Cant seem to get a nice finish

[BazParticipant @baz89810]

To be honest I think any material would be an improvement, how about a piece of brass? What does the mating piece, the dovetail, look like?

[petro1headParticipant @petro1head]

Looks fine to me.

Ok, probable not the right thing to do but thought what the ****. I have machined it nice and flat. Done a temp reassemble and its sooooo much better.

So just waiting for a delivery from Warco of the new lead screw and the big reassemble and test.

Edited By petro1head on 20/02/2023 17:09:16

[charles woodward 1Participant @charleswoodward1]

I agree with the previous correspondents who said it was vibration from the single phase motor you are probably using. I had the same problem and it vanished when I fitted a 3 phase motor. I think the marks will only appear on fine cuts.

[Pete RimmerParticipant @peterimmer30576]

Posted by Baz on 20/02/2023 16:45:43:

To be honest I think any material would be an improvement, how about a piece of brass? What does the mating piece, the dovetail, look like?

Best to avoid brass for gib strips. It's generally a poor choice, it wears fast and gets very grabby when the oil is squeezed out. Bronze is good, steel also, cast iron very good.

[HopperParticipant @hopper]

Posted by petro1head on 20/02/2023 15:46:49:

Removed the top slide and that seems Nice and flat.

I have ordered a New Cross slide screw and nut from Warco. I also asked about gib strip but it seems they don’t do them now.

Looking at the existing gib stop it looks very worn (see photo below). So it looks like I will have to figure out how to make a new one. Does it have to be steel or could i use somit else?

Edited By petro1head on 20/02/2023 15:56:45

That is horrific. Is that on the sliding surface? If so there must be something horribly horribly wrong to do that to a gib strip. You need to check the cause of that before it does it again to your remachined surface. Did you do the checks with a feeler gauge per the video posted above?

Or was that groove in the gib strip machined in there at the factory for the ends of the gib adjusting screws to locate on, on the non-sliding side of the gib strip?

[HuubParticipant @huub]

I had the same problem on both my lathes.

On my small lathe is was only visible when moving the top slide. The cause was to much play in the gibs combined with a dry nut/feed screw. After cleaning and oiling the feed screw and nut and adjusting the gibs, the problem was gone.

On my bigger lathe, the problem was only visible when moving the carriage (power feed). It was caused by not enough / no play between the rack and pinion that moves the carriage. The problem was gone after removing the rack. Cleaning the rack, scraping some paint of the bed and removing some high spots (light sanding), under the rack, solved the problem.

[petro1headParticipant @petro1head]

Posted by Hopper on 20/02/2023 22:47:45:

That is horrific. Is that on the sliding surface? If so there must be something horribly horribly wrong to do that to a gib strip. You need to check the cause of that before it does it again to your remachined surface. Did you do the checks with a feeler gauge per the video posted above?

Or was that groove in the gib strip machined in there at the factory for the ends of the gib adjusting screws to locate on, on the non-sliding side of the gib strip?

Yes i did check and it was fine

The grove was on the mating side. Again i have checked the dove tail and it feels ok

[petro1headParticipant @petro1head]

Posted by Huub on 20/02/2023 23:31:38:

I had the same problem on both my lathes.

On my small lathe is was only visible when moving the top slide. The cause was to much play in the gibs combined with a dry nut/feed screw. After cleaning and oiling the feed screw and nut and adjusting the gibs, the problem was gone.

On my bigger lathe, the problem was only visible when moving the carriage (power feed). It was caused by not enough / no play between the rack and pinion that moves the carriage. The problem was gone after removing the rack. Cleaning the rack, scraping some paint of the bed and removing some high spots (light sanding), under the rack, solved the problem.

One i have the new lead screw i will do some macining checks. If the problem still exists i will remove the sadle and inspect

[HopperParticipant @hopper]

Good stuff. One step at a time.

Hard to see how that groove could have been worn in place like that. Maybe it left the factory like it? QC can be a bit hit and miss over there. It will have to improve things with a full smooth face bearing on the dovetail!

[samuel heywoodParticipant @samuelheywood23031]

Have you tried manual feed rather than powered feed?

Might be worth a try, see if it makes an difference.

I only ever engage the leadscrew for screwcutting, though i'm probably in the minority??

Also you could try~

**LINK**

Works for me every time i'm having problems with finish.

