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lathe
01-24-2016, 06:52 PM
So I've been learning some basic machining on the Atlas/Craftsman Commercial 12" lathe. Lately I have not been able to bring the crosslide back very well. It feeds forward smooth, but it takes significant pressure to bring it back. Sometimes it will come back smoothly but this is getting to be more rare. Feels like something is binding or I'm not sure. I loosened the gibs on the cross slide and actually took the compound and the nut that moves the compound off to see if that could be causing the problem, but was still having the same problem. I oiled the oil holes.

Any ideas of what could be going on? Is there a gear that the power feed mechanism uses which could be causing the problem? Thank you in advance.

J Tiers
01-24-2016, 07:04 PM
When you retract the crosslide toward you, the pressure on everything is opposite what it was for cranking it forward. Specifically, the dial side of the screw bearing has pressure on it. That includes also the dial, as the stackup includes the dial on most Atlas, IIRC. If the area behind the dial is not oiled, or if it has dirt in it, that will certainly change the friction.

Leadfootin
01-24-2016, 07:23 PM
My HLVH has a long tapered wedge on the cross slide. If it is not tightly held by the adjuster at each end, it can move forward and back when the cross slide is reversed, causing exactly what you describe. This happened when first adjusting the machine after cleaning - seems stuff I buy has always sat long enough to need a near complete disassembly and cleaning.

lathe
01-24-2016, 07:48 PM
I'm hoping I won't have to take it all apart but If I have to to clean it then I probably will. The hard part is getting it all back together and working properly. You do learn quite a bit with disassembly and reassembly.

Doozer
01-24-2016, 07:54 PM
An Atlas lathe does not have a tapered gib like a Hardinge.
It is like comparing Yougo to a Ferrari.
The Atlas has 3 set screws on the compound gib.
When I owned my POS Atlas, I added 2 more,
for a total of 5 set screws. This was to help with rigidity.
Is your gib cast iron? I have seen some late Atlas lathes
with nylon plastic and also steel gibs. I seem to have read
somewhere that the 600 Group was passing off mild steel
strips as Atlas gibs. This trash just won't work, even on a
POS lathe.

--Doozer

Tim Clarke
01-24-2016, 07:56 PM
I had a Craftsman Commercial about 15 years ago. In many ways it 's the best of the Atlas lathes, the heaviest bed, yadda,yadda. This does NOT include the gibs, which, at least on mine were some sort of nylon/plastic material.

Your best bet would be a disassemble and inspection of the cross slide, and gib. I found my gib had cracked in the area of the adjusting screw seats. I made new ones from scratch from brass strip. I sawed 'em from some plate, filed the angles, and used a transfer punch to mark the dimples where the adjusting screws
seat. I cut the seats with my drill press and whatever size drill it needed. It was a pretty crude fix, it reflected my abilities and equipment at that time. What a difference!

I didn't experience the same symptoms as you, I was having trouble with overhanging tools. (boring bars) Sorry I can't remember what size stock I used, the machine has been gone a long time now, probably 12 years or so.

Best of luck, and keep us posted on what you find
TC

lathe
01-24-2016, 08:32 PM
I think the gibs are ok because I was still getting the problem with the compound removed from the lathe. I will likely try to take the apron/cross slide off the lathe and try to disassemble it and clean it. To me it seems like the problem must be close to the handle but I guess you can't see inside it until it's disassembled. I did in fact remove the handle along with the dial but this didn't solve the problem either.

It's just a weird problem because sometimes it will work fine, but then other times I have to use all my strength to be able to retract it.

Gary Paine
01-24-2016, 08:32 PM
Check the nut under the ballcrank on your slide. If loose and not secure, it can/will tighten against the dial when the screw is turned counterclockwise to retract the slide.

lathe
01-24-2016, 09:06 PM
Check the nut under the ballcrank on your slide. If loose and not secure, it can/will tighten against the dial when the screw is turned counterclockwise to retract the slide.

