# Making a Compound Gib



## RobinHood (Feb 5, 2020)

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)


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## Brent H (Feb 5, 2020)

Awesome Good Sir Robin!

I will commence repairs on my magnetic table ASAP as it looks like it  could be handy.  I have some cast iron bar stock that should do nicely for a new gib.  

I am good for at least $450 in tooling etc without going over the cost of a new gib - hahahaha!!!


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