It seems like yesterday when we first came across Jo Kerr's well-traveled '30 Ford coupe parked on the outskirts of the NSRA Street Rod Nationals in Louisville, Kentucky. What immediately grabbed our attention was so many of the unique parts it wore. A closer look revealed a cast finish so well executed that we had to track him down for the lowdown on how he created the parts. These were all signature items personally machined to work into hot rods being built at his shop, JoKerr Fabrication. Kerr tells us that there are a number of finishes that can be created when using billet aluminum, from highly polished to a sand-blasted look. However he longed to recreate a cast-style finish and that's wherein the magic lies. We finally convinced him to let us have a closer look at how the parts machined from, believe it or not, solid billet aluminum. This isn't the billet of the past as you remember; it's a whole new deal. Let's take a closer look as he creates two of his very own signature items.
When designing one of his shifters, careful consideration is taken to the ergonomics of the driver with regard to seating placement and shifter height. Typically, with the hot rods being built at his shop the shifters created are 16 inches tall. To get started a section of 1-inch-diameter T-6061 aluminum stock was cut to the exact length. Since the shaft will be tapered, a measurement is taken at 2 inches from the bottom and marked with a coating of blue machinist's dye. The dye establishes a guideline to use as a base to begin turning the taper from. Prior to securing the stock in the lathe, the top of the shifter was measured to locate the center and was then drilled with a 0.250-inch bit to establish a hole to secure it in place to the live center on the lathe. To take on the job, Kerr used a Kingston Machine Tool HQ1440 lathe and secured the base section in the three-jaw chuck while making sure both ends were secure. The tapering attachment was then set at 1/2 degree and while wearing safety glasses, 0.050 inch was removed from the surface with each gradual pass. This continued until the desired graceful taper was achieved. The shifter was then completely coated in machinist's dye, and once dried, it was removed from the lathe and set back onto the layout table.
To add some edginess to the design, a height gauge was used to scribe locations for lightning holes starting at 3/4 inch above the taper line and from there every 1 inch until 11 total holes were marked. The shifter was then moved to a first vertical mill where the base was secured in a Kurt vise. The upper section was then placed in mill clamp stands. Kerr tells us that proper setup is everything and that it's imperative the part is secured tight to ensure there is absolutely no movement or vibration during the machining. A center finder was then used to locate the center of the first hole prepared for drilling. Starting at the bottom of the shifter the first four holes were drilled using a 5/16-inch drill bit, followed by four using a ¼-inch bit, and the final three using a 3/16-inch bit. With the holes completed a ball mill was set up while still on the center of the last hole drilled. Wanting to add a groove to the left and right shifter sides, a ½-inch two-flute ball mill was used. It's important to be sure the shifter is still level in the vise before proceeding. In order to remove 0.150-inch, three passes were made removing 0.050 inch from the surface with each sweep.
1. To create a shifter, Jo Kerr starts with a 16-inch section of 1-inch round T-6061 aluminum rod. A 2-inch guideline is the applied to one end using machinist's dye to mark the start of the taper.
2. Using a Kingston Machine Tool HQ1440 lathe, the taper attachment is set at 1/2-degree starting at the top of the shifter and it is gradually worked toward the 2-inch base.
3. At this point a number of passes have been made removing 0.050 inch from the surface in each cut till the desired taper is achieved.
4. The shifter was removed from the lathe and recoated in machinist's dye. Using a height gauge it is then measured 3/4 inch above the taper line for lighting holes every inch.
5. The shifter was moved to a First vertical mill where its base was secured in a Kurt vise. The top is then secured tight in mill clamp stands to avoid any movement or vibration.
6. A center finder was used to locate the exact center of the first hole to be drilled at the base. Using a 5/16 bit, the first four holes were drilled.
7. Moving up the shifter a 1/4-inch bit was used for the next four holes followed by a 3/16 bit for the final three at the top.
8. While still on center, Kerr used a 1/2-inch two-flute ball mill to start the groove process. Three passes were made removing 0.050 inch from the surface with each sweep.
9. Secured in a bench vise, a metal burr wheel for steel was used to create the surface texture with a precise repetitive motion in each direction gliding it from left to right.
10. Finally, the finish was completed by sandblasting the part followed by a thorough cleaning with an air hose followed by brake cleaner.
11. To give you an idea of the work involved in creating his signature fuel block you can see the three stages here of how the part evolves from a solid section of T-6061 aluminum.
12. A 2-inch square by 4-inch long-block (coated with machinist's dye) is used as a base of the fuel block. A center hole is first scribed to the block bottom for the fuel inlet.
13. Using a height gauge, the mounting surface lines are scribed at 1.2 inches from the top of the block and then 0.575 inches leaving a 5/8-inch mounting band.
14. The fuel block was secured in a vise to drill a 2-inch deep inlet hole using a 7/16-inch drill bit. The hole was then tapped with a 1/4-18 pipe thread.
15. An old fitting was then installed to give the unit something to secure to the lathe. Also a small center hole was measured and shallow-drilled on the other side as a live center hole.
16. The block was then mounted to the lathe. Kerr advises great care should be taken here to properly mount the section as the square edges can easily shatter while being cut.
17. Using a facing insert tool, the process starts by making 0.100-inch cuts below the marking surface. This continues until the unit becomes completely round.
