Thumb for mini hoe

[BobRip]

I would like comments on the different uses people have found for the thumb. So far I have heard of picking up logs and rocks and pulling up brush. Any other uses and descriptions of how you do this would be appreciated.

 

[BobRip]

I have attached two more pictues on the thumb parts.

 

[MossRoad]

My biggest problem seems to be that the parts would shift after welding. I would have everything lined up and then weld and it would not be lined up. Does anyone have suggesting to correct this. Maybe I should drill the holes after welding.

I have attached a few more pictures.

Put pins through the holes before welding.

Spot weld everything first.

Only do about an inch of weld on one side at a time so the heat does not deform or move things.

Build a jig and assemble the things in the jig.

Use welding magnets to keep stuff square.

 

[BobRip]

Put pins through the holes before welding.

Spot weld everything first.

Only do about an inch of weld on one side at a time so the heat does not deform or move things.

Build a jig and assemble the things in the jig.

Use welding magnets to keep stuff square.

Moss, I did all of that, but welding only about an inch at a time. I will try that next time. Thanks for the input.

 

[SpringHollow]

Here is a link to a guy on Ebay who seems to have a nice thumb design:

Ebay Thumb Link

 

[MossRoad]

I've had the same problem with stuff moving on my backhoe project. Everything all nice and lined up, tacked in place, nice a square. Lay down an entire stick for a couple inches of nice weld, measure... YIKES!!! It's off 1/8 inch. Weld the backside from the first weld. Lay down another stick. It comes back, but not as far. So lay down another stick on the wide side, etc... back and forth from side to side keeps it pretty square but is a pain. This kind of welding is where a wire feed with gas shield would be nice. No slag to worry about. Just flip from side to side welding as needed to keep stuff square.

 

[BobRip]

I've had the same problem with stuff moving on my backhoe project. Everything all nice and lined up, tacked in place, nice a square. Lay down an entire stick for a couple inches of nice weld, measure... YIKES!!! It's off 1/8 inch. Weld the backside from the first weld. Lay down another stick. It comes back, but not as far. So lay down another stick on the wide side, etc... back and forth from side to side keeps it pretty square but is a pain. This kind of welding is where a wire feed with gas shield would be nice. No slag to worry about. Just flip from side to side welding as needed to keep stuff square.

I have the mig with gas so maybe I can do better. Would this be the best approach.
1. Short welds with a wet rag to cool the weld prior to other welding.
2. Alternate sections so no area gets too hot over too big an area.
3. Clamp things in position prior to and during welding.

 

[MossRoad]

I don't know about the wet rag, but by moving around the workpiece and working on opposite sides of it, you can minimize the movement caused by the heat. Just check it often for straight and square.

 

[farm23]

ksimolo, I have ordered the Bio-Tec thumb and should receive it this month. I will post pics and let everyone know how it works. Richard who builds the thumb has been very cooperative and this will be the first he has built for a PT. I think it will work well but we will see.

 

[Mith]

Bob,
In addition to what Moss said,
I tend to tack everything together as much as possible, and weld it assembled where possible too.
Lots of clamps too, I grabbed some big chunks of alley angle to clamp stuff too, and as they are square you can use them to keep things at 90 degrees. The alley means that you dont accidentally weld your work to it
A big hammer works good too