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Old 05-24-2010, 07:18 AM
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Default Combination Line Boring Rig and Welding Table Build…

My wife swears I now have Adult Attention Deficit Disorder. I just tell her that my brain is now free to wander. But I do tend to jump from one project to another, maybe I just get bored easily.

I made a couple tripod stands for the shop a few years back. They are just over-sized jack stands with replaceable heads. When I poured my shop floor, I made anchor pots and put them in a four foot grid though out the entire floor. The tripods have ratcheting load binders in the base that allow me to anchor them to the floor pots when I need to get after something.

I have been planning to build a welding Lazy Susan that would fit into the tripod (Pic 3). It acts like a potter’s wheel and allows you to use your feet to rotate the table while welding around parts.

I picked up a couple 1 inch flange bearings and a piece of 1” 1018 TGP rod. I cut a couple pieces of pipe, and plate to make the bearing supports that would slide into the tripod (Pic 4).

After setting the assembly on the table, I thought “that looks a lot like a Line Boring Rig” (Pic 5).

I have a repair on my Bobcat that I have been avoiding since I rejected three possible fixes. The pin bore for the front tilt cylinder is badly worn and egged out so bad my cutting edge can float more than 4 inches. Bobcat wants like $800 to sell me a new bucket mount. A local machine shop they referred me to wanted $400 to cut off the ears and weld on new ones. Line boring was even more expensive. My solutions, while they would work would not insure the holes would be in alignment.
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Last edited by TriHonu; 05-24-2010 at 07:37 AM.
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  #2  
Old 05-24-2010, 07:24 AM
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So I drilled a 3/8 inch hole for a piece of HSS tool bit and a second hole for a 1/4 in set screw. I sharpened up the HSS and ground a flat down the length for the set screw seat (Pic 6). I turned down one end of the bar to 1/2 inch and milled a three flats for the drill chuck to get a good hold (Pic 7).

Viola, a Line Boring Rig! (Pic 8) The holes I needed to fix were badly egged out. I made a 3 tapered bushings to help index the boring bar to the center of the existing holes (Pic 9). My fix involved over-boring the existing holes to accommodate some Connex Spring Bushings that I removed from a backhoe bucket I bought for my Bradco. It was bushed for 1.250 pins. Mine has 1.375 pins and needed the larger ID bushings. The spring bushings allowed me to bore to looser tolerances since they have a fit allowance since they must be compressed to install (Pic 10).
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  #3  
Old 05-24-2010, 07:36 AM
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I installed the tapered bushings in the holes to align the bar and clamped the rig in preparation to tack weld the bearing supports to the plates (Pic 11). Final alignment was done after tack welding. The bolt holes for the bearing flange are over-sized in the mounting plate. Tighten the bolts after final alignment. I inserted the tool bit and by eye, adjusted the bit to make sure my first cut would cut the entire circumference.

I had a friend run the drill at 300 rpm while I slowly tightened the screw on the gear puller to feed the bit through the hole (Pic 12). A few shots of cutting oil and the first was through in about a minute and a half. I was enlarging a 1.250 hole to 1.620. I took 4 roughing cuts and 1 finish cut per side. I took about an hour to do both sides. Not bad for my first time doing this.

The first bore came out at 1.619. The second side was 1.628 (.008 over). I’m not sure what caused the over cut. It was really making noise on the final pass. I don’t recall re-checking the bit stick-out after I tightened the set screw. So it could be the bit moved or the bit got dull and was tearing some extra steel, or the fact that I removed the tapered guide bushing and had not made one to fit the finish bored hole. Either way, It didn’t matter since I just grabbed a different bushing that was a little thicker (I had 6 of them).

I had sharpened the bit so the cutting edge was 90 degrees to the boring bar. The next time I will angle it back to provide a little lead and direct some force back toward the boring bar. The finish was very smooth (Pic 13). The mark at 2 o’clock is from installing and removing the spring bushing to install a slightly thicker one.

I installed a new $7.00 rod eye bushing and the spring bushings. I made a new pin from 4140 and got it all put back together. After all this, the Bobcat no longer has any perceivable slop in the bucket tilt (Pic 14).

After all that, I got the welding table machined and the treadle wheel made. I’m still working on a friction ground so the current by-passes the bearings. I just have to find a larger diameter spring.

