Screw Wobble

Thread Starter

MrAl

Joined Jun 17, 2014
8,359
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.
 

click_here

Joined Sep 22, 2020
260
For the wood, you'll need to predrill the hole that the screw is going into.

i.e. Line it up, use a clamp, drill a hole (small enough so the thread of the screw still bites the wood when you put it in). Change the drill bit to whatever screw type you have (e.g. phillips head), and then drill in the screw
 

Thread Starter

MrAl

Joined Jun 17, 2014
8,359
For the wood, you'll need to predrill the hole that the screw is going into.

i.e. Line it up, use a clamp, drill a hole (small enough so the thread of the screw still bites the wood when you put it in). Change the drill bit to whatever screw type you have (e.g. phillips head), and then drill in the screw
Well i actually do that, but that only solves the problem when there are a small number of screws to be put in. I put in maybe 8 screws and had no problem predrilling pilot holes for the screws, but people who work in construction often have to put in hundreds of screws to hold sheetrock to walls and ceilings. You cant afford the time it would take to predrill every single hole, and that is not the typical way to do it nor is it what drywall screws were designed for. Drywall screws are designed to not need a pilot hole that is why they are so pointed. The new ones even have a "self tapping" groove we dont usually see in this kind of screw. That helps get the screw in, and i can tell you, they work really well when they dont wobble that is :)

So it is a good idea and i thank you for it and i will be using it for some years to come im sure. However, i would like to solve the key issue also and that is actually mitigating the problem itself without any extra on the job work required. I dont know though, maybe more expensive screws work better i got these off the web maybe that's the whole problem. I was hoping others might know something about this too such as using square drive screws that dont wobble.
 

click_here

Joined Sep 22, 2020
260
The Robertson sockets are not used too much in Australia, they mainly use Phillips or hex. In fact some people say that the invention of the hex socket made the Robertson socket redundant.

If you need lots of torque, then a torx is usually used, but you generally don't want to over tighten a screw or bolt, because you risk stripping or snapping it, or making it impossible to remove at a later date

I had a major extention done on my house and just about everything was done with was a nail gun.
 

AlbertHall

Joined Jun 4, 2014
11,393
Wild idea: Have a tube (could be metal or wood) just large enogh for the head of the screw and long enough so the head of the screw is inside the tube when starting off. Then the tube can hold the screw straight until it has started into the wood. Then you can remove the tube and continue.
 

Thread Starter

MrAl

Joined Jun 17, 2014
8,359
The Robertson sockets are not used too much in Australia, they mainly use Phillips or hex. In fact some people say that the invention of the hex socket made the Robertson socket redundant.

If you need lots of torque, then a torx is usually used, but you generally don't want to over tighten a screw or bolt, because you risk stripping or snapping it, or making it impossible to remove at a later date

I had a major extention done on my house and just about everything was done with was a nail gun.
The square drive must have been used here a lot maybe 5 to 10 years ago because Home Depot had a large stock at that time. Now they have only a few squares and they are actually hybrid square and Phillips.
Maybe what made Phillips invent his famous screw drive was over torque of the other types and he made sure you could not tighten the Phillips head screws too tight.

Yes i use Torx now and maybe go to that exclusively except for the stock of other types i have right now i will use up too at some point.

You use a nail gun for sheetrock too?
 

Thread Starter

MrAl

Joined Jun 17, 2014
8,359
Wild idea: Have a tube (could be metal or wood) just large enogh for the head of the screw and long enough so the head of the screw is inside the tube when starting off. Then the tube can hold the screw straight until it has started into the wood. Then you can remove the tube and continue.
That may help, but when the square drive bit is inserted into the screw head recess hole it is a very tight fit, and so the bit and screw become almost one single piece that work together. When the bit rotates it is very solid inside the screw head so if the hole is not aligned with the screw body it really makes the screw wobble. If you stop the screw from wobbling then the bit wobbles and so the drill motor wobbles.
Once the screw gets into the wood maybe 1/2 inch or so the screw naturally stops wobbling, but that si when the bit and drill motor start to wobble and that's kind of nuts too as the thing shakes.

Now if the square drive bit square point was slightly under size, the screw could stay straight and the bit could stay straight, sort of like a cheap universal drive shaft. I would still have to hold the screw straight though by hand or with your idea of a tube or pipe maybe a clothespin :)
 

shortbus

Joined Sep 30, 2009
8,699
Only engineers would see this as a problem. To people that do this day in and day out there is no problem. Tapering the driver would make it cam out of the screws dive socket, ever tried to drive or remove a Philips head screw with a worn out Philips screw driver?
 

