Model Railroading > Need some metal cutting advice

OK, total metalworking ignoramus needs help.

I'm working on an HO diorama that will include a soil boring rig--one of those big auger drills that's used for collecting engineering and environmental samples.  I recently discovered that ordinary sheet rock screws, with the drive heads and tips removed, are a dead ringer for the 5-foot sections of auger that's typically used by these rigs.

But sheet rock screws are really, really hard steel.  I need to make nice neat cuts, top and bottom, on about 10 screws. 

Available tools include a drill press, a couple of variable speed Dremels (both hand held motor tools and flex drive versions).  So far, the experience with Dremel grindwheels has not been very good.  Bolt cutters don't leave a nice square end behind.

Any ideas?

Bolt cutters then grind the end flat?

I'm not sure the purpose of depicting a drill rig for in your diorama. but the type of auger you're describing is useful for digging a hole, and nothing else. Both engineering and environmental samples require intact soil structure - particularly the former to assess soil characteristics for geotechnical purposes. Environmental samples would also need such information to evaluate sub-surface contaminant transport and concentrations at specific depth intervals. There are a number of different drilling methods used for geotechnical and environmental assessments, but all share the ability to collect an intact "core." If you use a big screw auger, all you get is a pile of dirt.

Elizabeth

The objective is to depict an environmental investigation at an abandoned industrial site.  I'm familiar with the drilling technology, having logged upwards of a thousand soil broeholes in my earlier career.. 

The augers used in soil sampling are "hollow-stem augers", made up of pipe segments with auger  flights welded in a spiral around the outside..  The split-spoon sampler is inserted through the middle of the flight of augers and advanced ahead of the lead auger to take a sample of the soil at depth that hasn't been chewed up yet.  It's pretty much the industry standard for collecting soil samples at depth.

The hollow stem part of this process is too fine a detail to depict in HO, so using screws is an acceptable approximation.  But any soil boring rig that is at work will have a stack of 5 foot auger sections sitting around the work site.  Clean ones waiting to go in, or dirty ones ready for decontamiation when the hole is done.

I'm sure we have a resident geotechnical engineer that could explain this better but here goes: on a recent project I was able to observe the firm we hired for soil borings doing the actual drilling. For the particular site, it was a two step process using an auger and a split spoon sampler. The auger drills and removes spoil for 4-5' and then is raised from the hole. The tube with the split spoon device is then lowered to the bottom of the hole. It then hammered with with a know weight falling from a set distance both of which are recorded. The tube is lifted from the hole and the split portion opened up. Soil samples are taken from the split spoon section and sent for testing. The operation is repeated until the hole is drilled to the depth desired. It's an interesting and time consuming process to obtain the samples. In the Chicago area, we often need to go all the way to bedrock which can be 80+ feet below the surface.

Looks like we have another expert :^)



Edited 1 time(s). Last edit at 07/24/17 09:37 by kevink.

The Dremel will work perfectly for cutting screws. The tool needed is the cutoff wheel, not the grinding wheel. Once you see the cutoff wheel zip through metal, you will find a thousand uses for it around the house and garage. Get the reinforced kind, they are not so brittle as the thinner ones.

This will last you a long time and will cut through your "auger".

Rick

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Oooh, hadn't seen a Dremel diamond wheel.  Gotta get me a couple of those; hopefully they don't disintegrate like the cutoff wheels I've tried so far.  (Yes, I use eye protection!)

The other thing you could try is using a propane torch to anneal the screw (heating it up to almost a dull red then letting it cool very slowly). I've used that trick before to get hardened metal to bend and I'm thinking it will to make the screw soft enough to cut.

best regards,
Mark G.
NVN #40



Edited 1 time(s). Last edit at 07/24/17 12:26 by MarkG.

Make sure you wear safety goggles if you use the diamond wheel or any other cutting wheel.

I'd say clamp em down somehow and use a hack saw...dress the ends with a file. Done.

Edit: or just drive them into scrap lumber. Then back them out with some pliers once cut. Probably less hazardous than Dremel parts flying all about.


Dave

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Edited 1 time(s). Last edit at 07/25/17 10:04 by Setandcentered.

You can't cut hardened steel with a hacksaw unless it might have carbide teeth. The reinforced Dremel cutoff wheel will work just fine.

Good point...better go out and get a BOSCH® angle grinder and some cutoff wheels.

Dave



Frisco1522 Wrote:
-------------------------------------------------------
> You can't cut hardened steel with a hacksaw unless
> it might have carbide teeth. The reinforced
> Dremel cutoff wheel will work just fine.

Posted from Android

Thanks for the suggestions, all. I will be ordering the diamond wheel and will let folks know how that goes. 

BTW, even a premium hacksaw blade is utterly ineffective on these guys. 

Post some pictures when you can. It sounds like it will be an interesting scene once it's all done!

Dave

Posted from Android