Clarke CL500M longitudinal feed screw

[Peter Seymour-HowellParticipant @peterseymour-howell39349]

Hi Stuart

I basically have the same lathe although under the Warco badge, I've had mine since 1998 and they are very capable machines. As noted above the cross slide works on the same priciple, ie you tighten the bolt to take up any slack. You do need to keep them oiled just like any other lathe. My own cross slide 8s getting a little worn now although Warco sell the parts. I have found the dials a fraction out but a DRO can take car of that.

As Howard said above, our forebears produced excellent work on equipment less able than these humble machines. They are very rigid and can produce excellent results, they also have double the capacity of a Myford in turning.

Pete

[Stuart Cox 3Participant @stuartcox3]

Posted by martin perman on 09/01/2021 21:51:34:

How do you mean, this is the underside of the traverse lead screw, showing the guard from both sides of the traverse which also shows how its mounted.

Martin P

I'l have look at my machine tomorrow, I'm sure it will make sense.

Thanks Martin, much appreciated

Stuart

[Danni BurnsParticipant @danniburns84841]

I have a very sloppy crossslide. It won’t adjust out, without becoming so stiff that it becomes unusable.

Looks like I will make a new Nut (part 11).

Does anyone know the thread size for CL500M crossslide?

Parts 11 & 39.

While I am asking, did anyone make an Acetal Leadscrew Nut?

cheers

[BazyleParticipant @bazyle]

First determine whether it is nut (A) or leadscrew (B) wear or just adjustment of the mounting (C) of the leadscrew in the saddle.
A) move the cross slide up close to the handle end where the screw is least worn. Push the handle in firmly and hold to take up slack then see how much the slide can be moved. This is wear in the nut.
B) repeat A in the middle or most used part of the screw. The difference between A and B is the wear in the screw.
C) Push then pull the handle without rotating it. This is the miss-adjustment of the mounting.

When you have the results we can discuss the solutions.

[Danni BurnsParticipant @danniburns84841]

A) is 0.3mm

B) is 0.3 or 0.4mm

C) is approx 0.5mm

Turning the handle from Zero to carriage movement is approx 0.8mm (e.g. 1/4 of a turn)

[BazyleParticipant @bazyle]

Well that’s not looking too bad. The B result is not bad (<4thou) so little wear in leadscrew.
You must adjust items around 40/41/46 to reduce that play. As well as the nut (46) there may be another threaded item so the two can lock. It is not unusual for adjustment here to be infuriatingly difficult owing to the coarseness of the thread. Is this the area you have been trying to adjust already?

Is the nut split? is that what you have been adjusting?

[john halfpennyParticipant @johnhalfpenny52803]

Danni, I have the same problem, but am living with it with the aid of a dro. In my case I think it is due to the spigot on the nut being a little loose in the cross slide bore, so that the screw angles up and down depending on the direction of screwing – this adds a bit extra motion which manifests as backlash. Is your spigot a tightish fit?

 

 

[Danni BurnsParticipant @danniburns84841]

Yes, the nut is split. I have adjusted that with some success, but then it becomes too stiff to turn. I have used a very long screwdriver, so I’m adjusting in the areas where I use it. The current state is where the handle feels right (not too tight or loose).

I see what you mean now (A & B), and the nut looks OK condition. But that 0.8mm play is not acceptable.

So you think it’s mostly (c) 0.5mm play? I haven’t tampered with that recently. It feels nice and secure at the moment (I mean that the 46 [domed cap nut] is not coming loose or anything).

I will dismantle the parts around the Handwheel and see what is worn/loose.

cheers

[BazyleParticipant @bazyle]

Hadn’t thought of the spigot. Have a look at the Boxford/SouthBend solution.
The spigot is cross drilled and a ball bearing or small brass rod with angled end is inserted in that hole. The spigot is drilled and threaded for a pointed end grub screw. That screw bears on the angled end of the rod above to wedge it in the hole. Think hard about which way the hole should face – some diagrams show it the wrong way round.

