locking cross-slide?

[Perko7Participant @perko7]

Trolled through the forum headings but could not see anything related to this question.  I have had problems turning longish shafts like loco axles in the lathe and getting an even diameter along the length. The problem is not with the lathe alignment which I have checked, the problem is the top-slide moving during the traverse. The lathe is a Sieg C6 and there appears to be no way to lock the top-slide in position while traversing the carriage along the lathe bed. Has anyone else had this problem? Currently I have to hold the topslide leadscrew handle during the cut which is awkward. The topslide leadscrew wants to move during the traverse and I can’t see how to tighten it. There is also a bit more backlash on the topslide leadscrew than I would like but I can’t see how to overcome this as the exploded diagram in the owners manual is a bit hard to follow.

I thought about tightening the gibs to lock it in place but then I would have to loosen them again after every traverse to return the carriage to the tailstock end ready for the next cut.

Any advice appreciated particularly from any Sieg (or clone) owners.

Thanks in advance

[John HaineParticipant @johnhaine32865]

Could you just tighten one gib screw?  Or if you are confident, dismantle the topslide and add a new threaded hole for a locking screw to bear on the gib.  Topslides are generally more trouble than they are worth IMHO.

[JasonBModerator @jasonb]

Set the topslide parallel to the lathe axis then any movement will be in the same direction of the cut and not alter the diameter.

Are there adjusting screws on the cross slide nut? most imported lathes seem to use this method to take up wear.

[Chris CrewParticipant @chriscrew66644]

I think GHT designed a simple top slide locking arrangement for the Myford. Perhaps this could be modified to suit the Sieg. This mod had been applied to the S7 top slide I bought when enhancing my 7R to S7 spec. and it works well.

[James AlfordParticipant @jamesalford67616]

I do not know whether your lathe has two or three adjustment screws on the slides. My Flexispeed has three. To make locking the slides easy to do, I replaced the central screws with longer ones and glued a lever to the heads. Now, to lock the slides, I just need to use the lever to turn the screws by a fraction of a turn. It has made life very much easier.

James.

 

 

[Clive FosterParticipant @clivefoster55965]

+1 for the GHT top slide lock arrangement as suggested by Chris. In fact another + for doing the whole slide and gib upgrade process taking great care to seat the new or refurbished gib cleanly up into the top of the gib.

I did the full monty arrangement on the top and cross slides of my, ahem, somewhat less than new SouthBend 9″ lathes which transformed the performance from “Gotta make serious allowances for it being old and well worn” to “I doubt if it was better than this when it came off the factory floor” . OK I did redo the screws too as I got fed up with compensating for loads of backlash but that was more convenience than necessity.

I’ve done the slide lock and gib work for other folk too with universally satisfactory results. Gaining an entirely unwarranted reputation for knowing what I’m doing in the process.

I agree with George than any affordable machine with conventional gibs, even if factory fresh, would benefit from the process. The careful hand fitting involved in going from “works well enough for quite a few years” to “best of breed, lasts nearly forever” is just totally unaffordable in that market. (Of course if you are Smart and Brown selling 5″ centre height lathes than cost more than a house the economics are a teeny bit different!).

I used rollers scavenged from defunct needle roller bearings for the thumb handles as my stash was just the right size. I find such rollers handy for small dowels et al.

Whatever you do don’t futz around with the gib adjustments. Take your time to get them properly adjusted, I prefer to pull the screw and slide back and forth so I have a good feel for whats going on, lubricate well and leave them alone. After a round or three of fiddling one to act as a lock you won’t have clue as to adjustment.

Unfortunately I have to disagree with Jason over making the normal position of the slide parallel to the bed. Fundamentally a bad idea because it puts the longitudinal cutting loads through the top slide screw which is inherently weak and not designed for the job. It also gets in the way. Even on my big lathe, a P&W 12 x 30 Model B with a relatively short topside and up angled bevel gear drive, putting it parallel gets in the way enough to be annoying. On a typical model engineers small bench lathe my time from setting to incoherent fury when slide, handle or tool post argues with the tailstock at the most inconvenient part of the job is measured in minutes. Tried it once on a Pools Special. Never again. I have bed stops if I want accurately measured longitudinal cuts.

My topsides live at 25° off perpendicular so moist of the loads go through the ways and the handles are well out of the way. Also ready for screw cutting using the “Zero-2-Zero” process.

