Do you have a question on rebuilding I could help you with?

[Suzuki4evr]

Yes I always try to get the work as low as possible, but it gets tricky sometimes, as you know, a specially when using a dividing head in the vertical position or rotary table.

 

[Cadillac]

I have a question for you Richard. I have a tapered gib on the cross slide of my 14x40 lathe. I decided to take apart the cross slide and check it out to see if I could better anything. Found the gib is bowed in both directions. Can this be fixed or should a new one be made? I have been able to straighten the dovetail surfaces but haven’t addressed the top and bottom surfaces. If the gib is in its position the bow is frowning.
Another question now that I think of it is how tall should the gib be in relation to the dovetail. Mine is about flush with the top of the saddle dovetail with about a 1/16-1/8 to the bottom side of the topslide. Ive experienced the gib raising up in the dovetail when adjusting and I put copper shims between the topslide and gib to keep seated in the dovetail. I believe it’s because of the bends in the gib causing it to not seat correctly?? Should the gib be taller than the dovetail?
When dealing with scraping a cross slide, if it has a bow in it. Where do you start to scrap? All surfaces were machined and it bowed so everything has a bow top, bottom,dovetails, etc all going the same way frowning high in center. Thank u for your time and expertise!

 

[MontanaLon]

Very good information, thank you Richard. I hadn't considered looking at the rack to see the wear there. Now I wish I had on a couple of machines so I could compare the other things that made me pass. One of the lathes I looked at was really nice looking but when I tightened the saddle lock to just give resistance to the hand wheel it would move about 4 inches toward the tail stock and then go no further. I had to loosen it up considerably to get it to move again and then it was fine the rest of the way. I bet the rack at the headstock was sharp. When I lifted on the saddle there was visible movement in the whole thing. Actually, when I checked the cross slide, the whole saddle would rotate side to side. Other than that it was in good shape. No crash damage on the compound, no gear damage in the headstock. At the right price it would probably be good for some parts but the bed was shot in my estimation.

 

[Janderso]

Hey Rich is back. I thought you went camping.

 

[Richard King 2]

Very good information, thank you Richard. I hadn't considered looking at the rack to see the wear there. Now I wish I had on a couple of machines so I could compare the other things that made me pass. One of the lathes I looked at was really nice looking but when I tightened the saddle lock to just give resistance to the hand wheel it would move about 4 inches toward the tail stock and then go no further. I had to loosen it up considerably to get it to move again and then it was fine the rest of the way. I bet the rack at the headstock was sharp. When I lifted on the saddle there was visible movement in the whole thing. Actually, when I checked the cross slide, the whole saddle would rotate side to side. Other than that it was in good shape. No crash damage on the compound, no gear damage in the headstock. At the right price it would probably be good for some parts but the bed was shot in my estimation.

Scroll to 5:29 minute in this You Tube show.

99.9% of the time if the machine was made by a good builder and not some Asian crap machine the gib was made correctly. The back of the gib match fit the back and front side. So if the gib is bent it is from wear on the front side and the gib front has the frown and the back is normally scraped flat, so you need to bend it so the back is straight and then match fit the front side to the scraped ways it rides against.

If the gib tightens when one side moves up of down the problem is the dovetail angles on the riding way and the dovetail slide. Many never check the angles. It is simple to get them matched that many never do, because no one has ever told them or showed them. Self taught and reading the Connelly book. Before match fitting the short moving dovetail slide to the long dovetail way. tip the slide on the side and check the dovetails with a prism or angled straight edge. Both the riding side and the dovetail that the gib rests against. They are both 90% of the time are high in the middle. The middle needs to be scraped out so it doesn't rock. As I tell students, how the heck can you hinge the dovetail slide when you bluing it up? You can't so you prepare before bluing them up.

On the side behind the gib VERY IMPORTANT is to rub the tapered gib side of the short slide up against the base or longer slide and "match" fit that side the gib back sets against blues up all the way from top to bottom so it is parallel top to bottom of the 2 surfaces. Then when you scrape the gib and it hits on the side top or bottom side of the gib you not only scrape the long taper to fit you scrape the face of the gib front. I hope this makes sense as it is a real pain trying to explain . It is unimportant if it is a 44, 45, 46 degree angle as long as both side match fit each other. . Also you have to be sure the gib end faces are at right angles to the length. so when you tighten the gib screw it doesn't twist the gib in. Another issue many forget is a bent gib screw. Then if the gib goes into far you epoxy some Rulon 142 or Turcite B to the front side of the gib.

I have never seen a gib bent top to bottom as you described. You machine must be a cheapo machine or someone dropped the gib. I tell students .010 to .020" thinner then the opening top to bottom. Most of the time you have to mill down the clearance surface or top of short side top of dovetails. One has to watch out for the feed screw alignment too.

 

[Cadillac]

Thank you for the response Richard. The machine in question is fairly new so I’m not dealing with wear issues on the gib or cross slide it’s poor fitment from the factory. Is what it is so I am gonna make it the best I can.
Unfortunately the gib is bent up and down I can fit a .015 in the center. First picture is the way it lays in machine. Bow in center I am pushing down on other side so you can see air gap on fat end of gib. Second pic is upside down can better see the bend .015 in center consistent arc to ends.


Gib height is .065 smaller than opening, its a smidge taller than male dovetail on saddle. I’m really considering making a new one. I’m in the process of scraping a straight edge to check the dovetails. If all goes good with that it might give me the confidence to make a gib. Then I won’t have to worry about realigning everything and have enough on the original and most worry some is straightening the pretzel of a gib.

 

[Richard King 2]

Harbor Freight? A student brought one of those to a class and it was fit that way. A new gib would make sense after seeing that joke. Looks like the ground surface of the cross-slide needs to be square cut or 1/2 moon flaked.

 

[Cadillac]

The bottom of the cross slide was ground on all surfaces and the bottom had flaking that’s it no scraping or fitting. Cross slide also had a slight bow I scraped the flats and am working on the SE for the dovetails.
The lathe is a 14x40 optimum lathe I’ve seen sold through grainger. Didn’t have problems with surface finishes or tolerances surprisingly. Only issue was that gib floating up. Watching videos of Stephan rebuilding a compound and the easy of the slide made me curious and I started investigating and found what I did so now I have to fix it.

 

[Richard King 2]

Stefan has taken 2 of my classes. One in Norway and one in Germany. I asked him to be my interpreter for the German class.
Pic's L to R : Stefan showing the group how my King-Way worked while he scraped his small surface grinder table : Stephan turning the small test bar we used to show the group how to test Tail Stock alignment and where we taught that class in Stuttgart.

 

[eeler1]

How to straighten a bent gib;