[PeteParticipant @pete41194]

There should be one or more screws (part #12) holding the feed nut (#11) in the fixed and proper location, make sure it or those are tight. There’s also various methods of holding the cross slides feed screw (#39) in it’s fixed axial location to the cross slide itself. If it’s loose or out of adjustment, that can also greatly affect how much perceived backlash there is. There should be just barely enough clearance to allow smooth rotation of the hand wheel, but almost no axial end play. On a lot of lathes, the hand wheel is also used to help axially locate the feed screw and the amount of end play. Without the lathe in front of anyone here, it’s very difficult to be sure of what the exact cause is. It can also be a combination of more that one issue.

I firmly believe top, cross and even the carriages are meant to be taken apart, properly solvent cleaned, re-lubricated and reassembled every so often. Any moving part slowly wears in service. With a machine tool, they can also accumulate lot’s of contamination just from what there being used to do. Any time the lube oil being used is very dark or black on the slides and feed screws, that means it’s contaminated and needs to be flushed clean. It also means your not lubricating often or with enough between those solvent cleanings. Not doing so is literally wearing out the machines individual parts multiple times quicker than if there kept clean AND properly lubricated. Most at the amateur level never lubricate often or with enough. And that fresh lubricating oil serves two purposes, lubrication, and to help flush or wash out those wear particles and any contamination. George Thomas for example recommended that disassembly and cleaning after “turning cast iron” on his Myford due to the possible extra wear and damage caused by turning castings.

While it’s not impossible to make new feed nuts, most of our smaller machines use fairly small diameter feed screws and the same for the nut threads. That makes single pointing the proper imperial or metric ACME profile thread very difficult or even impossible in some cases. Without question the original manufacturer would have used the correct ACME taps for your feed nuts that few of us would have access to because of there expense. With some diameters and thread pitches, the proper ACME taps may not even be available as a standard off the shelf tap, and an extremely expensive custom ground tap would be required. If your lathe does use a common diameter and pitch, and new OEM replacement nuts are no longer a stock item, oversize feed screw nut blanks with the ACME threads already done are available from some of the better industrial level feed screw and nut manufacturers. With those, you machine the exterior to the correct size and duplicate the original mounting method. It can still be a touchy job to use those though. The center line of the nut threads have to properly align with the center line of the feed screws exact location, so they require some fairly accurate measurements and machining.

For some machine tools, the feed screws bearing or bushing hanger just behind the hand wheel aren’t doweled for there vertical or side to side location. With those, you leave the mounting screws slightly loose and withdraw the side all the way back towards the operator until it stops. Then you final tighten those mounting screws. That helps self align that bearing or bushing to the feed screws nut C/L. Not doing it in that way will almost always create binding and very high rates of wear on the feed nuts and feed screw threads. Mechanical issues always have a cause and a correct solution if your willing to take some time to properly understand how the assembly is supposed to work when it’s correct, and analyze what the faults could or might be using some logic when it isn’t.

[Danni BurnsParticipant @danniburns84841]

Hi John (long time …)

Sorry, I didn’t see your post.

I think I know what you mean. There is some up and down movement if I wiggle the back of the Cross Feed Screw (39), that is mostly why I thought the nut was very worn. BTW – I have also checked that the nut is fixed into the underside of the Carriage (BTW I still don’t know how that is attached/fixed – maybe via the ball oiler/nipple). I’d like to double-check that if you know how.

 

Regarding the spigot fit – Are you referring to 39, 40, 42?

As I mentioned to Bazyle – I will dismantle the parts around the Handwheel and see what is worn/loose. It would be grand if I could insert a 0.5mm washer somewhere.

Are you happy with the DRO? What model/part no. do you have? Ive never had one but relying on DTI’s for everything is a ballache.

OH also – what Gear oil are you using in the Clarke?

cheers

[BazyleParticipant @bazyle]

Re : cross slide nut. Again it will be difficult to adjust the backlash with that screw because you can’t see it and a fraction of a turn is several thou movement.
You could try a cap head screw (might be M4) and make an extra long hex key by soldering a cut off bit of allen key into a rod. This will stay in place better once you have found the hole to start with. On this rod put a dial or pointer that allows you to see precisely what position it is in. Think in terms of a clock minute hand so you set it to “25 past” not enough? set to “27 past”
When you dismantle the handwheel layout the bits and photo it so we can see how it is made up. It may be beyond what you want to do at the moment but often people modify this area with thrust bearings so it can be tightened up to zero play.

