I recently looked inside a dual pawl 180T ratchet to see how it worked.
Dual pawl ratchets allows for a finer swing arc while also providing the strength of larger-toothed gearing.
There is a compromise – dual pawl ratchets often have greater head depths in order to fit in the extra pawl.
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Shown above is what it looks like with the cover plate removed.
Here you can see the two stacked pawls more clearly visible, with the drive gear removed.
With just one pawl, this would be a 90T ratchet. But it has two pawls that are precision-engineered to have offset teeth. The peaks of one pawl line up with the valleys of the other.
When driving a socket with the ratchet, one pawl is engaged with the drive gear at all times.
When the ratchet mechanism returns in the reverse of your selected driving direction, one pawl is released and the other is engaged. The drive gear advances through 180 positions to make one full rotation, giving the 180T ratchet a minimal swing arc of just 2°.
When one pawl is engaged, the other is not.
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Essentially, the two pawls take turns engaging with the drive gear. The alternate engagement of two pawls with the 90T gear creates the effect of a 180T ratchet.
If you swing the ratchet in the reverse direction, you will hear and feel 180 clicks as it makes one full rotation.
Why? Strength and durability. High torque delivery depends on a ratchet’s gear not slipping against its pawls. Dual pawl ratchet mechanisms allows for a shorter swing arc without compromising in strength and durability.
As mentioned, there’s a compromise, in how the ratchet head will be a little deeper in order to fit both pawls. The pawls cannot be made too narrow, because then the resulting reduction in engagement surface area would decrease the ratchet’s strength.
Grokew
I wonder if Hangzhou GreatStar will use the X-Frame 6 pawls system in a push through ratchet.
fred
Other than Craftsman – is anyone else making this style ratchet?
Dave in VT
This is not a snotty response; just answering your question: I Googled “dual pawl ratchet” and confirmed that, yes, multiple manufacturers produce them.
fred
I also Googled and could only find the Craftsman with 90-Tooth and dual pawl. I see other with 60-Tooth dual pawl. i also see a video touting swapping out a 90T head into a 60T dual pawl Gearwrench. Perhaps my search was faulty – but have you spotted some other 90T ratchets with dual pawl designs?
Stuart
These are – I believe – Craftsman’s first. I’ve used dual pawl ratchets by Gearwrench and Husky (likely made by Apex Tool Group), and have heard of others over the years.
Not all dual pawl ratchets are designed for minimal clearance; Snap-on’s dual 80 is completely different and primarily designed for greater strength.
T
While they are a round head ratchet, Wright has been making dual pawls for many years.
Robert
Stuart, thanks for that explanation. Even without the benefit of video it was clearer than many you tubes. Helps with understanding some marketing claims.
One question, what determines/controls the 2 degree swing arc?
Dave in VT
360° divided by 180 teeth = 2° per tooth engagement. Unless I’m oversimplifying your Q.
Robert
Hi Dave, I’m not sure. I’ve never used as fine tooth a ratchet, always cheap ones. So for swing arc, on this 180T one, if I’m applying force to tighten or loosen a nut, when I’ve ratcheted as far as it will go (before I have to ratchet back to start another application of force), 2 degree swing arc means the long axis of the tool has only swung 2 degrees from it’s straight on angle to the nut?
Dave in VT
If I understand what you are saying, the 2° refers to the minimum distance one would need to swing the ratchet before engaging a new tooth. This means that one could still work, for example, in a twice as small space than if they were using a 4° swing ratchet.
I hope thatakes sense.
Dave in VT
Put more succinctly, yes, you are correct.
Stuart
For one pawl, the rotational movement needed for the drive gear move one “click” over is equal to 360° (full circle) divided by the number of steps, which is 90 for the central drive gear.
This ratchet has two pawls that are offset by 50%. That gives the drive gear an additional 90 intermediate positions. In a full 360° rotation, it stops at 180 positions, each one 2° apart.
When reversing a ratchet, the minimal swing arc before the drive gear will re-engage the next tooth over, is equal to 360° divided by the total number of *steps* it experiences, which in this case will be 180, which comes from stopping 90 steps in a full circle for one pawl and 90 steps perfectly in between for the other pawl. 360° divided by 180 gives us the 2° minimal swing arc.
Visualize an analog clock, with (12) hard stops. Let’s say a minutes hand can only advance in full steps. This means it would stop at (12) stops 5-minutes apart as it travels a full 60-minute (360°) rotation. 60 minutes per rotation divided by 12 stops equals 5 minutes. 360° per rotation divided by 12 stops equals 30°.
Let’s say there are double the number of hard stops, either because there are (24) hard stops or two sets of (12) stops offset by 50%. The minutes hand can then hit a number every full rotation of at least 360°/24 = 15°.
