posidrive screw & bit combination burring out

[Ouch77]

Here's the slightly chewed up dewalt driver bit, used from new, and has done about 175 or so of these 150mm screws. You can see how the flanks have worn, mainly on the drive side, but also on the reverse as I've had to wind out a few screws that had hit some excessively tough timber (knots mostly).

 

[Ouch77]

Here's an almost fresh one, probably done less than a dozen screws, but under similar circumstances.

 

[Ouch77]

Here's a comparison with a cheap one from screwfix I picked up this evening. I've tried to align the tip of the screw head and you can see the end of the angled section on the flutes is a fraction higher. Interestingly I tried rsgaz's suggestion and the new, cheap driver bits will hold the 6" screw almost horizontal, and have almost no backlash, whereas even the 'almost fresh' dewalt bit won't hold it, and has a bit of slop in the head.

Given these newer 'cheapo' bits are fresh, it will be interesting to see how well they drive - didn't have a chance to test it tonight as the kids are in bed (all this shenanigans is in the loft).

 

[rsgaz]

Interestingly I tried rsgaz's suggestion and the new, cheap driver bits will hold the 6" screw almost horizontal,

I actually meant the other way round, good quality screws with a good quality bit, the screw can hold up a (small) drill...

In that last photo, the 'fins' almost look a different width. Very strange from, you'd hope, a good manufacturer like Dewalt.

 

[Notch7]

drilling at 5mm pilot, but my drill bit is only long enough to get 2/3 the way through the top timber.

If you arent all the way through, that will stop your timber pulling up tight.

A 6mm bit is needed unless no threaded portion is in first timber

 

[Ouch77]

If you arent all the way through, that will stop your timber pulling up tight.

A 6mm bit is needed unless no threaded portion is in first timber

I did consider that, however the amount of force (measured just now about 50kg) I'm putting on the driver, and the fact that the unthreaded shank is long enough to pass through the top timber means there's no gap between the two when (if) finally tightened.