Author Topic: Blade anatomies  (Read 1889 times)

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gary60s

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Blade anatomies
« on: September 12, 2013, 10:33:03 PM »
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Blade anatomies

One of the most used tools in model railroading is the hobby knife. Probably the most popular is the Exacto knife. While it may be the most popular, it may not be the best blade to use for your application. It all depends on WHAT you are cutting, and the TYPE of cuts you are making. Curved cuts of any kind, as well as cutting in tight places, are done well with the pointed end of an Exacto.  An Exacto also has unlimited other uses.

If you are making repetitive straight cuts in wood or styrene up to 1/8" thick, then a SERB (Single Edge Razor Blade) is best. The reason for this is the "included blade angle". Careful measurements and some basic trigonometry produced the data for the following sketches, which show the angles for 4 popular blades.









Clearly the SERB is thinner, and has a much more acute blade angle than the others.

If you cut (or score and then snap) styrene or similar materials with an exacto blade, box cutter, or utility knife, you may wind up with a ridge on the cut edge. Using a single edge razor blade eliminates this ridge, due to the thinner blade, and a more acute angle to the cutting surface. AN ADDED BONUS IS THAT IT WILL HOLD ITS EDGE LONGER THAN AN EXACTO BLADE. Also, no ridge means that sanding can be almost eliminated.
Blades are cheaper too (100 for about $6.00).

This thread is NOT to convince anyone to use a different blade. Look at the sketches and then decide for yourself. More importantly, use what you are comfortable with.

I made a cheap SERB holder and I have sketches and pics so you can make your own, if anyone is interested.

I wasn't sure which forum to post this in. The blade holder I made from scratch, but if admin thinks it should be moved, thats fine.
Gary

wazzou

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Re: Blade anatomies
« Reply #1 on: September 12, 2013, 10:43:42 PM »
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In addition to my Chopper III, for which I obviously need a supply of SERB's, that is all I use in the situations you describe.  I generally only use Exacto blades for cutting sheet material.
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Chris333

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Re: Blade anatomies
« Reply #2 on: September 12, 2013, 11:24:02 PM »
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Always thought box cutters held razor blades?

wazzou

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Re: Blade anatomies
« Reply #3 on: September 12, 2013, 11:29:12 PM »
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Always thought box cutters held razor blades?



He may have meant utility knife?
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C855B

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Re: Blade anatomies
« Reply #4 on: September 13, 2013, 12:42:04 AM »
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Box cutters hold SERBs.

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GaryHinshaw

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Re: Blade anatomies
« Reply #5 on: September 13, 2013, 05:45:15 AM »
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Just out of curiosity, I checked my SERBs and found that they are .010" thick and have a blade bevel of .030" tall, making a blade angle of 19 degrees.  So I guess not all SERBs are created equal.

My #11 blades have a compound bevel: the overall blade thickness is .020", but the final bevel starts at a blade thickness of ~0.010" (to the best of my ability to measure) and has a depth of ~.015" (again, hard to measure), making an angle of more than 30 degrees.  Curiously, the main bevel is asymmetric, with one side starting at 0.055" above the edge and the other at 0.070".

I wasn't sure which forum to post this in. The blade holder I made from scratch, but if admin thinks it should be moved, thats fine.

This forum is fine the information, but please don't leave your blade holder here; you're likely to lose it. ;)

DKS

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Re: Blade anatomies
« Reply #6 on: September 13, 2013, 07:27:01 AM »
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If you cut (or score and then snap) styrene or similar materials with an exacto blade, box cutter, or utility knife, you may wind up with a ridge on the cut edge.

This is why I hold the X-Acto knife backwards; it will make a score that removes material, rather than just make a narrow indent, which will indeed have ridges. The backwards-blade score is always clean. The only time I hold the knife property is if I'm shaving off a tiny amount from the edge.
“Everyone leaves unfinished business. That's what dying is.” —Amos, The Expanse

basementcalling

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Re: Blade anatomies
« Reply #7 on: September 13, 2013, 08:25:54 AM »
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This is why I hold the X-Acto knife backwards; it will make a score that removes material, rather than just make a narrow indent, which will indeed have ridges. The backwards-blade score is always clean. The only time I hold the knife property is if I'm shaving off a tiny amount from the edge.

Just don't forget you are holding it backwards and put an index finger on the "back" of the blade to add pressure to the tip for the cut. Just saying, but not admitting how I learned this.   :facepalm:

Also, with Xacto blades, do the different # blades have different data for shape and angle? #11 is by far the most popular blade size for our hobby knives, but it isn't the only blade made for hobby use in these knives.

Any blade will dull the cutting edge over time so don't forget to swap the SERB end for end in those Choppers. I wonder what percentage of the actual cutting surface of the blade we really use when making our cuts.
Peter Pfotenhauer

DKS

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Re: Blade anatomies
« Reply #8 on: September 13, 2013, 09:07:37 AM »
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Just don't forget you are holding it backwards and put an index finger on the "back" of the blade to add pressure to the tip for the cut.

Hasn't happened in 51 years of modeling. (That's not to say I've never cut myself other ways...)
“Everyone leaves unfinished business. That's what dying is.” —Amos, The Expanse

Philip H

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Re: Blade anatomies
« Reply #9 on: September 13, 2013, 09:12:05 AM »
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Box cutters hold SERBs.



And don't forget that utility knives come in two types - the score and snap bade type, and the "carpet knife" that has the reversible rhomboid blade.

Gary,
Nice thread.  Care to share your SERB holder design?
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gary60s

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Re: Blade anatomies
« Reply #10 on: September 13, 2013, 09:23:33 AM »
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My box cutter has the 1/4"break away type blade. My utility knife blades are the trapezoidal shaped blades, and are held by 2 knife halves screwed together.

Quote
This forum is fine the information, but please don't leave your blade holder here; you're likely to lose it.

Where should I put the blade holder thread? If you meant that my idea will be stolen, thats ok. It's been public domain for years.
Gary

GaryHinshaw

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Re: Blade anatomies
« Reply #11 on: September 13, 2013, 03:51:46 PM »
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Where should I put the blade holder thread? If you meant that my idea will be stolen, thats ok. It's been public domain for years.

I was just making a silly comment about the grammatical construction of your sentence.  The thread you posted is fine.

Sorry for the confusion.

magi46

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Re: Blade anatomies
« Reply #12 on: October 04, 2013, 09:25:22 PM »
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Well Gary, I see your here.  :D

gary60s

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Re: Blade anatomies
« Reply #13 on: October 04, 2013, 09:57:03 PM »
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I'll see your "here" and raise you a "present and accounted for".
Gary