Plug Cutter-Posted Here as ET People Dig Deep

[grumpyolman]

A friend I made here on the forum wants a plug cutter with a larger diameter than the Target Buddy. We have visions of a 5-6" diameter tool that will allow you to pinpoint the target and then put the tool over the center of the target, push into the ground 5-6", and then pop the plug out of the ground. Lay the plug on a ground cover of some kind; look inside the plug with a pin pointer and recover the target...or push the cutter back into the ground and take another bite out of the hole deeper than before.
I made a prototype that has a 4 3/4 inch diameter with about a 3/16" wall. I have a T-handle at the top, tapered to sharpen the cutting edge, and cut serrations into the bottom of the cutter. Problem: I go out into my grassy front yard and get on my knees and try to make a hole in the grass. I push, twist, (curse a little), and I can't get the tool deeper than 2". Maybe a large diameter plug cutter just won't work. I did see a man who modified a bulb planter and put foot pegs around the shaft of his and he really had to stomp the dickens out of it to get it into the ground. It's diameter was about 2".
I started thinking, really trying to solve the problem with some simple physics and logic, and have come to a preliminary conclusion it just won't work on a large diameter plug cutter. Here are my thoughts and hope some with a different experience can help me with this. A Predator digging tool when pushed into the grass has a 'footprint' of about 1 1/2 wide times the thickness of the blade with which they are trying to penetrate the grass and soil. With a plug cutter, even a 4" cutter, if you straightened the cutting circle. you would have a 'footprint' that needed to penetrate the ground about 12" long times the thickness of the metal.
I then thought of other times I needed to put a cut in the grass. Ever use an edger shaped like a half-moon on which you had to stomp the flat of the half-moon to get it to cut an 8" length of the grass and 'edge' your lawn? What ever physics is going on with the edger has to also be going on with the 5" plug cutter. I am thinking I would have to have a stomping peg on the cutter to get it into the ground or have it mounted on a hydraulic 'vertical log splitter' type device(not practical) to force it into the ground. I sure would appreciate some comments and solutions if you see any. Thanks...Jim

 

[jimpugh]

take the plugger you have 4-6 inch radius......put a shaft on on it like the guy advertising on late night TV as the Weed thingy with cordless drill........basically looks like a paint mixer........anyway put 1/4 -5/16 shaft on the plugger welded next buy a wicked tree saw blade with the teeth digging in the insertion rotation .......simply attach the blade around the outside diameter of the plugger with small rivets or brads(pre-fit..... maybe a band saw blade would be cheaper and build more pluggers...........and for replacement teeth.....
I think this with a good cordless Drill would get you thru roots and ground a lot faster with a lot less effort ......just my ideal ....you are pretty much half way there.....

Happy Trails
Jim Pugh

 

[John LA]

n/t

 

[grumpyolman]

Here are the pictures of the prototype. It looks pretty good but DOESN'T work for @$*^! Measured the wall thickness and it's 9/64. I am missing something here, besides a few IQ points, as it will not penetrate the grass surface? It's been tapered and sharpened. You can see the serrations I cut into the lip. Still not go machine.
I too have thought about pop-riveting a band saw blade to the bottom. Maybe that and longer handles to put more torque on it. This is only 3/4 of an inch bigger than the Target Buddy and my forum friend says his TB digs like a champ. Any help or ideas would be appreciated. Thanks for the kind words about 'marketing' it. Can't do that it if doesn't do what it's designed to do. Maybe I could market it as a novel paper weight. Regards...Jim

 

[UWLocator]

That reminds me of a grass plugger, except those are 3 inches square. I can tell you, after putting grass plugs in to cover 3 acres, that those things are too much work. After fighting with that plugger including sharping the edge, which helped some, I realized that I could do the job faster and easier with a post hole digger. That plugger was working me to death. It was taking about 15 minutes per plug with that thing and less than 3 with the post hole digger.

Rip

 

[Hungry]

Mate, some time ago i posted some pic's of the plug cutter that i made, and my thoughts on it, if you think it's hard to get into the ground, wait till you try to get the plug back out, you need a bloody sledge hammer, and mine was only 3" diameter, I made the shaft go through the plunger disc about 2" and put a point on it so you could push it into the ground to centralise it on the pinpoint, and hold it there while you turned it around while pushing it into the ground. It's too much trouble for me, i just use my 1 1/2" diameter scoop, it works for me. If you punch in my user name it should come up under one of my posts. HH. Bob

 

[TerryR]

I wonder if bigger teeth (like 1/2" long spaced 3/4" apart) would help cut through the grass mat and make for easier digging. I just bought one of the old Hole Hoggs off Ebay cause I always wanted one and it was really cheap. Don't give up but bigger teeth might help.

 

[mike - in]

When you push anything into the ground the soil is displaced by the shape and thickness of the object. When you try to push a round tube into the ground the soil on the outside moves away somewhat easier (not by much) than the inside soil which is being compacted because it is all try to move to the center. Add to this the large surface area of the circle compared to a trowel and it's no wonder you can't get it in the ground. And, the friction increases exponentially as you try to drive it deeper too. There's no simple, good solution to your problem unfortunately. Two things you could try. First, use the strongest "but thinnest" metal you can get. You said yours was 3/16" thick which would have a huge surface area. Some 1/64" surgical SS would slice in much easier. Second, cut down on the total surface area of the circle by having cut-outs partway up the sides. It might have only three or four, say 1" to 2" wide points around the circle that does the actual cutting as you turn it. I would leave only enough of the solid part of the tube to hold the top 2" or so of the sod. Hope this will give you some ideas that will help! Good Luck!

