Does anyone have tips on how to cut a uniform depth trench in foamboard? An example uniform trench is shown in this tortoise installation publication. I have 1-inch foam board glued to 3/8-inch plywood. I want to create a trench down to the plywood (1" deep trench x 1" wide x 24" long) for a scenic divider and a shallower trench for a servo. A utility knife could work but would be a long messy process and not very consistent...
If I needed to do what you are asking I would try:
Dremel 565 by Edmund, on Flickr
https://a.co/d/09RAIny
The Dremel 565 attachment and follow along with the vacuum hose as I cut. Affix a guide for the tool to follow to keep the cut straight. Make a template for the cutout needed for the Tortoise placement.
There are several 1/8" shank cutting bit sets that include an "end mill" type cutter that would make the flat recess cuts easer. For the slot cutout I would not try to remove the entire 3/4 width but just outline the slot using the smalleds "roto-zip" style bit then remove the foam piece with a chisel or flat scraper.
Good Luck, Ed
hot wire
you can bend 12 gauge copper wire into the shape you want with a ridge that rides along so balsa on top of the foam to set the depth
greg - Philadelphia & Reading / Reading
I had to cut ~uniform depth trenches to clear my roundhouse inspection pits. I took a yogurt cup and cut it down to the correct height, then taped it onto my hot wire cutter. Worked great! Here's my friend Walt using it to cut out for my inspection pits (cutouts became more uniform as he went):
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton
Hello All,
Genius!
Pure genius!!
Would you post more on the process?
Especially how to initiate the cut with the hot wire.
To cut uniform trenches in my pike I used a 1/2-inch wood chisel. (The dimension of the finished trenches are 1/2-inch X 1/2-inch.)
I used the flat edge of the chisel to establish the walls of the trench in the foam.
Then I broke up the sections of foam to be removed from the trench every inch or so.
Using this method the foam comes out in chunks with little or no "dust" and no need to use in a "Well-Ventilated Area- -ONLY!"
To make a 1-inch trench, use a 1-inch wood chisel.
You can find sets of wood chisels at your local hardware store or home improvement center.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
Hot Wire Foam Factory, and others I would presume, makes a shapeable hot wire cutter specifically for projects like that. Harbor Freight also has a hot knife but nor sure if any of their kits come with a shapeable wire. Wouldnt hurt to check. Youd be surprised how often youd use a hot knife after using it once.
Awesome suggestions! Thank you! Four votes for a hot wire cutter, one vote for a dremel, and one vote for trenching with a chisel.
I chisels so would be easiest to use going down one inch to the plywood base. Lots of big chunks but no smoke or dust to contend with...
I do have a dremel but not the attachment suggested by Ed. I'm still a newbie with using a dremel but can clearly identify other uses for this "mini router" attachment as well as this project. Kinda concerned about getting dust everywhere in the train room. Need to figure out a dust collection method that doesn't get in the way yet collects most or all of the dust. This one would do the job but yikes, very spendy... This inexpensive version should be on every MR'er workbench!
The hot wire method is intriguing, especially the method used by Pruitt's friend! I have the yogurt container, now I just need to know what the hot wire cutter looks like! Greg linked to a webpage showing several possible hot wire cutters as well as a suggestion for making my own with 12 gauge wire... Interesting idea but I'm concerned about ventilation and smoke in the train room (non-existent at this time) and not very doable to run existing layout components upstairs and out to the garage. Could work for future modules though, especially before attaching plywood base...
There is a fireplace in the train room that is not used for it's intended purpose, perhaps I could jerry rig a fan to blow the smoke etc out the chimney! Not sure of the physics for sending air up a chimney plus would need to have intake air... Hmmm, probably not possible...
Would be really slick if there was a dust collector for the Dremel rotary tool. This video describes a 3d printed dust collector for the Dremel 3000/4000 and the link for the 3D project
The Youtube video looks great but had limited traffic and no clue if the 3D printing has worked for others. I don't have a 3D printer, anyone interested in giving it a try? Wonder if it would work with the Dremel router attachment?
These 9mm box cutters work very well for cutting 2-inch foam and may work better than chisels for cutting deeper trenches. Here is a video comparing different hand tools for cutting xps foamboard.
a hot wire works well because it can cut the bottom of the slot.
perhaps another option is to use a long bladed knife to cut all the way through the foam, then glue the piece back in place at the desired depth
Hi there. Using a saw, I would do two cuts and remove the middle parts using a knife. For better precision, you might try clamping two pieces of wood for guiding the cut.
Simon
Hi Rick
Looks like you have some good suggested methods for cutting out your trench here. Like anything, there's more than one way to achieve ones objective for any given task. Sometimes it's just a matter of which method works best for the individual doing it.
