Starting from flat plate stock 3/8" thick, and a range of 12" to 24" diameter circle, how best to form an auger, or helicoidal surface with fixed pitch?
The plate stock could be plasma cut to circular shape, then a center hole could be punched to 4" diameter to act as a strain relief.
A radial cut could then be added from I.D. to O.D. allowing the plate to be formed in the shape of an auger.
The question now is how to form the plate into a helix. The shape would be much like a lock washer, but thicker and much wider...
If anyone can offer experience regarding a type of rolling machinery that forms these shapes, or a simpler way to form the sheet, it would be nice to read...
Unless you want to go into the business of making auger flight full time, just buy what you need from Replacement Flight Supply and save yourself a pile of grief.
Its called flighting and you can buy it in sections and weld it onto a hollow shaft or solid shaft. Unless you are going into the mfg. business I would recommend buying it already rolled.
How much of a helix you need will depend on the type of soil? or whatever you plan to auger with it and who is doing the augering. Ive used a farm tractor mounted/driven auger 12in dia and that takes some horse power just turning it into reasonably soft clayey ground.
Also a hand held engine driven ditto up to 4in. this can be an arm breaker when it hits a rock.Let alone lifting it out loaded with soil. to clear the hole. Despite all of that, if I had to improvise what your after, assuming youve had the plate cut as described, the minimum tooling youd need will be Some log splitting wedges, a sledge hammer an oxy propane cutting torch with all associated reguators tanks etc. a big leg(read smiths) or engineers vice, some crowbars big adjstable wrenches. And an angle grinder One you have all this, clamp the plate in the vice, radial cut horizontal drive into the slit a splitting wedge vertically downwards. Put into the opened slit a crowbar and twist to seperate the slit into a helix form. Get some strong person to hold it in that position while you heat up the sides of the slit so there bent either back or forward depending wether you want to auger to cut clockwise or anticlockwise. Depending on its proposed use, open up the slit to whatever gap you think you can manage. 2in will be enough Grind the downward cutting edge sharp like a wood chisel.
you may want to bend this cutting edge down some more. Heat some 2 in back from this edge, and use the wrenches set to 3/8ths to bend the steel along the heated line. then of course youve to find somecentral shaft to which youll weld this disk. 4in is too big. 2in is enough. On the bottom of this shaft youll need a point and maybe a smaller helix so it screwsinto the ground like a wood auger. Well need a lot more info as to its use to refine these general ideas into a working auger. The only folk ive seen using a 24in auger are the soft ground piling teams. there driven by 200hp hyd motors. How do you plan to turn it to work? not by hand ? surely?
You are bang on! Soft ground pilings is indeed the application. There is a company that drives pilings. Only issue is that they advocate plain carbon steel with electrical corrosion protection. As with most companies, prices tend to go crazy at the mention of ss or refuse to do it, mostly because they don't know how to weld it, as well as availability, working effort...
The end application is for a waterfront property built way back when laws allowed greater proximity to river. Hard packed clay is main constituent of the soil, and as you might imagine can be saturated with water owing to proximity to waterline.
As you might imagine, corrosion is an issue. Confidence in electrical corrosion protection is not 100%. Have seen a lot of steel stuff vanish over the years especially with anything below the waterline.
Considering effort and investment in making pilings. Realize that having them made is the way to go, as always. Since only one, or a few sections are ever used for each piling, there is temptation. Also have the welding gear and weld ss.
It did sound as though making a custom jig would be the most feasable option, short of obtaining the rolling machinery. The alternative would be to find a shop that has the rolling or forming machinery.
From the sound of the DIY solution, most likely would be in the form of using a hydraulic cylinder temporarily welded or bolted to the plate to force the bend, in combination with propane/oxygen heating (cheap, clean). Pitch control would not be great. Since it's for a piling, this is not critical.
Flighting, thank you for the information! Will look into obtaining pre-formed, or finding a shop with proper rolling. DIY is last resort.
Thank you again for sharing your experiences and advice, it is appreciated!
Well~!! its amazing how one can get it wrong for the lack of enough information. How deep do you think youll need to go? Now here in the UK for piling we use the auger to drill a hole then put in the reinforcement and fill with runny concrete vibrated in to ground level. you are planning I assume, to screw a long auger into the ground and use that as a piling. Now Id do it a much simpler way . Id make up a rig to run a drop/piling hammer on top of a greenhart pile. the size of this will depend on the weight your planning to support, how many piles etc. they have a square point on them which is of cast iron. you drive them into the ground till they wont go any further then cutoff where you plan to put the cross beams. the drop hammer is usually about 400lbs. youll need to be careful using ss. Sailboats that use ss bolts to fix the cast iron or lead keel do have serious corrosion problems with the ss. Because its out of the air, in an oxygen lean environment. Many sail boats have lost their keels through using ss bolts. they have to be bronze or kunifer 10, a anti sea water corrosion alloy. I use it myself .
Screw pilings that I have seen were little more than a steel pipe with a couple turns of very heavy flighting on the bottom end. Serious horsepower to drive them into the ground, too.
Not much in common with auger flighting other than the helix shape.
Try talking to other pilings companies. Talk to companies that will come to your area, not just the comany that is local. You will at least be able to get a building inspection signed off that way. Bets are that no matter how good you build it, your solution will not please any of the many people that will have to be pleased in order to inhabit, finance, insure, or sell a building like that.
If you want longevity, drive steel pipe for the pilings and have rebar frames and the proper grade of concrete poured inside. But get it done by someone that will enable it to be signed off, otherwise you are holding the bag on a white elephant.
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