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Replacing the tapered wobbled out holes with bushings in the boom arms.
HarryN
Well-known member
- Joined
- Aug 28, 2011
- Messages
- 117
Is that mounted in a drill press? How long did it take to cut that out? Did you use lubrication? More pictures when you can..... looks interesting.
so what I am looking at is the boom off the machine and laying on it's side with a hole drilled thru the a-taper .......wow , I didn't think a hole saw would last up against steel that thick .............. what I do is tack weld a flat plate to the boom which is still on the machine , the plate gived the mag drill a flat surface to grab to as gravity is working against you , also support the drill with an engine hoist or such to take some of the weight off the magnet and to make it safer I have also use a small ratcheting strap and go around the boom and magnet , use a high speed drill bit with cutting oil and step up with the bit as I go to 2 inches ... Bobcat sells a replacement a-tapered bushing , but I have had good luck with the Contruction Tool bushing , about 3-4 hour job for both sides including removing of the Bobtack plate
I tack welded a washer that I cut out with the hole saw before hand to use as a guide.The mag drill has a clamp on it also. The hole saw will only cut 1.5 deep do to a step in side of it.Thats why I went around it with a ball bit in the die grinder,doing so allowed the hole saw to make it all the way and create a chamfer for welding it in.
I did something very close to this on my 743 as the previous owner drilled them out and put 1 1/4" bolts through as pins...... I found to line the pins up so they were dead straight was to get a length of bar, cut the bar off at the needed length and then cut the required tapers at the ends. Install the tapered bushings and shaft into the end of the arms. Lock them in with bolts or just the taper. Now both tapered bushings are held dead straight with each other. Weld the tapers into the arm. Cut the bar with the tapers off at the side of the arm. Use a punch to knock the tapered piece out of the tapered bushing that is now welded into the arm.
Presto, new tapers in perfect alignment.
I hope that makes a little sense.
I actually cut my own pins too, as the lathe was already set for the angle of the pin, it was easy to cut the bar and tapered bushings. I used 4141 steel for the pins and got them heat treated, 5 years and 600 hours later, there is still no wear on them.
I did it the same way to line the drill up and will to locate them the same way. when I weld them. And like you the bushings will have extra long step to locate it on the bar that will be cut off after welding.The OEM pins are at 45 Rockwell if anybody needs to know.
Keep the pictures coming!
Golden Gate
Active member
- Joined
- Jun 18, 2011
- Messages
- 37
nice job!
Heres the new bushings made of 4140 the taper measures 3.5* using an optical comparator.
Bushings in and tack welded ,I will weld them when I weld the new brackets on for the dual tilt cylinders . I need to preheat the bushings to approx 400* (4140) at welding time.
