‘STIFF’ Compound Slide

[kevian64Participant @kevian64]

Hi, having recently bought my 1st ‘proper’ lathe an ML7 I’ve just started making chips. I’ve been watching a guy (Steven Jordan I think) on YouTube and following his idea of grinding 3mm off the back of a toolpost holder so I can use 12mm stock.

Its my 1st machining since 1980 and loving it. I’ve noticed that the compound slides movement is VERY stiff compared to that of the cross slide. Is this normal or should it be just as ‘smooth/easy’?

 

Cheers Kev

[Grizzly bearParticipant @grizzlybear]

Hi,

This might sound stupid, have you tried to adjust it?

Three grub screws with lock nuts.

Good luck……….

[BazyleParticipant @bazyle]

hello, welcome to the forum. We have better advice on here than other places on the ‘net which can sometimes be a bit dubious. “stock” is the material you put in the chuck to make things out of. Do you mean tool? If so stop watching this idiot on youtube. You only need 1/4 in tools, or perhaps up to 3/8 on a Myford. Do not grind bits off your lathe until you have several years experience in using it and ask us first.

[Bazyle]

On Bazyle Said:

If so stop watching this idiot on youtube.

Spot on there!  I used to watch some of his videos – just to see how <b>not</b> to do it.🙂   My impression of his channel was that he reviewed anything, that gained him brownie points, from cheap chinese trash merchants.  Glowing reviews, of anything they would send him free of charge, even if the quality was at the cheapest and nastiest end of the market.

 

[Charles LamontParticipant @charleslamont71117]

With something stiff on a newly acquired lathe I would be inclined to strip it down and investigate.

Strip, clean, examine, adjust and reassemble. With the feedscrew and its bracket removed, you should adjust the topside gib screws so that you can just move the slide backwards and forwards smoothly without tight spots. When refitting the bracket, wind the feedscrew fully home in its nut before tightening the bracket mounting screws.

[Nigel Graham 2Participant @nigelgraham2]

Yes, the slides should move easily without shake, but not too freely.

Seems a bit odd that the top slide should be so stiff.

Possibly the last owner tightened it for some specific purpose of his (I can’t think / dread to think what) and forgot to reset it.

Or lubricated it with grease and that has hardened off! (Use only oil.)

….

“grinding the back of a tool-holder…” EH? I am not clear what is meant here but this suggests a Quick-Change Tool-Post (QCTP) system, which has three basic parts:

1) The body with built-in clamp that you fit on the top-slide, in place of the simple clamp originally fitted.

2) The tool-holder; a block of rectangular channel section fitted with various clamping and adjusting screws, and which clamps to the body. You need a set of these, at least four to start with. You can add more later.

3) The tool itself, either an HSS tool usually of square-section, a carbide-tip shank or the parting-off blade carrier; which is held in one of the tool-holders.

All of these, certainly the better-quality ones, are precision-made to co-operate to give you repeatable, reliable tool-changing. The lowest-cost ones available though “our” suppliers or other recognised retailers, rather than dubious on-line supermarkets, are usually fine for most of our purposes, though the most basic type does have some drawbacks.

I treated my Myford ML7 to a Myford-branded QCTP and find it eminently satisfactory, so please do as we do: buy tools appropriate to the lathe and its fittings. Don’t try to copy bodges seen on t’Net.

 

I think I have occasionally seen admissions on this site, to having machined the underside – not the rear – of a insert-tool shank to fit a particular QCTP. That though is an exception, carried out properly, on a milling-machine, by an experienced machinist; and to modify the tool shank itself, not the tool-holders.

The most likely reason is having acquired some second-hand tooling, modifying it to suit the machine.

 

Taking a grinder to any of the working faces on any of those elements, ruins it by removing its whole point!

Others have said don’t do it – I agree – but your post reads as if you’ve already been and gone and done it. Oh dear….

I rarely look at Ewe-Tyoob but notice there are one or two contributors respected by others here; either for model-engineering and related activities directly relevant to us, or large-scale engineering of interest for its own sake. However, you also sometimes see on this forum warnings about bad workshop habits, poor techniques, sometimes dangerous practices, depicted in many videos.

