My SM1340 had the compound gib broken off when I got the machine years ago and made the compound all but unusable. A replacement was going to be about $450. So I made my own out of mild steel (did not find any CI at the time for a reasonable price). I may make one out of Durabar in the future, now that I have come across a piece.
Here are some pictures of the process. Some of the set-ups where pretty sketchy, but they worked with light cuts.
A gib is basically a parallelogram with top and bottom flat and parallel and the sides at the same angle as the mating dovetail, but one of them at a taper angle to the other.
I started by machining the top and bottoms first. I used the dovetail angle from the compound itself to set-up the vice.
Here is the bottom done. Note I did not go all the way to the end - I needed that for workholding and maintaining the original angle later...
And the top...
Quick trip to the bandsaw and oh nooo.... the thing was bent like a banana (a view as it sits on the surface plate) because of the internal stresses that were released after cutting it off the block.
I decided to straighten it in the press - that worked fine.
Here I am machining the non-tapered side. The extra material on the ends allows me to hold it easily to the mill table at the correct angle.
Next I setup for the tapered side. I used a big block of cold rolled as a "sine plate". (a magnetic sine table would make this easier - I do not have one). I used the old gib to verify the correct angle.
Then I superglued the unfinished gib to the "sine block" and machined the taper angle.
Remove it with some heat; trim the ends; and install the retaining slot. New one on the bottom, old short (broken) on top.
I did not have any scarping equipment (or surface grinder) at the time so I just finished the critical sides on sand paper glued to the surface plate. The compound was functional again with the new, longer gib.
Last year, I went back and surface ground the gib and scraped it and the compound for an even better fit and better lubrication. (no pictures, sorry)
Here are some pictures of the process. Some of the set-ups where pretty sketchy, but they worked with light cuts.
A gib is basically a parallelogram with top and bottom flat and parallel and the sides at the same angle as the mating dovetail, but one of them at a taper angle to the other.
I started by machining the top and bottoms first. I used the dovetail angle from the compound itself to set-up the vice.
Here is the bottom done. Note I did not go all the way to the end - I needed that for workholding and maintaining the original angle later...
And the top...
Quick trip to the bandsaw and oh nooo.... the thing was bent like a banana (a view as it sits on the surface plate) because of the internal stresses that were released after cutting it off the block.
I decided to straighten it in the press - that worked fine.
Here I am machining the non-tapered side. The extra material on the ends allows me to hold it easily to the mill table at the correct angle.
Next I setup for the tapered side. I used a big block of cold rolled as a "sine plate". (a magnetic sine table would make this easier - I do not have one). I used the old gib to verify the correct angle.
Then I superglued the unfinished gib to the "sine block" and machined the taper angle.
Remove it with some heat; trim the ends; and install the retaining slot. New one on the bottom, old short (broken) on top.
I did not have any scarping equipment (or surface grinder) at the time so I just finished the critical sides on sand paper glued to the surface plate. The compound was functional again with the new, longer gib.
Last year, I went back and surface ground the gib and scraped it and the compound for an even better fit and better lubrication. (no pictures, sorry)
