Grapple build question

[jthibodeau89]

How would I use the bushings without a lathe? I'm struggling to visualize how this would work. I can think of one way but that would require using a larger ID tube on the ends and just inserting the bushing.

You got it, larger ID tube sized for bushing. Here are a couple pics of the pins on my MTL grapple. Not sure if it has bushings. Pin is 1". If you plan on a single wide claw, you may want to consider 3 or 4 separate hinge pins, not just one on each end.
View attachment 695820

 

[fried1765]

You need to decide on how sloppy you want your fit.

Start with google "greaseable pin hole tolerance chart"

also consider using bronze bushings and beef up your pin bosses.

Sloppy fit + high force loads = unhappy customer

I modified my new (low end ) grapple to include both brass pins (greasable) and bronze bushings.
Any measurable wear will be easily correctable, by replacing the pins and/or bushings.
I was able to find 1" bronze bushings only .0625 thick.

 

[fasttruck860]

You guys have been a wealth of information. This is exactly what I needed. I'm going to modify my plan a bit and make sure I order the correct ID pipe for the brass bushings. One last question, can one end of the pin free float or is it better to bolt both ends?

 

[metalbender]

A little different take on home built. Mine was fabricated from old rod weeder parts. No bushings, just big bolts. Made this as a grapple/ rock digger. Bottom spikes are 3/4 inch thick. Tops are 5/8. Good quality steel in those old implements. Not perfect but the price was right.

 

[jthibodeau89]

You guys have been a wealth of information. This is exactly what I needed. I'm going to modify my plan a bit and make sure I order the correct ID pipe for the brass bushings. One last question, can one end of the pin free float or is it better to bolt both ends?

See my pics above for pin lock.

 

[fasttruck860]

See my pics above for pin lock.

I can't seem to view your attachments above.

 

[fried1765]

You guys have been a wealth of information. This is exactly what I needed. I'm going to modify my plan a bit and make sure I order the correct ID pipe for the brass bushings. One last question, can one end of the pin free float or is it better to bolt both ends?

You can order most any size bronze bushings online, or on E-Bay.

I put nuts on the ends of my two primary pins (had to thread the pins).
Others, I just drilled holes through, and used "hair pins" at each end.

 

[jmc]

Random thoughts...

Anecdotally, TBN member IslandTractor reported taking apart the jaw pivots on his inexpensive, but well used grapple and found that the axles were just regular bolts. So their wearing surface was the threads' crests. there were no grease zerks and the thread crests show some wear but not enough to replace, IIRC. I wouldn't build mine that way but it suggests that maybe those pivots are forgiving.

IIRC, a bolt's unthreaded section, if it has one, is usually smaller than its nominal diameter. (that might be because a rolled thread increases the major thread diameter so they undersize the blank) If that's the case, that undersize might be enough clearance with a tube ID that's precise. Still, with only a few thousandth of an inch clearance, a straightness problem with either component may require more slop or correction.

Maybe try a long bolt with a useful unthreaded length and cut off the excess thread.

I'd use the softest axle steel available since it's easier to replace an axle than the tubing.

 

[jthibodeau89]

How about now

 

[fried1765]

Random thoughts...

Anecdotally, TBN member IslandTractor reported taking apart the jaw pivots on his inexpensive, but well used grapple and found that the axles were just regular bolts. So their wearing surface was the threads' crests. there were no grease zerks and the thread crests show some wear but not enough to replace, IIRC. I wouldn't build mine that way but it suggests that maybe those pivots are forgiving.

IIRC, a bolt's unthreaded section, if it has one, is usually smaller than its nominal diameter. (that might be because a rolled thread increases the major thread diameter so they undersize the blank) If that's the case, that undersize might be enough clearance with a tube ID that's precise. Still, with only a few thousandth of an inch clearance, a straightness problem with either component may require more slop or correction.

Maybe try a long bolt with a useful unthreaded length and cut off the excess thread.

I'd use the softest axle steel available since it's easier to replace an axle than the tubing.

Mine came with the same sloppy steel pins, and bolts with threads.
Changed all that to brass/bronze pins and/or bushings at all wear points, and added zerks.