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farmwrench@aol
10-24-2001, 12:32 AM
My lathe is tired. The ways are worn but have not given me too big of a headach. What has is the cross feed. The screw and the gibs are badly worn (sadled) unevenly. The problem with the screw is that crossing into or out of the worst of the wear gives me junk numbers. Say I want to knock off 10thou- I would advance the screw 5thou and sometimes I get 7 taken off and others 13. The other problem is that depending on where you are affects tool hight as the tool post rises and falls (that is how I can get 13)(how can I mesure that in relation to the spindle?). Luckly Chater is not much of a problem as when the gib is tight (single screw tapered adjuster) you can't budge the cross slide in other extreems. (the sagy spot is small but it hits in the under 2" range) I at first thought that it was tool wear but it is so repetable once a sharp tool is in the tool post. If it wasn't for the rise and fall of the tool I could cheat and get a dro and forget what the dial says. So should I start talking to a place that will fix her up, and If so should I go for metal spray, grind and rescrape or are there other options.(cost) I hear the new stuff has crome? I can make stuff I can live with but it is anoying and frustrating almost like not having micrometer dials at all. BTW it is a '53 South Bend 13" motor under bed. Thanks Vince. I have thought about makeing a jig to set tool distance on my 4 way and then make a chart to cope to aid repeatability. I would welcom other copeing stratagies.

[This message has been edited by farmwrench@aol (edited 10-23-2001).]

Thrud
10-24-2001, 12:49 AM
Farmwrench,

Check out www.machinerepair.com (http://www.machinerepair.com) before you do anything. They rebuild machines and have classes on scraping. Unless a machine has cracks in the castings most of them are worth rebuilding. You end up with a more stable machine after rebuilding because all the castings are "well seasoned" from use.

Hope that helps.
Dave

MikeHenry
10-24-2001, 11:01 PM
I believe that Roseville has gone out of business, although Michael Morgan still seems to be selling books and tools.

Gary Reif
10-24-2001, 11:12 PM
<font face="Verdana, Arial" size="2">Originally posted by farmwrench@aol:
My lathe is tired. The ways are worn but have not given me too big of a headach. What has is the cross feed. The screw and the gibs are badly worn (sadled) unevenly. The problem with the screw is that crossing into or out of the worst of the wear gives me junk numbers. Say I want to knock off 10thou- I would advance the screw 5thou and sometimes I get 7 taken off and others 13. The other problem is that depending on where you are affects tool hight as the tool post rises and falls (that is how I can get 13)(how can I mesure that in relation to the spindle?). Luckly Chater is not much of a problem as when the gib is tight (single screw tapered adjuster) you can't budge the cross slide in other extreems. (the sagy spot is small but it hits in the under 2" range) I at first thought that it was tool wear but it is so repetable once a sharp tool is in the tool post. If it wasn't for the rise and fall of the tool I could cheat and get a dro and forget what the dial says. So should I start talking to a place that will fix her up, and If so should I go for metal spray, grind and rescrape or are there other options.(cost) I hear the new stuff has crome? I can make stuff I can live with but it is anoying and frustrating almost like not having micrometer dials at all. BTW it is a '53 South Bend 13" motor under bed. Thanks Vince. I have thought about makeing a jig to set tool distance on my 4 way and then make a chart to cope to aid repeatability. I would welcom other copeing stratagies.

[This message has been edited by farmwrench@aol (edited 10-23-2001).]</font>

halfnut
10-25-2001, 12:59 PM
I've ran several of these here well broken in machines.

One question, what does a dial indicator say about your leadscrew. I think this is your problem.

Ok, if you have a .003 thous error divided by 2 for radius. At 2.00 dia or 1.00 radius the tool would have to drop .054 in this .005 movement to make this error, ain't possible. Geometry, that is the thing to study, it is all geometry.

Cross slide leadscrew, has to be.

Good luck, watch those center heights, and all should be well, I have an old Bradford thats swaybacked as an old Horse, amazes me how well she will cut if I keep tool on center.

farmwrench@aol
10-25-2001, 01:26 PM
The nut wasn't super tight and is very worn. Could chips find a way into the nut? and then out, staying with the screw? I had more junk in there than I thought. Cleaning has helped.

toff
10-25-2001, 09:09 PM
Hi,
Sounds as though the crossfeed lead screw is at fault. The space between the crests (tops) of the threads actually changes due to wear. On an old machine, this could account for up to 20 thou. Easiest fix is a better screw and nut. New is pricey, but check some suppliers from HSM (i.e. Meridian, Sobel or others for selected used stuff.)A simple fix is a simple bracket to hold a 2" dial indicator and somthing to butt the plunger against. Have one lathe with saddle, crosslide and tailstock so equipped.
luck
toff

farmwrench@aol
10-26-2001, 09:02 PM
A friend gave me a copy of MACHINE TOOL AN MANUFACTURING TECHNOLOGY (his text book) from a tec school. It went on to great lengths about the advantages of DRO. I can goof stuff up at an alarming rate and keep a clip board with calculator to triple check my self before disaster. I need to use my machine more often, so that some things become second nature. I would like to rebuild just to narrow error down to me. I like the Dial idea and will set that up. Thanks Vince

docn8as
10-29-2001, 01:06 AM
have been told that follower rest keeps tool on center(bending bar) ,practically negating all uneven bed wear ....sounds good . may be worth the hassle of set up !!
best wishes
docn8as

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docn8as

farmwrench@aol
10-29-2001, 09:07 PM
I don't have follow rest. But the goffy readings I think are caused by a worn screw and nut. My cleaning swarf with a shop vac and then a little compressed air drove chips into the slot that the screw resides. The chips would then find their way into the nut and roll around or spring. That is my best diagnoses. THe last owner did a lot of grinding and that didn't help any.

Thrud
10-29-2001, 11:56 PM
Farmwrench,

Hey, what did I tell you guys about safety! DO NOT USE COMPRESSED AIR TO BLOW METAL CHIPS! Even using a vacuum has the possibility of blowing slivers in the air from the exhaust port unlesss you put a HEPA filter in it. It would really suck if you blind yourself with a flying sliver.

Think Safety First....

dave

In fact, throw that blow gun in the garbage now - you could put your eye out with that thing. (see, your Mom was talking blow guns, not sticks!)