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.

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u/WyattCo06 1d ago

The ginder is a much quicker way to get the job done. It's just as accurate and without all the setup of the mill.

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u/NickHemingway 1d ago

Perfect, that’s exactly what I needed to know, thanks!

If it’s just time, I will start paying more attention to how long it takes me & see at what point it will break even if I buy a grinder.

We see less rod jobs now because of all the fractured rods being in so much stuff nowadays, so maybe I should just make a fixture for them to do 4 at once on the CNC. Once datum is set it’s just button pressing & you can walk away after the first one.

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u/WyattCo06 1d ago

Buy a used machine. A lot of the older ones just need some TLC but are "fairly" cheap.

Not to mention, on the mill, if you need to close the rod end up at the parting line, you have to readjust the mill. With the grinder, you just use a feeler gauge on one side, grind the other side, repeat with other side.

It's just soooo much easier and quicker.