Why You Still Need a Good Rotary Depth Crank in Paving
Asphalt paving training tips to level out your paving performance
There is an adage: “If we always do what we always did, we’ll always get what we always got.” Now this subject is all about the reason (as I see it) for the screed rotary depth cranks (or screws) and why they’re included on U.S. style screeds but not on European screeds. Why does one European paver and screed manufacturer not even install threaded adjusting screws on the screed at all? Let’s look at why these are important and when and why you should use them. There are a lot of fundamental misconceptions around the above, which I would like to use to stimulate conversation.
Balance the Screed
To clarify my thoughts, I am not suggesting that there shouldn’t be a manual, rotary depth crank on the screed. I absolutely believe there should be as it is essential for balancing the screed and keeping the nose in the ideal attitude.
I like to think of the depth cranks as being very similar in operation and theory to the rear horizontal stabilizer and elevator that you find on the tail of most modern jet airplanes. Basically, the elevator is adjustable (just like a rotary depth crank) and is the method that the pilot uses to maintain the optimum, slight nose-up attitude or horizontal pitch of the airplane during flight. It’s always slightly nose-up to give lift; just like a screed.
A motorboat is usually fitted with a similar device called trim tabs. These are right at the rear end of the hull and are also used to adjust the planing angle of the craft to also create a slight nose-up attitude. This is the same principle a screed requires to float.
We require a means to adjust and dial in the optimum angle of attack to provide a tight, dense mat texture. I believe though, once you have established this optimum angle of attack (1/8-inch to ¼-inch slight nose-up typically), you shouldn’t start messing with that setting during normal paving operations. This procedure should be done at the start, then left alone.
Because if you use the depth crank instead of the tow point, invariably you will upset and change that initial, ideal slight nose-up angle of attack. This can lead to the screed planing on a less than ideal angle of attack (either nose-up too high or low), which can result in a variable mat texture, transition lines and in extreme cases, excessive and uneven wear to the leading edge or rear tail of the screed with uneven compaction. This will often create issues like the screed being difficult to control and a poor mat texture.
I had this discussion with a well-known industry expert from a leading original equipment manufacturer (OEM) at World of Asphalt in 2024. He basically agreed with me and believed the reason so many operators use the depth cranks to adjust mat depth, rather than using the tow points, comes down to tradition; or “we’ve always done it that way.”
Instill Best Paving Practices
I don’t advocate removing the depth cranks (as one OEM does on the European tamping screeds it makes) or taking the handle off and leaving an adjustable threaded rod (like most E.U. screeds have), as that creates other problems. I’ve seen people using the screed at an incorrect angle of attack for a certain mat depth it was not set up to achieve because adjusting the threaded rod was difficult or they didn’t have the wrenches on site to make adjustments. That’s just as bad as playing with the cranks and changing the pitch during paving.
Also, I absolutely agree with using the depth cranks to “buy back cylinder” in certain situations such as when following a variable grade or using slope on one side. I do that myself when required so it’s important to have depth cranks for this.
What I’m suggesting is once the operator has established and dialed in the correct angle of attack, after checking the screed is planing at an ideal angle and the screed pivot point is fairly parallel to the tow point pin, he or she will use the tow points to adjust mat depth after that (in both manual and automatic) and leave the cranks alone. After all, if you carefully think about the concept and practice of correctly setting the screed pitch or angle of attack, you want to maintain that ideal setting, not change it.
Changing Practices
I appreciate that some folks will almost certainly have strong views either way about this, and that’s a good, healthy subject to discuss.
I recall about 15 years ago, I first obtained a copy of the asphalt “Bible” I regularly consult. This is the same U.S. Army Corps of Engineers’ “Hot-Mix Asphalt Paving” handbook 2000 (AC 150/5370-14A Appendix 1) I referred to in my previous article “Control the Feed to Control the Screed.” At that time, I had been full time in the asphalt industry for around 25 years, and I had been taught in the mid ’80s how to compact asphalt in the “old school way.”
This procedure involved “nipping the joint” or basically rolling the longitudinal joint match first by about 1 to 2 inches to push the joint down so it looked nice. I thought that was the only way and the right way.
However, upon reading this handbook, I discovered in the compaction section that the old method was no longer a best practice. It was not a recommended procedure due to quality issues that methodology often created. Well, it caused me a great deal of personal angst, and I struggled with the concept that what I had done for 25 years was now “wrong.” And it took me about three years to accept the idea. It was kind of like I was thinking to myself, “You mean to tell me I’ve been doing it wrong for the past quarter century?!”
But sometimes you have to reconcile yourself to realizing that as time passes, often new knowledge, learning and understanding of evolving processes can come to light. Now, I’m a complete convert in the current U.S. best practice compaction methodology. I realized eventually that what I had been doing for all that time wasn’t “wrong” for that time. Instead, knowledge evolves over time, and we all must be prepared to re-evaluate some things if new lessons come to the fore.
After all, it was George Bernard Shaw who so accurately stated: “Progress is impossible without change, and those who cannot change their minds cannot change anything.”
Let me know what you think about the use of rotary depth cranks and tow points and other long-held paving practices. It’s a challenging vocation we share, and it’s not for everyone, but I wouldn’t trade it for anything.
Benjamin Everett is the owner of About Asphalt Ltd., and has worked in the asphalt industry for nearly four decades. For more information, contact him at bjeverett@aboutasphalt.co.




