If I had your task of cutting through 1" of foam down to the 3/8" plywood (1" wide by 24" long) I would grab my standard razor saw, a 1" forstner bit and one of those 9 mm retractable rasor knives suggested here.
I would draw pen lines to the shape of the cutout. Then slowly bore a 1" forstner hole (at high speed holding firmly) inside both ends of the trench. Then take the razor saw and place the tip of the blade in the edge of the hole and drag it towards the center on the line over and over on all four runs until you get down to the plywood. Then take the 9 mm knife and clean up the corners.
All the risers supporting the cookie cutter cut out in this picture we're done with a razor saw using that method. The cookie cutter was cut with an ultra fine toothed jigsaw.
You just need to let the razor saw do most of the work using light pressure, dragging over the foam a few times to get a clean cut and it cuts beautifully that way. You'll be surprised how quickly a razor saw cuts foam mostly on its own. The only other thing is keeping the blade plumb as you're making each pass.
If you get too greedy, aggressively trying to cut through the foam faster per pass, the foam will ball up in the teeth of the blade and give you an ugly cut. A little practice on a scratch piece and you get the hang of it rather quickly.
An ultra fine tooth jigsaw could be used for your task if you felt comfortable doing it. I've done those kind of tricks.
One can pull the blade down to the lowest blade stroke and then make a piece of foam the correct thickness and tape it to the jigsaw base to take up the extra space difference. Now the blade only comes down 7/8 to15/16" on the downstroke. Of course check on a scrap piece of foam that the blade doesn't cut all the way through the foam thickness before cutting the real one.
Then you could cut the trench without the blade hitting the 3/8" plywood. Then just finish up the bottom of the cut with your 9 mm knife.
Honestly, since you only have one of those to do, I would use the razor saw and do it by hand, unless I had a bunch of them to do.
There's a lot of different ways I've noticed other carpenters doing the same tasks at hand out in the field. Now and then I've adopted other carpenters methods if I saw they had a better way to do things than I did.
I wish you success with your foam trench
TF
Lots of ideas and suggestions! Awesome, thanks!
Right now I'm leaning toward Track Fiddler's suggestion for the 1" deep trench. I will be ordering a razor saw, a 9mm box cutter, and a 1" Forstner bit. Should work well for the scenic divider trench! I have additional uses for each item so minimal cost to make the trench.
I did not provide much detail on the other shallow trench for the servos. It will be a combination trench. The very top portion will be 1" wide x 3" long and 1/4" deep. Inside that rectangle, I will trench down to the plywood (dimensions 3/4" wide x 3" long x 1" deep). The servo will be attached to a 1x3 piece of 1/4" pine set in the trench with the top surface being level with benchwork and covered with cork roadbed. I will need to drill a hole through the plywood for the servo control wiring and may need to remove more for the servo to fit.
Ed's suggestion for the Dremel 565 multipurpose cutting kit should work very well for the shallow top trench. I like that I could dial in the depth of cut. I'll try it out in the garage on some scrap foam+plywood. I'm a bit concerned about foam dust getting everywhere. Been daydreaming about making a Rube Goldberg box that has a 10-inch office box fan to pull air through a furnace filter and out the back. There will be cardboard sides and a top in front of the filter to collect and/or direct the dust to the filter. Basically, I'm trying to mimic the $250 fan system I linked in yesterday's post. It will be slick and inexpensive if it works! It would be a win if it just collected the foam bits by the filter but even better if collected on the filter.
I need to do more investigation on the hot wire cutters. My existing layout has a flat surface. Getting a hot wire cutter could be an excellent option for sculpting scenic relief in the foam and creating hills with foam board.
Once again, thanks guys for all the thoughtful replies and suggestions. Extremely helpful! BTW TF, loved your foam layout! Very well done, almost a shame to bury it in a layout!
Pruitt I had to cut ~uniform depth trenches to clear my roundhouse inspection pits. I took a yogurt cup and cut it down to the correct height, then taped it onto my hot wire cutter. Worked great! Here's my friend Walt using it to cut out for my inspection pits (cutouts became more uniform as he went):
Mark,
I'm a total newbie when it comes to hot wire cutters. I found many single wire pen cutters but nothing with shapeable cutter wire. Could you provide more detail on your cutter? Which model? What cutting wire did you use? How did you shape it? The yogurt cup is cut to the appropriate height and taped to the hot wire cutter?
My layout room is right next door to the laundry room so any use of a wire cutter would most likely have to be in the garage or outside... Is there much odor and/or smoke?
