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Cross Slide started "Stick-Slipping"...

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middle.road

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#1
Cross Slide started acting up while threading some 7/8-32 tubes.
Decided to tear it down and find out what was up.

All I've got equipment wise to check this is (4) pieces of granite from a CMM that was getting scrapped.
(2) pcs. @ 3" x 6" x 32"lg.
(2) pcs. @ 2" x 4" x 24"lg.
I don't have a proper surface plate yet.

Now if (and that's a big 'IF') I blue'd this correctly, it looks like to me that the top piece is convex and the carriage is concaved.
Also interestingly, the gib is bowed again. I had it straight back in '14.

Ya know, when I bought this hunk I really thought that since it was mfg'd in 1998, in Taiwan, it would be fairly decent. Goes to show you.
This puppy was in a maintenance shop of a granite counter top mfg. A former manager was at the auction and said it saw infrequent use.

I don't see _any_ signs of scraping on the top piece but the carriage does.

Since I don't have any of the tools needed for scraping and since I also do not possess the necessary skills set to perform said function, I'm going to have to come up with a shabby 'shadetree' solution in order to get it to operate somewhat more smoothly.


1112181855_r023.jpg
Third attempt at bluing the top slide.
1117181611a_r038.jpg
2nd attempt, I think I had to much on the roller...
1117182055_r045.jpg
Blu'd the carriage with an edge of one of the 24" plates. Rotated it 180° both sides.
1117182102_r050.jpg
Top piece laying on the floor. I don't see any signs that it was ever scraped.
1117182102d_r054.jpg
Just for grins I did the bottom of the compound... No scraping on it either.
1116182217_r036.jpg
 

Richard King 2

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#2
If you have a few days I think I can help you via the internet and a phone call or 2. Last year a fellow in Germany had a Cylindrical grinder that had stick slip and I was able to help him. I have a PDF of a hand scraper and if you write I can send it so you can make one. Ore you can buy one and I can direct you to where.

In Taiwan many of the crappy machine builders use angle grinders to shape the parts close before scraping, that's what appears you have. If you just want to make it better and usable with-out spending a lot of time and money, then you can scrape in new oil pockets or small reservoirs for the oil to adhere to the surfaces better and way grind the smooth side. Please don't consider grinding or scratching in grooves as at a later date if you want to do it the right way it will be harder.

You would be a good candidate to attend one of my scraping classes. Gibs bend over time because they get worn on one side and not the other, it like cutting of grinding thin material, it tends to bend convex on the worn side. You can PM me and I will give you my phone number and email. Rich
 

middle.road

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#3
Thanks Rich! I'll take a copy of that for sure.
I thought I had a couple of 3/4" wide blades with carbide soldered on floating around in my auction finds, but after a few days searching they haven't been found. I also could have sworn that I had an Anderson style scraper in my stash.

Plan 'B' was to silver solder up some used up insert, but of course I gave away my silver solder supplies since I wasn't using them.
Then of course a couple of years later I score an Oxy/Acetylene tank setup for next to nothing.

I've got a few of these inserts from a project several decades ago. If IIRC they are C6. I was thinking of attempting to grind one down to the proper geometry and then fasten it to a handle of some sort. They're a tad think @ .190" and they're pos-rake so it'll take a bit of grinding.
I was thinking of hauling my ol' 6" grinder out onto the driveway and using a green wheel on one.
Unfortunately I don't have any better wheels than the greenies.

And then there is the Skills factor. After binge watching videos on Youtube*, I really wonder about having the proper 'touch' to perform scraping.
It all makes sense to me, I saw it firsthand four decades ago when I worked in the toolroom, but I have the feeling I'll end up with gouges and not scraps.

(*) Stefan's videos of your classes in Europe are neat, too short though. :grin:

Round-Inserts.jpg
 

middle.road

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#4
In an attempt to figure this out and alleviate my stressing, I thought I'd try shimming it...
............................................................................................................................................................................................ (didn't do much.)

1118182249.jpg
 

Ulma Doctor

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#5
Hey Dan,
i have a scraper you can have.
 

middle.road

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#6
I'll take it!
(Guess I'd better get the lead out of my arse and pack up the vintage motor for your lathe. :grin: )
 

Bob Korves

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#7
If stick slip is the only real current issue, my first question is if you are using way oil to lubricate the machine. Way oil is formulated to reduce stick slip. Stick slip is caused by the flat and shiny surfaces sticking together from the oil squeezing out, then it sticks until enough force overcomes it, then it repeats -- chatter. With you not being trained at scraping, I would not try any overall scraping of surfaces, you might cause more problems than you solve without proper training, practice, and understanding. If the oil is correct, you could do what many surface grinder owners do with worn machines that have stick slip, which is to break up one of the surfaces that are sucking together, making small pockets for the oil to stay in. Use a scraper with a fairly small cutting edge radius, somewhere around 2" (50mm) would work. Scrape in a checkerboard pattern on only one surface, scraping a spot, then leaving a spot, alternately in both directions, until it looks like a checkerboard. Only one pass, use real cuts, not just scratching the surface. Doing the upper surface would probably be best, but either will work. Lightly stone the surface with a fine flat stone afterwards to remove the burrs. Practice on a piece of cast iron scrap, or at least something you don't care about, before attacking the lathe parts.

