Auger extension

[Timmer92]

Hey all,

I am sinking fence corner and other posts 5' and my auger only goes down 3 feet. After hand digging the last 2 feet for 5 holes over 2 days, I figured there had to be a better way. I have a County Line/SpeeCo auger with a 2" round drive shaft. I searched for weeks for an extension with no success. I do not have welding equipment, but got to looking at the standard sizes of black pipe. Here is what I found:

SCH 40 Pipe 1 1/2 in
Outside Diameter 1.9"
Inside Diameter 1.61"

SCH 40 Pipe 2 in
Outside Diameter 2.375"
Inside Diameter 2.067"

The inside diameter of the 2" pipe would be .067" (approx 1/16") wider than my auger receptacle on my existing auger bit (part that attaches to auger head)
Inserting the 1.5" pipe into the 2" pipe would have 0.167" (approx 3/16") clearance
Inserting the 1.5" pipe into the auger bit would have .1" (approx 1/16") clearance

This all sounded like pretty reasonable tolerances, so I decided to make my own extension. Another idea I had that I didn't take advantage of, is by having one pipe inside the other, you could potentially make the length of the extension adjustable. I found, for at least my skills and equipment, getting holes lined up was very difficult, so makeing it adjustable was next to impossible.

Here is what I built.



I used clevis pins on each end to make swapping easy. However, that displaced shear pins, so there may be some risk with that. I am in sand and am not digging near my woods-lines (roots), so I figured I'd be ok.

It took one auger hole to become efficient and learn some lessons. When we started on the first hole, we drilled until the auger was buried, then added the extension, then drilled way down, then learned we couldn't pull it back up! That was a hard lesson. I had to dig the dirt off the top of it, then dig down beside it and get dirt of the blade. Lesson learned. I'm not sure if it's the perfect process, but on the second and third hole, things went very well and rather fast, so we are sticking with it:

• Drill the whole twice with just the bit, pulling it out and pulling/knocking off the dirt each time.
• Lower the bit into the hole until the top blade is just above ground level, then put a board across the blade to hold it in place.
• Disconnect the head from the bit, raise it, and attach the extension. Doing the head first is key, as you can turn it to match the holes in the bit, whereas the bit is in the hole and turning that would be very hard.
• Lower the auger with extension down and connect it to the bit.
• Drill until the soil goes over the top blade. Raise it and pull/knock off the dirt. Repeat to desired depth.
• Lower into the hole until the top blade is just above ground level. Put a board across the blade to hold it in place.
• Disconnect the extension from the bit. Raise the head, remove the extension.
• Lower the auger and connect to the bit. Pull it out. Hole done.

Yesterday we got 3 holes done before we got rained out. Doing the math, it looks like it takes 25% of the time (75% less) than digging 2/5 of each hole by hand. It's totally worth the time and money for the extension.

 

[Rebeldad1]

great job. Just like the big boy drills with screw on drill stem.
Lot of work but in the end it gets the job done.

 

[LS Tractor Owner]

Sounds like you made your project a lot easier! Good job making the extension. Any wobble to it or are the tolerances close enough?

 

[rScotty]

Post holes are difficult and depend on what your soil is like. Here I generally pull the auger up every foot and spin the dirt off and then drill farther.
I have heard that the worst way to stick a drill downhole happens if you drill into an old set of buried bed springs or fencing wire.

Anymore I just use the backhoe. Haven't used my post hold drill since we got the backhoe.

 

[Timmer92]

Sounds like you made your project a lot easier! Good job making the extension. Any wobble to it or are the tolerances close enough?

I had a little bit of a hard time lining up the holes between the pipes. It took a small bit of filing and encouragement with a hammer to put together. As such things are tight. The inside pipe is against one side of the outside pipe instead of perfectly centered. When drilling everything looks fine. No wobble or anything out of alignment.

