how to straighten drill rod?

j ferguson

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I have a 36 inch length of .375 drill rod. It looks wonderful but has a bit of wow in it. I need a 12 inch length which I would like to be as straight as possible maybe to a couple of tenths. I would lke to hold one end in a collet and use it top align other parts of my equipment. Obviously if I know the eccentricity I could add/subtract it from my readings to arrive at the number I'm looking for in the setup, but...

My thought was that it would probably be better to straighten the entire lengh, then cut the best 12 inches out of it. I'm assuming that the bow (wow) is spread over the length but I'm going to set it up and indicate the length to see if this is true.

My plan if the bow is even over the length is to set it up in wood blocks on each end, and whack it with a mallet until it is straighter. Is this a good idea, or is there some other scheme that might work better. I could also use a clamp with a bar to more evenly distribute the force to squeeze the high side down.

I don't have a press.

How would you do this?
 
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I would buy a linear bearing rod that has specified straightness. Then you KNOW what you are getting, rather than trying to get close. They don't cost much and are precision ground.
 
My thought was that it would probably be better to straighten the entire length, then cut the best 12 inches out of it.

I've never had to straighten bar stock before chucking it in the lathe, but doubt you will ever get it straight/accurate enough for what you want to do just by whacking it with a mallet.

Most drill rod (or any bar stock, for that matter) I've purchased isn't 100% perfectly uniform along its whole length either...close, but not perfect.

ttabbal's idea would be the best route IMO, but if you wanted to try a home-brewed solution I would start with say .500" rod (does it have to be drill rod?) x 13"-14" long (supported in TS, obviously) & with a follow rest turn down a 12" section to 7/16" or 3/8" (whatever size collet you want to use). Part it off at your desired length & voila....one (relatively) straight bar with no "wow" in it. Won't be quite as good as a precision-ground rod I admit, but *should* be sufficient.
 
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Look at the methods and tools to straighten aluminum arrows.
 
I would lke to hold one end in a collet and use it top align other parts of my equipment.

Drill rod is ground to a consistent diameter (mostly) but is not straight, especially over a 3' length. If you are using it to align things with then you are better off getting some linear shafting as @ttabbal said. Even with a hydraulic press and v-blocks it is a challenge to get such a rod to run out under 0.001", let alone into the tenths.
 
The linear tracking rods in printers and copiers are an odd size. I removed one recently and it looks very well made, ground, polished and very straight, but an odd diameter. Looks like stainless steel. Thomson linear shafts are OK, straight to .001" per linear foot, if you want something fairly accurate. Not expensive.
 
Just took apart a printer that my wife was going to toss. I've collected a fair # of these rods and other components. Not sure exactly what I'll use them for, but too nice to throw out. The largest out of this one is 5/16"x10", very straight, and appears to be a high grade stainless. Makes me wonder how large the ones in a large commercial printer are. I've seen several for free on craig's list. May have to break one down and see. If you've ever taken one of these apart, It's mind boggeling how many gears, drivers, linkages, mechanisms, motors, electronics, laser, multi function etc, are in one of these things. The engineering is pretty impressive. That they can make this for $200 is equally amazing. I know, volume, volume, turn up the volume. Keep it 3-5 years, and in the dumpster, because it cost more to fix it than buy a new one. Pretty poor use of resources, but, hey, it's all about the profit right. I know it's totally Nieves, but wouldn't it be nice if company's and the human race in general would do more of the "right" thing, and a little less of the "profit at all cost" thing. Oh-ohh, rambling again, must be time for a beer. Cheers, Mike
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Hi guys,
it thought that witjh the v-blocks straightening the 36 inch length as best I can and then cutting the best foot out of it would work out. I see a lot of ads for linear positioning rod on the net but no straightness specs. It could be that I haven't happened on the exact name for what I want.
 
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