Big Boring Machine

JohnG

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My woodworking was tending toward delicate pieces. I started thinking about a change of pace: something big, structural, imposing--a pagoda perhaps. I called this a gazebo when I talked to my wife about it. We know people who have those. It sounded more practical.

The timber joinery I’m thinking about uses wooden pegs or dowels, much bigger than any I’ve used. This would require a large drill, capable of boring precise holes 1” to 2” in diameter and up to 8” deep into the sides and ends of timbers up to 8” square. This will be made mostly out of stuff I had lying around, especially pieces of old production machines I had history with.

I started this in January. Most of the time I was pretty sure it wasn’t going to work. The axial alignment needed for the long travel of the drill worried me. There is actually nothing at all practical about this project; but, despite my misgivings, here it is: so far, so good.

timber borer a.jpg

I started with this 4 ½” diameter heavy wall steel tube, old well casing, I think. I needed 6” off one end. My cut off saw was at this a while.
timber borer b.jpg
I turned the tube’s o.d. and set it up in a 4-jaw chuck and steady rest. I don’t have the ability to broach the large keyway needed for the gear rack that will move the quill, so I turned two plugs like the one on the lathe carriage. They have milled slots that will become the keyway when the plugs are pressed into counterbores in both ends of the tube.
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I planed a hardwood stick about 18” long to a snug fit in the slots and used it to align the two end plugs as they were pressed into the tube. They were bolted in place, and I was ready to finish bore the quill guide.
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The depth of the keyway slots is about 0.020” shy of the o.d. of the quill bore. I thought I’d get a smoother, truer bore if it was an uninterrupted cut. My ability to grind a boring tool was much improved at this point.
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A little work with a hack saw blade and a file cut out the two slivers of steel left across the gear rack slots.

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The quill is made from a drill drive shaft like this one off a patio door machine originally built in 1968. Sliding wood doors were built by the hundreds of thousands in those days. This was a heavy machine, built for continuous production, made just to cut the slots and holes for door rollers and locks. It ran until 1990. I rebuilt it in 1991 to install European mortise locks that were the latest thing then, and it continued working until 2000. I brought home a few components when it was scrapped.

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I turned plugs for the bearing bores at either end of the tube so I could mount it between centers and turned the o.d. I set an indicator against the tailstock and budged it a thousandth or so to get the same o.d. at both ends, but there was a slight, barely detectable, bulge in the middle. The quill slid into the bore about 1/3 of the way and stopped cold. A little blue layout dye found the exact spot. I was able to feed the grinder in at that point and just skim the center portion of the quill.

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The fitted quill went over to the milling machine to get a slot for the gear rack.

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I milled down the rack a bit and set in into the quill with 3 cap head bolts from the back side. I worked the stiffness out by sliding it back and forth a few times by hand to burnish the machined bore with the ground quill.

timber borer j.jpg
 
Some very nice work there. Cheers, Mike
 
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Excellent!
Martin
 
Nice project....you do know that craftsman do and did this kind of work with a "brace" by hand, right?
 
I don’t know if I’d be up for too many 2” holes with a brace but one of these might be interesting to have a few tries with…
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I’m liking JohnG’s project — nicely developed and a worthy construct from mostly salvaged parts. :encourage:

-frank
 
I like the project also.
Seems like he built a mini gun drill...well sorta
 
I like your lathe. I had a 13 x 30 P&W like yours. In spite of having been abused and badly worn it was the sweetest lathe I ever ran. The feed stop on the cross slide and the single revolution clutch on the leadscrew made it great for threading. Mine had a Buck & Hickman property tag and a 400 volt motor so I know it had been to England and back. It was probably nearly worn out doing war time production.
 
I am very fond of my P&W lathe. I know it was built in 1950 and has tags indicating it was originally used in an armory. I bought it from a high school machine shop. Neither it nor I need to earn a living anymore, and we just have fun together.
 
The quill needs to sit on a pedestal that will put the center line of the drill about 5 ½” above the machine base. I set the housing on a surface plate and laid out 4 coplanar holes for pins to support it in the milling vise. The flycutter uses ¼” shank single point lathe tools. I bought a box of these with carbide tips from China. They need to be ground before use, but this has become my go to tool on the mill. There’s a lot of lateral cutting force, so I have a piece of heavy angle iron bolted to the mill table as a backstop.

timber borer k.jpg

The pedestal is 2 pieces of 1” x 6” channel iron stacked on top of each other. I had to make several cuts on the mill so they would stack machined surface on machined surface. This flat on the top piece will match the flat I just made on the underside of the quill housing. The channel iron wanted to squirm around in the vise, and the bar clamps stopped that.

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The quill housing has gone over to the drill press to get holes drilled and tapped for 4 bolts and drilled for 2 locating pins.

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Here’s the quill sitting on its base. I don’t think the ½” chuck that was originally mounted in it will be up to the task I have in mind. Fortunately, the end of the shaft is just the right size for the 1” x 8tpi screw mount of this 5/8” headstock chuck. I milled shallow flats on the back side for a thin wrench, set the shaft in the 4-jaw chuck truing it off the bearing, and turned the threads for a very tight fit. My biggest worry in this project was the alignment of this chuck on the drill spindle.

timber borer n.jpg

The pinion gear needs to go into position to drive the quill rack. I milled this slot by sinking 2 narrow slots across the housing, taking out the pillar between them with the fly cutter, and finishing it to width for the axle block. I didn’t think I could accurately locate the bottom of this to put the gear axle at the right clearance from the rack, so I cut it to what I hoped was just a little deep. Then I sunk the entry hole for the gear.

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I had to buy the pinion gear. I sunk a second hole though the ¾” bar that will hold the ½” axle.

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I’ve always felt awkward positioning an indicator at the 4-jaw chuck. Something gets bumped the first time the chuck turns. Something doesn’t quite reach. Something blocks the view of the dial. I learned a few moves doing this project.

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After drilling, the hole for the pinion gear axle is hand reamed.

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Before the handwheel hub is drilled and tapped for spokes, it gets a bevel on one side to dish the spokes for hand clearance. There’s a ½” mandrel in the bore to align it.

timber borer s.jpg

It did take a 0.015” shim under the axle block for the pinion gear to mesh smoothly with the rack.

timber borer t.jpg
 
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