Can anyone else provide guidance on where to buy a hotwire cutter that will accept a shapeable wire?
an easy to make hot wire cutter [for smaller areas] can be made with ordinary sixteen gauge house wiring [like the wires in your wall] with the insulation stripped off, and mounted in a weller [or similar] soldering iron. the one i used was a pistol grip style with 100/140 amp rating. worked well for years, and easily shapeable, gradual bends by hand and sharp bends with aid of pliers .. and no dust was the best part of it all ... did a 16 foot by 15 foot layout this way, pretty well all foarm on the top of it ..
Awesome, thanks for the info! I was only finding DIY table top cutters but your suggestion is very easy to do! I already have a soldering gun (somewhere in storage). Just a quick trip to HD for solid gauge wire, a little bit of shaping, and done!
*** oops, I have a solder gun and a solder station, both are different than what you used... I would need to buy a weller.
Add in, just read piano wire can be used in a hot wire cutter. I have some available for my servos.
Thank you for your kind words. The cooky cutter foam on risers and pre figuring all the elevations and radiuses was one of the funniest projects I ever took on. Honestly, I wish I could do it again!
I just wanted to share something else with you Rick. Before you bore your 1" forstner bit holes. First cut a 3-4" square piece of 3/4" board and drill a hole in the center of it with your forstner bit for a guide. Drill a couple of 3/16" holes kitty corner in the corners or maybe all four of them to hand tighten 1 1/2" temporary screws into the foam where you're working to hold it stable.
Those forstner bits can become quite squirrely and wander off on you drilling into foam without a guide.
IDRickMy layout room is right next door to the laundry room so any use of a wire cutter would most likely have to be in the garage or outside... Is there much odor and/or smoke?
In a pinch you could turn on your dryer on the "No Heat" setting. While not exactly a devoted exhaust fan it will force a bit of an air exchange by driving out some of the existing air and pulling in air from an open window or another part of the house.
Cheers, Ed
Rick,
The cutter I used came from B&B Hobby Supply in Bridgeport PA (www.hobbytools.com). Here it is:
That's a really stiff, heavy wire - not like the very thin wires that come with most hot wire cutters. It also has a really hefty wall wart that's hard wired to the unit. It's about 8 1/2 amps output, but the label also says 1.1 volts. I'm a bit sceptical of that last.
I didn't see a model number on it. The wire is removable, and I think the unit came with a bow attachment also, but that was years ago and I have no idea where it went. The wire you see came that way, and was just the right size for my inspection pit clearance trenches. I've never tried to create other wire shapes.
I cut the yogurt cut to the right depth and just taped it to the handle.
Not much at all from these things in the way of smoke, but there is some melted plastic smell and some fumes. In a high concentration (like a house fire) the fumes are deadly, fast. But I didn't have any trouble at all in a several-hundred-square-foot basement. When I was carving away at my canyon with a Woodland Scenics cutter about six months ago I would work for about 15 minutes and then vacate for half an hour or so to allow any accumulating fumes to dissipate.
I tried to order a bow for the cutter I used for the trenches so I could cut wider sections of foam, but they apparently don't sell this unit anymore - it doesn't show up on their website, and neither does any accessories for this (which is why I bought the WS cutter).
Sorry I can't help more.
Mark, thank you for the very thorough reply! I'd buy your type of cutter in a heartbeat if sold today... We do have commercial options today that will do a similar job but they also have added sophistication and are very expensive (well over $100).
There are many youtube videos on how to build your own pen or table-type hot wire cutter. The DIY pen type uses a pencil soldering iron with a copper wire wrapped around the tip and extending beyond the tip. Unfortunately, it appears the shape of the extended wire changes when cutting foam. The shape may be more stable if molded into a U shape but I have not found any videos testing straight versus U shape.
IMO, the success of your foam cutter is the stiffness of the wire, the squareness of the bends, and the dual connection to the U-shaped wire. I was able to find a somewhat similar U shape cutter where the DIY'er used a soldering gun and wire from a coat hanger. See this: instructable. The soldering gun had a 1.2 amp output and 120-volt input.
I have a similar soldering gun (100 Watts, 1 Amp). I'm going to give his instructable a try. A U-shaped wire attached to my gun will have a 5/8" spread requiring more than 1 cut per one inch trench. I plan on testing two wire types: coat hanger and stripped 16 AWG solid copper. My guess is that coat hanger wire will retain its shape better than copper wire, we'll see...
Thank you for the discussion on smoke and odors. I cannot smell (no olfactory nerve) so never know when something is causing an issue so try to be as cautious as I can. Thanks again!
Thank you TF and Ed for your additional suggestions and comments!
WVGCA I think my soldering gun is similar to yours so well trying your suggestion. Thanks!