Sounds pretty strange right? Right, and that is because it is strange and very annoying and troublesome.
The problem with some of the somewhat newer drive heads and bits used to put in screws of may types (like square, star, etc.) is that sometimes the precision just isnt there and this causes the screw to wobble as it is being driven into some material like wood or steel. What happens is that when the drive bit is inserted into the screw head it can fit very snug indicating that the maker(s) got the size of the bit and screw recess right. The only problem is, that's not the only specification needed to make a good screw and bit. If the bit fits sung, and it should and that in itself is good, then the axis of rotation of both the recess hole and the screw (or bolt) body must also be along that same rotation axis, other wise the tip of the screw wobbles.
Believe me, if this were not that significant i would not even bring this up, but it makes putting a screw into something a lot harder to get right. Not only is it strange to get it started in say wood, but also once it gets started it still causes wobble and that makes the drill drive motor shake back and forth. It is quite significant, probably depending on the quality of the screw.
I tried several types of screws with different drive heads and several bits and several drill motors. What seems to be happening is as above, if the bit fits snug then the screw head hole and body must rotate along nearly the same axis. If the two axis are not the same then the screw wobbles. Interestingly, if the bit does not fit snug then there is some wiggle room so you can hold the screw straight while driving it in and that works ok i guess. The best would be more close alignment though.
So, it looks like the remedy might be to grind the bit itself ever so slightly so that it does not fit snug in the head of the screw and thus giving it some wiggle room. This would be especially for a square head drive where we could very slightly grind each side of the square head thus making the square head ever so slightly smaller than the recess in the head of the screw.
If anyone else experienced this it would be good to hear about, but be aware that screw wobble can also be caused by many other factors like a bent bit, bad chuck, even bent screw, etc. For my tests i made sure it could be nothing else other than the head and body axis alignment, at least in my case, and the worst cases where with square drive screws. I have to wonder if this is why many contractors went to star drive screws instead of square when they used to favor square drive.
The problem with some of the somewhat newer drive heads and bits used to put in screws of may types (like square, star, etc.) is that sometimes the precision just isnt there and this causes the screw to wobble as it is being driven into some material like wood or steel. What happens is that when the drive bit is inserted into the screw head it can fit very snug indicating that the maker(s) got the size of the bit and screw recess right. The only problem is, that's not the only specification needed to make a good screw and bit. If the bit fits sung, and it should and that in itself is good, then the axis of rotation of both the recess hole and the screw (or bolt) body must also be along that same rotation axis, other wise the tip of the screw wobbles.
Believe me, if this were not that significant i would not even bring this up, but it makes putting a screw into something a lot harder to get right. Not only is it strange to get it started in say wood, but also once it gets started it still causes wobble and that makes the drill drive motor shake back and forth. It is quite significant, probably depending on the quality of the screw.
I tried several types of screws with different drive heads and several bits and several drill motors. What seems to be happening is as above, if the bit fits snug then the screw head hole and body must rotate along nearly the same axis. If the two axis are not the same then the screw wobbles. Interestingly, if the bit does not fit snug then there is some wiggle room so you can hold the screw straight while driving it in and that works ok i guess. The best would be more close alignment though.
So, it looks like the remedy might be to grind the bit itself ever so slightly so that it does not fit snug in the head of the screw and thus giving it some wiggle room. This would be especially for a square head drive where we could very slightly grind each side of the square head thus making the square head ever so slightly smaller than the recess in the head of the screw.
If anyone else experienced this it would be good to hear about, but be aware that screw wobble can also be caused by many other factors like a bent bit, bad chuck, even bent screw, etc. For my tests i made sure it could be nothing else other than the head and body axis alignment, at least in my case, and the worst cases where with square drive screws. I have to wonder if this is why many contractors went to star drive screws instead of square when they used to favor square drive.