Quick’n dirty nuclear option is to replace the top slide with a solid lump, such as The Tubal Cain Gibraltar design, for all normal work and pop the topside on for short tapers and angled infeed screw cutting.

Clive

[JasonBModerator @jasonb]

I supppose it depends on the lathe. Mine lives straight across and only gets moved when angled cuts are needed ( I thread with a straight in feed). I don’t find the tailstock gets in the way and I don’t recall it being a problem on the two Emco machines before the Warco. Might be a sthese lathes have an asymmetric tailstock casting rather than the symmetrical one of say a myford which gives more clearance.

With a lock and the lighter cuts that an import has to take I have not found the loads going into the TS lead screw to be a problem either Though I seldom lock it when turning along the lathe anyway.

Do you swing it round to 65deg whenever you are facing to keep the loads the same as turning parallel?

EDIT, a quick look through Sparry, Harrold Hall and GHT book all show them turning with the topslide parallel to the lathe axis so at least I’m in good company.

 

[JAParticipant @ja]

On my old Myford Super 7 I used a very simple clamp that used the travelling steady bolt holes. This appeared in the ME quite a few years ago.

Since these two holes are not on my current lathe I use a GHT top slide type lock, frequently.

As for “storing” the top slide I put it at 0degrees, parallel to the lathe’s axis. If you do this make sure it is at 0degrees……

JA

 

[Martin KyteParticipant @martinkyte99762]

Totally agree with the GHT style top slide lock whose main function is to stabilise and make more rigid the top slide which carries the tool post.

The Cross Slide is best locked by locking the lead screw which can be achieved by a small locking screw on the micrometer dial. Again see GHT.

Although I do like JA’s arrangement.

regards Martin

[Clive Foster]

On Clive Foster Said:

 

Unfortunately I have to disagree with Jason over making the normal position of the slide parallel to the bed. Fundamentally a bad idea because it puts the longitudinal cutting loads through the top slide screw which is inherently weak and not designed for the job.

I’ve been thinking about this some more. It is the first time in 40yrs I have heard this said. Clearance and threading are common enough reasons but never heard of loading the screw.

What do you do when you want to cut a short or steep taper where a taper attachment or offset tailstock can’t be used as using the topslide will put the load directly down the screw and that is how all the books etc I have seen show it being done.

[JasonBModerator @jasonb]

looking at the GHT lock this is in effect what my two Emcos and the current Warco have with a cap head screw. Keep meaning to add levers but never do. Similar on the two Sieg lathes which have bristol type levers

[Neil LickfoldParticipant @neillickfold44316]

I did something different again. I drilled a 4mm hole through the gib. Then ground a piece of urethane rubber that has about 0.5mm or so preload. Initially I had 1mm of compression, but made the slide too tight to move. So just took small amounts off until it was easily moved on the handle, but not loose that is moves from vibrations. I set the gib set screws without the pad in place. Then slide it out and install the pad and the nut and screw. The lock screw idea works well if you want to lock an axis solid. I like the feel of drag on the cross slide and the top slide.

I agree , that if you have the time to refit the gib, it is well worth the effort. Often on the hobby lathes , they only sit on a few places where the screws press against them.

[Perko7]

On 15 August 2024 at 00:26 Perko7 Said:

… There is also a bit more backlash on the topslide leadscrew than I would like but I can’t see how to overcome this as the exploded diagram in the owners manual is a bit hard to follow.

I thought about tightening the gibs to lock it in place but then I would have to loosen them again after every traverse to return the carriage to the tailstock end ready for the next cut.

 

Are you talking about the topslide or the cross slide? It sounds more like the cross slide if you have to back it out to return the carriage. Whole different ballgame from the topslide.

For turning long diameters you can lock up the topslide gib screws and leave them locked. For the cross slide, the one that affects the diameter you are turning, you have three choices: fit the locking screws ala GH Thomas as described already, or nip up one of the gib screws and realease it every time for the return. Or adjust the gib screws so your cross slide can move but with a bit of resistance so it does not move under its own power, which it should not do.

Also on most lathes, you can tighten up the handle and or graduated collar on the feedscrew so the screw does not rotate freely but needs a bit of hand pressure to move it. Not sure on the Chinese stuff but Myfords use a fibre washer in there to provide a bit of friction when the handle is tightened up on the screw a bit.