Thread Starter

MrAl

Joined Jun 17, 2014
8,359
Only engineers would see this as a problem. To people that do this day in and day out there is no problem. Tapering the driver would make it cam out of the screws dive socket, ever tried to drive or remove a Philips head screw with a worn out Philips screw driver?
Well i think it is a problem across the board especially for contractors that have to put hundreds of screws in during one day's work. If you ever tried this you would know right away that there is a marked difference in using a good drill, good bit, and good screw. There is no problem putting in a good set, but as soon as one of them wobbles, wow, it makes it much more difficult. The problem is that the pointed end of the screw forms a small circle as it turns and so when you try to start it the point moves around rather than digs in, it's really nuts. If you have quality screws and quality bits and you want to see the effect, just BEND one of the screws and try to put it into a piece of wood like a 2 by 4 piece of lumber. You also have to have a tight fitting drive though too because that takes control away from the user. If there is wiggle room in the bit to head fit, it makes it a little nicer although still not that great.
Also, i wasnt really talking about tapering the bit just grinding it to a smaller size, very slightly. I could see a taper working too although as you said it may start to cam out with higher torque.
Yes i saw brand new Phillips screw bits and drivers cam out and that is because Phillips heads were designed to do that in order to limit the torque on screws. A stupid idea in the modern age where we have better metals being used, hence the trend to not use Phillips heads anymore.
I had designed a new shape Phillips head driver bit that would not cam out but i cant find it now.
There is a somewhat 'new' commercial type of Phillips too now sometimes called "Phillips II" or "Phillips Plus". This bit has tiny ridges on the part of the bit that meets the screw recess walls and supposedly there are screws that are made Phillips II also but i have not seen any yet. The ridges may help with regular Phillips heads too i am going to test that later today.
The Pozi drive Phillips look promising too but i have never seen screws to match those yet either.
For now though i am sold on Torx because i had no problem using those screws, and the 2 inch screws go all the way into a 2 x 4 lumber with no cam out problem.

I just checked one of my square drive bits made by Bosch and wow that one bit was bent too. I never saw a rotating tool that was sold when it was bent. That always causes vibration at the very least. Maybe they figured that slow rotating machinery can put up with an off center bit, but with this application that doesnt work out well at all.
I got five of these for about 3 dollars. My older bits were all cheaper but none of them is bent. The difference is that these have a mostly circular cross section shank while only a short section being hex, while the old ones have a hex shank either the entire length or most of the length.
I estimate the bend of the Bosch bit from one end of the bit to the other is about 30 thousandths of an inch while the good bits are right on maybe less than 5 thousandths. So we are talking maybe 0.030 inch versus 0.005 inch which apparently is significant.

So as i said, to mimic this problem with good screws and bits and drill just bend one of your screws a little, just a little, and then try to put it into a piece of construction lumber. Try it with a non bend screw too and notice the difference when starting as well as when screwing it all the way in. Since i am working with 2 inch screws i would say try this with one that long or longer or at least 1.5 inches long.

I tried another Bosch bit and it is straight. It is funny too that these bits are made for impact tools also so they are supposed to be able to take a beating. The Makita bits are ok.
 

shortbus

Joined Sep 30, 2009
8,699
I learned how to do the screw and drill driver thing from my middle son, he's a journeyman carpenter. If you do things like they do it works out just fine. Your not putting enough pressure on the screw before starting the drill rotation. Most contractors buy the cheapest screws they can find and the guys have to use them.

Exactly how much wobble are you talking about?
 

Thread Starter

MrAl

Joined Jun 17, 2014
8,359
I learned how to do the screw and drill driver thing from my middle son, he's a journeyman carpenter. If you do things like they do it works out just fine. Your not putting enough pressure on the screw before starting the drill rotation. Most contractors buy the cheapest screws they can find and the guys have to use them.

Exactly how much wobble are you talking about?
The amount of wobble is not that much but it does make it harder to put a screw in. Try the test i proposed.

One bit i have is bent and it's only bent a little but why would a rotating tool be bent like that. It's a bad bit. I checked another bit from the same lot and it is not bent and so works better.

You'd have to ask him about the wobble if he ever experienced it. But really you have to try it yourself dont rely too much on what someone else tells you they may not have the same thing going on.

And as a little update, i tried the 'ribbed' Phillips head bit and it works much better than a regular Phillips bit even on regular Phillips head screws. I drove a 2 inch screw into a 2 by 3 lumber all the way in with one shot and no cam out. The ribs seem to help a lot.
The names of these bits are one of many:
Phillips II
Phillips Plus
ACR Phillips (Anti Cam Ribs Phillips)
ACO Phillips (Anti Cam Out Phillips)
I will be using this bit type for Phillips screws from here on out never going back to the old ones.

Also, all of these screws can be very hard to remove if they are long. I was thinking of trying some freeze spray on the head just before using the power drill and bit. The cold should contract the metal making the body of the screw slightly more narrow. Phillips can be hard to remove because the heads get rounded on the inside corners and so the bit slips a lot.
 

shortbus

Joined Sep 30, 2009
8,699
I'll share something about Philips screws. One of the places I worked molded and assembled plastic parts for cars. The parts were held together with small Philips head screws, and used air powered drivers. The driver bits were getting replaced a few times per shift because of problems of them not working good or going bad, so we thought. The engineering department called in somebody from the company selling both the bits and screws.
The tech came and told us to take the bits and grind about 1/64"(0.015") off of the point of the bit. And after doing that the bits would last 3 or 4 days without replacement, running 3 shifts a day.

Seems that while the bits have to be made to a tolerance the screw slots don't. The bits were bottoming out in the internal point of the screw, and not letting the "fins" of the driver bit do the work. After learning this when ever I have to buy a new Philips screw drive that is the first thing I do grind a small amount of the point off. Doing that I end up losing/misplacing a driver before they wear out or start slipping out of the recess..
 
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