Member
FWIW, I have cut "blueboard" polystyrene sheets with a regular TS blade and it worked fine aside from making a huge mess and gumming up the blade. You will probably want to clean your blade after.

I wonder if it would work if you reversed the blade? Especially if you had an old one without carbide teeth?
 

gator

George
Corporate Member
Check Amazon for "rotary scissors". The are used in sewing and come i manual or electric. Amazon has many many to chose from. One of these should suit your need.
George
 

junquecol

Bruce
Senior User
If your cutting edge isn't wider than the body of the blade, the sides of the blade will rub against the foam, causing it to melt. If you can get needed height, I would try a Diablo 7 1/4" blade from HD. To clean melted foam of any blade, you will need a solvent, with my favorite being CLEAR PVC primer.
 

marinosr

Richard
Corporate Member
If your cutting edge isn't wider than the body of the blade, the sides of the blade will rub against the foam, causing it to melt.

Bingo. This is why it's a bad idea. And woe be unto anybody who would use a knife edge blade with the beveled side facing the fence... instant and disasterous kickback. I'm guessing this is why such a product doesn't exist... very limited application due to the rubbing issue, and very ready possibilities for somebody to hurt themselves.
 

smallboat

smallboat
Corporate Member
I've cut both foam core and corrugated board, and thicker foam insulation for that matter on the table saw with a carbide toothed blade and never had any problems with melting. Tear out may be an issue if you aren't using a zero clearance insert. I'm generally knocking things down to a manageable size for finished cutting with a knife, or cutting panels to fit into a frame where edge quality doesn't matter. But the TS is a great way to make controlled straight cuts quickly if you have to process a bunch of board. My experience says you don't need a special blade at all.

For the record as Sam says, blue insulation foam sheds millions of little styrene beads that static cling to everything.
 

Pop Golden

New User
Pop
I know this from being raised in the corrugated box industry. Dad 2 uncles & 3 cousins and myself for a few years worked in this industry. Corrugated board is cut with a machine called a slitter. The blade is not 1 blade, but 2 running together. This causes a shear action which is very clean cut.

Pop
 

junquecol

Bruce
Senior User
I've cut both foam core and corrugated board, and thicker foam insulation for that matter on the table saw with a carbide toothed blade and never had any problems with melting.
That is because the teeth are wider than the plate of the blade, creating clearance.
 

Gofor

Mark
Corporate Member
Just a thought: How about an electric carving knife for the foam? Cheaper than a new saw blade.
 

nn4jw

New User
Jim
Would something like this work?

https://www.amazon.com/Circular-Han...+rotating+saw&qid=1563719857&s=gateway&sr=8-6

187557
 

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