18. The cuts were then adjusted to 0.050 inch and worked till the desired diameter was reached, in this case 1.875 inches. It was then reversed and cuts were made to the top of the fuel block
The shifter is then removed from the mill, blown clean, and set up in a bench vise. To create the cast-look takes far more attention than simply trying to blast the part with any type of media. Kerr prefers to use a metal burr wheel for steel secured in an air-driven drill to create the texture. He tells us that an aluminum one can also be used but that it will create a far rougher surface. To achieve the grain pattern, a precise repetitive motion in the same direction should be used to lightly glide from left to right starting at the top of the shifter downward. If you stop, the wheel could create a divot on the section being worked. It's best to start off the metal and finish off the metal on the other end with each sweep to create uniformity. Once completed, Kerr sandblasts the part using basic play sand available at any hardware store. Once the part is completely clean, it is washed down with either brake cleaner or water to remove the majority of the sand residue. A final blow with an air line will remove the rest. The final look gives the perfect illusion of a cast part looking decades old.
Shifting gears to take on the fabrication of a traditionally-styled fuel block, Kerr begins with a 2-inch square by 4-inch long-block of solid T6061 billet aluminum. The stock is then coated in machinist's dye. The bottom of one end of the block was measured to establish the center for the fuel inlet. Using a height gauge on a granite layout table the mounting surface lines were measured and marked using a scribe at 1.2 inches from the top of the fuel block with a second mark at 0.575 inch from the top. This results in a 5/8-inch band for the mounting surface. The block was then moved to the First mill and secured in a Kurt vise to drill a 2-inch-deep hole in the base for the fuel inlet using a 7/16-inch drill bit. The hole was then blown clean, tapped with a 1/4-18 pipe thread, and an old fitting secured to allow it to be secured to the lathe. A small pilot hole was also measured and added using a 0.250-inch drill bit to the opposite end to secure it to the live end of the lathe. The block was then moved to the lathe making sure it was square on all edges when mounted. Since the block is rectangular, particular care needs to be taken to avoid shattering the cutting bits as the block is being turned. A facing insert tool was set up and cutting commenced below the mounting surface, removing 0.100 inch at a time. This step takes quite a bit of time to get the section completely round. To achieve the desired diameter of 1.875 inches, the cuts were adjusted to 0.050 inch till completed. Note that the total area being turned was 0.575 inch. The block was then reversed and the same amount was removed from the top while allowing the 5/8-inch mounting band to remain. Finally the block was coated with machinist's dye and measured using a Vernier caliper for stylish fins to be cut next with each being 1/8-inch thick. A total of eight fins were marked starting from the bottom of the block to create the layout.
Once lined up, beginning at the bottom of the block a 1/8-inch grooving tool was used. After moving the cutter in place lightly touching the block, Kerr "zeroes" out the handle dial to ensure the same will be cut, here the amount is 0.300 inch per fin. This amount is again confirmed with a dial indicator as each fin is completed. Kerr tells us that it's all about maintaining the accuracy and balance of the part as you move forward. The block was then flipped and re-secured in the lathe with a carbide bit used to add a neat bevel to the top of the block. The block was then removed from the lathe and secured in a vise to prepare to drill the fuel outlet holes. After measuring 2 inches from the bottom of the fuel block a 7/16-inch bit was used to slowly drill into the block, making sure to intersect the fuel inlet hole. While still on center, a center guide was then used to make sure the tap holes were perfectly straight for using a 1/4-18 pipe thread tap. The mounting surface was then finalized with a disc sander to round off the front sides for a clean look. The flat mounting surface was then drilled with a 0.159-inch drill bit and tapped with 10/32 thread. To complete the fuel block its surface was prepared in the same way as the shifter, giving it the old-time cast look of a part that would have been at home on a dry lakes racer in the late '40s and to us that's just plain bitchin.
19. Here you can see the upper and lower portions of the initial cuts to the fuel block completed.
20. With a quick spin in the lathe Kerr coated the body of the fuel block with machinist's dye to prepare it for its next set of cuts.
21. To mark the fins a Vernier caliper was used to measure them out. Starting from the bottom, eight fins were scribed in place, each 1/8-inch thick.
22. With an 1/8-inch grooving tool installed, Kerr meticulously makes his first cut to 0.300 inch depth starting at the bottom of the fuel block.
23. It's a good idea to keep a dial indicator on hand to measure from fin-to-fin as production moves forward to ensure all measurements are accurate.
24. The fuel block comes to life once the fins were completed, giving the part a very traditional vibe.
25. The fuel block was then reversed in the mill and a carbide tip blade was used to give the top edge a very subtle bevel.
26. With the block in a vise, a 7/16-inch drill bit was used to drill the fuel outlet hole 2 inches from the bottom of the block.
27. Carefully, the drill moves through the block making sure to intersect the fuel inlet hole.
28. Using an Enco disc sander with a 36-grit disc, the front sides are rounded off for a nice custom look while the rear mounting surface will remain flat.
29. A 7/16-inch drill bit was used to drill an additional fuel outlet hole.
30. With the block still secured in the vise, the holes were then tapped with a 1/4-18 pipe thread. Mounting holes were also drilled and tapped on the rear mounting face.
31. A metal burr wheel for steel was then used to begin the surface texturing process. Kerr slowly worked his way around the fuel block massaging all surfaces.
32. The worked-over fuel block (top) lets you see all of the completed surface preparation and once sandblasted the final product (bottom) looks like it was hand cast decades earlier.
33. There are a number of parts JoKerr Fabrication has started offering, including this downright bitchin carb topper for dual-quads, featuring extremely unique velocity stacks.