# Milling radius grooves



## Jasteven (Aug 24, 2019)

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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## Alexander McGilton (Aug 24, 2019)

Buy or make one of these tools in first link. I would hand grind a tool from HSS round stock or a broken endmill shank. If the shank is too small for the boring head then buy or make the item in the image.





						Face Grooving Tools - Full Radius - Series 73
					

Internal Tool



					internaltool.com


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## RobertB (Aug 24, 2019)

Have you seen the cutters designed for this?


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## Cadillac (Aug 24, 2019)

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.


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## pstemari (Aug 24, 2019)

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.

Sent from my Pixel XL using Tapatalk


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## Jasteven (Aug 24, 2019)

RobertB said:


> Have you seen the cutters designed for this?


 
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


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## RobertB (Aug 24, 2019)

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.


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## Illinoyance (Aug 24, 2019)

It looks like the cutter was ground from an on-edge threading insert.


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## RobertB (Aug 24, 2019)

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.


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## Jimsehr (Aug 24, 2019)

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.


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## kd4gij (Aug 24, 2019)

Aligning the grooves with the grooves on the head with the block will be the most challenging.  With out the templet.


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## Jimsehr (Aug 25, 2019)

Do you have a pic of the head. Showing where the top radius cut goes ?


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## kd4gij (Aug 25, 2019)

Jimsehr said:


> Do you have a pic of the head. Showing where the top radius cut goes ?


 


It is in post #1 a little small


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## Jimsehr (Aug 25, 2019)

I mean the part that will mate with the radius. It’s easy to find the center of the bore .
But how do you find the center of the mating part . So both top and bottom mate.


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## Jasteven (Aug 26, 2019)

Jimsehr said:


> 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.
> 
> View attachment 300892



Thanks jimsehr, I agree, that would be more desirable than a boring head. I'll give it a shot

My comp engine has a fire ringed head and block, but the black has been decked since and lost about .006 of groove depth. As far as locating the grooves, I have the block and head in front of me to pick up the dimensions from. I also have the junk head I spoke about, which I have no problem using as a test mule.  I would like to purchase, or build my own tooling to use to cut these receiver grooves deeper on the existing head, and possibly a back up head. 

This is more of a project I want to figure out how to do, rather than a project I must do, as I could use a thicker headgasket, and my existing head grooves would fall into spec. It's a project I'm interested in performing as I'm an average Joe with a very expensive hobby and would like to learn how to do as much of my own work as possible.


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## Jasteven (Aug 26, 2019)

Oops, the head has been decked since.  Not the block. Grooves on the head are lacking about .006 for STD thickness HG


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## Jimsehr (Aug 26, 2019)

If you post a pic of both mating parts I think I could come up with a simple way to line up both the top and bottom radi. 
Might  not be as good or fast as a production one. But  one that would work for a home shop.  
Pic should be as big as you can get. 
Jimsehr


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## Jasteven (Aug 26, 2019)

Having trouble posting pics... File too large


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## Jimsehr (Aug 26, 2019)

Don’t need whole head , just around where the radius goes.


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## Latinrascalrg1 (Aug 26, 2019)

Jasteven said:


> Having trouble posting pics... File too large


The easiest way i found to solve this issue if you dont have a resizing app on a smartphone is to simply open the picture on your phone and take a "Screen Shot" of the picture in question and then post the screen shot duplicate.  The default setting on my screen shot is small enough to post here without a problem without messing with my camera's settings.


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## Latinrascalrg1 (Aug 26, 2019)

Jimsehr said:


> Don’t need whole head , just around where the radius goes.


It wouldn't matter if he zoomed in close or out as wide as possible because it has nothing to do with the pictures actual image.  It has to do with pixel size being larger then the sites limits setbin place to conserve memory space.


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## pontiac428 (Aug 26, 2019)

Back in the day, we would call these "o-rings" and use .015 stainless wire.  Grooving was cut with a boring bar or a facing tool with a shop-made radiused groove cutter, and only the block was done because a deck job was cheap and many builds could survive a .015 decking compared to decking the heads.  Nobody cut two o-rings and opposed (mated) them on the block and heads.  So with these diesels, the minimum wire is .049 and it is run on both sides of the gasket.  That's quite a bit different than the nitrous and blower motors of the 80s and 90s.  What's changed to require two fat o-rings?


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## Jasteven (Aug 27, 2019)

pontiac428 said:


> Back in the day, we would call these "o-rings" and use .015 stainless wire.  Grooving was cut with a boring bar or a facing tool with a shop-made radiused groove cutter, and only the block was done because a deck job was cheap and many builds could survive a .015 decking compared to decking the heads.  Nobody cut two o-rings and opposed (mated) them on the block and heads.  So with these diesels, the minimum wire is .049 and it is run on both sides of the gasket.  That's quite a bit different than the nitrous and blower motors of the 80s and 90s.  What's changed to require two fat o-rings?




Hey Pontiac!  That is correct. And O rings still are alive and well, and are still used. O rings are just a more street friendly version of a firering, firerings beings really for competition use only. In an O ring application, the o ring in the head helps clamp down on the firering inside the headgasket to help seal. In a "Firering " application, an aftermarket headgasket with the firering removed from the gasket is used, and .105"x4.550 rings provided, and instead the receiver grooves are cut and firerings are recessed into the head/block. It's fairly old technology I believe, same old school rules apply, but is more commonly found in diesels due to extreme exhaust gas temperatures and boost pressures. Comp diesels using multi-turbo applications can see 2000* egt,  and boost pressures of 100psi +, this is where the firerings come in, aiding the headgasket, and clamped down using 26- 14mm fine thread head studs. Also these engines have comp ratios of 16.5:1, some newer engines 19:1, and in a performance scenario can use all the clamping/sealing available


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## pontiac428 (Aug 27, 2019)

I could see why competition diesel is on the extreme end of cylinder pressures.  So is the fire ring a one piece deal that sits in recesses in both the head and block, or are you using two rings and butting them together?  The one piece ring might require more precision than you can get with a boring bar indexed off of the stud bosses.  Hitting a tight tolerance on both mating halves would require a skill level more like die making than old school performance shop machining.  I suppose that's why people buy those very expensive tools and alignment plates to do the job.  I wouldn't hesitate to do an o-ring job in my home shop, but this seems to be something different.  I could grind a custom radiused bit for you if you get to that point.


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