Mike

 

[grumpyolman]

Thanks to all for the ideas! I am beginning to think that because of the physics of this thing it' just not gonna work. I am going to try one more out of 3/64 stainless and will put longer narrow serrations so there is less surface contact area where it meets the grass. Don't want to blow the $$ on 1/64 surgical quite yet. It's darn interesting, fun, and a challenging to try to custom make something that should make the recovery time less and easier. If it works, I'll be happy to let others know about it. Regards...Jim

 

[big-ears]

as far as design of cutting teeth goes it is not hit or miss. You will learn quickly that the slightest design flaw will cause failure. One is apparent, in your first picture I see the front of your cutter is conical like the end of a bullet. That won't work. It is all in the design. Draw a curved surface and looked at it. Any point on the curve is also trying to enter the ground, if anything is outside or inside the cutting teeth it won't go in the ground. Its hard to visualise, so let me put it another way. Look at a chainsaw blade, if you cut into a log 6 inches and back it out what do you have? You have a cut channel that is what 1/3 of an inch wide, correct and you can't push the whole chainsaw through that channel can you. Same on your cutter it can only follow the width of your teeth into the ground. Anything going into the ground must be behind the round channel cut by your blade. Your cutter must be straight from top to bottom. Hope this helps.........Mitch

 

[Erik in NJ]

I have the TargetBuddy which has a 4" diameter cutter - when you flip it upside down and put your weight on it it's not very hard to eject the plug. I think it's all in the design of the unit.

 

[Hungry]

I think you are right on that Erik, I also think that the composition of the soil has a lot to do with it as well, if the soil is a loose sandy type, it should come out fairly easy, but if it is a slightly damp clay, best of luck.

 

[grumpyolman]

big-ears...what you say makes perfect sense. How could I expect it to go into the ground when the ID is LESS than the OD? Duh!! I'll try it the way you suggest. Have nothing to lose as it doesn't work this way. I understand what you are saying but if that is the case why does the pointed or sharp edge of a Predator or Lesche cut into the ground more easily after it's sharpened and shaped like a bullet if you look at it towards the pointed end? Dang a machinist!! I'm just a home shop tinkerer. I'll take all the coaching I can get. Wanna come over to my shop and help me? Thanks!! Jim

 

[Tinfoil]

n/t

 

[McNickle]

n/t

 

[Neilo]

I made a stainless steel plug removing tool with a central shaft to push out the plug. It did cut a nice neat plug but if it did a plug over three inches deep. It was very difficult to push out the plug especially in clay like soils. I finished up making a shovel which is also a partial round shape roughly one third of a circle. This meant that I was able to cut a round circular plug in three digs. Then there was no problem with removing plug on a complete circle, and also if I cut s a partial circle I could simply flip the sod back get the target out from under it then simply push it back in place. Another thing about removing a circular plug is the fact that you are cutting all of the surface roots this will end up killing the lawn in the plug. Whilst cutting a partial circle does not cut all of the surface roots and the lawn can recover. good hunting seeya Neilo

 

[EZrider]

Covers all your plug cutting needs

 

[big-ears]

if you want to force it into the ground, or do you want a cookie-cutter type cut. Two totally different problems. So your first choice will be right there, than from there you can move forward. But as I said earlier you will be surprised how complex that cutting edge can be, start with point angle, cutting edge lip, clearance angle, and you can go on and on. You notice at your local Lowes there are different bits, cutters, blades for different materials, the ground is not going to be any different. If I were going to make a coin digger I believe I might try one of the suggestions you recieved in one on the post with a variation. I would have a t-handle maybe knee high going down to a core-cutter type design. For weights sake use a minimal of material, nothing more than a 1-inch wide piece shaped like an "H" the cross-bar I would drill out right at center and thread and the top of the H cut off, like an upside down glass than I would weld the two pieces from the top of the h on the bottom, thats what my feet would step on, that would be on each side as I start turning the handle which is heavily threaded to start down, this would put your full weight on the cutter and give you extreme leverage on a small cutting surface. Its hard to describe but thats where I would start. Just an off-hand idea that came to mind first. Also remember that on a cutter or drill bit you have to remember that the material you remove has to go somewhere, up the fluke, somewhere, if it doesn't it will just stop. Same with the dirt, those serrations you cut are not slotted upward so nothing is being remove from the hole hence no downward travel into the soil. It just won't magically disappear.( which is what I thought happend when my instructor first asked me where the material went.) He did not quite see the humor.

 

[Bill/Wa]

Teeth shown in the picture are not effective, not large enough and deep enough. They would get plugged up immediately. Keep "pluggin away at it" you'll get it. An A+ for effort and welds are beautifull. Good job!

 

[grumpyolman]

Thank you for all the suggestions and the interest in this little project. I was looking at the serrations and drew some teeth on the outer edge of the existing cutting cup to get an idea what it maybe should look like. I may give the thing a trim job and see what happens. Anyone know what the difference in cutting potential would be between making equilateral triangles vs. making right triangles for the teeth? Right triangles would only cut in one direction (I think) clockwise or counter clockwise. The equilateral triangled teeth should allow it to cut in both directions. Another issue I wonder about is how many teeth per inch should I have? If the circumference measures about 12" (I think that's close) should I have 2 teeth per inch or one? I know if I was cutting soft metal, I'd want about 18 TPI, but if I was cutting hard stuff, 32 or more TPI would be better. The machinists manual doesn't talk about cutting grass and soil. Any thoughts from those of you who have followed this post? Later...Jim