Made in advance, the die-struck copper sabot was positioned in the sand mold and then the molten iron poured in with the nose down. The founders expertly monitored the temperature of the iron, allowing it to cool sufficiently as it approached the sabot to ensure minimum melting. The two holes, three holes, wedge cuts or simple round interior (I've seen all of these on those early Reads) had already been punched when the basic sabot was struck into its "jar-lid" shape (as opposed to the Read-Parrott's cone shape). His 1856 patent called for some serious striking "by the use of male and female dies under a stamping press, which could be so arranged as to cut the discs and punch the necessary apertures all at one operation." I wonder if it is accurate to call those solid cast copper sabots seen in so many of the Virginia Reads "Reads" at all? The original patent suggested optional "apertures" including four "wedge-shaped" cuts equally spaced around the opening "to facilitate turning in and flattening." He further recommended the addition of a series of smaller holes "through which the molten cast metal may pass in founding, thus forming large rivets by which the cylinder (i.e., sabot) may be made to adhere firmly." Again, he had heavy projectiles in mind when he wrote the patent.
Read concluded with "a simple round central opening would suffice."
If you don't mind, I'll copy some of the unpublished material from Thunderbolts to further explain what happened.
Dr. Read's six year-old patent design was closely followed when several Deep South and Tennessee foundries commenced the production of his field-caliber projectiles in late 1861 and early 1862. That happened because Read arranged the contracts and had the first of the sabot-stamping dies made and installed himself. While visiting the Memphis foundry of Quinby & Robinson (a.k.a., "The Tredegar of the West") on December 5, 1861, Dr. Read personally oversaw the fabrication of "two patterns for Read's 3 inch Rifle shot," and one for the matching "shell." (Quotes from vouchers.) In addition, he had "one small wrought iron mandrel for 3 inch Read stamped." A "mandrell" was a cone-shaped fixture that fit over the projectile's nose to impart the turning motion of the lathe. It is clear from a third entry on the same voucher (i.e., "Patterns for Read's 32 pounder sabot"), that the "patterns" he ordered for the 3 inch projectiles included sabot-stamping dies as the descriptions and costs were nearly identical.
Hurriedly written at the bottom of the voucher was a revealing note by Quinby's partner and foundry superintendent - Robinson.
"The above bill of articles was made by order of Dr. J. B. Read and taken by him to other places for the purpose of facilitating him in having his shot and shell cast."
Now, this is current writing to summarize the story. Read returned to Ala. and contracted a north-state foundry to make 3 and 3.67 inch Rifle shells from wrought iron. That was the only sabot material prescribed by his patent. After a couple of weeks, the foundry backed out of the arrangement because of difficulties obtaining or working with the iron sabots. Read informed the other foundries that from now on, all Read sabots were "to be copper, or its equivalent of strong brass at least two-thirds copper." Dr. Read returned to Memphis in January 1862 and oversaw the production of another "six sets [of] Read's Stamps and Dies."
There is a sad story here for those with feelings for the South. Here, the new Confederacy had a world renowned projectile inventor employed by the Ordnance Bureau and his work was ignored by Richmond. I know we're all not supposed to be judgmental in this modern era, but "Damn, Boy!" (That's Tom talking from shell heaven) it mattered. One patriotic Rebel who was fully aware of all of this was Capt. Hoplite Oladowski who was a local ordnance liaison working across the Department of Florida, Alabama and Mississippi. In the course of distributing guns and ammunition in early 1862, he had opportunities to test the Reads and compare their performance to the other projectiles currently being mass-produced - the Archers, Burtons and CS James - all bolts, no shells. It wasn't even close. Oladowski, Gen. Bragg's future Chief of Artillery, shouted from the rooftops about the superiority of the Reads but no one listened. When Leeds & Co. of New Orleans replenished the stocks expended at Shiloh in April 1861, they sent more of the worthless Archer, Burton and James bolts to the LA batteries. In a April 21st note to Oladowski, Leeds explained "As yet, we have no orders for any projectiles of that kind (i.e., Reads), for field guns."