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Mini-Mill Modifications for Quartersawing Lumber

Mini-Mill, Model G555B is available from Granberg International, P.O. Box 2347 Vallejo, CA 94592-0347, 707-562-2099 or on-line at The Mini-Mill must be modified before it can be used as described in, "How to Make Quartersawn Lumber with a Chainsaw". I have no experience with any other chainsaw attachment that is useful for making quartersawed lumber. I own both the Alaskan MKIII Saw Mill Attachment and the Alaskan Small Log Milling Attachment. These are wonderful for flatsawing logs into lumber. I have not found them useful for quartersawing logs. It is not that they can not be used but to use them would require moving the log for each cut. The Mini-Mill will do the job on a quarter log without moving the wood at all. Each cut down the quarter log produces lumber with bark on one edge. The first few boards are true quartersawn with the last boards described as riftsawn but still very stable when air dried.

It took me about 4 hours building this Mini-Mill modification plan that will take a well tooled shop about 2 hours to complete the modifications. I spent another few hours in front of the TV writing down all the steps. If you have the materials and some metal working tools you should be able to made the modifications as described. You will need a drill press, hacksaw or metal cutting bandsaw (the latter will save a bunch of sweat and time), Letter F size twist drill bit, 5/16"-18 and 3/8"-16 taps and an arc welder.

The metal needed:

  • 2 each, 5" x 3/8"-16 hex head bolts (Grade 8 bolts are ideal for strength but lesser grade bolts will work).
  • 2 each, 5/16"-18 x 1¼" hex head bolts (any grade will do).
  • 2 each, 11" x 1 ½" x 1 ½" x 1/8" thick bed frame angle iron (I like to recycle and bed frames are strong, thin, and available).
  • 1 each, 11" x ½" x ½" x 1/8" thick angle iron (available in many hardware stores in 36" lengths).
  • 2 each, ½" x 1" x 1" solid iron bar stock (this will be drilled twice each so a longer piece will be easier to handle at the drill press, cut to size after drilling).

General Modification Plan (Photo 1 shows a fully modified Mini-Mill):

Photo 1 - Fully modified mini-mill.A stepwise plan is provided but you should get the general idea about the modification before tackling the steps. The Mini-Mill comes disassembled. If you already own one disassemble it down to only the welded together parts. This assembly will be mounted in a 4" x 4" block of wood for drilling into the ends of the round rods of the welded assembly. The drilled holes are then threaded to accept the 3/8" bolts. These are the fence guide rods that are important in setting the fence to bar distance for the thickness of lumber desired. The heads of the 3/8" bolts are cut off once they are securely tightened in place.

The guide fence requires cutting, drilling and welding. Each step is described below.

One additional change is recommended but not required. This is an additional angle iron welded to the side of the long square tube. This addition is an extra guide when sawing narrow quarter logs. It is really worth the small amount of extra work.

An alternative modification method is stated before Step 2 for a shop that has a metal lathe.

Keep in mind during the guide fence construction that the Mini-Mill must be reassembled and placed on a V-Rail Guide for positive alignment.

Step 1:
Make the 4" x 4" x about 12" solid wooden drilling jig. Mark one side of the wood for center line from end to end. Measure the distance from the center of each of the ½" rods on the Mini-Mill, this should be 6" (if not use the measurement you found). Mark the center line on the wood for drilling 2, ½" holes 6" apart. Note there are some weld piles on the long square tube of the Mini-Mill. These will interfere with seating the long square tube flat to the wood so the top of the holes must be made larger. Once the holes are drilled, press the Mini-Mill assembly into the 4" x 4" for drilling. Be sure the long square tube rests firmly on the wood surface.

Step 2: - Method 1
Photo 2 - Wooden support drilling jig.Drilling and tapping the 2, ½" rods on center. Here I had a bit of trouble. I center punched the ends as close to center as I could on each of the ½" rods. Then starting with a small drill I drilled in about ¼" to assure a good place for the larger 5/16" drill to bite and not wander. It worked pretty good, not perfect but good enough. Drill each rod then with a 5/16" drill bit about 1" deep. See Photo 2. Then thread the holes with a 3/8"-16 tap. I had some trouble keeping the tap vertical to the hole. You would think the tap would seek the hole perfectly, it did not, so my bolts needed a bit of bending to get them straight with the Mini-Mill rods. Screw the 5" bolts firmly into the newly threaded holes and saw off the bolt heads. File the edges of the saw cut smooth. Adjust the rods to get them reasonably parallel to the ½" rods in the Mini-Mill. Reassemble the Mini-Mill. By the way, using shorter bolts will limit the thickness of the lumber you can produce. 5" bolt will allow you to make 4" thick lumber. I seldom cut lumber thicker than 2" as it take too long to dry, 1 year for each year of thickness. So you can use shorter bolts if you want, I used 4" bolts.

Method 2
Recently I have changed my modification method for the Mini Mill. I now take the mill apart and cut and drill out the 2, 1/2" rods. This allows me to install longer 1/2" rods which are stronger than the 3/8" threaded attachment method that I mention in the procedure on my web site. Cutting and drilling out the 1/2" rods is a lot simpler than it might seem but it is less work than the drilling and tapping the end of the 1/2" rods.

Here is what I currently do to modify the Mini-Mill.

