Hex power bits with necked down shaft - Why?

[308guru]

I’ve long wondered what the reason was for some manufacturers necking down the shaft of hex power bits. I find it very annoying for some reason, likely because I don’t know why it is done. There must be a reason as it’s costing them money in machining to make chips out of that material. Other (reputable) brands leave it full diameter or full hex all the way to the business end. It doesn't seem to be related to bit size as you can find examples of each in all of the sizes.

Any ideas?

 

[The Cobbler]

I'm not sure, it seems to be a trend . I just bought some cheapos ( that actually work really well & seem to hold up) that were like that.

 

[CallumRD1]

It actually serves a purpose. It's to allow the bit to twist up slightly under impacting, spreading the force out over time. This reduces the shock to the screw, makes it less likely to snap, and extends the lifespan of the bit. It works just like a torque stick on an impact wrench. The big difference is that driving a screw takes a tiny amount of torque but benefits from spreading that torque out over time as it's a soft joint.

Edit: this only applies to impact bits, which is why you won't see it on bits targeted at constant-torque driving applications like screwdrivers, drills, electric screwdrivers, etc.

 

[WhataTool]

It actually serves a purpose. It's to allow the bit to twist up slightly under impacting, spreading the force out over time. This reduces the shock to the screw, makes it less likely to snap, and extends the lifespan of the bit. It works just like a torque stick on an impact wrench. The big difference is that driving a screw takes a tiny amount of torque but benefits from spreading that torque out over time as it's a soft joint.

Edit: this only applies to impact bits, which is why you won't see it on bits targeted at constant-torque driving applications like screwdrivers, drills, electric screwdrivers, etc.

Rarely do I see such an accurate and complete answer this early in a thread. Pack it in boys, just discussion for the sake of discussion below this

 

[KnurledNut]

Power tool companies are constantly in competition to make the most powerful impact driver and have exceeded the useful limitations of 1/4” hex. The necked down torsion zone of impact rated bits limits torque transfer and keeps them from snapping.

 

[SweetD]

I've had great luck with Milwaukee impacts like pictured above. Homeowner/DIY use. Have lasted me many years now. As a matter of fact I just screwed in some Tapcons this afternoon into our foundation using the 1/4" Milwaukee T-25. Worked great. Obviously pre-drilled with correct masonry bit and hammer drill.

 

[WildBill]

Rarely do I see such an accurate and complete answer this early in a thread. Pack it in boys, just discussion for the sake of discussion below this

Yeah, that was weird. Nobody even asked for pictures of what he was using them on or told him to buy something unrelated and expensive.

 

[Hannahranga]

On the excessive power of 1/4" impacts I'll also add that a bit snapping at the base that's stuck in the tool sounds like it'd absolutely **** to remove, much better to snap at the head

 

[tiredoldironworker]

Well said Hannaranga!

 

[308guru]

On the excessive power of 1/4" impacts I'll also add that a bit snapping at the base that's stuck in the tool sounds like it'd absolutely **** to remove, much better to snap at the head

Why would it snap at the "base" or behind the scalloped area (for the ball detent to retain the bit)? It's a fully supported hex all the way out the end of the anvil, it's not driven by just a portion of the bit inside.

 

[niget2002]

On the excessive power of 1/4" impacts I'll also add that a bit snapping at the base that's stuck in the tool sounds like it'd absolutely **** to remove, much better to snap at the head

Not an issue on my DeWalt driver. I've done it. Just pull the little release collar and hold it 'bit side' down and the base fell out.

 

[CallumRD1]

Not an issue on my DeWalt driver. I've done it. Just pull the little release collar and hold it 'bit side' down and the base fell out.

It's usually not an issue, but I had a bit snap at the base in a DeWalt impact driver and in the process, wedge the base into the hex so it couldn't fall out. I had to disassemble the bit retention system to get it out. It was a very unpleasant 15 minutes working without proper tools. (I was working on-site and didn't have access to any of the tools that would have made it easier.)

 

[AEAdam]

I bought those in great quantities and was worried. They act like a torque stick and lessen the torque delivered by the tool. Blah blah blah, I really like them. Mine have lasted a really long time (months). Even the Phillips are good. I burned thru DeWalt Phillips like no tomorrow. Switched to Apex. Now Milwaukee. They are good. I like the long ones a lot. If I have room, I prefer those. Mine might be 3" long.