How do I make this gib? Materials + order of operations.

[ErichKeane]

As some of you know, I have an old Navy ship lathe by Reed Prentice. I noticed the compound is really sticky, so I pulled it apart, and noticed my gib is pretty well hosed. its got a nice bend to it, and seems to either have been broken/welded since. The big part of the problem is the slot for the adjustment screw is too long, so it ends up binding every time the compound slide is moved. I figure I can make a new one on my milling machine!

First, I would think I need to do cast iron for this, right? Any idea what kind? Is there a good place to get small items like this? I have a metal supply on the way home, but I'll have to see if they can sell me a smallish amount. Everywhere online wants to sell me 1.25" square at minimum, when I need about half that in each direction.

I whiteboarded/measured the end of the material as you can see from my whiteboard measurement. It has a 60 degree angle on it, which I suspect I can cut with a dovetail cutter (I think I have one big enough) or by tipping the head or using a sine bar. The problem is, I also have to cut out the little notch on the left in the pictures. Additionally, I have to cut the taper, where it gets narrower as it goes 'away' from you in the drawing (and in the picture).

Anyone have any ideas on workholding or order of operations? Or a good source of smaller pieces of cast iron about a foot long?

 

[benmychree]

Use class 40 iron.

 

[Briney Eye]

The seller says that this is Class 40.

 

[Cadillac]

McMaster Carr is a good source for the cast. As for order of ops a gib is a little tougher. Use a mag chuck or some sort of jig for machining. I’d cut The ruff shape out minus the taper then do all the notches and features, then I’d either find the taper using a indicator or use the old gib set the new piece on top the old and it will transfer the taper angle.

 

[ErichKeane]

I looked at it a while and thought about it further. I realized the width of the tab is unimportant, as is the overall height. Only the distance (in the drawing) from the bottom of the tab to the bottom of the gib matters.

My thought is to make it upside-down, cut the angle with a dovetail cutter, then find a way to set the angle and cut the flat. Then, cut it off on the bandsaw.

I'll use the surface grinder (since it has the mag chuck) to just finish off the top.

 

[benmychree]

Another thing; do not cut the adjusting notch until the taper is finish scraped , and keep it as long as possible until all fitting is complete and the tapers match by bluing them in and scraping to fit, then it may be cut to length and the notch cut.

 

[ErichKeane]

Another thing; do not cut the adjusting notch until the taper is finish scraped , and keep it as long as possible until all fitting is complete and the tapers match by bluing them in and scraping to fit, then it may be cut to length and the notch cut.

Good points, thanks! I'm unfortunately not going to be able to scrape it, but I planned on bluing it, then using some abrasive to take down some of the high spots. Sort of a 'poor man's scraping'. Either way, better than the pitted, shop made mess that I've got!

 

[benmychree]

There is nothing difficult about scraping, maybe you might give it a try ---

 

[ErichKeane]

The seller says that this is Class 40.

speedymetals ended up being about the same price for a little more material and quicker shipping, so I went with them. Mcmaster ended up being about 2x the price!

I think the extra material that I got will be useful, since I want to do all my operations above the vice so I have room to do them!

 

[pstemari]

That's the sort of thing I would do clamped directly on the table, not in a vise. Put a piece of sacrificial material underneath it and clamp along the length with toe clamps from one side. Face it, moving clamps out of the way as you move along the length, and replacing them after you pass them. Flip it over and repeat the process, facing it to thickness. Next, mill the step along the side. You shouldn't have to move any clamps for this operation. Finally, adjust it to the correct angle using an indicator and the old gib as an angle reference, and then mill the angle on the side. Once you have the basic gib finished, you can go ahead and cut the notch in the end.

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