[PeteParticipant @pete41194]

While it was about his Super 7, George Thomas was a believer in removing the feed screw support bracket and feed screw while then properly adjusting the gib screws. For any machine tool using the same gib adjustment design, I have to fully agree with his opinion. It makes getting the correct, smooth but without any excess clearance or tightness much easier by just sliding the compound or cross slide back and forth by hand as the gib screws are being adjusted. You’ll know instantly if any adjustment screw is moved to where it’s even slightly too tight. George also mentioned that he thought most M.E.’s almost always had there slides adjusted too tight which worked against making very small movements of the slide. And it also increases the wear rate by a lot on all of the moving parts.

Without taking your compound apart, there’s no real way to be sure what the actual cause is for it being that tight. Logically it should be just incorrectly adjusted gib screws. But the previous owner may even have added an additional slide lock? I’ll add that machine tool slides were never designed to be completely ignored for there whole life. And those slides really ought to be taken apart once in awhile for a thorough solvent cleaning of all the parts, feed screw and nut, relubed and reassembled.

All slides, feed screws and nuts obviously wear due to use, and will also collect cutting swarf and contamination, especially turning any cast iron. That all helps to wear the parts out much faster. When the lubrication and cleaning are ignored for too long, those wear rates start increasing exponentially. The machine tool is then starting to destroy itself far quicker. Darker or even black lube oil on the slides surfaces as it’s moved back and forth is a sure indicator. After it’s cleaned and relubed, any dark colored oil that’s created later means your either not using enough each time, or applying it often enough. That extra oil helps to wash out the contamination and any mechanical wear particles. It’s also why most machine tools use an oil lubrication and not grease. Either still uses oil as it’s basic lubrication, except grease helps to then trap everything where you don’t want it.

Solvent cleaning once in awhile and enough lube to stay mostly clean while in use will always help extend any machines lifespan and it’s long term accuracy by multiple times more than one that’s neglected. I’ve yet to read any machine tool user manual that really even mentions that part tear down and solvent cleaning when it needs it. That doesn’t mean it’s not required. I’ll usually do that solvent cleaning any time I think the gib or feed nut needs adjusting and that seems often enough. For a comparison example, if any automotive engine oil got to that dark or black color, would the owner not do an oil and filter change? We have to do the same. And since there’s no other way, it has to be done by separating the parts and hand cleaning them.

[Howard LewisParticipant @howardlewis46836]

If you are a relative newbie, I would counsel against stripping a machine, any more than is absolutely necessary.

Unless you know what you are doing, the result might be less accurate than when you started.

With regard to a stiff Top Slide, if some oil does not ease things a little, resetting the gib adjusters may help.

(On a ML7 they are likely to be BA rather than metric)

Ideally, remove the complete handwheel assembly (holder, leadscrew, etc as a unit) and adjust the gibs until the slide moves fairly easily, but without any slop.  Then replace the leadscrew/holder/handwheel assembly.

Don’t slacken too far, backlash (slop) reducing rigidity could result in chatter. They need to be tight enough to prevent to slide moving because of backlash.

Excess tightening, will cause wear to the adjuster nut (On a ML7 they are light alloy, possibly intended to wear rather than the leadscrew.

HTH

Howard

[Howard Lewis]

On Howard Lewis Said:

If you are a relative newbie, I would counsel against stripping a machine, any more than is absolutely necessary.

Unless you know what you are doing, the result might be less accurate than when you started. […]

Wise words, Howard 

… but, that said, stripping down an ML7 top-slide is about as simple as it gets

I would just disconnect the feed and play with the gib-adjusters for a while, to get the ‘feel’ of the sliding action.

Then, if it can’t be adjusted to taste … come back here for discussion

MichaelG.