I think this solved it. I just went out and tightened the outermost nut from the handle and it seems like it is working again. Thank you so much!

J Tiers
01-24-2016, 10:00 PM
Hey Dooz.....

What's wrong with mild steel on that type gib?

What do you think is better?

Lots of machines use that, and it works. I've even used brass. The material's not very critical, even the plastic ones probably kinda work.

CCWKen
01-24-2016, 11:21 PM
He's in the wrong forum. He believes that unless you have the best of everything, your tools are trash. Many forget this is a Home Shop machinist forum.

J Tiers
01-25-2016, 12:39 AM
Yabbut, what is actually "not the best" about them?

I surely do not think cast iron would be better it would probably shatter. if not that, then what?

Carm
01-25-2016, 07:24 AM
"What's wrong with mild steel on that type gib?"

Mr.Tiers, scrape some mild steel.

Brass, bronze, cast iron all good. Hard steel, well that takes some work.

Dunno plastic. It gets better all the time but I wouldn't use it in this app.

Richard P Wilson
01-25-2016, 11:27 AM
"What's wrong with mild steel on that type gib?"

Mr.Tiers, scrape some mild steel.

Brass, bronze, cast iron all good. Hard steel, well that takes some work.

Dunno plastic. It gets better all the time but I wouldn't use it in this app.


OK, so what is wrong with mild steel for this useage? I've had loads of lathes and other machines with gibs made out of mild steel, usually around 1/2" -3/4" x 1/8" or 3/16". cast iron would be no good here, too thin. I've never found one with brass or bronze gibs. Yes, thicker, taper gibs are a better design, but in the case of a thin strip gib, IMO, theres nothing wrong with mild steel. Theres more issues with the detailing, like how many adjusting screws, what thread on the adjusting screws, what the end shape of the adjusting screws is, dowelling of the gib to prevent unwanted longitudinal movement, than there is in the material.

janvanruth
01-25-2016, 11:52 AM
i have taken apart, scrapped, some machines over time
old fashioned reasonable quality machines
i have yet to find one single, rather thin, non-tapered gib made out of cast iron, brass or bronze
they all were, rather mild, steel, either planed or milled or ground ,none of them had scraping
all of them had more wear near where the setscrews were
none of them were really flat any longer

J Tiers
01-25-2016, 12:15 PM
"What's wrong with mild steel on that type gib?"

Mr.Tiers, scrape some mild steel.

Brass, bronze, cast iron all good. Hard steel, well that takes some work.

Dunno plastic. It gets better all the time but I wouldn't use it in this app.

I have in fact scraped mild steel. It's a bitch. Gummy, nasty, no fun at all. And you don't really get a great surface either.

But I see NO REASON to scrape for this type gib. In case you are not aware of it, the screw-adjusted gib need not be anything special except reasonably flat, and able to fit in the space. The screws will adjust it to the desired clearance, and the gib itself is usually thin enough to conform as needed. Surface grinding the front side would be perfectly fine to do.

There is NO reason to scrape this type gib, and every reason not to do it.

Carm
01-25-2016, 05:15 PM
In response to Mr.Tiers and Mr.Wilson, with a nod to CCWken (since I can't speak for Doozer).

I did not say there was anything wrong with mild steel. My point was there are better candidates. A HSM can do whatever they want...lignum vitae, rock maple, bakelite, tufnol, Celeron among the unorthodox.

Mr.Tiers, I figured you had scraped mild steel and anticipated your response - gummy. Therein is my objection. It is not ideal for coefficient of friction here. I am aware of properties a gib should have..."need not be anything special except reasonably flat, and able to fit in the space " should include ease of sliding. Would you consider a 300 series stainless?

If section thickness limits the use of cast iron, brass or bronze are better used as the cost and labor are negligible vs. the outcome, and they won't sacrifice a casting. There is a graphite impregnated sintered bronze on the market which has appeal though I have no experience in linear use.

