# Cutting styrene



## fsts2k (Jan 13, 2009)

Hello all, 

I have started to do some scratch building with Styrene, my initial project is a small MOB wagon based off an LGB wagon. I am struggling with two things:

1) What thickness Styrene should I use for the walls and floor? I have .125 and it seems fine but I did not know if others have better success with different thickness. I am using .030 for detail parts. 
2) How in the heck do you keep a straight line when using a razor to score the .125 Styrene? Is there a tool I can purchase? I am using a straight edge but it still pulls from side to side. This has caused the most frustration for me. Would this help: http://www.micromark.com/DUPLICATE-IT,9546.html



Thanks for your help, I will post pictures as soon as I am farther along.


----------



## SteveC (Jan 2, 2008)

Posted By fsts2k on 25 Dec 2009 07:05 PM 
{snip...}[/i] How in the heck do you keep a straight line when using a razor to score the .125 Styrene? {snip...}[/i] I am using a straight edge but it still pulls from side to side. This has caused the most frustration for me. {snip...}[/i]

From your use of the term 'razor' it leaves a question as to just exactly you are describing.

If you are using a single edged razor blade like the one depicted in the following images, used in scrapers or box-cutters. Then you are using the wrong type of tool.























If you are using a 'Utility Knife' type as depicted in the following images...

It's better to use a dull used blade for scoring, less tendency for the cutting edge to cause wondering. But you still need to keep the leading edge angled slightly toward the straight-edge. Because of the angle of the blade inverting and having the cutting edge up (i.e. as described in the X-acto knife section below) isn't very easy with this type of knife.

















If you are using an X-acto type knife (see the following images)...

Then, instead of having the normal cutting edge of the blade pointing down, turn it over so that the cutting edge is up and use the tip to score the plastic using the straight-edge. You'll need to make multiple passes (e.g. 3-5), then place the score line over the edge of a table and snap it.
















They do make a specific blades/tools for scoring plastics, as depicted in the following images.










Depending on the thickness of the stock that you're cutting, you can also use a rotary type cutter too. But here again you need to get used to keeping the blade against the straight-edge.


----------



## Torby (Jan 2, 2008)

Main thing is you want a blade that doesn't flex on you, causing it to "ski" away from your straight edge.


----------



## Trains West (Oct 4, 2008)

I use Plastic/Laminate Heavy-Duty Ratchet-Lock Cutter (P-800) from olfa

http://www.olfa.com/utilityknivesde...&id=58

and do the scribe and snap


----------



## tom h (Jan 2, 2008)

I bought a square that is raised so it goes along the edge of the styrene, kind of like a T-Square, but L shaped, Micro-Mark sells it, that is going to help a LOT, you could use a table saw if making a lot of cuts, just use a blade with lots of teeth.

Tom h


----------



## Pete Thornton (Jan 2, 2008)

But you still need to keep the leading edge angled slightly toward the straight-edge. 
And, if the blade is fairly sharp, keep your fingers out of the way, as the blade may climb the straight edge (especially if it is a metal ruler) and try to chop the end of your finger.


----------



## fsts2k (Jan 13, 2009)

Thanks for all the replies. I am using an Exacto knife, a #2 like the one above. I may be pressing to hard which is causing it to "ski". I am also using a square but it has a level on it and is not flat, I will try using a flatter straight edge and a scoring knife. 


Along with this question, how do you cut a radius? Do you use a compass? 


All of these different cuts have me a bit confused. Thanks for the continued assistance.


----------



## Totalwrecker (Feb 26, 2009)

For the radius cuts I'd use a coping saw on the thicker stuff. Clamp a piece of wood to your bench so that it overhangs the edge, Cut a V slot about 3"deep and 2" wide. Keep the blade vertical and near the bottom of the V, 2 7/8ths" in. Turn your work as you saw, be sure the 'keeper' side of the cut is supported by the 'benchpin' underneath. Another thought is to clamp it onto scrap wood and saw it out with a fine toothed blade, the wood will support it. If you go too fast the plastic can get soft and tears instead of cutting, let it cool. File to final shape. 

For thinner stock; repeated passes of the knife should work. I rarely try to make the cut on the final line as the cutting sometimes raises edges and removing them removes my line. 

FYI; that's a #2 handle, but more important, it's a # 11 blade. 

When I scribe non ferrous metals for sawing, I use a round tapered scriber. I use 6 - 8" hand files; half handle, half file. When one gets dull, I'll cut off the file part and grind the end to a pencil taper, for plastic stop here, for metal; then sand and polish and temper. When I was being paid, I was more fussy and did a double temper; first to glass hard and then softer. The result was a strong core, yet protected from being too brittle with the soft candy shell... sorry too many treats yesterday! ...softer tempered outer portion. Note; when quenching ferrous metals in water add a layer of oil on top (light and clean) 3 in 1 is ok . 1/32" or so... for smaller projects, thicker for bigger... 
The round shape is easier to keep next to your straight edge or curved edge. Since taking mechanical drawing in high school, I've always had a set of French Curves in my shop. [Translucent plastic drawing aids with multiple compound curve cutouts and edges.] 
The round tip won't mar your edge guide either. 

Using the scriber first, the knife should follow better...Many light cut are easier to manage than a heavy gone astray! 