Possible ME&W article building up here.

[Danni BurnsParticipant @danniburns84841]

Also, a couple of vid clips here.

i) shows the sloppy movement that JH and myself was discussing (probably) and

ii)  shows that the backlash is still present after removing most of the handwheel parts.

I may install a bronze bush to remove that wiggle i)

Download link (22MB)
https://we.tl/t-SOqW8Au2r8

Note that the clip links will only be available for 3 days.

cheers

[john halfpennyParticipant @johnhalfpenny52803]

Danni, your first picture ( with the handwheel) shows the top of the spigot in its round hole. When you turn the screw forward and back, does the spigot move up and down a little? That is my problem, which I must get around to fixing. The loads are quite small, and I think the spigot was originally a press fit. Mine is now quite sloppy (after 35 years), so it needs something to anchor it. This thread has encouraged me to look at it again this week.

I have arc euro cheapy dro on both axes, cut to length. Works well enough for me. One behind the saddle along the bed, and one on the right side of the saddle.

 

 

 

 

 

 

[john halfpennyParticipant @johnhalfpenny52803]

I recollect that another source of slop is the grubscrew in the side of the blue front housing, which engages a recess of the bush in the bore (you can see the recess in one photo). Make sure this is tight – it took me a while to find it.

[BazyleParticipant @bazyle]

The leadscrew flange is trapped between the cast iron saddle (good bearing surface) and the bush item 40 which looks like steel. The bush appears to be held in the seat item 42 by a grubscrew so its position thereby sets the backlash. However under the thrust of cutting this is not solid enough to be rock solid permanently.
Quick fix is to reassemble all except final dome nut. Then see if there is a gap between the nut fully tight and the handwheel. Fit washer to take up gap. It looks like this is where you are already going.
Improvement – this design seems ideal for fitting thrust roller bearings either side of the leadscrew flange and thinning the bush to compensate. Still have to shim out the gap.

[BazyleParticipant @bazyle]

For full control you need a fine thread where you have the dome nut coarse thread. Not sure of an easy way. I have not got round to it on my Boxford yet.

[old martParticipant @oldmart]

A cheap, nasty way of backlash adjusting, the Taiwanese round column mill we have at the museun had them on the X and Y axes, they soon got replaced by fixed and adjustable nuts. Mind you, the Smart & Brown model A, a top quality toolmakers lathe had one hiding under the cross slide until I replaced the leadscrew and used a pair of nuts which are adjustable. The compound and tailstock both have proper adjustable nut pairs, and the longitudinal leadscrew has one adjustable half section nut, which I renewed with a 50% longer shop made one, and at the same time added telescopic spring covers to keep the leadscrew clean.

[old martParticipant @oldmart]

I realise now that the OP was refering to the compound feedscrew nut. I would guess that the thread would be a Metric one and likely right hand thread. The cross slide threads are usually the same pitch, but left hand.

[john halfpennyParticipant @johnhalfpenny52803]

The cross slide screw is unsupported at the back, which is why it can wag up and down as thrust is reversed. Today I made a simple brass bearing to support the back end, and the action is much improved. Also eliminates the backlash generated as initial rotation of the handwheel wags the screw between extremes.

[Danni BurnsParticipant @danniburns84841]

Brilliant. So it’s a blind clearance hole, preventing up/down and backward movement?

Is that going to get full of swarf or gap? cant see any light under the Cross Feed Screw

I will set up a mock-up (with clamps) and see if that sorts out my backlash.

cheers

[old martParticipant @oldmart]

There are always three things which hopefully can be improved.

The nut to leadscrew backlash.

The security of the nut in it’s housing.

The endfloat of the leadscrew.

Often the leadscrew is most worn on the part which gets the most use, so addressing nut backlash has to be a compromise unless a new leadscrew can be obtained.

[john halfpennyParticipant @johnhalfpenny52803]

It’s a 12mm blind hole in a piece of hex brass, but has axial clearance so doesn’t aim to control end float. Yes, I might need a shield on the back of the slide to prevent swarf dropping in, but for my work the nut is mostly covered by the slide.

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