[Robert Atkinson 2Participant @robertatkinson2]

On the tool holder modification, this seems to be the video

Fortunatly the modification is not as bad as it sounds. At worst it might weaken the toolholder a little. Basically he removes the bottom few mm of the dovetail section so it clears the top of the topside and move down a little.

Robert.

[kevian64Participant @kevian64]

Hi Robert, yes that’s the 1 and I’ve successfully completed my toolpost holder modification and it works an absolute treat.

[kevian64]

On 19 May 2025 at 17:04 kevian64 Said:

Hi, having recently bought my 1st ‘proper’ lathe an ML7 I’ve just started making chips. I’ve been watching a guy (Steven Jordan I think) on YouTube and following his idea of grinding 3mm off the back of a toolpost holder so I can use 12mm stock.

Its my 1st machining since 1980 and loving it. I’ve noticed that the compound slides movement is VERY stiff compared to that of the cross slide. Is this normal or should it be just as ‘smooth/easy’?

 

Cheers Kev

Please don’t get sucked in by his fantastic idea of lapping the ways together with grinding paste, it’s literally one of the worst things you could possibly do to your machine slideways.

As for your compound, it could probably do with a good strip and clean then re-oil but if you’re not up to that just loosen the gib,wind it all the way bothways liberally spraying with a release agent like GT80, WD40, anything similar to dissolve and wash out the dried gunk then re-oil the ways. Loosen the two screws that hold the screw mount end plate to the slide. Wind the handle so the screw is all the way in then nip up those two screws again. Now adjust the gibs for your preferred balance of lash vs drag on the slideway. That’s about the best you can do without scraping etc.

[Andy StopfordParticipant @andystopford50521]

It’s possible a previous owner tightened up the gib strip to increase rigidity for some demanding use – e.g. parting off large diameter work or knurling.

I leave the adjustment nipped tight on my lathe for this very reason – it’s a small machine and needs all the help it can get when used hard. It’s the work of a moment to back off the adjusters slightly on the fairly rare occasions when I actually need to use the compound slide.

[PeteParticipant @pete41194]

G.H. Thomas put a lot of thought into how these set screw adjusted gibs work, why they tend to self tighten, and the adjustment method work far less precisely than it should. Even when brand new, the points on the ends of the adjustment screws work as miniature wedges the instant the slide is moved in either direction, and that makes the very slight clearance adjustments tighter than ideal. I’d agree 100% with GHT’s logic, but it definately wasn’t something I’d properly understood until reading them. His thoughts and the simple fix are all in this book. https://www.teepublishing.co.uk/books/in-your-workshop/model-engineers-workshop-manual/

I also completely agree with what Pete has said about that ‘lapping’. The idea might only seem correct or even logical to some. The reality is that there’s absolutely no control over where and how much of the material will be removed. If it could actually work, then industrial machine tool manufacturer’s and rebuilder’s would be doing the same. Controlled lapping can be even more accurate than high precision surface grinding, that’s inarguable. Trying to remove very specific amounts of material in exact areas due to past wear over any slides travel while maintaining or even correcting any slides accuracy, parallelism and 3 dimensional alignment isn’t one of them.

The only real item to watch for when reassembling your top slide would be to leave the feed screw support bracket bolts slightly loose until the slide is moved to get that bracket as close to the feed nut as you can. Then fully tighten them. What that does is help float the bracket bore both vertically and horizontally into alignment to center that end of the feed screw to the feed nuts fixed position. If it’s not done in that way and just tightened in any position, you’ll feel the hand wheel / crank get tighter the closer the support bracket gets to the nut because of the misalignment and binding that causes.

[Pete RimmerParticipant @peterimmer30576]

Apart from the uncontrolled nature of lapping a slideway the one thing you don’t want in a slide is perfectly matching faces with no clearance. This will squeeze out the oil and wring the faces together so that they are not sliding on oil but rubbing with no lubrication. It’s one of the most important functions of scraping, to create oil pockets that lubricate the ways.

[bernard towersParticipant @bernardtowers37738]

Has Kevian64 found the answer to his stiff slide yet?

