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I think I need a new cross slide...

KeeponDragon

KeeponDragon

no problems... just challenges
It started with wanting more rigidity.
First the AXA tool post with the "steve bedair special" tool post mount. :)
It could also be the iron used in the slide. :p
I feel like the first cause was a lack of T-slot nuts when I took this lathe over. :rolleyes:
The original owner seemingly made it habit to horse the fasteners down with a 3/4 breaker bar. (sarcasm of course lol) o_O
The locations where the original 2 bolt clamp were, are erupted. If that's proper use of the word in this case.
Now with the 4 bolt clamp, I'm getting the same eruptions.
I use a 5inch long, 10mm wrench to tighten the clamp bolts. There isn't a lot of leverage to reef on it like a 300lb gorilla :cool:

I'm posting this, while getting paid to do the day job lol...so I can't even snap a pic to show you folks what I'm babbling about.
I will soon though...
My question to the crowd...is there somewhere north of the 54-40 that makes these for sale?

thanks all
-Drags
 
Pic 1 n 2 shows the damage from the PO...3 is what's starting to happen under the new clamp
I think I'll make a set of sliders that fit the Tee grooves. Make em as long as the clamp is deep so the load of tightening is applied across a larger area.
That should work eh?


20230406_171101.jpg


20230406_171123.jpg


20230406_171046.jpg
 
/\ agreed, you need to make yourself some T nuts, or something that is going to spread out the clamping load more than those little nuts
 
KeeponDragon said:
Pic 1 n 2 shows the damage from the PO...3 is what's starting to happen under the new clamp
I think I'll make a set of sliders that fit the Tee grooves. Make em as long as the clamp is deep so the load of tightening is applied across a larger area.
That should work eh?
Click to expand...

When I look at the damage, I see the result of incorrect clamping in cast iron. I think it's important to avoid high tension loads in cast iron. Cast iron does not have great tension loading characteristics because it doesn't deform well. Instead it cracks and breaks.

That is the reason why most T- nuts are not threaded all the way through. You don't want the bolt pressing the t nut up against the slot. The slot will break. The same thing happens if the nut is pulled up against the slot from above.

However, cast iron is excellent in compression. All T-nut systems should clamp the slot not pull on the slot rails. Here are a few hand drawings to illustrate.

20230407_084058.jpg


In the top two examples of the photo, the good clamp Clamps the slot ears. The bad clamp pulls up on the ears.

In the bottom two examples, the good screw does not bottom out in the slot. In the bad example, the screw bottoms out in the slot.

Longer t-nuts will help but only to a point. The solution is proper clamping, not bigger nuts.

You can also search the forum on T-Nuts and T-Slots to get a better understanding of the issue.
 
What does the under side of the compound? look like, hollow like Susquatch's top bad drawing?
Clamping force can be changed by going to a finer thread pitch (increased), not needed here, but needs to be thought about when up grading/improving things, eg. well I don't have a course nut or bolt to replace damaged one that's there. I'll just use a fine thread and replace both pieces, great, remember to use less torque when tightening them up. That part of the class was a long time ago, involves lever length, force applyed to lever, ramp angles of threads, probably some other things. But I have slept since then.
 
Bandit said:
What does the under side of the compound? look like, hollow like Susquatch's top bad drawing?
Click to expand...

Usually, they are flat, which would be ok. If I had to guess, it's the second scenario that is the problem here. The screws are too long. They will feel good when tightened. But the compound will still feel loose which causes the operator to tighten screws even more more and suddenly..... CRACK!

I suppose that a large hole in the compound base for the screw might also be a problem. In this case, a compression sleeve should be used.

In any event, the cast iron of the T-slot must be in compression, not tension.
 
@KeeponDragon - further to my notes above, I see that @DPittman had bolts in his slots instead of nuts like you have in yours. Flipped upside down like @DPittman is good because it's impossible to bottom out the screws.

I also LOVE the new TNuts he made. They certainly would spread out the load and help the situation. But they won't prevent breakage if you have tension though. That's because they are steel and steel bends under load. So the steel will bend, and the cast iron will break. Cast iron T-Slots MUST be loaded in compression no matter how big the nuts are!

The best solution is longer nuts in compression.

Since yours is already broken in several spots, you almost have no choice but to use longer nuts to avoid careful positioning every time you move your compound. You will also have to remove that bump. Otherwise the bump will virtually guarantee that an adjacent bolt will be in tension because it will lift the compound and guarantee a space under it.

A few more comments. That raised bump is actually proof that there was tension in there. Compression cannot do that. Compression pinches the slot ears, it does not pull up on them. The only way that bump could form is through tension with a space under the compound or a screw that bottomed out.

Lastly, lots of folks poo-poo the need for proper torque. Each to his own I guess. However, your situation is an example of where too much torque could get you in trouble. There is no need for gronking on those TNuts. It only takes a few foot pounds to stop the compound from sliding. A well done user manual should specify the torque. If not, I'd look at a few similar manuals (especially Grizzly) to see what they say. Failing that, you would have to do a calculation to determine maximum torque. Yours will not be a simple calc because this joint isn't about failure of the fastener, nor even similar to a threaded hole. It's only about adequate compression clamping of the ears to prevent sliding of the mounted compound. Again, it doesn't take a lot of torque to accomplish that. My own compound has a similar design but only uses two nuts on curved T-Slots. Contrary to my own advice above, I confess that I just use a small T-Wrench to tighten them with my fingers - a few foot-pounds at most. That's been plenty enough to hold my compound rock solid for the 10 years I have owned that particular lathe.

