Aciera F3 vertical stucked

Hi

All axis mowed very easy on my F3 until one morning.

The vertical was heavy to crank , and it went worse quick .


I am dismantling the vertical slide to find the problem

I following the steps in the manual

But I cant get the slide up to the top so the feed screw cames out of the nut

Everything is loose what i can see and feel.

I even took the gib away and tried .

Can the problem be between the nut and screw ? I need to get it apart anyway
but seems impossible when I cant crank the slide of the leadscrew


Anyone else had this problem and now what i should do ?

Thanks Johan

Did the vertical axis gib move itself tighter and wedge the vertical axis slide? Can you back out the gib?

Im not sure what gib is ?

I can move the slide upp and down if using much hand power .

But I cant move the slide all the way upp to the top . It get compleatly stucked befor

Gib is the tapered flat piece with which you adjust the slide

Peter

Thanks .

I can take the Gib away . Its still stucked

I have dicambled everything

The nut is stucked on the screw

I have to cut the nut to get it away I think .

Anyone know a good sorce that sells aciera spare parts ?

Preferly in Europe .

Thanks Johan

Another pic on the nut . It looks like someone have done repair before

I have ordered Aciera parts from https://www.swissmachines.ch/en_aciera-spare-parts,103.html

They are friendly.
Aciera is not in business anymore.

Perhaps cheaper to have it machined Not that complicated on a cnc

I'm not sure how heavy the support and table are. But if they are fairly heavy then you don't need a tight-fitting nut because gravity will preload it. So if the thread is a standard one, just buy a standard bronze nut and machine the exterior or braze it into a sleeve.

The thread seems to be non standrd on the vertical slide 24X4

If I gonna cut the thread in a lathe .

Is there a diffrent tool for every diffrent pitch ?

Are they called Acme thread in English

Johan.A said:

The thread seems to be non standard on the vertical slide 24X4. Are they called Acme thread in English

Click to expand...

That's too bad: 24 x 5mm TR seems to be a standard size. In English they are called "Acme" but that has a different thread form than the European standard, which is called "TR" or "Trapezförmig".

Sometimes a nut can be so worn out that it slips down on the OD (major diameter) of the screw and just locks up.

With a vertical slide, one does not even know it is worn because you don't feel the backlash because the weight/force pushes only one way, down.

A good test is to set the head on a woodblock and then feel how much free play there is. With getting over a half turn Freeplay one should start looking for a new nut... *But yes too late when a machine is stuck.

Sometimes one can whack a stuck brass nut in the other direction and so get it loose. Careful to not bend the screw so a slide hammer device might be good, and light tap, tap whacks in the "go up" direction.

often the screw is still good/OK and just needs a new nut.

Johan.A said:

If I gonna cut the thread in a lathe .

Is there a diffrent tool for every diffrent pitch ?

Are they called Acme thread in English

Click to expand...

Yes there is a different tool for each pitch, but you can cheat.....
In the US we use 29* Acme threads.
The tool pictured is a gauge you use to grind the tool to cut such a thread....I am sure there is a Euro equivalent....
The "Vee" is 29* and you grind the tool to match that angle keeping the tool straight with the line that bisects the angle...(equal angles on each side of the tool and totaling 29*)

Once you have the sides ground including the side relief...the front of the tool is ground flat (with clearance) until it just fits the correct notch for the pitch you are cutting....

Usually you will turn or bore a straight portion at the start of the thread at the correct minor diameter as a aide in cutting to depth....
You can make a narrow tool cut a wider groove by advancing the compound some to make the tool cut wider than it is...(favor one side of the thread) Leading edge clearance must take into account the pitch of teh screw.

Coarse leads need greater leading edge relief...



Cheers Ross

Buy a tap on Aliexpress
Available there and they work for bronze
Peter

To buy a bronze nut and fabricate it to fit your need might be best.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=bronz+acme+nut&_sacat=0

NEW DUFF-NORTON Bronze Acme Nut, Screw Dia.: 1.000", 4 Turns Per Inch, 100NB025 | eBay

I have experienced the lead screw nut slipped in the thread and locking up.
We saved the machine but it was a machine that had to be set one place to remove that stuck screw with nut locked on. You may have to whack the nut a half a thread (.250 or so) for it to come free and then hand turn it off the end.

One might lathe turn the OD of a bought nut and then Loctite/set screw it into a steel bushing made to fit the machine's need...with it having a raised shoulder at the go-direction to support the weight.
*Oh, I see Bruce mentioned this, good.

Trying to lathe turn the bad nut off one might be careful how to hold it so a wreck would not bend the screw, Perhaps put the out end in a steady and hold the other end close. Still breaking loose a chunk might slam/wedge the tool post,

I would likely set it on the surface grinder horizontal and parting wheel/cut off wheel (reinforced for safety) it to .oo3 higher than the screw diameter (perhaps on two sides) and then split/break it off. Yes not held in a vise because when it got thin the vise would tighten on the part on the sides of my parting wheel and so break my parting wheel.

But most likely the Whack it up a little would make it free. Even free it night jam nut onto a thin thread section inside the nut body, so the cut-off split may still be needed.

This condition results from the inside threads of the nut getting so thin in the go direction that the weight or pressure just breaks the last of the thread right off..Likely about .010 - .015 in this case.

That is a nice source for the bronze nuts...That mill is built in Switzerland and the original screw is metric...being 24MM OD with a 4mm pitch.
Not a standard and changing it would negate the micrometer collars on the machine.....

Cheers Ross

AlfaGTA said:

That is a nice source for the bronze nuts...That mill is built in Switzerland and the original screw is metric...being 24MM OD with a 4mm pitch.
Not a standard and changing it would negate the micrometer collars on the machine.....

Cheers Ross

Click to expand...

Agree one would need to find the correct thread and alter the OD with trying to fabricate a nut from some standard..or just make one from scratch if a catalog replacement could not be had.

Thanks for all the help guys

I tried to get the nut off by heating it . It dident mowe

I ended upp to turn it down in diameter and wind the last of the nut off

The screw looking good what I can see

Another solution to make a nut is to mold one from SKC 60, see Slideway Coatings – SKC Gleittechnik. This is an epoxy-like 2-component material, which cures into a very tough and hard, self-lubricating plastic.

First you turn a steel "shell" which fits over the screw. Give the shell an internal shoulder or shoulders to support the molded nut, so that if the bond breaks between the steel shell and the molded nut, your mill table does not fall down.

Second, you spray some mold release on the screw and wipe off the excess.

Third, you fit the shell over the screw, and inject it with the molding compound

Wait a few hours for it to harden, and screw it off.

If you mold it over the end of the screw, where the screw is not worn, it should fit everywhere.

This is quick and easy, and works well. SKC is happy to take smaller orders and offers good support on the phone (at least in German, I have not tried English).