Hackjob repair for a table/gib that's worn in the center of travel? Cincinatti 2MH

[Dope]

I'm sure this is a fairly common issue, and I know the right way to fix it. Sure, re-grind the table/gib, scrape it in, done.

However, in my case, I'm using this machine - a 1938 Cincinnati 2MH - for roughing out larger pieces that don't need tight tolerances. I'm hardly a real machinist, more of an artist/weaponsmith that uses machine tools. So the stuff I make doesn't have high tolerances. I bought this machine for a few hundred dollars and have fixed it up pretty well to the point where it works nicely.

However, the table is EXTREMELY worn in the center of travel. When I say extremely, I mean that with the table anywhere near the center of travel, the gib adjustment screw for the X-axis bottoms out, with still plenty of slop in the table. Conversely, on the extreme ends of travel, I literally cannot move the table even with both hands. Even after backing out the gib screw 4 or 5 turns, I can just BARELY move it.

When milling, I have quite a chattery finish due to the wear in the table. If I do a full-length cut (28"), the cut will start out perfect, transitioning to a very bad pock-marked surface finish (with associated noise), and finally back to a perfect finish again as it reaches the opposite end of travel. I'd like to improve this situation without spending dozens of hours or thousands of dollars. If I were going to do that, I'd just scrap the machine and start with something in better shape.

Is it worth trying to hackjob fix this? I've considered:

1) Just leaving the gib over-tight and letting the ends of travel wear themselves in. Not sure how long that'll take LOL
2) Shimming the gib and only using the center portion of travel
3) Milling the gib flat-ish and then shimming it. Or hell, even grinding it with one of the other (much better shape) mills with a jury-rigged setup.
4) Possibly looking into something like turcite or a similar product. (I have zero experience here but I've been advised about it)

I do not have a surface grinder and I have zero hand-scraping knowledge.

Please try not to lynch me too badly, I realize this is akin to sacrilege to many. But I'd rather not haul this machine off to the scrap yard and I'd rather not spend 5x the machine's worth to fix it. It might be the ugliest machine in existence but I enjoy using it and it really does work pretty well other than the table issue. It's got the toolmaker's powered overarm and it's surprisingly versatile.

Thanks in advance,
Dope

 

[Demon69]

Its a bodge and might depend on what type of gibs you have but you could try and relieve the centre of a surface and hold the opposing side with a somewhat flexible centre bearing surface. Think supporting via 3 points.

Wont make things straight or square but you could solid things up. Remember theres likely wear in all siding components, table knee and saddle. Its up to you be sure whats giving you the most trouble and have some understanding of what youre trying to do before taking metal out.

 

[Tyrone Shoelaces]

Are you using the machine in the horizontal mode or the vertical mode ?

Regards Tyrone.

 

[john.k]

All thats needed is to shim the gib with feeler strip ,or whatever thickness is needed to restore the gib adjustment......obviously this wont eliminate wear,but will make a huge difference...(strip goes on the static side of the gib,not the wear side...as it might get dragged in.)

 

[Tony Quiring]

Remove and inspect the gib.

Everything that slides wears and if gib is softer than machine it may be worn more.

Really need to remove table to see where wear is but gib inspection easy.

Others way better suited for additional suggestions.

Sent from my SM-G781V using Tapatalk

 

[Richard King]

The table is worn and it is bent too, it is convex on top and concave on bottom. I would guess it is bent .010" and worn .020" if it gets stuck on the ends. I hate giving 1/2 assed advice. You may want to try what Demon said. The gib is worn on the ends making it high in the middle. You can epoxy on some Turcite as it squishes. It is soft and slippery.

To figure it what size to put in there, move the table to the middle and loosen the gib screw out to the extreme out position and screw it in about 1 or 2 turns, then push the table back against the saddle. Then with 2 feeler gage sets, slide them in on both ends of the gib until you figure out how thick the Turcite should be.

Turcite can be bought in .010", .020",.030",047", ,062", .090", .120". Then buy some and take the gib out and clean it up with lacquer thinner, sand blast the wear side of the gib and wwipe off the gib and tucite dark side and epoxy on the Turcite. Lay some wax paper on a steel table, mix the epoxy up, spread it on the gib and turcite, flip it over so turcite is on the wax paper and clamp it down with C-Clamps every 4".

Let it dry overnight, trim up the edges and then cut in some oil groves in Turcite, oil it and slide it into the table. Try to clean the table and saddle where the gib goes. Oil the gib and slide it in. snug the gib up in middle and you can slide in .005" shim between gib and table and try it. You would put a long strip on the entire gib. Check out the slop and let me know. I may have some Turcite or can tell you where to buy it.

You can call me too. You won't need to scrape the turcite for a 1/2 assed job. If this doesn't work, you should get the table planned and put the Turcite on the saddle and gib. Message me for my phone number.

 

[Dope]

Are you using the machine in the horizontal mode or the vertical mode ?

Regards Tyrone.

Both. Mostly vertical I'd say.

 

[Dope]

Its a bodge and might depend on what type of gibs you have but you could try and relieve the centre of a surface and hold the opposing side with a somewhat flexible centre bearing surface. Think supporting via 3 points.

Wont make things straight or square but you could solid things up. Remember theres likely wear in all siding components, table knee and saddle. Its up to you be sure whats giving you the most trouble and have some understanding of what youre trying to do before taking metal out.

That's an interesting idea. So basically you're talking about using some sort of shim approximately in the center of the gib to bow it out slightly? I like it, seems easy enough to try. It's just a standard tapered gib BTW.

