Need suggestions/coaching with making a lathe gib

Curtis said:
Ken;

In that pic I see what look like small holes (black spots) - are these holes for the screws that you are talking about using to hold the gib material in place for machining?....
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Yes, that is the screws holding the gib to the fixture. I should have clarified myself on this. I used three 10-32 soc hd cap screws, inserted from the back side or under side of my fixture, to hold the gib. If you are careful at what you are doing, sometimes I'm not, use as small screw as you think you can get away with. Don't use one too big either. Could break off your gib!
 
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4gsr said:
C36000 half hard brass will not stress relief. All you doing to it is changing the temper to it if the temperature is high enough. And machining it just adds stresses to it, too!
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Oh! didn't know that. I had given up on the brass for a gib in any case since I was getting nowhere fast using it. I will try HRS next.
 
Curtis said:
Oh! didn't know that. I had given up on the brass for a gib in any case since I was getting nowhere fast using it. I will try HRS next.
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Why do you think the gib that came with the machine was too thin? I think you could make one out of a piece of plain cold roll steel and even get by without cutting the angles on it.
jimsehr
 
Jimsehr said:
Why do you think the gib that came with the machine was too thin? I think you could make one out of a piece of plain cold roll steel and even get by without cutting the angles on it.
jimsehr
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Because it binds the slide in some spots, movement is hard and sticky, again in some places along the slide's movement, the gib screws need to be screwed in quite a bit to hold it in place, the gib is/was bowed ( I tossed it aside after repeated attempts to straighten it with my 12 ton press only made the problem worse ) so much that it is obvious when you look at it without even laying it on a flat surface. Also, the gib strip is simply an oval shaped piece of steel that was sheared to length at the factory. No attempt had been made to fit it to the slot that it goes into. It is neither tall enough, nor wide enough for the cross slot that it fits into. But the bowing was the main problem.


Curtis
 
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Re: Need suggestions/coaching with making a lathe gib (stress relieving brass)

There is (I think) a lot of debate and confusion about stress relieving in brass. Here is a short version of what the Copper Development Association has to say about it (short version): "In order to relieve internal stresses without loss of properties a low-temperature anneal such as 1⁄2 to 1 hour at 250-300°C should be used, dependent on section size." I did some online research on this a while back, and summarized my findings at the link below, for anyone interested in more details: https://sites.google.com/site/lagadoacademy/machining---lathes-mills-etc/brass---stress-relieving
 
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Kevin,

You can do all the stress relieving you want to on Brass. The moment you start cutting on it, it starts moving on you. Especially if you don't flip it after cuts. This happens on most thin materials used for gibs, including cast iron, too!
 
You only rough shape the gib with a mill, you need to scrape it in to get good bearing surface. Look at the machine restoration section to find out more. This is not something you just slap toghether if you want good sliding surfaces. I would also use cast iron for the gib, it will last longer. Tim
 
Re: Need suggestions/coaching with making a lathe gib (stress relieving brass)

kevin said:
There is (I think) a lot of debate and confusion about stress relieving in brass. Here is a short version of what the Copper Development Association has to say about it (short version): "In order to relieve internal stresses without loss of properties a low-temperature anneal such as 1⁄2 to 1 hour at 250-300°C should be used, dependent on section size." I did some online research on this a while back, and summarized my findings at the link below, for anyone interested in more details: https://sites.google.com/site/lagadoacademy/machining---lathes-mills-etc/brass---stress-relieving
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Kevin;

Thank you for the link to your website above; I took a look at it and there is a lot of information and the site is interesting so I bookmarked it for future reference. Also, since I am very interested in the tapered "gibs" (saddle plates?) for the mini-lathes I found that section of the site especially interesting. All of this stuff is useful to me and I appreciate it very much.

Regards,

Curtis
 
I’m guessing that the brass is that half-hard brass. I’m wondering if maybe you tried to anneal it before machining... maybe that would help. I too have had brass do that to me when I made a gib for my SB lathe. I’m pretty sure I annealed it and then finished making the gib... filing and sanding it to dimensions.
*****
Just noticed Kelvin’s post. I think he has the best suggestion. Looks like a winner there. Good post on brass stress relief. I’m going to try that. Yeah.... just noticed I’m commenting on a 7 year old thread. Oh well. FWIW...I was looking up old threads because I need to make a small gib.
 
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Gibs on my mill and lathe are all cast iron. Not sure if brass would be a good choice because of the ware factor. Keith Rucker has a video on making a gib
 
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