Milling radius grooves

Jasteven

Jasteven

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Hey guys, I am taking on a new project for myself, building a backup cylinder head for my comp truck. The current cylinder head was machined before I purchased it, but since then have taken interest in reproducing some of its features. I am interested in cutting Fire Ring grooves in the face of the cylinder head around the combustion chamber. Attached is a photo of the firerings grooves. Grooves must be radius .120 x 4.445 diameter x .014-.016 depth

What tooling should I use to cut these grooves? Can a boring head, with a bar mounted in the horizontal position with a downward protruding radius achieve these results? I assume it would work, but having difficulty finding a 1/2" bar and .120 radiused insert... But, I do not have alot of experience here. Still pretty novice with the Bridgeport and tooling
 

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Use a boring head then grab a 1/2” shank tool and grind your dimensions on the end of the HSS bit. Keep as short as possible. Once your tool is ground get your diameter set on the boring head and control your depth with the knee of the mill.
 
Thinbit makes a variety of face grooving tools that should meet your needs. In particular you can get inserts in any number of stock radii and custom radii if you need them.

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Last edited:
RobertB said:
Have you seen the cutters designed for this?
Click to expand...

Robert, yes I have seen the fixture plate/hand cutter before, but there damn expensive for a one/two time use. I have a mill and lathe in my garage, and would like to give them a short. Have a head here that fail magnaflux testing that I will be my test mule

My boring head is a 3" model, but using a cutter in the horizontal position should work, but I don't know if a ground 1/2" blank will work as the cutting edge wouldn't protrude beyond the face of the boring head. I believe If I use a homemade cutter I would have to braze a tip onto the blank In order to protrude past the boring head, mostly why I have been shopping around for a premade bar. Possibly like an internal o ring cutter for the lathe, or something similar that would fit my 1/2" boring head
 
Grinding a radius cutter to the precision needed for a fire ring I think would prove very difficult.
In ready made inserts, a 6mm one is about as close to .120 radius as you are likely to find but you would have to braze it to a bar to fit your holder. For a one off job having a custom radius cutter made would be cost prohibitive. Even the ready made inserts are pretty spendy.
 
It looks like the cutter was ground from an on-edge threading insert.
 
Here you go: http://bhjproducts.com/bhj_content/products/blocktooling/org.php

From their page:
Replacement cutting Inserts are available in standard widths of .039”, .048”, .050”, .060”, .085”, .120” and .125” and
are also available in custom widths on a special-order basis.

They have a good closeup of the end of their tool holder, you should be able to fabricate a similar holder to fit your boring head.
 
With a bore head it will be hard to set dia of radius. I would take a 5 inch disk of stock about 1/2 inch thick and center it on mill. Then drill and bore a 3/4 bore on center then move off center half of radius dia and then drill and bore or ream dia of needed radius. Then use a 3/4 piece of stock inserted into disk as a shank to hold in collet in mill. Then insert a round piece of carbide into disk. You would have to grind
Needed radius on end of carbide.

1566686457135.jpeg
 
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