Manufacturing of an increment borer

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#1)  Manufacturing of an increment borer

Postby jcruddat » Mon Jan 01, 2018 2:34 am

Hi all,
    I have recently taken on the challenge of machining a 28" to 30" long increment borer at the CNC machine shop of my school, Worcester Polytechnic Institute, for the purpose of drilling closer to the pith of the 150+ year old tulip poplars, 250+ year old sugar maples, and other old growth trees here in Connecticut. So far I have made a fair virtual 3d representation of the threaded tip in a CAD program called SolidWorks which is available to view or download at https://grabcad.com/library/increment-borer-1. I you wish to view the file but do not have access to SolidWorks then I can upload the file here in a different format such as in the .STL or .OBJ file format, viewable in free software. Right now I am trying to refine the design of the threads since the rest of the borer is pretty straight forward. I am currently trying to base the threads on the JIM-GEM style borer which looks very similar to the old Djos/Suunto style borer. I prefer the JIM-GEM borer over the more common Haglöf borer because the spreader bars are made in-line with threads instead of the behind the threads. This allows for much easier backing out of the borer from the tree since there are still threads behind the cams re-engaging with the sometimes soft or rotten wood. The previously compressed walls of the wood surrounding the hole from the spreader bars tends to spring back into place and can sometimes lock the Haglöf borer in place. I have had the Haglöf borers get stuck multiple times, usually when hitting a pocket of rot or cavity within the tree, but almost never with the JIM-GEM borer. The hardest part of modeling the threads is the fact that the geometry of the threaded borer tip is very difficult to measure such as the curvature of the face of the cone/barrel that the threads are made on, along with the geometry spreader bars that are in-line with the threads. Does anyone have information as to the dimensions of the tip of the borer or the process in which they are machined? Also, if anyone has some input as to the most effective style of increment borer then that would also be very helpful. So far I have not been able to find much useful information on the internet as to how they are machined or how they are dimensioned other than one simple schematic and a cross section view both attached at the end of this post. I assume that the threads are machine on a 5-axis CNC mill or lathe and then welded to the shaft along with the square end that fits into the handle. I have heard that the old Djos, Mattson, and particularly the Sandvik increment borers were of well respected and rarely broke or got stuck. The Djos style borer looks similar to the JIM-GEM style borer I am using now but I have not been able to find any information or photos on the geometry of the old Sandvik borers. Perhaps someone has one lying around and could post a picture of the threads or some insight as to the schematics of such devices?

Regards,
Jack Ruddat
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JIM-GEM Style Increment Borer Thread Dimensions.png
JIM-GEM Style Borer Cross-sectional view.jpg
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#2)  Re: Manufacturing of an increment borer

Postby DwainSchroeder » Tue Jan 02, 2018 2:04 pm

You have taken on a very challenging project.  Years ago, I toyed with the idea of making a 30" borer to look at growth rings on a giant burr oak in Goll Woods Preserve (northwest Ohio), for a precipitation history study.  The tree was already dead but still standing   The Preserve has a strict "no disturbance" philosophy though I believe I could have gotten permission to bore the dead tree.  Long story short - I gave up on the idea after considering the design difficulties including that the wood would be somewhat dry and very hard; and also my interests moved on.  I was in Goll Woods this Spring, but my failing memory won't let me recall if that tree has fallen yet....

Unfortunately, I don't have any specific details on the design aspects of borers to offer, but I still would like to respond.  I have a 14" long "Suunto" borer which has worked well for me.  I believe it was made in Sweden.  It has three screws which I have been told, but it is not necessarily obvious to me, allows for easier and more efficient engagement than a two screw design.   I believe what you call spreader bars, are located between the threads, but the last thread is tapered to allow for easier extraction.  I believe that 28"/30" bores are available commercially but are quite expensive, and the idea of a do it yourself project is always interesting and educational.

I'm sure you already know, but material selection would have to be critical for your project.  Borers are subjected to very high stresses.  A 30" long borer may also be somewhat vulnerable to a "torsional squirm buckling" action - perhaps not, but something to look at when calculating the required wall thickness.

Good Luck!

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#3)  Re: Manufacturing of an increment borer

Postby jcruddat » Tue Jan 02, 2018 5:52 pm

Hi Dwain,
    Right now I am considering making the shaft out of 4130 chromoly steel and the threads out of some hardened 4340 chromoly steel. This is what was suggested to me by some guys in the discussions I started in the PracticalMachinist and CNCZone forums (http://www.practicalmachinist.com/vb/cn ... el-339531/ and http://www.cnczone.com/forums/machinist ... 4-cnc.html). I am also going to do a simulation in SolidWorks to determine the maximum torque that can be applied without significant twisting or breakage of the increment borer. Your giant burr oak reminds me of some large white oak wolf trees I came across once in Cowles Park, East Granby, Connecticut. I might be interesting to see how old those large trees are in order to determine when last the forest was a pasture.
               
                       
288.JPG
                       
Large field grown white oak #1
               
               
               
                       
302.JPG
                       
Large field grown white oak #2
               
               


Jack
Last edited by jcruddat on Tue Jan 02, 2018 10:44 pm, edited 1 time in total.
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#4)  Re: Manufacturing of an increment borer

Postby Larry Tucei » Tue Jan 02, 2018 10:19 pm

Hi Jack-  I hope you succeed on your Project 4130 will work but the wall thickness and length will be the issue. I thought about doing this about 2007 when I first joined NTS but never got around it. I'm a Welder with access to our Machine Shop. Keep us posted on your results. Some of the Hardwoods will be difficult to core.  Good luck Larry
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#5)  Re: Manufacturing of an increment borer

Postby jcruddat » Tue Jan 02, 2018 10:43 pm

Hi Larry,
    I agree that the wall thickness is definitely something to consider when it comes to very long increment borers. Do you know if the wall thickness increases with length on Haglöf borers? I hear that Sweden has access to some very high quality iron ore deposits which they use to make what one guy described as high yield "unobtanium" alloyed tubes from companies such as Sandvik.

Jack
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#6)  Re: Manufacturing of an increment borer

Postby Larry Tucei » Mon Jan 08, 2018 10:41 am

Jack- I'm not sure what the thickness is on their longer Borer. Perhaps you could contact them.. If you are successful yours would be the one I would purchase. One note Unobtanium is a term coined by  NASA referring to rare metal back in the day. It's a fancy name for titanium which would be lighter but not stronger than Heat Treated 4130 of 4140 steel.   Larry
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#7)  Re: Manufacturing of an increment borer

Postby jcruddat » Sun Jan 14, 2018 5:39 pm

Looks like I finally finished the model and It's as close as I can get to the actual thing. The tapering of the cone changes slightly near the shaft but that seemed to me to be unnecessarily complicated for such a part so it was overlooked. The files are attached in a .zip folder below in .STL file format which can be viewed on Windows 10, etc.

Jack
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Increment Borer (Revised).zip
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