The Home Machinist!

Can anyone lead me in the right direction to find information on the lost art of piston knurling? Also known as resizing or expanding. I am looking for a book articles or manuls. I recently purchased an old Hastings Manufacturing Co. (Micro Knurler). Model M1. Any info will be greatly appreciated. Chuck Brown.

If you can't find a manual, I can give you a quick tutorial. Hanz

Chuck,
Isn't piston knurling one of those lost arts better left lost? [img]/ubb/images/graemlins/grin.gif"%20alt="[/img]
"Piston expansion" was another one, and valve guide knurling too...

Hi Chuck,
When you say knurling I assume you mean knurling the skirt of old worn pistons to take up the slop.

Many years ago, when I went to sea and was doing my time our instructor in college was a Morris Minor fanatic always doing up engines, bodies etc and we apprentices worked on these as part of our "training". We did many things to restore old worn engines.....eg. taking out ovality in crankpins with plenty of emery tape, then relieving the bearing caps/shell faces to compensate....all definitely not "accepted" practice, but the engines ran and ran well. Anyway piston skirt knurling was often done..........from memory no great science........we made up a neat fitting spigotted plate to fit into the aluminium skirt (first lightly machining the internal cavity), centre drilled it and supported it with the tailstock. Then used the lathe kurling tool to make a couple of knurl rings around the skirt.

Rod.

Actually I have built a couple old worn out industrial engines that knurling the piston skirts worked quite well.

I was able to hone the wear on each cylinder back to a round & non tapered with a Sunnen precision hone. Not really paying much attention that they were each sized the same. Then "knurled" the skirts of the pistons to expand them larger than the bores. Then comes the real work of bringing them back to size for each individual cylinder.

Of course after that the standard ring kit had end gap that could be measured with a tape measure. LOL

In both engines I built this way, rings were aval. in .020 oversize which allowed me to cut the end gap to what I needed.

20 some odd years later I still have one of them in a fork truck. & it still is dependable & quiet.

For a High performance engine or any engine cranking over 2500-3000 rpm definitely not a good idea. But in this case did save me many bucks....

Chuck
Check out the book Automobile Enging Rebuilding and Maintenance second edition by Harold Glenn. ISBN 0-8019-5230-1 It has the information you seek on knurling pistons.. If you cannot locate the book contact me and I will see what I can do to get you the information.

lnjgalvin at proaxisdotcom

lg
no neat sig line

What about "Ramconizing®". That was a competitor to "Knurlizing®". Both of these methods were used during the last year or so of WWII when a lot of engines were worn badly and no parts available. I know either process could result in failure of the piston skirt though this may have been caused by inexperienced mechanics "overdoing" the resizing in an effort to stop piston slap noise.

About 1948, a friend of mine who ran an auto machine shop in Jackson, TN showed me some pistons that had been Ramconized in Texas and five of the piston skirts cracked coming to Tennessee. Ramconizing, for those unfamiliar with the term (may it rest in peace or pieces as the case may be)involved a small high speed sort of hammer thingie that was inserted in the piston where it hammered and stretched the skirt.

Unka(As was mentioned a couple of posts back, both of these methods are best left as historical items and not actually practiced)Jesse

My shop, and I 'KC engineering' have been knurling pistons for decades. Also RPM of the engine in question, is not the factor to worry about. Piston speed however may be. This used to be a question on our written mechanics test : which engine @a given rpm has the fastest piston speed will always be higher / fastester piston speed a 1980 HD FLH, or a 1980 KZ1000R? (Motorcycles) you may be surprised that few answered correctly, and the ones that didn't, could not be convinced what the correct answer was.
KC Engineering eliminated this question from the test 27 years ago. A test, I will (say),that was also used by the largest motorcycle dealer's service dept. in California. The now defunct Golden Gate Cycles, Honda, Kawasaki, Victory, Suzuki, and Yamaha.

