I have been pondering the best way to shorten some bridge piers that are made from plaster. The best choice seems to be a hand saw and most likely a hacksaw blade.
Any other ideas?
Cheers, RustyKen
I just reduced the height and width of some plaster tunnel portals using a power sander. Plaster is very easy to break, so sanding is fast and easy with less chance of breaking. If I used a saw, it would be a jeweler’s or razor saw. A Delta circular power sander or a belt sander on a stand would be ideal.
A Zona type saw works well. Sanding also works well, I’ve used a random orbital as well as a bench top belt sander. A hacksaw with a fine tooth blade should work as well. With the random orbital I placed the sander in a work-mate type table and used it as a fixed sander.
With the saw I use very light pressure. Excessive down force can fracture the casting. Trust me on this one. [:$]
I have used my Dremel tool. It cuts without damage, but the cut surface takes a diluted wash differently than the original surface. Is there a way to fix that?
A jigsaw should work just fine - use a fairly fine-toothed blade at high speed, and don’t force the cut. You can also use the “score and snap” method: use a machinist’s square and a utility knife to score a deep line on all faces of the casting where you want the cut. I’d suggest cutting the portion which you wish to save a little bit long, then sanding it to the final size. Place the section to be saved on the edge of your workbench, with the waste portion hanging over, then, while pressing down to hold the casting firmly in place, whack the waste area with a hammer. It should break off fairly cleanly at the score line. To clean up the bottom, tape a piece of coarse sandpaper, face-up, to your workbench and drag or push (working in only one direction helps to prevent rounding the edges as you change directions) the piers across it.
You can also cast your own piers using simple home-made moulds of sheet styrene, as described HERE. (Non-members won’t see the pictures, but you can check out the method, then join if you wish - free, of course.) If you’re building a multiple span bridge over already-in-place scenery, even a valley of varying depth, you can often get by with only a single mould for all of the different pier heights.
Wayne
If you’re shortening bridge piers, you should remove the unwanted material from the bottom. On a bridge crossing a low area of varying depth, the piers are generally all the same width at their tops, with the bottoms becoming wider as height increases.
If, for some reason, you need to cut the top (one reason would be to introduce a step into the top to enable bridge girders of different depths to be supported), don’t worry too much about the colour. Flat surfaces will collect and retain more dirt (weathering) than will vertical surfaces. Piers which support steel bridges will have fairly heavy rust stains on their tops, along with the usual dirt and grime.
Here’s an example of stepped piers, cast as shown in the link in my previous post.
None have yet been weathered, but the bridge is easily removed, allowing access to the piers and abutments.
Wayne
I’ve always used a scroll saw. It can be adjusted to speed and the hold down helps to prevent from braking or chipouts. Use a medium to course blade.
A fine tooth hack saw blade is how I’ve done it. Remember to clean the blade a couple times during the cut to prevent binding, which will cause the blade to crack the casting. Here’s a two track tunnel portal I lowered to fit my scenery better. It was reassembled with simple white glue. Wax paper will keep it from sticking to the table.
Thanks. I don’t have a power sander suitable for this so I used a hacksaw with a fine tooth blade. Worked out very well. To finish the cut took a little hand sanding.
Cheers, RustyKen