Adult ADD? Maybe...
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Old 05-24-2010, 08:35 AM
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That is a neet setup you made there. Good work.

My wife says the same thing about me, I don't tend to worry much about it
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Old 05-24-2010, 08:41 AM
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Pretty neat. I like the anchor pot and tripod idea. Very handy looking

I have been wanting to build a line bore for some time now. I have a lot of bushings to do
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Old 05-24-2010, 09:22 AM
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Good work on the line bore.
I think the rotary welding table has alot of merit, except for the ground through bearings issue.
Wondering if you could use the back end of a car or truck starter motor. Use the part that has the brush holders and springs on it and make a steel pipe drum on the shaft, that is approx the size of the old starter commutator. Have the shaft pass through the center of the old starter end cap(might have to enlarge the hole) and hook up all the brushes to the ground lead. They are meant to carry up to a thousand amps at 12 volts.
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Old 05-24-2010, 11:11 AM
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Great slide show & article. Thanks.
I bet you had to really bear down & focus to type all that, what with your Astounding Adult Whatchamacallit Disorientation, you know.
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Old 05-24-2010, 12:12 PM
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Great post!!! and a excellent job A-1!! I know that I wouldn't have gone to that length. I would have made new ears and welded them back on but the way you did it is the professional way to do it. As far as grounding threw those bearings I have a jig made using the same kind of bearings for 6 years now grounding threw them without a problem. At first I grounded the work which was a real pain, finally I said screw it and just went threw the bearings.
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Old 05-24-2010, 12:34 PM
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That's a good setup on the boring bar rig. Saves you money and you get to do it yourself. Can't beat "no longer has any perceivable slop". Great job.

We have a commercial align boring setup but had to make up some bars of different sizes. There is a cutting toolholder insert available that gets pressed in a round hole and has a square hole in it for the tool. I'm not sure what they are called or how much they cost. They tend to hold the cutting tool better than a round hole. If I find them online I'll post a link.
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Old 05-24-2010, 09:58 PM
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Quote:
Originally Posted by Ironman View Post
I think the rotary welding table has alot of merit, except for the ground through bearings issue.
Wondering if you could use the back end of a car or truck starter motor. Use the part that has the brush holders and springs on it and make a steel pipe drum on the shaft, that is approx the size of the old starter commutator. Have the shaft pass through the center of the old starter end cap(might have to enlarge the hole) and hook up all the brushes to the ground lead. They are meant to carry up to a thousand amps at 12 volts.
We are thinking along the same lines. What I have on the bench right now are a couple 1" OD graphite rods, various sizes of carbon arc electrodes and a small pile of solid copper EDM electrodes. My thought is to spring load one of them to press against the underside of the table or the table mounting bushing. I will then attach the ground clamp to it. I'm leaning toward the underside of the table to have the ground as close to the center of the table to focus any arc blow toward the center of the table.

As I type this I just pictured a teeter-totter arrangement where the weight of the ground clamp pulls down on one side which would press the electrode firmly against the bottom of the table...

Future enhancements will be on the method of rotation. I was looking for a small 90 degree gearbox that I could attach to the bottom of the shaft and drive with a set of bicycle pedals. This would allow for easier speed control. The other option is I have a couple of car window motors. I have plans for a small Pulse Width Modulator that I would use to dial in the speed. Since it rides in bearings I don't need much torque to rotate it.

Quote:
Originally Posted by cutter View Post
Great slide show & article. Thanks.
I bet you had to really bear down & focus to type all that, what with your Astounding Adult Whatchamacallit Disorientation, you know.
Cutter, I typed it last night so I could get my thoughts down uninterrupted.

Quote:
Originally Posted by digr View Post
As far as grounding threw those bearings I have a jig made using the same kind of bearings for 6 years now grounding threw them without a problem. At first I grounded the work which was a real pain, finally I said screw it and just went threw the bearings.
Good to know. I assume you have not had a problem keeping a stable arc?


Quote:
Originally Posted by Pyro J View Post
There is a cutting toolholder insert available that gets pressed in a round hole and has a square hole in it for the tool. I'm not sure what they are called or how much they cost. They tend to hold the cutting tool better than a round hole. If I find them online I'll post a link.
Thanks, I would appreciate the info if you find it.
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