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any tips on boring a con rod on the mill table?

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.
 
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.
 
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.
 
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.
 
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.
 
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.,
 
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.
Like I said you must straighten first for best results.Two long rods makes it so easy.
If you have a fixture great, if not that is a lot of work for 1 bore.
 
S&S Cycle sells an accurate checking pin for harley rod alignment. I use that and a Storm Vulcan rod alignment machine for all the Harley engines I do. Sunnen made rod alignment machines too. You can check bow and twist easily and correct any issues.
 
If you bore out the small end, you need an oversize piston pin. Do they make pistons with oversize pin holes?
 
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.
The spud sounds like a good idea, but I need it to expand and lock the rod perfectly square with table. I rebuild 2 sizes of rods, 45" rods and big twin rods. Each time the big end gets sized, The I.D. gets larger, so I need to figure out how to make an expansion spud ?
 
S&S Cycle sells an accurate checking pin for harley rod alignment. I use that and a Storm Vulcan rod alignment machine for all the Harley engines I do. Sunnen made rod alignment machines too. You can check bow and twist easily and correct any issues.
I have the S&S checking pin, and the Sunnen hone and dozens of mandrels. I'm just trying to re invent the wheel, if I can make both bores perfectly parallel, then I won't need to bend the rod. Any chance you could post a pic of your storm vulcan rod alignment machine? Thanks
 
The spud sounds like a good idea, but I need it to expand and lock the rod perfectly square with table. I rebuild 2 sizes of rods, 45" rods and big twin rods. Each time the big end gets sized, The I.D. gets larger, so I need to figure out how to make an expansion spud ?
You should be looking for a Berco rod mschine. More flexible than the TA.
Uses expanding mandrels to locate and hold rod big or small ends.
Cheers Ross
 
Here is a shot of my AB320
Rod mounts vertical (no sag due to gravity) \
Spindle mounts solid boring bars (40 taper)
Expanding mandrel mounts to slide that sets the rod length. Different mandrels cover a size range.
Can hold the rod either way and bore either the big end or the small end.
Bed provides the long power feed

full


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2and photo taken after adding DRO to long feed to control facing cuts (White metal rod applications)

Looks like there is one on bid spotter.....

Cheers Ross
 
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