Replicating the look of the edge left by a cutting torch

[billmart]

I want to build a 1:13.7 scale model of a small mining car that was built primarily from 1" diameter to 6" diameter pipes that appear to have been cut to length with a cutting torch.  I'm looking for suggestions on methods I might use to replicate that rough-cut look on styrene tubing.

Thanks in advance for your assistance.

Bill Martinsen

[Design-HSB]

Hi Bill,
why do not you use brass tubes that come in every imaginable diameter.

There is also the pipes in the MS 63 you can turn good.
Of course, all pipes and solder very well.
MS tubes of semi-hard 58 can be cut well, drilling, etc. Unfortunately, not only bend then break the good easy.

Maybe you have a picture of the model I would of course be very interested.

[Malachi Constant]

Cut it roughly!  

Photo shows styrene tube cut with the photo-etched saw shown ... clean that up kinda roughly and/or practice refine from that and you might get there ...   (hopefully)

Aluminum tube cut with a stiffer razor saw ... would ordinarily need some clean-up, but could also be a starting point ...

PS -- When you cut styrene tube with a little razor saw, it gets fuzzy edges ... maybe hit that with some solvent and then mush the edges a bit.  Does that make sense?       The fuzzy, rippled edges could be mushed down to look like the rough edges you're describing ... I think ... second photo ... quickie experiment ... used solvent and fingernail to mush it (vs. getting fingerprints into solvent) ... needs refinement, but seems like it could work ...

Cheers,
Dallas

[billmart]

Helmut -
I could build it from brass tubing, but I prefer working in styrene, and styrene is easier to paint.

Dallas-
Thanks for the suggestions.  I appreciate you taking the time to try an experiment and take photos. 

Bill Martinsen

[marklayton]

Bill -

Cutting torches don't necessarily leave a rough finish - the result is totally dependent on the skill of the person doing the cutting.  I've purchased flame-cut 2" plate from a local distributor who uses a computer-controlled torch that leaves a surface almost as smooth as a machined surface.  On work that I cut on the shop, the most hurried and messiest cut edge I can recall had cut marks less then 1/16", which at your scale are going to be something like 0.004".  I think the guys are right about using styrene.  I think maybe making score marks by dragging a very fine saw across the cut edge, turning the tube to create roughly radial scrape lines, and then gently blurring those marks with solvent.  The effect should be subtle - too coarse and it may look like messy modeling!

Mark

[Gordon Ferguson]

Hi Bill, I need to do something similar in 1/24 .............. going to experiment with some plastic tub which I will ream out first to reduce the wall thickness and use a soldering iron at a low setting to form the weld/cut marks ------------ was also wondering about trying a medium cut metal file

Will post some results at the week-end

[billmart]

I have nearly finished the little mining car (built to carry timber supports for the tunnels), so thought I'd better post a pic or two so you can let me know how I did.  My aim was to make the car look as though it had been built from pipes, etc., found in a scrap pile.  The cutting and welding were to look as though the work was done by a shop assistant during his first week of employment.

I dragged the cut ends of the styrene tubes across the teeth of a wood rasp to get the uneven look.  The tubes are 5/16" diameter so I needed something coarse to produce the look I wanted.

Bill Martinsen

[Malachi Constant]

Well, I'm no expert on scrap pipe ... but that looks darn good to me! 

PS:  Thanks for updating the thread.  One is often left hanging in these "how should I...." threads ... wondering if a usable solution was found.  Glad to see your results.  -- Dallas

[lab-dad]

The "cut" looks excellent.
My only (minor) comment would be I think the cut part should have weathered a different color, slightly but that is just splitting hairs.
-Marty

[billmart]

Well, I'm no expert on scrap pipe ... but that looks darn good to me! 

PS:  Thanks for updating the thread.  One is often left hanging in these "how should I...." threads ... wondering if a usable solution was found.  Glad to see your results.  -- Dallas

Thanks, Dallas.  I must admit, I have sometimes been guilty of leaving folks hanging.  I'll try remember to post updates when I've actually done something.

Bill Martinsen

[billmart]

The "cut" looks excellent.
My only (minor) comment would be I think the cut part should have weathered a different color, slightly but that is just splitting hairs.
-Marty

Thanks, Marty.  Perhaps I should add a little of that yellow rust look to the ends.  That always reminds me of relatively new rust.

Not the yellow I used on the model.  That's supposed to look as though the pipes were painted yellow at one time, probably years ago.

Bill Martinsen

[Gordon Ferguson]

I don't understand the chemistry but a lot of steel I have seen cut with a welding torch does not seem to rust along the cut line ...... from memory it seemed to stay a sort of gunmetal/dark grey colour where the rest of the sheet/pipe rusted as normal.

Deep in the recesses of my brain think it was something to do with whither or not you knocked the "slag" off after the cut/weld ...... something you would do if you needed to check quality of weld but not if you were just chopping up stuff

Anyway I think it looks great, just the thing to put behind you Ford powered critter .................. how about showing that here ?

[finescalerr]

Most adequate. The pipe ends neither make nor break the model; tempest in a teapot. -- Russ

[marklayton]

Good catch, Gordon.  When steel is flame cut, the heat-affected region is heavily oxidized.  That oxide layer can protect from rusting for a time.  But I think this cart has been outside long enough to rust all over!  Looks very nice, Bill.

Steel that I forge gets the same oxide on the surface, but because forging temperature is lower than cutting temperature, it doesn't coat as well.  Some falls off during forging, so there's always a pile of 'scale' around the base of the power hammer.  When the forging is complete, any remaining 'scale' can be popped off by gentle heating with a rosebud tip on the oxyacetylene torch.

Mark

[Lawton Maner]

Nicely done.  Has the effect of something built out of necessity, on site, and in a hurry.  BTW, what are the mine props made of?  I'm always looking for bark textures like you have for 1/48 scale logs and am getting tired of the yard cuttings I get each year as I trim the garden.