Making Half-Round Channel -- Report #1

In lieu of a blog, I'll report here on the progress in making the half-round channel I need to represent the round variety of HO-scale rain gutters ---
square gutters are pretty much already done with C-channel in both styrene and brass from various suppliers.
My first try was to use the Dremel in a "router table" stand with a .040" diameter round cutter to create a semi-circular groove in a solid nylon block. I then used .003" thick shim brass stock and a .045" diameter brass rod to press the sheet into the groove and form a somewhat rounded crease. Removing the brass from this "die", I then manually wrapped it half-way around the rod and formed a U-shaped piece. The curvature at the bottom is perfect, but the sides are way too long. The best I could do on the first try was to cut the sides down with precision scissors but getting a clean cut all the way along the 4" length of this sample was very difficult.
Conclusion #1: I need a deeper groove. A simple semi-circular trench isn't sufficient and I need more of a U-shaped groove than a simple half-round. If I can do this, I may be able to clamp the brass under the rod in the channel and then bend the sides over to form a good crease for cutting. I'll try to do this today if I can find the appropriate cutter burr.
Norm
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Make more passes on your table going deeper each time until you get the depth you want. Try instead of creasing the brass file even with the top of your groove.
Norm Dresner wrote:

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Norm Dresner spake thus:

This has probably already occurred to you, but instead of taking it out of the jig, how about cutting the sheet on both sides while it's held down by the rod? Would be tricky, but could work. You'd have to hold the rod down somehow with one hand and cut with the other.
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Norm and all. I just attempted to make some gutters using clear plastic sheet from a box that had a display window. I wrapped it around a dowel rod tightly and used a hair dryer to heat it up a little. Then I clamped it tightly on a wire rod using a straight edge on both sides to hold it tight. More heat then cut. The clear piece appeared kind of funny but a shot of paint took care of that. The end result was a very thin but sturdy little U shaped gutter piece roughly 6" wide in HO that looks great. Using a smaller wire rod I see no reason why the shape could not be made to scale out around 4". Painless instant gutters! Thank you Steve! If you had not mentioned hair dryers I would have never thought to try this and would have still been making paper & epoxy gutters. Bruce

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REPORT #1 | In lieu of a blog, I'll report here on the progress in making the half-round | channel I need to represent the round variety of HO-scale rain gutters --- | square gutters are pretty much already done with C-channel in both styrene | and brass from various suppliers. | | My first try was to use the Dremel in a "router table" stand with a .040" | diameter round cutter to create a semi-circular groove in a solid nylon | block. I then used .003" thick shim brass stock and a .045" diameter brass | rod to press the sheet into the groove and form a somewhat rounded crease. | Removing the brass from this "die", I then manually wrapped it half-way | around the rod and formed a U-shaped piece. The curvature at the bottom is | perfect, but the sides are way too long. The best I could do on the first | try was to cut the sides down with precision scissors but getting a clean | cut all the way along the 4" length of this sample was very difficult. | | Conclusion #1: I need a deeper groove. A simple semi-circular trench isn't | sufficient and I need more of a U-shaped groove than a simple half-round. | If I can do this, I may be able to clamp the brass under the rod in the | channel and then bend the sides over to form a good crease for cutting. | I'll try to do this today if I can find the appropriate cutter burr.
==================================================REPORT #2 I got the Dremel mounted to the router table and then routed a channel .045" diameter and equally deep. Using a .045" steel wire as a die, I hammered .002" brass (shim) stock into the groove and while it's still in the groove I run over it with a heavy straight edge to flatten out the wings. Once it's taken out of the groove and turned over (cupped-side up), it's "easy" to run an Xacto knife with a sharp #11 blade along a straight edge and cut the wings away, leaving the channel. In the future I'll probably leave a little of the wing to accommodate mounting the channel as a gutter, but it's a pretty good C-shape around .055" across.
For the next experiment, I'll try some very thin styrene and see if this is any easier to work with (it'll certainly be easier to cut).
Norm
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