Machining hard steel

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seadragonfoundry

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I need to machine two shallow grooves in the OD of a 6304 2D deep groove ball bearing and also a shallow hole for a locating pin. This is to replace a bearing that has been unavailable for twenty years or more. One groove takes the thrust of the bearing, the other allows oil flow and the pin stops it rotating.
I have little experience machining hard materials in the home workshop so I am asking for advice. Just by looking online I believe the hardness may be around 60 -65 Rockwell C. TIA.
 

HennieL

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Would it be possible to rather grind the grooves than to machine them? I'm thinking of perhaps mounting a Dremel tool in your lathe's toolpost, if the bearing's ID is large enough to accommodate one of those Dremel grinding disks...
The other option would be to anneal the bearing, do your machining as per normal, and then re-harden the bearing (I gather from your user name that you have a forge to do this in...).
There are lathe tools with very hard inserts made to machine hardened steel, but I think that 65Rc would be pushing the envelope on this.

I hope you come right, and will be following this thread to hear other opinions.

Hennie L
 

danallen

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There are diamond coated carbide inserts available but using them requires a very beefy rigid lathe or they just rub. Good luck.
 

bikr7549

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CBN tooling may work. I have found that even with pretty light cuts that the Dremel spindle at 1/8" diameter deflects quite a lot. Maybe not an issue if precision not required.
 

SmithDoor

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I just used carbide and grind with a 7° to 10° rake.
The cutter will last for one bearing

Dave
 

seadragonfoundry

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Thanks to all for your replies. I have a tool post grinder and perhaps a thin metal cut off disc wIl rough the grooves and finish with a carbide tip. Maybe a CBN slot drill for the hole? Dave, was that rake that you ground positive or negative?
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SmithDoor

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roncohudd

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I need to machine two shallow grooves in the OD of a 6304 2D deep groove ball bearing and also a shallow hole for a locating pin. This is to replace a bearing that has been unavailable for twenty years or more. One groove takes the thrust of the bearing, the other allows oil flow and the pin stops it rotating.
I have little experience machining hard materials in the home workshop so I am asking for advice. Just by looking online I believe the hardness may be around 60 -65 Rockwell C. TIA.
I use ceramic. I have a few diamond shaped that fit my MTFNR-12-3 holder. They're almost like having gold when you need them.
 

ajoeiam

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I need to machine two shallow grooves in the OD of a 6304 2D deep groove ball bearing and also a shallow hole for a locating pin. This is to replace a bearing that has been unavailable for twenty years or more. One groove takes the thrust of the bearing, the other allows oil flow and the pin stops it rotating.
I have little experience machining hard materials in the home workshop so I am asking for advice. Just by looking online I believe the hardness may be around 60 -65 Rockwell C. TIA.
Hmmmmmmmmmmm - - - - is it maybe easier to figure out how to alter what the bearing mounts into and then use only a spring pin for locate and that spring pin's center hole for oil flow?

That might be an easier do than grooving a bearing in that fashion.

That's some serious groove depth.

Instead of cutting that groove on a lathe you might want to use a cutter on a mill and rotate the bearing for another option.
 

ajoeiam

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Excuse me, triangle, not diamond.
Hmmmmmm - - - - dunno if that 'shape' of tool would work.
Cutting a groove takes something much more like a cut off tool.
You can use the triangle shaped tool to rough to either the width or the depth (maybe both if you're lucky) but its not very easy to cut a rectangular shape using a triangular shaped tool.
 

Badhippie

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Do you have a rotary table if you do then use that with a end mill with a ALTIN coating I my self have to cut oil grooves or slots for non rotation in bearing races up to 36 inch Diam.
Since you mentioned being a home shop I doubt you will have enough H/P to use ceramic’s but I may be wrong. What ever you use you won’t be able to take a very large DOC
But I use the ALTIN coatings and have had great success with them. But they will cost some money
Thanks
Tom
 

john g

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Has Anyone ever dressed a cutoff wheel to be square on the end?
use a Norbide Dressing Stick . its a very hard and brittle stone . holding by hand use the edge against the diameter of the cut off wheel , it will cut it easily . buy through a machine tool supplier . they are made by Norton the grinding wheel company
 

SmithDoor

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I have used a Dremel in past for a very thin Grove. It hard to make a square bottom.

I did find most work the carbide tool bits was faster and gave a square bottom.

Dave

Has Anyone ever dressed a cutoff wheel to be square on the end?
 
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