[JA]

On JA Said:

On my old Myford Super 7 I used a very simple clamp that used the travelling steady bolt holes. This appeared in the ME quite a few years ago.

Since these two holes are not on my current lathe I use a GHT top slide type lock, frequently.

As for “storing” the top slide I put it at 0degrees, parallel to the lathe’s axis. If you do this make sure it is at 0degrees……

JA

 

If the topslide is parallel to the bed I find it’s always in the way, colliding with the tailstock. I have mine usually about 39 degrees off. For the limited use it gets I’m tempted to take it off and have a solid lump. I don’t turn tapers or screwcut very frequently

[duncan webster 1]

On duncan webster 1 Said:

On JA Said:

…..

 

As for “storing” the top slide I put it at 0degrees, parallel to the lathe’s axis. If you do this make sure it is at 0degrees……

JA

 

If the topslide is parallel to the bed I find it’s always in the way, colliding with the tailstock. I have mine usually about 39 degrees off. For the limited use it gets I’m tempted to take it off and have a solid lump. I don’t turn tapers or screwcut very frequently

Yes, this is a problem with Myfords. I live with it and only set the angle away from 0 degress when I have to.

JA

[Clive FosterParticipant @clivefoster55965]

I’m a little surprised that Jason hasn’t heard tell of the effects of loading the screw. Big Den, my first mentor told me about such effects being possible when dealing with obdurate materials. Especially on smaller machines.

When I sold my second lathe, a Pools Special, the prospective buyer bough a very experienced with small lathes guy with him to advise. Sensible. On test the experienced man surprised me by demonstrating cuts probably three or four time greater than I’de ever been able to successfully use. “just got to load up the feed screws so it doesn’t vibrate” quoth he. “like most folk you’ve been taking lighter cuts as soon as it starts to vibrate rather than pushing through so it stabilises in the cut. Actually it’s a nice solid little lathe but you can’t drive it like a Colchester Triumph and rely on mass for stability.”.

Prior to the GHT modifications my first SouthBend the cross slide could be driven into resonant oscillation when parting off suitable material with the tool moving back and forth about 1/8″ as the cross slide screw bent and released under cutting loads. Stable and quite safe with a steady hand on the tiller.

Having access to nanometre sensitive Hedenhain optical probes I did a bit of measuring some time back and the shift under load is definitely greater when going through the screw.

Longitudinal cuts tend to be much heavier than facing ones, In my hands at least, so the extra stiffness of getting the loads mostly into the ways is most beneficial there.

Worst thing about loading variation is the way you need to take spring cuts and check measurements when getting down to size rather than working straight off the dials.

Clive

[Perko7Participant @perko7]

Thanks for all the replies, and sorry for the confusion in my terminology.

I will trawl through the responses and see what suits my particular situation and hopefully respond in a few days with the eventual solution.

[PeteParticipant @pete41194]

Just about every book written about milling will almost always mention locking any slide except the one in use. But lathe slides are somehow different? GHT also gave the reason why our smaller lathes will sometimes allow the screw to move on it’s own under some cutting conditions. Page 181 of The Model Engineers Workshop Manual book. “The feed screws on many of our small lathes are small in diameter in comparison with their pitch, with the result that we frequently have mean helix angles of about 6 degrees. A screw of this lead angle will tend to turn under vibratory or intermittent loads, and it is for this reason that it is advisable to lock the slide.”

So if your lathe doesn’t have something like quick to operate lever type slide locks, we can add them. As others have also mentioned, I’d follow what GHT had to say about pinning the gib for any lathe without tapered gibs. And for the very logical reasons GHT also goes into detail about in that book.

 

[derek hall 1Participant @derekhall1]

On my Myford super 7 I fitted the top slide lock as per GHT, works very well.

I also modified the cross slide (non powered) with the modified cross slide dial and lock, a well worth modification.

I generally have the topslide turned around to say 30 degrees just to avoid the tailstock. But making the Gibraltar tool post to Tubal Cain’s design has been a revelation. I tend to use this more often now than the top slide.

Going back on topic there was a cross slide lock described in MEW a few years ago, but that was also for the Myford.

[JasonBModerator @jasonb]

Clive as I said I have never read or seen anyone else suggesting angling the topslide due to loading it’s screw. My own experience with small lathes is that they can have all three screws the same diameter and pitch which just would not apply in your “not designed for the load” was the case.

