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dav-1

drilling spring steel

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dav-1

i finally got my hands on an original spring tooth harrow. it arrived last week and has already been run thru my veggie patch. it is missing one spring; it has 6 instead of 7. i doubt i will ever find an original spring so i am modifying a spring from an old farmall harrow. i took the plow off a simplicity tool shank which uses a 3/8 carriage bolt. the farmall spring is made with a 5/16 square hole. i want to drill this hole to 3/8. can i do this or is spring steel some kind of funky hardened can't be drilled without breaking all the bits steel?

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steve-wis

You can drill spring steel.  Drilling a square hole out makes it alot harder tho.  First, make sure you have a good drill bit, not a cheap throw-away one.  Then, resharpen it if you are able to do that.  The point on a regular drill is 118 degreees.  You will want to "flatten out" the point for harder steel, not all the way flat but to 135 degrees to 142 degrees.  Then, run the drill very slowly and feed it hard enough to keep it drilling.  Use a good quality cutting oil on the drill if you have it, if not at least put something on it to help lube it and keep it cooler.  If the drill gets dull, stop right away and resharpen it.  If you let it rub it will "work harden" the steel and make it about impossible to drill.  

Good luck!

Steve

 

 

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Edited by steve-wis
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kwt
4 hours ago, steve-wis said:

Then, run the drill very slowly and feed it hard enough to keep it drilling.

And this is why I occasionally miss having a good drill press and accessories.

 

In my situation I would carefully enlarge the holes with an oxy/ace torch.

Edited by kwt

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kwt
9 hours ago, dav-1 said:

i thought that using the torch would destroy the springiness of the metal. am i wrong?

It would. In the localized area annealed.

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kwt
15 hours ago, dav-1 said:

shank which uses a 3/8 carriage bolt. the farmall spring is made with a 5/16 square hole.

Are you looking to make a square hole larger? A little patience with a sharp triangular file could accomplish that task.

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RAC

5/16 up to 3/8 square? Use a 1/8 carbide tile cutting burr in your Dremel or rotozip.

You could always just use the 5/16 bolt and a thin sleeve spacer in the 3/8 round part of the hole.......

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dav-1

i want to use the carriage bolt on the shank side. since the donner has 4 springs, i think i'll just try the torch on the first one. if it works right, that'll be the end of it. meanwhile, i plan to contact a local spring shop to see if they can make replacements and at what price.

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kwt
11 hours ago, 720nut said:

I'd put it in my mill and use good carbide endmill

My father was a machinist. I'm not. My knowledge comes from him and is obviously second hand. Perhaps my understanding of a mill is lacking, as I don't understand how you can create a square hole with a rotating tool. Perhaps you are talking about square enough with a small diameter tool. Please enlighten me.

 

When I think of square holes as part of a manufacturing process, I think presses and a broach or an EDM.

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steve-wis

In the original post he said he wanted to (drill) the holes bigger, so I assumed he wanted to go to a round hole.  Got me thinking now tho also.  If going to a 3/8 square, he would only be romoving .031" from each face of the square.  I would think a couple of good files would do it with some patience.  A die grinder and carbide burr will not cut a square corner, nor will any rotating tool.  And, you would have to be better with a torch than I am to do it that way and have it be anywhere near right size.  GMHOsm01

Steve

 

 

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