Back to knurling. We've used the knurling machine, for years made by 'Perfect Circle', It's name is the 'Knurlitzer'. It was designed for PISTON knurling exclusively. the 'chucking mechanism was made up of little 'jaws, that fit perfectly inside the ring groves (no marking,maring, or damage to the piston(s) whatsoever)., some racers would Knurlng

An older drag racing friend ,once told me, back in the 60's some racers had brand new pistons knurled. The idea was , because the piston(s) 'rode' only on the 'peaks' of the knurling, and the 'groves would hold oil, the resistance/ friction in the cylinder(s) would be greatly deminished.
Years later Ken Tiptonn of 'MTC' piston fame, said that knurling carried with it 'grit', and 'grime', and led to premature piston, ring, and cylinder wear. (so "6 of one,or half a dozen of another".
Go figure. All I know for sure is the first piston I, (or rather my Dad), knurled was on a Ducati 250 'Dianna'rode it through high school, and after, then sold it to a friend of mine. As far as I know (he lived only a block away), had no problems with it. The only 'knurled pistons' I've seen 'fail', were 'knurled' on a lathe', (never-ever do that).or were put in motors with longer strokes and improper clearance(S). Now a days, when I knurl a piston(S) I Insist on having the Cylinder(s) brought in with it. Easy to do on motorcycles - with cars, not so much.
Kenny Creshy
415-706-9542

VmazKen wrote: ↑Tue Apr 03, 2018 6:51 pm The only 'knurled pistons' I've seen 'fail', were 'knurled' on a lathe', (never-ever do that

Hmmm. Causes me to ask why? Seems there must be some way to accomplish the task, assuming the piston is round.

H

Harold_V wrote: ↑Wed Apr 04, 2018 1:48 am

VmazKen wrote: ↑Tue Apr 03, 2018 6:51 pm The only 'knurled pistons' I've seen 'fail', were 'knurled' on a lathe', (never-ever do that

Hmmm. Causes me to ask why? Seems there must be some way to accomplish the task, assuming the piston is round.

H

I C Pistons are not round. From the oil control ring land upward they are round but the area that gets knurled below the wrist pin is cam ground or fat on the torque side of the piston. The skirt is the only portion of the piston that is knurled, and only knurled for a short distance on each skirt side. Since the skirt is usually a very thin section, the knurling machine supports the inside of the skirt where the knurling takes place on the outside. Knurling is considered 'custom' work because the knurled piston is hand fit back into its bore - the hand file then feeler gauge pull method.

BC

Thanks. I was aware of the cam grind, but have not seen knurled pistons before, although I have rebuilt a few engines in my many years. Of necessity, I replaced pistons instead of resorting to knurling (higher compression, or larger bore, depending on circumstances). Sort of reflects the limited number of experiences I've had, eh?

H

Harold_V wrote: ↑Wed Apr 04, 2018 1:20 pm Thanks. I was aware of the cam grind, but have not seen knurled pistons before, although I have rebuilt a few engines in my many years. Of necessity, I replaced pistons instead of resorting to knurling (higher compression, or larger bore, depending on circumstances). Sort of reflects the limited number of experiences I've had, eh?

H

As Kenny Creshy says (showing your age there Ken - ...but not me ) knurling is/was sometimes used as a cheap hop-up of an engine since it was used back before the Teflon, or other slick coatings on the scuffing part of a piston. It would also give an extended life to a tired engine by freshening it up with 'rings and bearings' and properly refitted (knurled) pistons. Most of the old ways are gone because of cheap replacement parts and sub assemblies but there is nothing wrong with that technology at all. After all, how modern is the IC engine anyhow? I had a Chevrolet 216 ci engine years ago that had no oil pump, dippers on the rod caps and cast iron pistons....and they were round too. It had a felt pad laid on the rocker shaft assembly as a drip oil supply from the mist from that whirling (3600 rpm max) ball of fire. An explosion going somewhere to happen...

BC