Grapple build question

[fasttruck860]

I'm just about to get started building a grapple after going back and forth over design and lead times. I have a friend that owes me a favor and is providing the cnc cut AR400 steel for free which will be all the tines. I'm going to fabricate the mounts, brackets and braces. The one issue I'm unsure of is the clearance for the hinge tubing and hinge rod. I'll be using DOM tubing and most likely a solid steel rod for the pin unless I should be using something else. I was thinking at least a 1" rod. What should I leave for clearance for grease, 1/16" or 1/8" or should it be tighter? I don't have a lathe so shaving it down will be difficult but I'm sure I can figure something out if I need to.

 

[texasranger556]

I just modified a bucket to fit my small backhoe by building new ears, ended up with about 0.030" clearance between the 1.25" pins and holes on the bucket ears.

 

[oosik]

I have no idea what the clearance is on my keeper pins on the "lid" of my grapple. It must be pretty tight. With the hydraulics disconnected on their connection to the upper lid - I can lift/shake the upper lid and it just moves smoothly up/down. No apparent looseness or rattle.

I have a Land Pride - SGC1560 grapple. 60" wide, 820#. The pins that hold the hydraulics to the upper lid, pins that hold the hydraulics to the bottom of the grapple and the pins that hold the upper lid to the grapple - all are 1.25".

 

[fasttruck860]

Okay. So it looks like I'm aiming for a tight fit or about 1/32" clearance. I'll have to look into increasing the pin size, although the thickness of steel around the mount would start to suffer.

 

[ptsg]

On my homemade loader, I left about 0.004" to 0.006" clearance between the pin and the bore on all of the pivot points. It's loose enough that you don't feel any play and grease can still go in just fine.

 

[mikester]

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

 

[fasttruck860]

What type of steel should i use for the pin? This will be a single lid so only one pin.

 

[LD1]

You need a set of dial (or digital) calipers for measuring pin clearences. something that will measure in .001" of an inch. Not a tape measure reading fractions. 1/32 is WAY too sloppy for a pin in a greasable bore. .004-.005" is sufficient. Any sloppier and your hole will be oval in no time. Not due to wear, but hammering.

You mention ONE pin because its a single lid. Not sure your design....my single lid has TWO pins at each end.

IF you dont have a lathe....shoulder bolts are a pretty exact size and quite hard. ANd if you get the right length you can secure with a nut and not worry about squeezing too tight and binding....and no cotters to loose in the brush. You can also get nominal size bronze bushings for pretty cheap

 

[fasttruck860]

That all makes sense and gives me more to think about. I think the size DOM tubing I'm planning on using has a tolerance of -.005" ID so I'll just figure on a tight fit and look into the shoulder pins. I was thinking a single pin because this will be a single piston upper lid, although I can easily make two pins work. A single long pin is going to be much harder to get aligned correctly especially if anything warps from welding.

 

[fasttruck860]

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

You need a set of dial (or digital) calipers for measuring pin clearences. something that will measure in .001" of an inch. Not a tape measure reading fractions. 1/32 is WAY too sloppy for a pin in a greasable bore. .004-.005" is sufficient. Any sloppier and your hole will be oval in no time. Not due to wear, but hammering.

You mention ONE pin because its a single lid. Not sure your design....my single lid has TWO pins at each end.

IF you dont have a lathe....shoulder bolts are a pretty exact size and quite hard. ANd if you get the right length you can secure with a nut and not worry about squeezing too tight and binding....and no cotters to loose in the brush. You can also get nominal size bronze bushings for pretty cheap

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.