How do I cut o-ring grooves

[Grasshopper]

I'm new at this and wanted to know if there is an insert for cutting o-ring groves. I want to add one o-ring to a shaft that presently employs only one o-ring. Has this already been covered elsewhere on this site? TIA, Kent

 

[kd4gij]

There are grooving inserts. Or grind a HSS bit to the with of the groove that is in there. The tool holder and insert won't be cheap. A parting blade can be ground to the right size.

 

[Jimsehr]

Also might look at quad rings. It’s almost like having two rings in place of one.
jimsehr

 

[benmychree]

Proper O ring grooves are not straight sided as to be cut with a parting blade, they are tapered at the sides and have radii at the root.

 

[Cadillac]

Proper O ring grooves are not straight sided as to be cut with a parting blade, they are tapered at the sides and have radii at the root.

Idk about that. I rebuild ALOT of hydraulic motors, cylinders and can't recall any being radiused at the root. Only time I can remember that scenario is some engines where a large oring is used to seal two mating surfaces.
I do know the groove size is critical to get the proper squish on the oring to seal correctly, and different pressure involved use different designs.

 

[OTmachine]

O-ring groove sides are pretty much straight. They can have taper, but are better if straight. Best tool profile is like a double hump camel face parting tool with the width of the tool narrow enough so that the top of the one hump will just pass over the surface cut by the top of the other hump. My .02

 

[benmychree]

So, look it up!

 

[BGHansen]

Here are some options for O-ring grooving. The inserts are MGMN style which are available in a number of widths. Search on eBay for MGMN 150, 200, 300, 400, etc. They are metric in size, divide the number by 100 for the width in millimeters (200 = 2 mm). They are available in external and internal set ups.


These happen to be MGMN200 and MGMN300 bits on boring bars ($10 or less with 10 bits from China)


Insert is replaceable and double ended



External MGMN200/300 inserts. I wrote the English width on the tool holder for DRO purposes ($10 or less with 10 bits from China).




Also pictured are a number of Rovi solid carbide pre-ground boring bars for grooving. These are available from a number of sources (i.e. Micro 100, Rovi, etc.).


These work really well, much better than the MGMN bits, but they are more pricey (~$20 each).



Or, as mentioned above, you can use a boring bar and hand grind a cutter to the width you need.





Bruce

 

[twraska]

So, look it up!

All specs I’ve ever seen were for a square bottomed groove. Do you have specs for round bottomed? I’d like a link for my information if you do.
Thanks
Tim

 

[Janderso]

I checked MSC for grooving tools. The first few that popped up did have a radius.
For example,
0.145" Groove Width, 1/4" Min Hole Diam, 5/8" Max Hole Depth, O-Ring Grooving Tool
In the specs of the tool, it showed a .040" radius.
I have no opinion, I'm just a hobby guy.

I also found this guide, it mentions -radius
<<<<<<Metric o-ring groove designs vary greatly and choosing the right one for your application is important for maximum o-ring performance. This metric o-ring groove design reference guide will help you find the right radius, back-up, pressure and other o-ring dimensions for basic applications. Once you find the exact metric o-ring you need, you can easily order online from the world's largest o-ring inventory network. >>>>>>>