Bolt hobbing discovery

Hey, all! I've bought a couple of hobbed bolts online and wasn't satisfied with either of them (one was not really hobbed, but simply splined). My attempts to "fix" them got indifferent results my "hob jobs" were rather uneven, as I was using 6mm 3 and 4 flute taps in my benchtop mill, running at slow speed, and every time a flute in the tap would come around I'd end up with a gouge in the groove that made for somewhat uneven feeding. I was digging through my toolbox at work the other day, and ran across some miscellaneous taps I have accumulated over the years (most had been broken off but had enough thread left to make me consider regrinding the tips for chasing out other threads). One tap was an SAE 10-32 spiral flute tap, which is very close to a 5mm tap. I looked at the spiral flutes and had an "AHA!" moment. Tried it out, and got BEAUTIFUL hobbing! The spiral design of the flutes, intended for rapid chip evacuation from blind or deep holes, means there is no real "gap" to cause a gouge.

10-32 spiral flute tap (MSC catalog image)

Could you show us how the hobbed bolt looks like then?

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http://www.marinusdebeer.nl/

Less than 10 bucks on ebay

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-David

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Ohmarinus
Could you show us how the hobbed bolt looks like then?

Have to wait a while - it's currently installed in my Mendel90, printing up a Yoda neckerchief slide in glow-in-the-dark green ABS for my Cub Scout son...

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MindRealm
Less than 10 bucks on ebay

Both of my previous hobbed bolts came from EBay, and as I said I was less than satisfied with either of them.