Bobtach repair/modification - dimensions of parts required.

[Tazza]

Here is the progress so far, all that I have to do now is make the long bushes that the wedge pins fit in and the weld on pivot that the handle swings on and start welding it all together.
It will look something like this when finished.
Tazza, would you mind measuring the pivot hole in the handle, this is the only thing I am not sure of and I want to keep everthing standard for interchangeability.

I'll try to remember to measure it tonight.

 

[Tazza]

I'll try to remember to measure it tonight.

Oki Doki..... My handles are rather worn, the smallest part of the egg shaped hole is 0.731" and the bushing that goes over the bolt that it pivots on has on OD of 0.586". I would simply add a bit of clearance to that, you don't want it too tight as you have a spring holding pressure on it so it won't flop around.

 

[Luthor]

Oki Doki..... My handles are rather worn, the smallest part of the egg shaped hole is 0.731" and the bushing that goes over the bolt that it pivots on has on OD of 0.586". I would simply add a bit of clearance to that, you don't want it too tight as you have a spring holding pressure on it so it won't flop around.

Good, thanks Tazza. I think I made the holes 5/8" which is probably about right.

 

[Luthor]

Good, thanks Tazza. I think I made the holes 5/8" which is probably about right.

I have finally had some time to get some work done on the Bobtach in preparation for some serious earthmoving in the upcoming Australian summer.
Here you can see the hole for the old style square pin starting to take shape to accept the weld in bush.

A view from the other direction.

One hole completed.

A view of the setup on the milling machine.

A lot of hand work was required on the mounting face.

The next step will be welding the bushes in. More photo's to come.

 

[TriHonu]

I have finally had some time to get some work done on the Bobtach in preparation for some serious earthmoving in the upcoming Australian summer.
Here you can see the hole for the old style square pin starting to take shape to accept the weld in bush.

A view from the other direction.

One hole completed.

A view of the setup on the milling machine.

A lot of hand work was required on the mounting face.



The next step will be welding the bushes in. More photo's to come.

Nice work! What mill are you using? It looks like a horizontal with the over-arm support removed.
With all the machining, I now can appreciate why Cavalry built one from scratch. He has a thread on SFT with some photos.

 

[Luthor]

Nice work! What mill are you using? It looks like a horizontal with the over-arm support removed.
With all the machining, I now can appreciate why Cavalry built one from scratch. He has a thread on SFT with some photos.

The machine is a Pacific FU1 or 2 Universal , horizontal and vertical head. The overarm support is actually on there, I just have it pushed back for this machining operation.

 

[Luthor]

The machine is a Pacific FU1 or 2 Universal , horizontal and vertical head. The overarm support is actually on there, I just have it pushed back for this machining operation.

The modification of the bobtach is finally finished and it is back on the machine and working much better than the old square type wedges at holding the attachments securely.
If I had known it was going to take so long I probably would not have started the mod. although I did not have much choice as the bobtach was almost unuseable and a new one is around $4000.00 Australian. I will post some pictures of the finished project.

 

[Luthor]

The modification of the bobtach is finally finished and it is back on the machine and working much better than the old square type wedges at holding the attachments securely.
If I had known it was going to take so long I probably would not have started the mod. although I did not have much choice as the bobtach was almost unuseable and a new one is around $4000.00 Australian. I will post some pictures of the finished project.

Finally some shots of the finished product.

 

[Tazza]

Finally some shots of the finished product.

Looks great. You should have made two sets *nudge*
How did you machine the parts for it? the tubes and wedges are easy enough and the levers i assume oxy or plasma? The hardest part that i can think to make was the one that the lever pulls and pushes on, how did you do that?

 

[Luthor]

Looks great. You should have made two sets *nudge*
How did you machine the parts for it? the tubes and wedges are easy enough and the levers i assume oxy or plasma? The hardest part that i can think to make was the one that the lever pulls and pushes on, how did you do that?

Yes Tazza the pivot is a little tricky although it didn't take long to make them. I started with an oversized block of steel and put it in a four jaw chuck and turned the spigot diameter then just milled away to the final shape and drilled the hole for the shoulder bolt.
I must repeat that this is a fairly intensive modification and I would not recommend anyone doing it unless they have a lot of time and resources on hand.

 

[waggles]

Yes Tazza the pivot is a little tricky although it didn't take long to make them. I started with an oversized block of steel and put it in a four jaw chuck and turned the spigot diameter then just milled away to the final shape and drilled the hole for the shoulder bolt.
I must repeat that this is a fairly intensive modification and I would not recommend anyone doing it unless they have a lot of time and resources on hand.

Thats a nice neat job! I have a spare bobtach that needs rebuilding , you have inspired me !