Broaching

[JoeG]

Letters look crip Bob from where I'm sitting and no machine line before the numbers, but I'm a couple of states away----I'd say nay on the machining ---But the cylinders looked bored too hell--

[Belair62]

Nah Joe...this is an 814 block...the 64 needs a 422...this one is still standard...so will the 422 be when I'm done.

[mrrec]

Bob:
I've seen untouched blocks with no apparent machine marks like yours. I've never liked the term "broach" as I don't think it applies to a one dimensional removal of material - keyways or holes are broached. My educated guess is that the "broach" marks everyone talks about are actually the machine marks left by a planer.

Unlike a rotary milling cutter (which were certainly in use prior to the 70's), a planer has a moveable bed which can be quite large (10'x 50' or more) so that a large number of blocks can be planed at once. The cutting tool(s) is fixed and the work piece (block) moves in relation to it. The tool "shaves" the iron in a straight line parallel to the crank. This method was apparently more economical for large production runs than milling using a rotary cutter in years past. Planers were widely used from the 1800's through WWII and are almost non-existant in production in any industry today.

I believe the planer (broach) marks could and did vary considerably depending upon the cut, tool profile, etc.

Dave

[Belair62]

Planing marks are what we all are used to...these are circular patter it seems but hairline...I know it was not restamped or monkeyed with so the only thing I can figure is a light cleanup with something circular...guess it doesn't matter anyway.

[Verne_Frantz]

Bob,
I'm very certain those machining marks are original, and so are the stampings. I'll email you another photo of an original you can post for comparison.
(what's the Julian date on the back of that 814 block?)

Verne

[Belair62]

320 Verne....thanks for the help with the 64 too..together we are going to figure this weird old car out !!!

[Mr70]

I would just sell it now & cut your loses while you can.

[Zedder]

Dave, you are absolutely correct, but they never left circular marks like on Bob's block. They are always parallel to the crank and varied in depth (some almost non-existant to the naked eye) depending on how sharp the broaching tool was. Some one (I think John Hinkley) wrote and article on the process for the NCRS driveline I believe.

Maybe it was sanded in some way to leave that pattern, but in NCRS-type judging it would not pass inspection.

[Verne_Frantz]

Mark,
With all due respect, I think you are referring to Flint machining operations (small blocks). These big boys are made at Tonawanda. Different method of deck grinding.

Verne

[Zedder]

Verne, I have judged and owned numerous Tonawanda big blocks and they all have "broach" marks. Now I can't comment on blocks earlier than '66, but my guess is they used that process back then also. I'm sure someone will chime in and clear this up for us all. I'll ask Art Armstrong and see if he knows...