1940indianchief
Plastic
- Joined
- Jan 18, 2023
- Location
- Rock Creek BC
Does anyone have a holding jig to hold a con rod on mill table, to bore small end parallel with big end?
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any tips on boring a con rod on the mill table?
- Thread starter 1940indianchief
- Start date
- Replies 6
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just Dave
Plastic
- Joined
- Jan 18, 2023
I have had good luck straightening with a long rod fit snug in each end ( bush if needed) . With the two 4 ‘ rods it is easy to see when you get it perfectly straight. Use eye for angular alignment and rod end to rod end measurement for parallel alignment. Once straight tie it down and bore. You can use alu. Tie downs if you have very small margins around bore and thick dense paper under to facilitate a thru cut.
john.k
Diamond
- Joined
- Dec 21, 2012
- Location
- Brisbane Qld Australia
Conrods that had white metal bearings always have two centre drill cuts ,just outside the rod bolt bores either side ...........these two cuts are held by two centres on the boring machine ,as is the small end held by a couple of opposed cones.............up to the 1950s,every small lathe had a fixture with two screw in centres to hold rods for boring.
1940indianchief
Plastic
- Joined
- Jan 18, 2023
- Location
- Rock Creek BC
I am working on vintage harley motors. The manual tells you to check for a bent or twisted rod, with a checking pin in wrist pin hole and laying across motor cases. and to straighten bent or twisted con rods by bending rod with a bar. This method does work, but I am trying to get away from that by boring a new wrist pin bushing that is perfectly parallel with big end of con rod. I am just trying to figure out how to make a jig that will hold the big end perfectly square with table. Thanks in advance for any replys.
Dan from Oakland
Titanium
- Joined
- Sep 15, 2005
- Location
- Oakland, CA
Make a spud with a hole drilled thru the center with the OD the same size as your big end bore. Make sure to face the end of the spud square with the OD. Bolt the spud on the mill table and put the big end of the rod around the spud. A small vise at the other end or better a simple block with two pointed set screws to bite the sides of the small end of the rod ..............hope you get the idea- square up your spindle and you're ready to go.
john.k
Diamond
- Joined
- Dec 21, 2012
- Location
- Brisbane Qld Australia
There is a device that was called a "SeaLion" that goes with every old rod bearing boring setup.........the instructions that go with this device explain testing and correcting bend in conrods.......incidentally,prewar engine rods were made to be bent for correction........basically ,you hand ream the pin bore ,and bend the rod to correct piston alignment .......Ive done this many times with Wisconsins,Ford flatheads,Harleys Indians,etc.
john.k
Diamond
- Joined
- Dec 21, 2012
- Location
- Brisbane Qld Australia
The factory always machined the rod held by the three centres .....one atop the small end,and two on either side of the bigend.....if your jig holds these three points rigid ,thats all you need ....check your South Bend lathe book for conrod bearing boring......Myford also supplied a similar fixture,also in the instruction book.,
