Boring a Cast Iron Gear

[Kroll]

Guys this is a gear for the South Bend Fourteen that I been working on so I though I would start making the repairs but I guess there's more to the repairs than I thought.Anyway I am using my Atlas 12" lathe and turning around 480 rpm according to the plate and I am using cutting oil.Looking inside the gear its has a wavy pattern,the last pass I tried just taking a clean up pass.You know just going back over it at the same setting,which the wavy pattern was there before the clean up pass.The insert is one for just mild steel,its not one that specifically made for cast iron but figure it would work.What am I doing wrong,do I need to speed up the rpms,I am using the power feed than I tried hand feed but same results.Thanks for some guidance-----kroll

 

[Wreck™Wreck]

Essentially chatter.

Nothing wrong if it measures, surface finishes often have visual artifacts created by inconsistent feed rates and vibration, also the insert has a large nose radius, this often causes problems when boring deep holes so try a smaller radius insert.

Keep the nose radius of boring inserts as small as possible, by the pic you have many multiples of the bar diameter extended, make this as short as possible.

 

[Kroll]

Well I be,had to come in and post let ya'll know what Wreck Wreck said work.I change out the insert to a finish insert(for steel,didn't have one for cast)and shorten the boring bar.Boy couple suggestions,what a difference nice and smooth for cast iron.Wreck thank you for your post,I'm all smiles-----kroll

 

[Wreck™Wreck]

Glad that it worked out, when boring vibration is often a problem. A large nose radius tool makes it worse, this is also true when turning long thin parts between centers. Never extend the tools more then needed.

I have been doing this for a living for nearly 30 years so I should have learned something, I do learn new things weekly, will never know it all however.

 

[TakeDeadAim]

You also would be better off not using any cutting fluid on cast. Cut it dry and your finish and tool life will be better.

 

[rwm]

I am still wondering...is it better to use a boring bar or a reamer in these applications?
Robert

 

[TakeDeadAim]

Boring is used to accurately size and make round straight holes. It is also common practice to use boring to make concentric holes and precision holes in specific locations, with the above qualities.

Reamers are used to size existing holes in their current location. In other words a bored hole will be round, straight and true where a reamer will follow an existing hole sizing as it is fed.


Sent from my iPhone using Tapatalk