Big end journal diameter

Dear All,
I need your help.
The standard size are (as manual says) 44.472/44.460 mm.
The regrinds coul be - 010, - 020, - 030, but i dont know if this measures are in inch or mm (may be inch).
Please, can someone convert re grind measures in millimeters?
Obviovsly this I need because I do not have his connecting rods!
Thanks.
Ciao.
Piero

I think the journal sizes are in mm but the replacement shells come in inch measures for standard step downs to fill in on re-grinds. Machinists shop would know this as well as suppliers of the shells, ie: what size per re-grind step. Some of mine came too tight but a razor blade made em just right - after some trial error cycles.

Yes,
But i need to convert -010 etc. in mm.
I dont understand if the regrind measure are - 0.10 or 0.010????
Please, could someone tells me and convert the correct measure in mm ?
Ciao.
Piero

.001" = .0254mm
.010" = .254mm
.100" = 2.54mm
1.00 = 25.4mm
10.00 = 254.00mm
100" = 2.54m

pierodn said:

Dear All,
I need your help.
The standard size are (as manual says) 44.472/44.460 mm.
The regrinds coul be - 010, - 020, - 030, but i dont know if this measures are in inch or mm (may be inch).
Please, can someone convert re grind measures in millimeters?
Obviovsly this I need because I do not have his connecting rods!
Thanks.
Ciao.
Piero

Click to expand...

I'm not sure where you got your numbers, but my Commando manual lists the standard big end size as 1.750", or 44.450 mm. The manual allows 1.7505" to 1.7500"/ or 44.450/44.463 mm. The .010, .020. and .030 regrind sizes in the manual are in inches, and that's the way the bearing shells are sold. The first undersize is ground to 1.7400"/1.7405", or 44.196/44.209 mm, the second to 1.7300"/1.7305", or 43.942/43.955 mm, and the third to 1.7200"/1.7205", or 43.688/43.701 mm.

Once reground, the crankshaft should have the undersize stamped on the cheek, you can't rely on that always being done.

Ken

lcrken said:

pierodn said:

Dear All,
I need your help.
The standard size are (as manual says) 44.472/44.460 mm.
The regrinds coul be - 010, - 020, - 030, but i dont know if this measures are in inch or mm (may be inch).
Please, can someone convert re grind measures in millimeters?
Obviovsly this I need because I do not have his connecting rods!
Thanks.
Ciao.
Piero

Click to expand...

I'm not sure where you got your numbers, but my Commando manual lists the standard big end size as 1.750", or 44.450 mm. The manual allows 1.7505" to 1.7500"/ or 44.450/44.463 mm. The .010, .020. and .030 regrind sizes in the manual are in inches, and that's the way the bearing shells are sold. The first undersize is ground to 1.7400"/1.7405", or 44.196/44.209 mm, the second to 1.7300"/1.7305", or 43.942/43.955 mm, and the third to 1.7200"/1.7205", or 43.688/43.701 mm.

Once reground, the crankshaft should have the undersize stamped on the cheek, you can't rely on that always being done.

Ken

Click to expand...

Hi,
The techical data on the beginning of the workshop manual says:
1.7509/1.7504 in (44.472/44.460 mm).
Another workshop manual says like you wrote, but not the same conversion, in fact:
1.7505/1.7500 in (44.462/44.450 mm): almost the same you wrote.
Also a third manual says 1.7505/1.7500 in (44.462/44.450 mm).
Unfortunately the crankshaft dont have the undersize stamped on the cheek.
In any case, now i have the total regrind underside.
Thanks.
Ciao.
Piero

Hi Piero,

the only place I have seen the 1.7509"1.7504" specification for a Commando was in a non-factory service manual for a wide range of Norton twins. All the factory service manuals I have seen use the 1.7505"/1.7500" specification. Norton designed the twins, including the Commando, using inch dimensions, not metric. I've seen some of the factory blueprints, including for the crankshaft flywheel, and all the dimensions are in inches. Any metric dimensions you see in the manuals are derived by converting the inch measurements into mm. If in doubt, start with the inch dimensions in the factory manuals, and convert to metric.

Ken

Yep, pays to check conversions.
Actually, the Mk3 workshop manual shows the 1.7509 / 1.7504 figures.
The Clymer manual ISBN 0-89287-158-X shows the 3 regrind figures , on page 80, in inches ok, but the conversions are wrong.
In the same manual, in the engine specifications on page 201, the cylinder bore conversions are wrong too.
Anyway, needless to say it is the machinist who determines the actual grind diameter once he has the rod and shells in his hands...

Interesting info, slim. I stand corrected. I have several Commando service manuals, but they are all pre-MK3. Makes me wonder why they changed the spec on the journals after all those years? The rod and bearing dimensions are the same as always, but they spec the journals larger, presumably for a tighter fit. If anyone knows why, this would be a good place to let the rest of us know.

Ken

PROBABLY TO USE UP ALL THE OVERSIZE RODS, sorry for shouting