Remove sheered alignment dowel

D

dansawyer

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I have a Lagun head with parts in a box. One of the parts is a casting that is part of the drive mechanism. The casting has 5 holes, 2 are threaded to hold it in place and 3 that have dowel pins. Two of those pins are sheered.
How can sheered dowel pins be removed?

Alternative, the pattern in the 2 mounting holes are at 180 degrees. The alignment holes are in a 120 degree pattern. I had thought about rotating the casting 180 degrees and drilling three new pin holes.

The casting is about 3 1/2 inches in diameter and the center drive hole is about 1 1/4 inch in diameter. The section that would have to be drilled is about 3/8.
Advice appreciated,
Thank you.
Dan
 
A picture would help a lot. Typically, dowel pins are used to hold assembled parts in a very precise position. So, rotating and redrilling would most likely not work out for you.

Most common dowel pins are just case hardened. You can probably drill and tap a hole in them and use a slide hammer to pull them out. I have also drilled in from the back side (when the situation allowed) and punched them out with a drift.

Whatever you do, try not to booger up the hole or the replaced dowel pin won't be able to do it's job and maintain the part in the correct position.

Ted
 
A puller set up that resembles a stuck case remover would work well. Drill and tap the largest hole possible in the dowel pin without breaking out the side. Use a grade 8 bolt or screw with a fine thread. The set up would go like this, screw the stud in the dowel pin, drop a spacer over the stud, drop a flat washer on top of the spacer, screw a lubricated nut down to the washer. Now you have a miniature puller with a tremendous amount of power. Also the more of the center you remove from the dowel pin, the more tension you will remove from its grip to the hole it is in.
I hope this is understandable.
 
Thank you. The top of the pin is broken at a slant. Is it feasable to mill that broken edge before dirlling? This would stand a chance of keeping the dirll in line.
 
This post needs PICTURES.
I have both fought dowel pins and rotated and drilled new holes but I dont know which way to go because I Can't See It!
lol
 
dansawyer said:
Thank you. The top of the pin is broken at a slant. Is it feasable to mill that broken edge before dirlling? This would stand a chance of keeping the dirll in line.
Click to expand...
Yes, mill the top flat, then start the hole with a center drill
 
I would believe this is the place for a carbide end mill of the diameter you might use to tap the dowel. The word of caution about not messing up the hole can't be over emphasized, Good Luck
Ray
 
I have a welder "personnel friend" that works for me & I would have him TIG a couple of set screw to the top of the dowel pins & be ready with a puller as soon as he finish welding each one.
This would save the slanted dowel being an issue.
 
Tinkertoy1941 said:
I have a welder "personnel friend" that works for me & I would have him TIG a couple of set screw to the top of the dowel pins & be ready with a puller as soon as he finish welding each one.
This would save the slanted dowel being an issue.
Click to expand...
Reasonable idea, however, that would depend on the diameter of the dowel pin and where is is sheared off relative to the casting.
Robert
 
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