I hope this helps more than confuses! lol 

John


----------



## Jack - Freshwater Models (Feb 17, 2008)

fts2k

The tool Steve showed as being specifically for styrene is the best one to use or you can make something like it by grinding the end of a spent hacksaw blade. Ordinary knife blades are strictly a wedge, is hard to push through the plastic, and they tend to wander. What you need is a blade that produces a scraping type cut rather than a slicing cut. Cutting with a scraping tool is easy, relatively fast, and accurate if you use a square or straight edge to guide the blade. It will require a series of cuts but they are easier to control and do than a knife blade. The scraping type tool isn't good for unguided curved cuts which might be better done using a jewelers saw or scroll saw. These same techniques work for cutting brass. 

Hope that helps.

Jack


----------



## fsts2k (Jan 13, 2009)

Posted By Totalwrecker on 26 Dec 2009 10:39 AM 
For the radius cuts I'd use a coping saw on the thicker stuff. Clamp a piece of wood to your bench so that it overhangs the edge, Cut a V slot about 3"deep and 2" wide. Keep the blade vertical and near the bottom of the V, 2 7/8ths" in. Turn your work as you saw, be sure the 'keeper' side of the cut is supported by the 'benchpin' underneath. Another thought is to clamp it onto scrap wood and saw it out with a fine toothed blade, the wood will support it. If you go too fast the plastic can get soft and tears instead of cutting, let it cool. File to final shape. 

For thinner stock; repeated passes of the knife should work. I rarely try to make the cut on the final line as the cutting sometimes raises edges and removing them removes my line. 

FYI; that's a #2 handle, but more important, it's a # 11 blade. 

When I scribe non ferrous metals for sawing, I use a round tapered scriber. I use 6 - 8" hand files; half handle, half file. When one gets dull, I'll cut off the file part and grind the end to a pencil taper, for plastic stop here, for metal; then sand and polish and temper. When I was being paid, I was more fussy and did a double temper; first to glass hard and then softer. The result was a strong core, yet protected from being too brittle with the soft candy shell... sorry too many treats yesterday! ...softer tempered outer portion. Note; when quenching ferrous metals in water add a layer of oil on top (light and clean) 3 in 1 is ok . 1/32" or so... for smaller projects, thicker for bigger... 
The round shape is easier to keep next to your straight edge or curved edge. Since taking mechanical drawing in high school, I've always had a set of French Curves in my shop. [Translucent plastic drawing aids with multiple compound curve cutouts and edges.] 
The round tip won't mar your edge guide either. 

Using the scriber first, the knife should follow better...Many light cut are easier to manage than a heavy gone astray! 

I hope this helps more than confuses! lol 

John 
Thanks! I will now need to google a bunch of this to understand it


----------



## fsts2k (Jan 13, 2009)

Posted By Jack - Freshwater Models on 26 Dec 2009 10:56 AM 
fts2k

The tool Steve showed as being specifically for styrene is the best one to use or you can make something like it by grinding the end of a spent hacksaw blade. Ordinary knife blades are strictly a wedge, is hard to push through the plastic, and they tend to wander. What you need is a blade that produces a scraping type cut rather than a slicing cut. Cutting with a scraping tool is easy, relatively fast, and accurate if you use a square or straight edge to guide the blade. It will require a series of cuts but they are easier to control and do than a knife blade. The scraping type tool isn't good for unguided curved cuts which might be better done using a jewelers saw or scroll saw. These same techniques work for cutting brass. 

Hope that helps.

Jack



Jack, 
Which tool that Steve showed? The scoring knife or the rotary cutter? 

All of this information is greatly helpful. 

Kevin


----------



## kormsen (Oct 27, 2009)

or you draw a simple pizza cutter weel alongside your rule. 
that is good enough, if you want to snap the piece.


----------



## Jack - Freshwater Models (Feb 17, 2008)

Kevin,

The scoring knife is the best! For thin plastic of say .020" thick or thinner you may do ok with knives or rotory cutter. For plastic .030" or thicker you really need to cut with a scraping cut. I first saw this in an article on cutting brass and plastic in a magazine. Rather than buying a cutter it is easy to just grind the end of a spent hacksaw blade to suit. The cutting end doesn't have to be pointed but does need to be sharp.

Another helpful tip is to forget hobby knives! I use either a large size surgeons scalpel handle with appropriate non-sterile blade, or a single edge rasor blade, or utility knife. The surgeons scalpel is usually my knife of choice for modeling. Buy one nice "B-P" handle with the large plastic grip and some #25 blades. The handle doesn't roll off the bench and the blades are much sharper than hobby knives. Buy them from a jewelers tool supplier for teh best price. You can get knock off handles and blades that are OK but they don't interchange with American blades due to different size mounting hole in the blade.

Jack


----------



## Russell Miller (Jan 3, 2008)

I used to try and use an EXACTO Knife with often poor results, now I use this: *SCORING KNIFE.* TAP Plastics also sells a *Plastic Scoring tool made by HYDE* in their stores. These tools not only work better but are also much safer to use instead of razor knives.
Russ


----------



## SteveC (Jan 2, 2008)

A picture of one type of "benchpin" that John (Totalwrecker) mentioned & a frame saw.


----------