I just did a quick search to see what I could find on the subject. Look what I found:
https://www.hobby-machinist.com/threads/oil-lines-on-a-bridgeport.16591/
 
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middle.road

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#8
I'm using ISO86, and I slather it on constantly. I don't believe that it's getting coverage where it should.
A couple of nights ago I did up an oil groove layout. I've laid them out so that they will carry oil to the rear edges of the carriage portion when face cutting 3" DIA. so just a bit over the actual travel of the slide. Which I realize isn't proper but she needs lube towards the back.
I'm also going to add a couple of access holes above the gib so that I can get oil straight onto the gib.
The Gits brand ball oilers are a tad expensive so I'll probably just go with set screws for the time being and then keep my eyes open at auctions and such. Of course yet again I thought I had a box of them floating around...

I noticed last night that in regards to the male portion of the dovetail on the carriage, the headstock side is fairly decent while the tailstock side is rough as h*ll. Like someone went at it with a chisel. I'm going to try to blue it and get some picts.
Perhaps that's what it was sticking on.
I'm going to clean up the gib and mill a slot pocket so that the screw will contact properly. It's all mangled right now.

I've got a couple of tops off of old table saws that I can practice on, I like the checkerboard idea.

What I'm leaning towards right now is to 'waste' one side of one of the 3x6x32 granite plates I have and lap the top piece - gently.
I've got Clover compound from 'C' up to '5A'.
I'd like to checkerboard the ends of the carriage and perhaps even it up a bit. With the 2x4 granite plate laying on them I can slip a .0015" feeler gage under it, but not a .002" at least.
Not sure what to do about the condition of the male dovetail. (14" mill bastard file? :grin: )

But you're correct, without proper training and the proper equipment to use I would end up making it worse than it is.
 

Bob Korves

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#9
Dan, the ISO86 oil is pretty thick for a home shop lathe, but I am not sure what lathe it is, looks Asian in the pics. Also ISO86 is just the viscosity, oils specifically made as way oil have additives to help stop stick slip.

Adding extra oilers cannot hurt and may help anywhere oil is not getting to properly. Just make sure to keep the grit out. Adding grooves for oil is also a good idea, they really should be installed on the upper surface, not the lower one.

You can use your parallels or a surface plate, or anything truly flat for lapping if you keep the grit off of them. Tom Lipton has several videos where he covers the granite with aluminum foil for the actual lapping surface, which is highly accurate and keeps the grit from wearing the precision surfaces. Clover compound does not work as well as diamonds in suspension, which are sold dirt cheap from China on eBay in many grit sizes -- for lapping.

Like the Hippocratic oath states, "First, cause no harm."
 

middle.road

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Dan, the ISO86 oil is pretty thick for a home shop lathe, but I am not sure what lathe it is, looks Asian in the pics. Also ISO86 is just the viscosity, oils specifically made as way oil have additives to help stop stick slip.

Adding extra oilers cannot hurt and may help anywhere oil is not getting to properly. Just make sure to keep the grit out. Adding grooves for oil is also a good idea, they really should be installed on the upper surface, not the lower one.

You can use your parallels or a surface plate, or anything truly flat for lapping if you keep the grit off of them. Tom Lipton has several videos where he covers the granite with aluminum foil for the actual lapping surface, which is highly accurate and keeps the grit from wearing the precision surfaces. Clover compound does not work as well as diamonds in suspension, which are sold dirt cheap from China on eBay in many grit sizes -- for lapping.

Like the Hippocratic oath states, "First, cause no harm."
Time to go binge some of Tom's videos then.
Gads, I like that idea of aluminum foil, never seen that or thought of it for that matter.
I've got three 5 gallons pails of ISO32, ISO46, and ISO86, that's why I use them. Picked 'em up a few years ago for $10 at an estate.
I've also got a oldie 5 gallon pail of 10w that I picked up with that vintage drill press for nothing. Haven't chased down the numbers yet.
I wipe it down all the time and apply oil liberally. I got in that habit with my Logan 210 since it has no oilers on it at all.
Another Old-Timer I knew, Harold told me when I first brought the Logan home: Any lube is better than no lube, just don't use detergent motor oil.
Then a couple of days later he dropped off a 1 gallon jug of some sort of way lube he went and scored from another friend, and told me not to be stingy with it...

The current problem child is a Birmingham CT1440GT. Mfg'd in 1998. It's been very good to me since I got it into this shop back in '13.
Still haven't taken care of that 'klunking' in low gear (had a post here back in '14 that got lost in one of the migrations.) and the gasket on the main shaft is leaking also.
I was planning on tearing into the head stock to finally find that darn 'klunk' this holiday season -- guess I'll do a carriage slide first.

Thanks,
_Dan
 

mattthemuppet2

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#11
oil grooves with cups/ ball oilers filled with proper way oil is your easiest fix. It'll fix your stiction problem in no time and help reduce future wear. I'd suggest doing the carriage too, where it sits on the ways. I'd personally suggest going with proper cups or oilers as that will make sure you actually use them. They're not that much for a one off, last a lifetime deal. I'd also suggest adding way wipers if your lathe doesn't have them - keeps the way oil in and the crud out.

Once you've got that sorted, then you can worry about scraping in the geometry, which is a much bigger task.
 

middle.road

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#12
Gib is bowed approx. .008" outwards from the center of the slide, as Richard pointed out above.
Do I bother attempting to straighten it out?

1542995481839.png
 

Ulma Doctor

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#13
yes!!!

straddle the gib lengthwise between 2 parallels in your press and put the bow up.
the parallels should be near the ends for the best use of the force applied.
put a dial indicator on the gib high spot and zero the indicator
press to -.010" (you indicated a .008" bend, you'll go about .002" past) and let the gib return to it's natural state
recheck and then repeat as necessary
 
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