If mild steel was my only choice 1018 annealed ground stock from a catalog would be a start and I would frost (flake) the sliding side. Small lathes often lack lube points here so access would be part of the job.

J Tiers
01-25-2016, 05:34 PM
Friction is OK with the other side CI, and a good oil film. Even two surfaces of CI are no good without oil.

Item one is good wipers. Item 2 is wet them down well with oil. Item 3 is get the oil put in between the surfaces if possible.

But there is a hundred years or so history of the mild steel gib, and it is still working. Sure, a tapered CI gib is nicer, works better. You got whatcha got....I believe you may be over-thinking this.

Doozer
01-25-2016, 08:05 PM
Someone said it. Mild steel is gummy.
It can start galling if someone forgets to
oil it for a while. Most all the gibs I have
ran across were cast iron. Yes, even the
small ones. I have a tiny cast iron gib
from the taper attachment of my Hendey
that is like 4" long, and it is snapped in half.
It is tapered as well, so I either need to
fixture it well and braze it or make a new
one on the surface grinder. I don't have
a sine magnet, so I might have to use the
vise held in a vise trick.
I really wish I could use a piece of mild
steel, as it would be easier. I scored a
piece of 2" Durabar 40 round from work
and I will try to get a flitch off of it as
material for the gib I need to make.

--Doozer

J Tiers
01-25-2016, 08:59 PM
Someone said it. Mild steel is gummy.
It can start galling if someone forgets to
oil it for a while. Most all the gibs I have
ran across were cast iron. Yes, even the
small ones.

.....

--Doozer

Ah, but do you have any that are 5 or so inches long, about 0.093 thick, a half inch or so wide, AND made of cast iron?

Didn't think so.... That size and shape is just not practical for a brittle material like CI. I mean, you could DO it, but I don't think it would be a good plan.

The gummyness is not a problem. It's gummy when you scrape it, but you need to remember, there is oil in there. And, one side is still CI, with the carbon content etc, that everyone thinks is magic stuff.

If you forget to oil, well, whose fault is that? Don't blame it on the material. If you forget to oil CI, it will grind against the other surface and mess itself up. If you forget to oil plastic, it will be worn away. If you forget to oil hardened steel, it will STILL be lapped by the CI, and get messed up.

The mild steel gib works fine, and has been used for many decades with excellent results. I do not think a CI gib of the same dimensions would last that long. Besides in gibs, you find mild steel (low carbon) stuff rotating in cast iron in many places.... For that matter, you find it rotating in mild steel with no issues.

Are you the guy who magically finally learned the truth? The guy that discovered that the mild steel gibs, etc, have actually been sticking, galling, and jamming up when running against cast iron all this time, and nobody noticed that stuff stopped sliding or rotating?

vpt
01-26-2016, 07:31 AM
One thing to check out, the screw uses a jam nut sort of deal on either side of the bushing. If one of these jam nuts loosens up it will tighten up against the bushing as you turn the screw primarily as you described when you are turning the compound back towards you because you would be turning the screw counter clockwise which would make the outside nut tighten up against the bushing.

I would take the handle off and check the nut(s) to make sure they are tight and not walking around on the screw.

Carm
01-26-2016, 08:29 AM
snip)
....I believe you may be over-thinking this.

Nah. You asked a question, I gave my opinion, whether concur or contest.

Sunset Machine
01-26-2016, 03:45 PM
I have a machine with steel (wrought iron?) shafts that have been running in plain iron bores for a hundred and fifty years on occasional drops of oil. There doesn't seem to be much in the way of wear or galling happening, but yet this same machine uses cast iron gibs, one of which is cracked and brazed.

The situation is kind of a puzzle to me, but perhaps the round shafting was in general production and the flat gibs came from the same place the main castings come from. Not so much a reason, but that it just fell out that way. Economy in manufacturing is my guess. I would use steel on cast any day.