Other posters here all seem to swing the slide for clearance with the tailstock. The SC6 like many modern machines, my own three included all have a tailstock design that offers clearance when the top slide is parallel so not  a reason to angle it in the OP’s case. I can happily turn 3mm dia with tailstock support using a revolving ctr and the top slide parallel so clearance is not an issue. Toolpost usually hits long before the slide/tailstock comes into play.

Interesting one of the comments about not turning many tapers and threads. Much like I said things can depend on the particular lathe, they also depend on personal use. I don’t turn many threads but I do quite a few short and/or steep tapers. A quick look over the most recently completed engine and I came up with 13 different instances where the topslide would have been set to an angle and there may be more. So in my own case a solid post would be more of a faff than useful as that probably equates to at least once a week at the rate I build models.

back to the question. Now we still don’t know if it is the cross slide as per title or the topslide as per the post but if it is backlash in the cross slide then this is what the SC6 can have done to it, probably a combination of the two.

Firstly if it is backlash in the screw/nut then that can be adjusted to a certain extent by screwing the two grubscrews No 510 in to spread the two halves of the nut.

If it is end float of the screw then the preload on the thrust bearing can be adjusted but loosening the small screw 505 and turning the nut 504 to increase the preload, tighten the screw after to lock the nut’s position.

As to the locking again if the slide in question is the cross slide (front to back) then I would suggest firstly removing the highlighted nut so the screw is free to turn. You can then use this to lock the cross slide by tightening it, loosen again and just left nipped up for normal use. If you find this works then the existing screw can be replaced with either a cap head or one with a lever both of which are easier to operate than the small existing gib screw.

[David George 1Participant @davidgeorge1]

I have never had the top (compound ) slide at any other than square to the crossslide axis unless turning an angle or for a clearance problem and as an apprentice trained operator and now retired toolmaker service engineer can see no reason to have it any other possition. The compond slide on my slide is almost always locked by the centeral gib strip grub screw, the cross slide has two extra holes taped and drilled for two locking screws and a saddle clamp has been added to my lathe at the front to enable the slides to be locked or just a small amount of extra friction to be added to the sideways on a dificult job with more load than normal etc.

 

David

 

 

 

[John MCParticipant @johnmc39344]

The biggest force generated when turning is the cutting force that acts, more or less, vertically downwards, the feed force is secondary. There is a tertiary force pushing the tool away from the work.  The resultant force is still dominated by the cutting force. (A generalisation, I know, but probably true for most turning)

To move the top slide it suggests to me that the slide gibs could be a little tighter?

The attached photo shows the top slide of a Colchester Triumph, the cap head screw clamps the (tapered) gib against the slide.  I usually leave it locked until the slide is needed.   I’ve duplicated the arrangement on my Chipmaster.

Incidentally, I leave the top slide at 45 degrees unless there is a need for another angle, handy for chamfering.

[bernard towersParticipant @bernardtowers37738]

My topside is always set to 5.7deg as per GHT so you have a 10 to 1 ratio, so much easier for those tenths

[HuubParticipant @huub]

My top slide is always square to the cross slide. I added an extra support to make sure the top slide angle can’t change under heady load (mistakes). Setting it square takes about half an hour so I always leave it square.

Every job I tighten the 4 gib screws by hand (finger tips, very, very light) and check if the cross slide moves without to much draft. To get the max rigidity during parting, I lock 3 of 4 screws so the top slide can’t move any more.

On the cross slide and carriage, my bigger lathe has a locking screw. I have never had the need to use them.

[Howard LewisParticipant @howardlewis46836]

FWIW, My C3 has no lock for the Cros Slide, so I made one.

Because the gib adjusters are on the Tailstock side of the Cross slide, I made and fitted one to the Headstocj side

It is a crude but effective device.

The rear side of the saddle was tapped  M5 but because the front side of the saddle is over the vee , I could only drfill and insert a short dowel.  A short piece of bar waas drilled with appropriate sized through holes, and tapped, centrally in the other plane. Into this wa screwd a simple knurled brass screw.

This bears on the Cross Slide to lock it.

Maybe an easier way would have been to replace the cenytral gib adjuster with a simple knurled screw, and used that as a locl.

Howard

[Author]

Posts