Production ProceduresAs with the evolution of component designs on the Model A, the riveting processes also evolved in the early years of Model A manufacturing. The assembly of the frame is a good example. Contrary to common belief, the initial process set the rivets cold. The basic steps in this process were:

1. Install and rivet the small (minor) brackets on the side rails. This was done on PA-4 Ferracute punch presses, set in a line for each operation. One line for the left frame side rail and another for the right.

2. Assemble the two side rails with the front, center and rear cross members using 42 rivets. This was a hand operation.

3. Set these 42 rivets using another two rows of PA-4 Ferracute punch presses.

Note: the running board brackets were not assembled as part of the frame, but instead were attached on the final assembly line.

This procedure required a fairly tight fit of each rivet in the holes to hold every-thing in place while the

frame was manipulated to line up with the punches in each press. The rivets were knurled to make insertion easier and to promote the swelling of the rivet when it was set. The holes were punched to a diameter of 17/64”. This must have created some difficul-ties in assembly as getting 42 holes to line up in order to insert the rivets requires some very tight tolerances in hole location. This difficulty is evident in the changes in the size of various holes (17/64” holes changed to 21/64” and back to 17/64”) from December 1927 through March 1928. The solution to this prob-lem appears to have been a combination of 17/64” and 21/64” holes strategically located to keep the parts secure.

Our examination of some 1928 frames seems to confirm the difficulty in using the knurled rivets and setting them cold in a punch press. We found the formed rivet heads were often greatly offset from the shank of the rivet. This would be caused by either a misalignment of the punched holes in mating parts or in a mis-alignment of the frame assembly in the punch press dies.

By disassembling frame cross members, we discovered that the use of knurled rivets had completely disappeared in the first month or two of 1929. Some late 1928 front cross members were found to be factory attached with a combination of knurled and plain shank rivets. We can presume this is indicative of the change from the early assembly process outlined above to the later more common procedure. A review of the Ford engineering releases for the frame seems to suggest that this change started in November 1928.

Frames assembled in early 1929 through the end of production utilized a hot riveting process. The advantage of hot riveting is an increase in strength due to the rivet swelling to entirely fill the hole and as well as shrinking (in length) while cooling and thus pulling the mating parts tighter together. Also, for frame assem-bly, it was no longer necessary to manipulate the entire frame for each rivet. The part could be assembled in a fixture prior to the start of riveting. The new procedure followed these steps:

1. Install and rivet the small (minor) brackets on the side rails. This was done on PA-4 Ferracute punch presses, set in a line for each operation. One line for the left frame side rail and another for the right.

2. Assemble the two side rails with the front, center and rear cross members using locating pins in special fixture. This was a hand operation.

3. Heat rivets to a bright red appearance, install one at a time and set each rivet using manually operated counterbalanced pneu-matic rivet squeezers. Separate rivet squeezers were on each side of the assembly line. Note: the running board brackets were not assembled as part of the frame, but instead were attached on the final assembly line.

Hot  Riveting  the  Model  APrepared  by  MAFCA  Judging  Standards  Committee

Knurled rivet (left), smooth rivet (right).

The Restorer8