  1. Measure the placement of all the parts of the Mini Mill so that when it will be reassembled it will match those measurements.
  2. Disassemble the mill.
  3. Saw the 1/2" rods off the longer of the 1"x1" square tube. Saw close to tube and through the weld. Knock the tube free from the rod.
  4. Saw the rods off the shorter 1"x1" tube.
  5. Drill or Mill out the remaining 1/2" rod from the short square tube. You don't have to be too careful in drilling or milling out the rod as subsequent welding the mill back together will take care of minor screw-ups in getting the rods out. Clean out as much of the welds in the short tube as possible.
  6. Obtain 2, 11" x 1/2" iron rods. I have a metal lathe so I turned one end down to 3/8" for 3/4" from one end to match the old rods. I used a 3/8" die and threaded this reduced end of the rod.

    Now you are ready to reassemble the mill.

  7. Assemble the 1/2" rods and the square tubes. Be sure and place the parts on a solid flat surface spaced with wood blocks and clamp. I use a stick welder so I welded the rods to the square tubes only on the inside of the tubes, just for looks. You can weld them as done by the Manufacturer.
  8. Now reassemble the rest of the mill.
Now you have a Mini Mill that is like new except it has 1/2" rods that are longer. Build your guide fence and follow my Step 3 directions for assuring alignment.

Step 3:
Build the guide fence, which is made up of 4 pieces of metal shaped and welded together with 2 adjusting screws.

I used old 1 ½" x 1 ½" bed frame angle iron for the main fence part. Bed frame angle iron is thin and strong. (Aluminum would be better but I have not learned how to work with it.) Photo 3 shows the 11" long bed frame angle iron with 2, ½" grooves 6" on center apart and a large grove to allow easy access to the bolts that lock the Mini-Mill to the chainsaw bar. These groves do not have to be real accurate. Photo 3, Guide fence with groves and the ½" angle iron welded on the bottom.The ½" wide groves should be ½" to 5/8" deep and the wide grove should be about ¾" deep and 3" wide for tightening the bar mounting bolts.

Drill 5, 5/16" holes evenly spaced down one leg of the 11" long ½" angle iron. These holes will be used to "plug weld" the ½" angle iron to the bottom of the 11" long 1 ½" angle iron with the groves that you just made. Photo 4, Plug Welded ½" angle iron.See Photo 3 for placement. The plug weld arm of the angle iron should be toward the grove side of the 1 ½" angle iron, leaving ½" on the other side, about in the middle of the wide angle iron and parallel with it. Clamp the 2 angle irons together and "plug weld" in each of the 5 holes. Plug welding provides a clean neat edge where needed for guiding the saw down the corner of a quarter log. What we don't want is welds on the back side of the ½" angle iron. That is the side that will guide the saw on the quarter log. Look at Photo 5 to get acquainted with a completed fence.

The guide fence now needs 2 attachments to the 3/8" rods. I used 2, ½" x 1" x 1" iron bar stock from an old iron gate. You should be able to get something similar at a local metal/welding shop. I use a longer piece for better control during drilling then cut to size after drilling and tapping. Mark the bar stock for size and drill a 3/8" hole through the middle of each 1" x 1" side of the attachments. Photo 5 - Completed guide fence.You may want to counter sink these holes on either side to help moving them on the 3/8" rods of the Mini-Mill. A little filing on the inside of the holes may be required if they are too tight. A little loose is better. Now before you cut the attachments from the bar stock you need to drill an "F" size hole on each one in the middle of the ½" x 1" side of the attachments. Drill clear through to the 3/8" hole. Tap the "F" size drill holes with a 5/16"-18 tap. Cut the attachments from the bar stock and file the saw cuts smooth. Install the 1 ¼" x 5/16" bolts, one each in each attachment. Now you are ready to complete the guide fence.

Place the assembled Mini-Mill on the welding table as shown in Photo 6 (the photo shows the Mini-Mill on plywood for clarity and not for welding). Note that the V-Guide is sitting on a section of the V-Rail. This is required for proper alignment. The aluminum rail to the left in Photo 6 needs to be held down with a weight or clamp during this alignment step. Photo 6 - Assembly and alignment of the guide fence with the Mini-MillImportant for this alignment is that there are 3 points of contact to the welding table, 1) the aluminum rail, 2) the V-Guide/V-Rail and 3) the bottom of the guide fence. The guide fence needs to be parallel with the square tubing of the Mini-Mill. With the attachments on the 3/8" rods and the adjusting bolts facing down to the floor, clamp them to the guide fence angle iron with small C-clamps. Tack weld each attachment to the guide fence. The guide fence can now be moved to a vise or other for completing the welding of the attachments to the angle iron.

Step 4:
Before you take the completed Mini-Mill off the welding table consider welding the last 11" x 1 ½" angle iron to the long square tube in the Mini-Mill. This is a simple job and will be well worth the effort when you are trying to cut very narrow quarter logs. Photo 7 - Optional angle iron guideA couple of notch on the angle iron will get it under the ½" rods, clamp it to the welding table and just tack it to the square tube along the top edge. See Photo 7. Now you are done except for clean up and maybe painting the new tool.

Mini-Mill Adjusting:
Mount the Mini-Mill on the chainsaw bar. I use a block of wood cut the thickness, plus 1/16", of the lumber I am to make for setting the guide fence. See Photo 8. For example a block about 2" long and 1 1/16" thick placed next to the bar with the guide fence pressed to the block of wood, tighten the guide fence adjusting bolts. You are ready to make 1" thick lumber, assuming you have a quarter log and the stands shown in the Quartersawing article on my web site.

If you have any questions or problems with these modification directions please send me an email or call 925-939-8052.

Photo 8 - Modified Mini-Mill mounted on a chainsaw with temporary wood spacer for setting lumber thickness

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