[blowlampParticipant @blowlamp]

Are we sure that this isn't an issue of material building up on the cutting tool and then breaking off in a repetitive cycle?

Does increasing the feedrate or applying coolant alter the pattern?

Martin.

[petro1headParticipant @petro1head]

Manual feed is better.

Its not build up and coolant does not help.

Like i have said i am awaiting a new feed screw from Warco plus i have sorted out the gib strip.

So its just a case of wating for reassemble and see how it goes.

I am also thinking about making a solid tool post to replace the compoud slide, but thats for the future

Edited By petro1head on 22/02/2023 10:39:29

[Tony Pratt 1Participant @tonypratt1]

I've skimmed most of the answers and it's pretty obvious it isn't your slides, easy to confirm by locking cross and top slides then take a cut. I would imagine the problem is some sort of rotational irregularity in the drive train or rack or both? My Warco 290V isn't of the best standard and I don't get this problem but then again I don't use change wheels which were of really terrible quality but instead use an electronic lead screw. Interesting and for you frustrating issue.

Tony

[JimmehParticipant @jimmeh]

I had the same issue with my WM250VF, and found that slackening the threading dial engagement with the leadscrew helped. In the end I just disconnected the threading dial completely!

Edited By Jimmeh on 22/02/2023 14:02:43

[petro1headParticipant @petro1head]

Again i would loike to thabk everyone forbtheir input.

Reassembled and now perfect. Just done a fine cut, slow feed abd bothing locked up, perrrrrrrrfect

Concider this thread closed

[Tony Pratt 1Participant @tonypratt1]

So what was the final diagnosis?

Tony

[petro1headParticipant @petro1head]

New feedscrew abd sorting the gib out

[HopperParticipant @hopper]

Problem would have been that shonky gib strip. Keep your old screw and nut for spares if the new one ever wears out.

Edited By Hopper on 22/02/2023 21:33:52

[Pete RimmerParticipant @peterimmer30576]

Hard to figure how either of those two things would produce that regular pattern along the length. Personally I think that the root cause of the markings must still be there, but the symptoms were exacerbated by the poor fitting gib or it's need for adjustment.

[petro1headParticipant @petro1head]

Posted by Pete Rimmer on 26/02/2023 08:54:41:

Hard to figure how either of those two things would produce that regular pattern along the length. Personally I think that the root cause of the markings must still be there, but the symptoms were exacerbated by the poor fitting gib or it's need for adjustment.

Time will tell

[SillyOldDufferModerator @sillyoldduffer]

Posted by Jimmeh on 22/02/2023 13:59:26:

I had the same issue with my WM250VF, and found that slackening the threading dial engagement with the leadscrew helped. In the end I just disconnected the threading dial completely!

…

The thread-dial is normally only engaged when threading, and is mounted so the operator can pivot it's gear clear of the lead-screw. Disengage when not in use 'just in case': for the same reason it's good practice to lock unused slides so they can't move before taking a cut.

Lead-screws bend easily because they're long, thin rods with a giant spiral cut out of them. So its best to engage half-nuts and threading dials to them with a minimum of bending force, otherwise the combination of cutting forces and the huge mechanical advantage of a turning lead-screw will lift the saddle and twist anything loose on it against the gibs.

Shouldn't see any obvious up/down or sideways movement when the lead-screw is turning. If a screw misbehaves, check alignments – half-nut settings, end bearing position, and don't push the threading dial hard into engagement. If the set-up is all good, make sure the lead-screw itself isn't bent! They're quite delicate. On an older lathe, wear and tear can cause trouble, and new hobby lathes aren't always assembled as carefully as they might be! It's entirely possible to misalign a lead-screw during assembly, or bend one by rough handling.

Dave

 

 

Edited By SillyOldDuffer on 26/02/2023 10:39:42

[Pete RimmerParticipant @peterimmer30576]

Posted by petro1head on 26/02/2023 08:58:44:

Time will tell

Well it will and to be honest if a bit of regular maintenance/adjustment gives you results that you're satisfied with then that's all that matters.

The only reason I mention it is because the cure doesn't fit the symptoms, so if another person comes along (as it seems is likely to happen) it would be wrong for them to get the impression that such a fault is likely to be caused by a poorly fitted gib, and certainly not any by lash in the cross slide screw and nut.

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