 

[Dope]

All thats needed is to shim the gib with feeler strip ,or whatever thickness is needed to restore the gib adjustment......obviously this wont eliminate wear,but will make a huge difference...(strip goes on the static side of the gib,not the wear side...as it might get dragged in.)

Sure, but I figure that's only going to make my issues with it being over-tight at the ends of travel even worse, I assume - right?

 

[Dope]

The table is worn and it is bent too, it is convex on top and concave on bottom. I would guess it is bent .010" and worn .020" if it gets stuck on the ends. I hate giving 1/2 assed advice. You may want to try what Demon said. The gib is worn on the ends making it high in the middle. You can epoxy on some Turcite as it squishes. It is soft and slippery.

To figure it what size to put in there, move the table to the middle and loosen the gib screw out to the extreme out position and screw it in about 1 or 2 turns, then push the table back against the saddle. Then with 2 feeler gage sets, slide them in on both ends of the gib until you figure out how thick the Turcite should be.

Turcite can be bought in .010", .020",.030",047", ,062", .090", .120". Then buy some and take the gib out and clean it up with lacquer thinner, sand blast the wear side of the gib and wwipe off the gib and tucite dark side and epoxy on the Turcite. Lay some wax paper on a steel table, mix the epoxy up, spread it on the gib and turcite, flip it over so turcite is on the wax paper and clamp it down with C-Clamps every 4".

Let it dry overnight, trim up the edges and then cut in some oil groves in Turcite, oil it and slide it into the table. Try to clean the table and saddle where the gib goes. Oil the gib and slide it in. snug the gib up in middle and you can slide in .005" shim between gib and table and try it. You would put a long strip on the entire gib. Check out the slop and let me know. I may have some Turcite or can tell you where to buy it.

You can call me too. You won't need to scrape the turcite for a 1/2 assed job. If this doesn't work, you should get the table planned and put the Turcite on the saddle and gib. Message me for my phone number.

This is also an interesting and simple enough idea. Thanks!

 

[Tyrone Shoelaces]

Both. Mostly vertical I'd say.

What sort of work are we talking about ? What Material you are attempting to cut ? What is your set up like ? What sort of cutter are you using ? What speeds and feeds etc. All these issues have a bearing on things like surface finish. A few photos are worth a thousand words.

Regards Tyrone.

 

[Demon69]

That's an interesting idea. So basically you're talking about using some sort of shim approximately in the center of the gib to bow it out slightly? I like it, seems easy enough to try. It's just a standard tapered gib BTW.

Or more simply than that, you could bend the existing gib (if its steel), or make a new gib (it doesnt have to be perfect) and bend that towards the table, in effect creating a spring that pushes the table towards the bearing points in the 3 opposing surfaces.

You already have the enough gib to bind the table at the ends of travel, so using a solid shim wont help much, turcite might squish enough as Richard suggests, depends how much wear you have in the table I guess.
In short, you want centre relief on the 3 surfaces of the saddle, and use the gibbed surface to press the table against these bearing points.

Worth taking a pic of your setup and tooling as Tyrone suggests. A bad setup and inappropriate tooling would exacerbate the slop in the table. Might be able to get the cutting result just by changing things up.

 

[Illinoyance]

I suspect the table is worn on the guiding surfaces. I doubt that messing with the gib is going to be of much help. Ideally you would remove the table and scrape the table and saddle guiding surfaces.

 

[johansen]

some folks may want to drink a beer and take your blood pressure meds before reading this..


A hack job repair would be to take the table off and flip it over.

Take a piece of 1" by 3" steel 2 feet long and machine an angle on it to fit the dovetail.

Then lap the flats only, keep the dovetail clean.

Use the machined bottom of the dovetail as a reference.

Alternatively, measure the thickness of the table and lap it until it's the same on both ends again and in the middle.

once you get close, cut your bar you used to lap the table in half, and then do both sides at the same time, with a sturdy bar to clamp the two together, but in an adjustable manner. you're done when you have the same friction on both ends of the table. I removed .003" of material from the flats of my lathes cross slide using a similar process. yes, it will end up twisted that's why you want to measure the thickness of the table on both ends.. the hack job part of this is that you're operating on the assumption that the table wasn't twisted, and was equal thickness at both ends before it got worn.

Even more hack job? Use a router to remove the bulk of the material.

Then add the material back to the saddle or carriage.

 

[johansen]

Another idea.. replace gib with plastic.

Put a fat spring in front of the table locks (I'm assuming they press on the gib). The pressure applied will hold the table down, the plastic gib can bend without breaking.

Grind or cut 20 divots per square inch in the gib for the oil to flow, it will make a big difference.

 

[Illinoyance]

If the table guiding surfaces are worn narrow in the middle no amount of f***ing with the gibs is going to help the problem.

 

[Demon69]

If the table guiding surfaces are worn narrow in the middle no amount of f***ing with the gibs is going to help the problem.

Are you sure you understand whats being discussed?

 

[Garwood]

I have a kind of beater 1 ton 4x4 truck with 400K miles on it. I've had it for about half it's miles and kept it well greased. Everything in the front axle is worn out. The U-joints, the balljoints, tie-rods, everything. But it drives great. let go of the wheel at 80 MPH no problem. It drives great because a PO ran the truck over something immovable and bent a bracket on the front axle up to where it pinches the steering tie rod that goes from knuckle-knuckle. No shimmies, no shakes, no idea the balljoints are toast unless I lift the front end and wiggle a tire.

I would do something similar for your mill. Rig up something between the saddle and table to keep constant pressure in one direction. You could get fancy and use a couple camfollowers with some heavy die springs or you could just take a chunk of old truck leaf spring and bolt it on the saddle so it slides on the front face of the table. A dab of grease now and then and put it to work.