If there is a 180-tooth drive gear and single pawl that meshes with it 1-to-1, or a 90-tooth drive gear with dual pawls offset by 50% that each mesh with it 1-to-1, the result is 360° divided by 180 positions (180 or 90+90) equals 2°.
The drive gear doesn’t know if it’s engaging with one pawl or dual offset pawls, its teeth slip and stop at the next engagement position all the same. It’s the total number of stop positions that matter, and how far they’re spaced apart.
Let’s say you’re working in a tight space where there are obstructions or side walls such that a ratchet of given length would hit the walls with a 6.5° rotation. Under ideal circumstances, a ratchet with a minimal swing arc of 4° would be able to advance (1) tooth at a time. A ratchet with a minimal swing arc of 2° would be able to advance (3) teeth at a time. If the drive gear cannot advance a tooth, it cannot engage to deliver torque.
So, with one ratchet advancing 4° at a time, and the other 6° (2°x3), the user will be able to complete their work faster.
Let’s say the fastener needs to be tightened half a turn, or (180°). With a 6.5° clearance, under ideal circumstances, the 4° ratchet would require 45 swings of the ratchet handle, and the 2° ratchet would require 30 swings.
If the obstructions are 3.6° apart, the 4° ratchet won’t work at all.
If the obstructions are 90° apart, the difference comes down to 22 full advancements for the 4° ratchet (88°) with each full swing, or 45 full advancements for the 2° ratchet (90°) with each full swing. Most users won’t hit the side walls or obstructions with their ratchet on both sides.
The more swing clearance you have, the less of a difference it makes.
Koko The Talking Ape
Nice clear photos and explanation. Thanks Stuart!
I wonder if there would be any advantage to a dual-pawl setup where the two pawls are interleaved plates. One pawl would be the first, third, and fifth plate, say, and the other pawl would be the second, fourth and sixth. Each set of plates would have to be connected somehow, maybe by an end plate. That would complicate tool assembly, but it would reduce the skew forces that the gear and its bearing experience, and maybe make the tool stronger or longer lasting.
Stuart
Thanks!
So what you’re suggesting is a laminated type pawl?
There’s no bearing; the drive gear can be considered a floating mechanism, with the ratchet’s inner side walls creating boundary conditions. There’s also a cover plate, but the square drive doesn’t ride along it. Some ratchets have floating cover plates secured by a snap ring, many sealed ratchets have their covers fastened in place.
The pawls take a beating no matter what.
Koko The Talking Ape
Exactly, a laminated pawl.
Aha, no bearing. That makes sense. That means there’s nothing other than the housing keeping the gear aligned.
I can see the pawls take a beating, but laminating them would mean that under load, the force bears more directly on the centerline of the gear, and then against the curved side walls of the housing. There would be no force trying to tilt the gear so that it presses against the cover plate or back face of the housing. If the case doesn’t fit the gear tightly, whether through wear or poor manufacturing, the gear might tilt enough to cross teeth with the pawls, wrecking both.
Stuart
The gears are fairly well constrained concentrically so that they shouldn’t be mashing against the side walls. It can depend on the ratchet.
I guess we can consider the drive gear constrained by the rear of the housing (if quick release) and cover plate as if it were tapped by two bushings. With some non-quick-change ratchets, the gear is only constrained concentrically by the cover plate. Screwed-on cover plates sometimes aren’t perfectly fixed in place and can tilt a bit.
The pawls don’t have room to tilt. When the torque overcomes the holding strength, teeth might deform or break, and the ratchet starts skipping. It can take a lot to break a good ratchet’s gearing. Sometimes the square drive will shear, other times the socket will break.
I once heard of a Snap-on cover plate cracking, but that’s not a typical mode of failure. I haven’t heard about the contact surface of the pass-thru hole wearing. Generally it’s teeth that wear, strip, or break. Should that happen, many brands have rebuild kits that replace every moving part.
andres+solis+castillo
Nice I see you got yourself a craftsman overdrive. How’s the head size compared to the older 120t? I think the biggest flaw that ratchet has is the sealed head design. This one solves that, but it looked considerably bigger in the fotos I’ve seen.
Stuart
I don’t have the 120T.
I’ve got the new low-profile 3/8″ ratchet in-hand, and all three Overdrive sizes.
I still need to do size comparisons, but overall I think they did a good job with the design.
With how it’s designed, the transition between head and handle isn’t gradual; there are shoulders rather than a taper, making the ratchets appear bulkier than they are.
I can’t tell if this is for style, to help the ratchet better clear bolts and obstructions, or a combination of form and function.
The Overdrive ratchets should be serviceable; from what I can see online, the same can’t be said about the 120T ratchets.
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