How To Chop A Top With Minimal Effort and Maximum Accuracy Part 1

Hot Rods by Dean’s Easier Method For Chopping On 1933 Ford DeLuxe coupe

By Chris Shelton   –   Photography By Brian Brennan

The world really doesn’t need yet another top chop story—or so I thought. Then ol’ Editor Brian Brennan visited Dean Livermore at Hot Rods by Dean and brought home these photos of the chopping of a 1933 Ford DeLuxe coupe.

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It wasn’t the chop itself that caught my attention—it’s a moderate cut (2-1/2 inches) on a somewhat common car. Rather, it was the way Nick Sinioris plotted his cut lines to minimize effort and maximize accuracy that stood out.

01 Nick Sinioris at Hot Rods by Dean carefully planned out his work and then worked his plan
Nick Sinioris at Hot Rods by Dean carefully planned out his work and then worked his plan–how’s that for a novel approach!

Welding Technique

Welding—specifically the preparation for welding—really eats up time. Strong welds that don’t distort favor tight, consistent gaps. While nearly anyone can get such a gap along a short run, it takes a fair amount of skill and time to get that kind of gap over, say…a foot or two. To get those tight, consistent gaps over that large area usually requires cutting a little wide of the scribe lines then creeping up on them with snips and files. And that kind of fit up usually requires making tabs to support the panels during the trimming process. The fit, trim, and repeat cycle takes a long time.

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Read More: Function and Form: The Art Of Channeling a Hot Rod

02 That meant horizontally through the sides of the window and just above the beltline
Sinioris plotted his cut lines at points with the least shape change. That meant horizontally through the sides of the window and just above the beltline. Connecting those two results in the vertical cut line to the right of the window.

Chopping The Top

In oversimplified terms, Sinioris cut the top off, slid it down until the base overlapped the top, drilled through the overlapped area for temporary panel fasteners, then pinned everything together. That lets the lid fasten to the body without separate tabs or brackets.

03 The main cut line follows the bead up to the area with the least area and shape change
The main cut line follows the bead up to the area with the least area and shape change. Note the parallel horizontal cut lines. They’re measuring 2-1/2 inches apart, the distance that the top will come down.

Sinioris’ method

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Though neat, the ability for the top to serve as its own fixture is a secondary benefit to Sinioris’ method. The cut edge of the overlapping panel doubles as a guide for scribing and/or trimming the underlying panel. Cut right on that guide or cut through both panels simultaneously and you’ll get a panel gap that measures exactly the width of the cutting blade. Close up that gap for GTAW/TIG process as Sinioris did or leave it open for GMAW/MIG.

04 The smallest and simplest 2 1 2 inch section of the A pillars hangs out just below the area where the lines straighten out
The smallest and simplest 2-1/2-inch section of the A-pillars hangs out just below the area where the lines straighten out. Again, note the parallel horizontal lines.

Correcting Method #1

Because the top tapers toward its crown, the pillars misalign when chopped (the top emerges too short, lengthwise). One correction method extends the lid part of the top lengthwise to realign the posts. That maintains the windshield angle, which preserves the windshield’s seal.

05 Sinioris cut along the plotted lines then removed the top
Sinioris cut along the plotted lines then removed the top. For the time being, he cut only one side of the parallel horizontal lines noted in earlier steps.

Correcting Method #2 Bonneville Chop

The other method leans the windshield posts back. Doing that streamlines the windshield, which made it a popular technique in landspeed racing in the middle of the last century (see the Spalding Brothers’ and SO CAL Speed Shop’s coupes for examples). You’ll sometimes hear people refer to it as a Bonneville chop, and it’s how Sinioris chopped this top.

06 After removing the top Sinioris returned to cut along the remainder of the parallel horizontal lines
After removing the top, Sinioris returned to cut along the remainder of the parallel horizontal lines.

Techniques To Improve The Chop’s Integrity

Along the way you’ll see a few other techniques that improve a chop’s integrity. For example, Sinioris uses a fixture to preserve hinge-pin alignment during reassembly, something that ensures that the doors will open and shut without binding. He also fabricated a lot of internal structural elements, like a tubular support that bridges the door jambs and ties them into the top and inner fender wells.

Read More: How To Custom Build and Upholster Custom Seat Cushions

07 These scraps represent the amount officially chopped from the rear window side bead and A pillar
These scraps represent the amount officially chopped from the rear window, side bead, and A-pillar.

Though some techniques are specific to 40 Model Ford Coupes, most of the process translates to other makes and models of the period, if only because they’re built largely the same way.

I still stand by my assertion that the world has enough top chopping stories. But as I’ve learned, for every rule there’s an exception. And so long as fabricators find those ways to improve the process and reduce the effort, we’re all eyes. MR

08 This is how the top looked immediately after it came off the car
This is how the top looked immediately after it came off the car. Note where the primer starts relative to the cut line.
09 The crew slid the upper part of the top down into the body by 2 1 2 inches
The crew slid the upper part of the top down into the body by 2-1/2 inches, concealing the bare area along the cut line. Then they drilled through the areas that overlapped and pinned the pieces with temporary panel fasteners. They trim the overlapped area in a later step.
10 They tacked in some temporary brackets to secure the roof
They tacked in some temporary brackets to secure the roof. They exist only for alignment.

11 They exist only for alignment

12 The top tapers toward its crown and because Sinioris maintains alignment of the rear section
The top tapers toward its crown, and because Sinioris maintains alignment of the rear section, the A-pillars land short. Some lengthen the top to correct this.
13 This is the foundation of the so called Bonneville Chop
But others change the angle of the A-pillars to realign them with the top. This is the foundation of the so-called Bonneville Chop, a design pioneered by the Spalding Brothers and Alex Xydias, among others. Sinioris began by severing the pillars entirely.
14 Modifying the top skin requires access to its backside
Modifying the top skin requires access to its backside. Sinioris cut away part of the inner structure at the upper corners.
15 Sinioris then split the top skin above the windshield and above the door jamb then pulled the tops corners forward
Sinioris then split the top skin above the windshield and above the door jamb then pulled the top’s corners forward. He cut the pie-shaped hole to minimize interference.
16 Pulling the top to meet the pillars opened gaps too wide to weld together
Pulling the top to meet the pillars opened gaps too wide to weld together. So, Sinioris shaped a replacement panel to fit.
17 He trimmed the panel to cover only the essential areas then used it as a template to scribe and then cut the top skin
He trimmed the panel to cover only the essential areas then used it as a template to scribe and then cut the top skin. Removing the inner structure gave Sinioris access to the panel’s backside so he could stretch the weld beads.
18 The windshield posts started life at 71 3 degrees
The windshield posts started life at 71.3 degrees. Now they lean back five more degrees to meet the top’s new location.
19 The windshield perimeter is no longer lined up after cutting and pasting and the tight area makes it difficult to reshape
The windshield perimeter is no longer lined up after cutting and pasting and the tight area makes it difficult to reshape. So, Sinioris made these dies to fit the power hammer.
20 The finished product restores the gentle radius that originally made up the windshield corners
The finished product restores the gentle radius that originally made up the windshield corners.
21 Once welded in the panel makes a seamless transition among the modified parts
Once welded in, the panel makes a seamless transition among the modified parts. All that remains at this point is welding the inner structure back in place.

Ready for Part 2? Check it out here: How To Chop A Top With Minimal Effort and Maximum Accuracy Part 2

Sources

Hot Rods by Dean
(623) 581-1932
hotrodsbydean.com 

Woodn’ Carr
(562) 498-8730
woodncarr.net

Leading Edge Machine and Design
(402) 660-8289
leadingedgemad.com

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