 

[lennyzx11]

I had just asked about finding an extension in another thread!
My frost depth is 60” here in Vermont. And I could get about 40 honest inches with my digger. I ended up digging the bottom thirds by hand. I’m going to make this. Thanks for the round stock sizes.

 

[Timmer92]

I had just asked about finding an extension in another thread!
My frost depth is 60” here in Vermont. And I could get about 40 honest inches with my digger. I ended up digging the bottom thirds by hand. I’m going to make this. Thanks for the round stock sizes.

I hope it works well for you with you! I'll share some more information with you that may help you. I likely would have done a couple of things differently if I wasn't pressed for time. It's more information than you may need to know, but it explains why I cut some corners. I live on the border between what the city has designated as rural and rural residential, and I'm on the rural residential side, even though the average acreage per owner all around me is probably around 20 acres (I have 14). I have an Interim Use Permit - Livestock from the city for which I have 90 days to build a loafing shelter and put up my fencing for which I only have a few weeks left. If I don't meet the deadline I have to start the process over and reapply for the IUP, which costs around $550.

Here are some more notes and resources:

- When I went online to store websites, I definitely proved that there are standard pipe sizes as the specs were the same across stores. Here is where I got my pipe data - SCH 4 Bare & Black Standard Steel Pipe On ANS Steel Co.

- I spoke with a welding guy and he was concerned about using Schedule 40 pipe. Apparently Schedule 80 is the standard for fabrication and use cases like this. I would have had to wait until a week day and travel around 60 miles round trip in order to get Schedule 80. I'm in sand, and not near any roots or anything, so I decided to risk it.

- I got my pipe from one of the big box home improvement store chains as it was readily available, and came in various shorter lengths. I generally would expect the product quality for what they carry to be questionable or comparatively low. There were definitely consistency issues with the pipe. See the next bullet for details.

- I continuously oiled while drilling. I also slowed down my drill press quite a bit after noticing it was getting hot in the first couple of holes. I drilled a total of 20 holes counting both sides of a pipe. 18 of 20 holes went quite well. Towards the end of one of the pipes, 4 holes destroyed 4 drill bits and required 3 trips to different hardware stores. The material was vastly harder. I don't know how Schedule 80 differs (thickness for sure, but hardness?). If I was dealing with harder metal like the last couple of holes, it would have been a project killer.

- Probably obvious, but do your outside pipe holes first with as much accuracy as possible. Then, anywhere a pipe goes inside another, mark the holes and drill one hole at a time (as opposed to drilling across and through the other side). As I noted earlier my earlier thread, lining up holes was a little challenging.

 

[Ford850]

Schedule 80 is thicker walled pipe to get it's strength, so your measurements would not be the same. I bought some black iron pipe recently for a simple welding project and found it to be even thinner than schedule 40. After checking the store's product description again, I realized they don't call it schedule 40, just "black iron pipe" with outer dimensions that match standard pipe so it's interchangeable. I'm bringing this up so you're careful when buying for uses like this, where you want good overlap fit.

 

[Timmer92]

Schedule 80 is thicker walled pipe to get it's strength, so your measurements would not be the same. I bought some black iron pipe recently for a simple welding project and found it to be even thinner than schedule 40. After checking the store's product description again, I realized they don't call it schedule 40, just "black iron pipe" with outer dimensions that match standard pipe so it's interchangeable. I'm bringing this up so you're careful when buying for uses like this, where you want good overlap fit.

Great point. Here is a resource for Schedule 80 measurements, assuming it is Black pipe as the site doesn't denote that - Steel Pipe Dimensions - ANSI Schedule 8

 

[davedj1]

I like it! Next time put your inner pipe in the outer pipe and either tack weld it at the ends of a couple pairs of vice grips and drill all the holes from one side right straight through. Were you using a drill press? I can't imagine the pipe having a different hardness part way down but who knows in this day and age!
I have never used a post hole digger but it's on my short list to have, do you drill the bit in then unhook it and add your extension or are you able to keep it installed from the start?