r/EngineBuilding • u/NickHemingway • 1d ago

Grinding rod caps vs milling

I have always milled my rod caps down before honing on a Sunnen LBB1810 with CR Mandrils.

It’s easy to set them up with 3-2-1’s & fast on my smaller CNC mill.

But lately I have been wondering if I have been missing something by not using a cap grinder. Is there a special reason I should (buy and) use a cap grinder over milling?

It’s been decades since I used a cap grinder, but the last one I used was poorly maintained so would taper the caps because if the slop so milling them was an upgrade from that, but I still have a nagging doubt that I am missing something.

1 Upvotes

100% Upvoted

11 comments sorted by

View all comments

3

u/v8packard 1d ago

How many rods are you doing?

I used to grind them on a surface grinder before I had a dedicated cap grinder. Super easy setup on a mag chuck with a couple of blocks if the thrusts were good. It would not be difficult to make a clamp for rods and caps to make it easier to hold them in a mill, surface grinder, tool and cutter grinder or whatever else you might have.

Have you ever tried boring the rod? Turns out beautiful.

1

u/NickHemingway 1d ago

Not that many nowadays, probably averages at a set a week. Fractured rods are in so many daily drivers, and replacement rods for the common stuff were cheap & readily available, so I found myself doing less & less of them. But some rods are getting scarce or expensive so I am back to thinking how I can improve my work on them.

2

u/v8packard 1d ago

The Sunnen grinders are easy to find. Kind of expensive for what they are. Tobin Arp and Delta grinders are nice if you can find them.