Polishing conrods

Please,
Someone can tell me what needs Polish the rods?
Thanks.
Ciao.
Pieo

You need to remove any nicks along the edges of the rods. Careful use of file or
sandpaper and smooth that out.
Bead blasting good too. Polishing mostly a feel good operation.
I did all the above. I feel better now.
Eyewash mostly.

Onder said:

You need to remove any nicks along the edges of the rods. Careful use of file or
sandpaper and smooth that out.
Bead blasting good too. Polishing mostly a feel good operation.
I did all the above. I feel better now.
Eyewash mostly.

Click to expand...

Thank you
But what does the polishing? What effect does it have?

Dinks and nicks are areas that fractures and cracks can start from.

By polishing these away, you minimise the stress points that these can originate from.

... oh, and it looks nice and shiny too :wink:

Technically, the final polish is with a high-speed buffing wheel and abrasive (some type of solid polishing compound). You have to make sure first the rod isn't bent because then it's trash. The goal is a hyper-smooth surface to avoid stress risers. An example of a stress riser is the line that is scribed on glass to cut it to size. Any rough edge on the body of the rod can act as a stress riser. As described above, the polishing can start with sandpaper but I'd think anything that actually required a file may be too large a gouge in the rod and maybe it should be replaced.

Anybody with before/after photos of rods they'd successfully polished??

I don't think it's a recommended practice. Clean them up, inspect them thoroughly, get them back in service. Any mishandling could be bad. I don't think that they are all that delicate but anything of that nature should be handled with care.

" Please,
Someone can tell me what needs Polish the rods? "

This is so if the crank(shaft ) goes through the bottom of the cases , it still looks cool & shiney .

Er . . .

Tends to make the surface less susceptable to damadge & should reduce drag on oil mist in cases . . .. we hope .
Generally youd use it on NEW Rods only , or at least ' As New ' . Unless its for putting on the matle piece as a ornament . :?

Generally polishing internals reduces drag & prevents ( we hope ) ' stress raises ' that produce cracks .
Crankshaft , sprocket teeth , pump gears & internal faces . Rocker arms , etc etc .

Valves & combustion chambers (part) of the ideas to keep it clean / stop the carbon build up .
Mostly the ports are ' cleaned up ' . Not ' Mirror Finished ' . thence ; propewrly polished parts : are MIRROR FINISHED ,
like our boots , you can see ypure face in them . :? 8) :lol:

As a rule the polish is up and down the beam not across it when done with a buff,if you going to that amount of detail it does not hurt to have the big end checked for size and they are straight as already mentioned.

The original Norton works did not polish the 650/750 connecting rods, the rods were forged aluminum and they roughly ground off the parting flash and were done with it. From 1963 onwards AMC started polishing the rods and the quality was spotty. You can look at Norton rods and see that they first ground the flash off the rod and they did not go lengthwise either, after the flash was off then it looks like they went lengthwise with a fine sanding belt.

Often though Norton did not get all the initial grind marks off the rods leaving notches in the corners of the beams in very bad places, the worst place probably.

A good polishing job done lengthwise to a near-mirror finish is going to be better than what the factory did, but remove no more metal than absolutely necessary. Glass beading would not be a good practice, as the glass beads fracture with use and end up putting a rough finish on the rods, so you are back to having thousands of tiny stress risers. Shot peening when properly done should produce the most reliable rod, it will not only remover the stress risers, but will leave a harder surface. I am sure that shot-peening is an art, requiring different pressures and shot for various metals.

Polishing is the poor-man's method, but can and has done the job and also it can be done artfully well or poorly.

Good luck......

Shot peening when properly done should produce the most reliable rod, it will not only remover the stress risers, but will leave a harder surface. I am sure that shot-peening is an art, requiring different pressures and shot for various metals.

Click to expand...

I believe (and I'm often wrong) that the Andover rods come shot peened? Mine were from an early remanufacture batch at the end of 2002 and they have a slightly rough finish. I have avoided polishing them unneccessarily but each time the engine has been opened for a cam or whatever, I am tempted to disassemble and polish them.

Well having just finished polishing rods for my Commando and my Trident, I can say that the
Triumph rods were more polished than the Norton from the factory. However they did the area
near the bolts left to right not up and down! There is, however, no flash visible from the forging.
On the Norton there certainly is. The grinding marks on the steel caps are pretty cobby on both.
My rods look great, I feel better and I doubt it matters one way or the other for normal street work.

It depends on whether the rods are steel or aluminium. Stress raisers should be polished out of aluminimum, and ground out of steel rods. It is pointless shot peening aluminium rods, with steel rods the peening creates a surface layer which has the effect of distributing the stresses . Japanese two stoke rods often dont have the marks ground off them, they are s hot peened then copper plated. When I built my methanol fueld T250 Suzuki, I balanced the rods end for end, by grinding weight of the little end of one of the pair , then I polished both. It was not good practice to remove the shot peened layer, however the rods did not fail in that motor, and after I sold it, the next owner won 28 races and five historic championships, with that bike. The Suzuki rods I used were from the T20 model which had smaller little ends, gudgeons etc, and supported a piston with a wider skirt on the inlet side, so the inlet ports were widened a lot.

Hi Sirs,
I read al your posts with much interest but i dont also understand why it needs, or not, polish the conrods!
Thanks.
Ciao.
Piero

Use the conrods as sold by Norton, unpolished , thousands of Commandos have been driven for millions kilometers without polished conrods.
When I don't know what to do and dont'l know how to do , I use whatever was designed by Norton factory engineers.

@pierodn: If you have small nicks or scratches in your connecting rods it is a good practice to smooth them over as they can act as stress risers; a point where a crack can start.

Smoothing over may infer polishing so it is a matter of degree as to how fine a surface you want to achieve.

The stock Norton connecting rods are very durable so for street use I doubt minor scratches will be of any consequence but still a good practice to smooth out and maybe spot polish. For street applications, polishing is unneccessary.

If it were me and I had the rods in hand; I would smooth out all nicks and scratches and polish as it is not a difficult task.

Well thank you, it sounds good.
Ciao.
Piero