tooth bar and clamp on forks for backhoe tractor

[gda]

So I'm just about done with a couple of items for my Dad's tractor. The double bonus was that I told my wife they were a Christmas gift so I got extra shop time, and my 6 YO son helped with cutting stock and drilling holes.

(Remember that this is for a tractor - so high precision not required)

Putting a chamfer on a piece of flat stock. A good use for a crest cut end mill that was still sharp on the shank, but worn on the face. Yes I tilted the head back!





Clamped up for tack welding with the mig.



Finished in place except for paint. I stick welded with 7018 since my Mig welder is only for light use. The bar bowed quite a bit as I expected, but I straightened it out. Some people who make these recommend clamping a "frown" bow into the bar before welding.

[gda]

The forks: Made from 2"x4"X 3/16" tube stock. Way overkill for this little tractor, but I figure they could be used on a larger machine as well some day.

For the 1" x 8 screw threads I made them out of stainless so they would not rust up is stored outside. I power tapped the female thread and single pointed the male thread. (sorry for the blur)



They are just tacked up for now - I'll burn them in later today. The lower picture shows a couple of extra pieces missing from the top photo (level pad and round stock for the bucket edge). I also tapped the end of the clamp thread so that I could bolt on some wider pads for where the screw clamps down on the bucket (top photo, left). This will distribute the force better and keep the fork from trying to slide out during the final clamping. (think of the swivel pad on the thread of a C-clamp).

[tmc_31]

gda,

Nice looking forks and digging teeth.

What material were you power tapping the 1"X8tpi threads in? What kind of tap did you use? What size hole did you start out with? Coolant/threading oil? Speed? Did you use a lathe or a mill? What horsepower?

I have to tap 50-1" thick A36 blanks to 1X8tpi so I am very interested in how well this worked for you. As you might guess I have never power tapped before.

Thanks,

Tim

[bborr01]

gda,

Nice job. Thanks for sharing.

Brian

[gda]

tmc_31: Thanks, The stainless was 303 or 304. I used a "new" 50+ year old greenlee 4 flute taper tap. I used a 7/8" hole. I also have a pretty big tap holder for the tailstock. The first one I spun the chuck back and forth as I went since the tap was not a spiral point. The second one I figured that the relief grooves were big enough that I would go for it in the back gear with some tapping fluid.

I read the thread about your job. If your friend is just making some lally columns for a temp job you have some leeway. If they are a permanent part of a building you may not have the leeway to change the thread %. Either case I would insist on an official print to work from. What tolerance class is the thread to be? If this is a real part of a building the print (or any changes) should be approved by a PE.

Power tapping is easy - the tap does the feed work for you. Try it with some "spiral point" or "gun taps" before the job. Just keep on it until the threads are cut so that when you stop the machine the tap is not still trying to remove metal. I'm sure there are many power tapping videos you youtube. Best of luck.

[Forestgnome]

I like the "tooth bar". Never seen teeth mounted on a bar like that.

[tmc_31]

Thanks for the info gda,

I cut 25 of the blanks today, will cut the rest tomorrow morning. I have ordered a spiral point 1"-8tpi plug tap and a mt3 7/8" HSS drill bit (I specified USA made), but I just found out they won't be here until Tuesday . I am looking forward to trying the power tapping.

Tim

[gda]

I finished burning in the parts 2 days ago and since it was warm today hit them with some paint from a rattle can. Paint job sucks but there is really no need to get carried away since these will get all scratched up in use anyways. They came out a little beefier than I intended, but overall I'm happy with them, and my father can't wait to get them.