753: Bob-Tach hinge bolt installation.

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Graham

Member
Joined
Feb 9, 2006
Messages
9
I have a 753 Bobcat, the hinge bolt that goes through the lift-arm to the Bob-Tach fell out. I assume it fell out and did not break as I can put a screw driver in to the depth of the bolt. I have a new bolt (17C-1064) and it screws in a few turns then it appears that the pin (6707042) just turns. I have removed the grease nipple and excess grease has been forced out. How do you hold the pin so the bolt can be tightened? The manual says to hit it with a hammer! All past experience tells me to use a hammer on a nail but not on anything threaded! Appreciate some wise words, Graham.
 

TriHonu

Well-known member
Joined
Apr 15, 2007
Messages
486
The threads probably got damaged when the old bolt loosened and fell out.
The bolt threads into a pin that is tapered on one end. The tapered end fits into a tapered boss that is welded into the end of the lift arm. Normally when the pin and boss are in good condition, they will fit tightly and grip as soon as the bolt draws them together.
If the pin was loose for any amount of time, the taper on the pin, and the taper on the boss are probably also damaged.
To remove the Bob-Tach, you loosen the bolt and smack it with a large hammer to release the taper pin from the boss. You then unscrew the bolt and use it to push the pin into the Bob-Tach. The hole in the Bob-Tach is deep enough to accept the entire length of the pin.
I would suggest you remove the bucket, then drive both pins into the Bob-Tach and pull it loose to clean an inspect it. You may be able to re-tap the threads in the pin. You also need to inspect the hole in a tapered boss. If the damage is minimal, you may be able to clean up the tapers enough to get them to seat an lock up.
If you want to try the quick and dirty method, you could try to thread in a bolt and use a slide hammer to try to seat the pin. I would highly suggest you take it apart and inspect it. The cost of replacement pins isn't too bad. A damaged boss can be reamed if the damage isn't too bad. However the reamer from Bobcat is $$$.
MaxW and OldMachinist have determined that the reamer is the same taper as a ball joints and tie rod ends. You can read the thread Pivot Pins 443B
There are numerous threads here on this repair.
 

Tazza

Moderator
Staff member
Joined
Dec 7, 2004
Messages
16,829
The threads probably got damaged when the old bolt loosened and fell out.
The bolt threads into a pin that is tapered on one end. The tapered end fits into a tapered boss that is welded into the end of the lift arm. Normally when the pin and boss are in good condition, they will fit tightly and grip as soon as the bolt draws them together.
If the pin was loose for any amount of time, the taper on the pin, and the taper on the boss are probably also damaged.
To remove the Bob-Tach, you loosen the bolt and smack it with a large hammer to release the taper pin from the boss. You then unscrew the bolt and use it to push the pin into the Bob-Tach. The hole in the Bob-Tach is deep enough to accept the entire length of the pin.
I would suggest you remove the bucket, then drive both pins into the Bob-Tach and pull it loose to clean an inspect it. You may be able to re-tap the threads in the pin. You also need to inspect the hole in a tapered boss. If the damage is minimal, you may be able to clean up the tapers enough to get them to seat an lock up.
If you want to try the quick and dirty method, you could try to thread in a bolt and use a slide hammer to try to seat the pin. I would highly suggest you take it apart and inspect it. The cost of replacement pins isn't too bad. A damaged boss can be reamed if the damage isn't too bad. However the reamer from Bobcat is $$$.
MaxW and OldMachinist have determined that the reamer is the same taper as a ball joints and tie rod ends. You can read the thread Pivot Pins 443B
There are numerous threads here on this repair.
Another possibility is that the pin has slid into the bobtach further than the bolt can reach. I have used a piece of welding wire with a hook on the end. This way you push it in and it will go through the pin and hopefully lodge in the threads and when you pull it back it will seat. Keep pulling and it will straighten out and pull through. Now screw in the bolt and see how you go.
Now, there is an issue with this method..... You will have grease on the taper, you want it dry to give a reliable seat so it does not move. The best way to do the job is take the bobtach off, clean out all the old grease, clean the pins and tapers, re-assemble then grease up.
 
OP
OP
G

Graham

Member
Joined
Feb 9, 2006
Messages
9
The threads probably got damaged when the old bolt loosened and fell out.
The bolt threads into a pin that is tapered on one end. The tapered end fits into a tapered boss that is welded into the end of the lift arm. Normally when the pin and boss are in good condition, they will fit tightly and grip as soon as the bolt draws them together.
If the pin was loose for any amount of time, the taper on the pin, and the taper on the boss are probably also damaged.
To remove the Bob-Tach, you loosen the bolt and smack it with a large hammer to release the taper pin from the boss. You then unscrew the bolt and use it to push the pin into the Bob-Tach. The hole in the Bob-Tach is deep enough to accept the entire length of the pin.
I would suggest you remove the bucket, then drive both pins into the Bob-Tach and pull it loose to clean an inspect it. You may be able to re-tap the threads in the pin. You also need to inspect the hole in a tapered boss. If the damage is minimal, you may be able to clean up the tapers enough to get them to seat an lock up.
If you want to try the quick and dirty method, you could try to thread in a bolt and use a slide hammer to try to seat the pin. I would highly suggest you take it apart and inspect it. The cost of replacement pins isn't too bad. A damaged boss can be reamed if the damage isn't too bad. However the reamer from Bobcat is $$$.
MaxW and OldMachinist have determined that the reamer is the same taper as a ball joints and tie rod ends. You can read the thread Pivot Pins 443B
There are numerous threads here on this repair.
Thanks, I will let you know how it goes.
 

farmshop

Well-known member
Joined
Mar 27, 2014
Messages
698
Thanks, I will let you know how it goes.
taper pins need to be pulled in. Use a piece of threaded rod screwed into the pin then use a nut on the outside to pull it tight. It will seat the pin and then you can locktight the new bolt and tighten it up
 

Mikefromcny

Well-known member
Joined
Nov 13, 2011
Messages
352
taper pins need to be pulled in. Use a piece of threaded rod screwed into the pin then use a nut on the outside to pull it tight. It will seat the pin and then you can locktight the new bolt and tighten it up
Try using an impwct gun in short bursts.
 
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