So sometime back i posted about a machine that i got back into service. Its a Tobin Arp cylinder head cam bearing line boring machine. (overhead cam heads)
Project was done to finish a set of DOHC heads for a V-8 50's Spanish car :Pegaso.
The project included finish boring the housings for the head cam bearings.
https://www.practicalmachinist.com/v...ghlight=Pegaso
Well the project continues. Final step in getting the heads finished is to make the required bearing shells that carry the cams in the head. (fits to the bores finished in the above work)
At first glance this looks like a simple job of making bearing shells.
Issue is that the shells are split in two half's so they can be installed ...
There are two ways to make this sort of bushing and i have used both methods for making all sorts of bearing shells for main bearings etc.....
The first process is to make the shells oversize on the OD and small on the ID.
Cut them apart, clean up the cut edges and carefully soft solder the half's together, re-chuck the assembly, finish the OD/ID then break the two half's apart.....
The second method requires double the number of parts be made , cut apart, slightly long on one side, then carefully clean the parting face to exactly half the OD of the bushing.
The first method takes longer to do, but saves material.
The second method requires the wasting of half the bushing material (recycled). I opted in this case for method #2.
I opted to make a fixture to make the machining of the bushings easier.
The parameters were that i wanted a repeatable holding setup, that could locate the half's for trimming at the parting face and allow cutting in clearance notches on the shell sides to clear the cap studs,
and drill/ream the shells for locating pins.
Here is my solution:
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Bushing fit to fixture. Bushing finished both ID , OD and length , Bore touched on the hone to give better finish.
Tool used without locating pin to drill /ream hole in bushing and cut in reliefs on the sides to clear the bearing cap retaining studs.
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Bushing completed, first step. Locating hole drilled/reamed, clearance notches for cap studs cut in.
Cheers Ross
Project was done to finish a set of DOHC heads for a V-8 50's Spanish car :Pegaso.
The project included finish boring the housings for the head cam bearings.
https://www.practicalmachinist.com/v...ghlight=Pegaso
Well the project continues. Final step in getting the heads finished is to make the required bearing shells that carry the cams in the head. (fits to the bores finished in the above work)
At first glance this looks like a simple job of making bearing shells.
Issue is that the shells are split in two half's so they can be installed ...
There are two ways to make this sort of bushing and i have used both methods for making all sorts of bearing shells for main bearings etc.....
The first process is to make the shells oversize on the OD and small on the ID.
Cut them apart, clean up the cut edges and carefully soft solder the half's together, re-chuck the assembly, finish the OD/ID then break the two half's apart.....
The second method requires double the number of parts be made , cut apart, slightly long on one side, then carefully clean the parting face to exactly half the OD of the bushing.
The first method takes longer to do, but saves material.
The second method requires the wasting of half the bushing material (recycled). I opted in this case for method #2.
I opted to make a fixture to make the machining of the bushings easier.
The parameters were that i wanted a repeatable holding setup, that could locate the half's for trimming at the parting face and allow cutting in clearance notches on the shell sides to clear the cap studs,
and drill/ream the shells for locating pins.
Here is my solution:
Bushing fit to fixture. Bushing finished both ID , OD and length , Bore touched on the hone to give better finish.
Tool used without locating pin to drill /ream hole in bushing and cut in reliefs on the sides to clear the bearing cap retaining studs.
Bushing completed, first step. Locating hole drilled/reamed, clearance notches for cap studs cut in.
Cheers Ross