Thanks. So are you saying there's an intermediate pozi bit in between the screwdriver bit and the screw, then? And it works with any size screw?
David
Yes. The bit holder comes without any bit at all. You put a standard 25mm Pozi bit into the hole & it locks in. The only part of the bit that protrudes is the pointy bit at the end. IYSWIM.
That goes into the recess of the screw & the black/blue section slides forwards to contact the flat part of the screw head. All done by magnets.
I've only tried 4mm Pozi screws about 35mm long max, but it should work with most.
The upshot is that it works a treat.
Well my "12v drill driver" provides more than 50Nm torque and it's a year or two old now so I suspect newer ones are better.
... and torque has nothing whatsoever to do with speed of driving screws.
50Nm? What make is it?
It doesn't? I'd like to hear the science behind that claim.
The message from "The Medway Handyman" contains these words:
I did wonder myself last night but decided to wait until morning before doing anything about it.
ISTM that Chris has fallen into a pedant trap. He appreciates the difference between force and work but overlooks the obvious - that force is an essential part of the work done in driving a screw.
I guess he was saying that if torque us adequate to turn the screw without labouring the drill, then the speed is dictated by the gear ratio and motor speed.
For example; the Makita 3 speed drills can produce prodigious torque in low gear, but at a max speed of 300 rpm. If you are sticking in dry lining screws and you don't need much torque, then using the top gear makes the whole exercise much faster even though it offers less maximum torque.
It's a Metabo.
Torque is the 'strength' of turning effect, nothing to do with the speed at which the driver can turn a screw. (Except to the extent that it must have sufficient torque to be able to turn the screw)
Your car produces lots of torque at the back wheels when it's in first gear but it can't go very fast, to go fast you have to change up into fourth or fifth gear where there is much less torque but more speed.
So a screwdriver *could* be geared down to produce almost any amount of torque you want but might only then go round at (say) 1 rpm which wouldn't drive your screws very fast.
Thats quoted as 22Nm 'soft' & 50Nm 'hard' torque - whats the difference?
But shirley the more torque it has in the first place, the higher the speed it can drive the same size screw? This is certainly the case in practice.
I have 3 Makita screwdrivers & 1 Makita inpact driver. 7.2v, 12v, 14.4v and a 12v impact driver. The torque qouted is 17, 25, 30 & 135Nm. They drive screws at a speed relative to the torque.
On a recent big decking job I got my mate Clive to give me a hand. I had the 14.4v driver & he had the 12v impact driver.
We were putting in 6 x 2 noggins with 6 x 90mm Turbo Gold Coach Screws. He could put two coach screws in before I could put one in completely.
It depends on the size of the screw. For anything up to 3" my drill driver will stick the thing in at any speed I select on the trigger in most cases. The process of driving the screw does not particularly slow the rotation (as is the purpose of feedback speed controllers[1]). In low speed that means up to 600 rpm. My impact driver runs at over 3000 rpm against no resistance, but probably slows to under a tenth of that in impact mode.
[1] it might be the case the not all the Mak's have this...The message from snipped-for-privacy@isbd.co.uk contains these words:
So you wouldn't accept that if a screw was driven home in half the time at least twice the torque would have had to have been applied?
Absolutely not.
The applied torque is required to overcome the friction. In many cases the friction, and hence the torque, will be unrelated to the speed. The torque will be near as darnit constant however fast you drive the screw.
What you will be doing is putting in twice the POWER. As it's for half the time, the energy expended will be the same.
Andy
No the torque applied only has to over come the resistance offered by the screw. Provided your driver can over come the resistance you can go at any speed you like.
There is a limitation derived from the power of the driving source. You are doing work (as in force x distance) thus the more powerful your driving source the faster it will be able to provide the required energy.
EG:
A 10W 1000 rpm motor through a 10:1 gear box drives a screw in 10s. A 100W 100 rpm motor without a gear box drives a screw in 10s.
The fact that things slow down in the real world as torque increases is a function of the abilty of the source to supply suffcient energy.
Presumably because it has a two-speed gearbox, the lower torque goes with the higher speed (for drilling) and the higher torque is slower for driving screws.
No the more *power* it has the faster it can drive a given screw.
If you require 50Nm at (say) 100rpm it needs twice as much power as
50Nm at 50rpm.No they don't! It's the increased *power* of the bigger drivers that allows them to drive screws in faster.
No, it's unlikely.
If the screw was driven home in half the time it *must* have been drive twice as fast, i.e. at twice the rpm of the slower driver. It's probable that a certain amount more torque is required to drive it faster but I doubt very much if it's anything like twice as much toorque to drive it twice as fast.
It's much more down to the power available from the drill how fast it will drive screws, power (for rotating machinery) is torque * speed. Thus doubling the torque with no increase in speed doesn't necessarily help at all.
In practice it's all much 'greyer' I suspect, the amount the drill slows down when producing the required torque to drive the screw is what determines how fast the screw goes in and that's all down to the torque/speed curve of the drill.
Ultimately, if the gearing is 'correct' for the particular screw you're driving it's the available power that will determine how fast the screw goes in. It's much the same as with a car, if the gearing is correct so the engine is at its peak power when going at top speed then it matters not at all what torque the engine can develop, it's just geared to produce the right torque at the back wheels.
'Driveability' (which in a cordless drill you might call ease of use or adaptability) is another thing altogether and the shape of the torque/power curve is more important then.
The message from Andy Champ contains these words:
If you were considering just friction then torque in excess of that required to overcome friction would lead to a constantly increasing rate of rotation but friction is usually only a small part of driving a screw. The major effort is expended in cutting the thread or otherwise deforming the material into which the screw is being driven.
The question I posed was indeed based on the supposition that the work required to drive home a screw was approximately the same regardless of the time taken but to double the power you have to double the force.
The message from snipped-for-privacy@isbd.co.uk contains these words:
I have just done what I should have done at the start and consulted my reference book.
"Work due to torque is the product of torque by angular distance" and "Power due to torque is the rate of work"
As I can no longer see why this shouldn't apply to both my argument and yours I shall retire hurt with yet another glass of single malt and leave it to everyone else to pour scorn on my logic.
Posidrive screws are superb. Even beter using one of these drivers. They real grab hold of the screws.
Pour us a glass of the malt and we can call it quits! ;-)
Maxie, was this a Morris dancing band?
Says you have to be over 18 to buy them. Must be because of the laser.
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