Sorry for posting another long discussion. I guess I just feel badly for you. Damaging my cross slide would be heartbreaking for me so I feel your pain.
 
Longer t-nuts would be a good idea as the top surface of the underside of t-slot has been pulled, damaged, removed in spots. Maybe only enough thread so bolt/ stud doesn't go all the way through the t-nut. A stud of good length, threads bottomed out against t- nut and lock tighted, excess thread through t-nut ground, cut, machined off. Run a file gently over upper under side of t-slot to remove a few uglies hanging down.
 
I really like this forum. No lie. The ideas, information and suggestions for a fix never cease to amaze.
Thanks to everyone that spoke up, and also to those that asked other questions.
I have looked online for tee slot nuts previously to fit this slide. But nothing to be found that didn't require buying a 100 count.
So I am going to use some brass stock I have. Then its cut, drill, tap, and then file to fit.
I definitely will block sand the top of the slide before I reassemble it.
I was quoted over 400 for a replacement through KMS tools here in Kelowna. And that is just not in my budget.
:cool:
 
KeeponDragon said:
So I am going to use some brass stock I have. Then its cut, drill, tap, and then file to fit.
Click to expand...

You are not gunna like me much......

Brass is great stuff in the right application. But brass would be a poor choice in this case. It's modulous of elasticity and tensile strength are much lower than steel. So it will deform too much when tightened which gets you right back into the tensile load you need to avoid. It will also result in a short bearing length as the nut arcs away from the pinched section and thereby fail to distribute the load to compensate for your broken slot sections.

A piece of steel long enough to make 4 long nuts is not that expensive. It's a simple milling job too.

Did you figure out how you ended up with a tensile load on your old nuts yet?
 
Susquatch said:
You are not gunna like me much......

Brass is great stuff in the right application. But brass would be a poor choice in this case. It's modulous of elasticity and tensile strength are much lower than steel. So it will deform too much when tightened which gets you right back into the tensile load you need to avoid. It will also result in a short bearing length as the nut arcs away from the pinched section and thereby fail to distribute the load to compensate for your broken slot sections.

A piece of steel long enough to make 4 long nuts is not that expensive. It's a simple milling job too.

Did you figure out how you ended up with a tensile load on your old nuts yet?
Click to expand...
I don't mind being corrected, so long as the effort doesn't carry the intent to make me feel stupid for not knowing the details.
I'm glad I got as far as marking the material out with a center punch lol.
I agree it is a simple milling job. Except that I simply don't have a mill. So I'm gonna make the bars to fit the slots as best I can.
As for figuring out the tensile load...I can't tell if you're being sarcastic or not...My summation of the problem is over tightening. By the PO and then exacerbated by myself until I started to pay attention to the slides deformation.
I stand by my last post tho.
I really like this forum.
 
t-slot dimensions?

Any chance you’ll luck out and some of these would fit?

littlemachineshop.com

T-Slot Nuts Individual Sizes 5976

Clamping Kits 5976 Black oxide finish; Heat treated 1040 steel; Case hardened; We carry a wide range of T-Slot nuts in both inch and metric measuremen...
littlemachineshop.com littlemachineshop.com

601C3EF9-82D3-49D8-B467-F9D21933D0FF.jpeg
 
whydontu said:
t-slot dimensions?

Any chance you’ll luck out and some of these would fit?

littlemachineshop.com

T-Slot Nuts Individual Sizes 5976

Clamping Kits 5976 Black oxide finish; Heat treated 1040 steel; Case hardened; We carry a wide range of T-Slot nuts in both inch and metric measuremen...
littlemachineshop.com littlemachineshop.com

View attachment 33385
Click to expand...
If your top slide is the same as mine I don't think you will find a commercially made t nut that will work. My top slide bottom groove is just over 10 mm wide and the top groove is just over 6mmm. The bolts the compound used to hold it down are 6mm (nominal) and so just fit in the top slot/groove. A typical 6mm t nut dimensions won't fit the slots of my top slide.
 
@KeeponDragon - do you have a welder?

T-nuts are easy to make, a piece of flatbar the right thickness and width for the bottom wide part, a piece of flat bar that fits the narrow part and weld them across the ends. Then drill and tap the hole, done.
Might not be the prettiest girls at the dance but at this time I believe you need function over form.

The other thing to do is to use a punch to collapse the threads on the bottom so you can't screw thru and jam on the bottom of the cross slide.
 
DPittman said:
If your top slide is the same as mine I don't think you will find a commercially made t nut that will work. My top slide bottom groove is just over 10 mm wide and the top groove is just over 6mmm. The bolts the compound used to hold it down are 6mm (nominal) and so just fit in the top slot/groove. A typical 6mm t nut dimensions won't fit the slots of my top slide.
Click to expand...
I would be in the same predicament as you then my friend. lol
 
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