BR class 2. Frame steel

I'm looking to start building a 5" gauge BR Class 2 tender engine.

What steel would you use for the frames.

1/8th EN 32B BMS or 3mm Black mild steel

Whatever else you do, dont use bms.....its been covered on here recently but it will bend like a banana when you cut it - I know as it happened to mine!

I have noticed the likes on laser cut parts use CR4 steel, does that bend when machining the Horns etc ?

I wouldn't use black ms on account of the difficulty of cleaning off the scale prior to painting.

EN 32B is described as case hardening material, which I'd not expect to use for frames.

I've used the sheared plate ms, as supplied by Reeves etc etc.with no problems. I think its in an annealed condition after rolling, maybe CR4. Get it over the required width and cut material from both long edges to bring it to width, otherwise the stresses in the sheared edges could cause distortion.

I would use CR4 sheet, probably 3mm. It is in the normalised condition so won't distort whatever cutouts you put in it.

If it is guillotined you will need to cut at least 1/16 of each side to get rid of the distorted edge from the guillotine.

You could buy laser cut frames from Model Engineers laser and save a lot of effort, they use CR4.

Michael

I used laser-cut black mild steel for my loco and by the time it's been drilled, milled, tapped, filed, blued, scribed, wire-brushed, scratched, sanded and otherwise mishandled during the marking-out and fitting of all the necessary bits and pieces there's not a great deal of mill scale left. What there was left i did not bother cleaning off and have had no problems with paint adhesion. I gave it a light rub over first with some fine wet&dry paper followed by a clean dry brush in all the nooks and crannies a clean rag over the rest, and used a good quality primer (Killrust in a spray can).

I've made 3 sets of frames from black mild steel. Takes paint OK, but I did get one set bead blasted mainly because I could get it doe for free. Laser cutting saves a lot of work, but if you have to do any filing to get exact size whizz across with an angle grinder first, the finish from laser cutrting destroys files. Before painting I dipped them in caustic soda, don't do this wth brass bits!

Many thanks for the views. Looks likes CR4 is the way to go.

Use hot rolled steel, don't worry about the mill scale, do you think structural steel in industry has the scale removed before painting? The paint sticks ok out side in all weather, on bridges, buildings, machinery. On the latter we use an etch primer as on this bale feeder used for feeding out bales of hay to sheep, cattle, and deer.

Ian S C