[kevian64Participant @kevian64]

Yes, as Howard said, I may end up with a worse machine if I start taking it apart as I have no idea what I’m doing. So for now, I will live with it stiff, for me anyway.

[Michael GilliganParticipant @michaelgilligan61133]

Oh dear

MichaelG.

[kevian64]

On kevian64 Said:

Yes, as Howard said, I may end up with a worse machine if I start taking it apart as I have no idea what I’m doing. So for now, I will live with it stiff, for me anyway.

Running any slide without oil will tear up the ways. You should do something.or you’ll eventually end up with damage like this:

[kevian64]

On kevian64 Said:

Yes, as Howard said, I may end up with a worse machine if I start taking it apart as I have no idea what I’m doing. So for now, I will live with it stiff, for me anyway.

Kev

How can you contemplate hacking 3mm off part of your lathe (mentioned in your opening post) and yet be wary of investigating the cause of the compound slide stiffness?

To be fair we dont know it is TOO stiff as all you have said is that it is VERY stiff compared with the cross slide, maybe it is the cross slide that is TOO loose!

Finding the cause of stiffness really is a simple task, I cannot think of one good reason not to do it

Ian P

[Ian P]

On Ian P Said:

On kevian64 Said:

Yes, as Howard said, I may end up with a worse machine if I start taking it apart as I have no idea what I’m doing. So for now, I will live with it stiff, for me anyway.

Kev

How can you contemplate hacking 3mm off part of your lathe (mentioned in your opening post) and yet be wary of investigating the cause of the compound slide stiffness?

To be fair we dont know it is TOO stiff as all you have said is that it is VERY stiff compared with the cross slide, maybe it is the cross slide that is TOO loose!

Finding the cause of stiffness really is a simple task, I cannot think of one good reason not to do it

Ian P

Hi Ian P

Grinding off 3mm from a toolpost holder didn’t involve disassembling any part of my lathe and now I’ve finished that project, my lathe is still fully functional. Like I asked in my original post, ‘should the compound slide be stiffer than the crossslide’

I enjoy ‘trying’ to do things, but I’m worried that taking ‘slides’ apart may result in a non functioning lathe. Apparently there is a model engineering club 70 miles away, so I may make my way there and speak to people.

[Pete]

On Pete Said:

G.H. Thomas put a lot of thought into how these set screw adjusted gibs work, why they tend to self tighten, and the adjustment method work far less precisely than it should. Even when brand new, the points on the ends of the adjustment screws work as miniature wedges the instant the slide is moved in either direction, and that makes the very slight clearance adjustments tighter than ideal. I’d agree 100% with GHT’s logic, but it definately wasn’t something I’d properly understood until reading them. His thoughts and the simple fix are all in this book. https://www.teepublishing.co.uk/books/in-your-workshop/model-engineers-workshop-manual/

 

I can only concur with Pete’s comments above, try and obtain GHT’s book, lots of information to help you keep your ML7 in good condition and make improvements. There is nothing complicated in adjusting or stripping down a compound slide.

Andy

[Charles LamontParticipant @charleslamont71117]

Kev, have you got a manual for your ML7?

[PeteParticipant @pete41194]

It’s his lathe, so his choice about what to do or not. But issues like this aren’t ever going to fix themselves, and always end up costing much more in repairs or replacement parts if they can even be found verses some simple cleaning, proper adjustments and adequate lubrication. An overly tight slide is going to wear the all important slide dovetails much more, and the same for the feed screw and nut. With a used machine, there’s no way to know how it’s been treated or maintained previously. But you won’t know what the actual cause is without checking.

 

And a top / compound slide is one of the simplest collection of parts on the whole lathe. For anything I’m unsure about, or for much more complex assemblies. I just lay the parts out in order and in the correct orientation as it’s being disassembled. Make any written notes, take pictures etc if you have to. Completely clean, inspect, possibly de burr each part individually, then lay it back in the same correct order until reassembly. I’ve watched many very experienced professional heavy duty mechanics do exactly the same over my working career. I find it extremely hard to believe that any lathe owner couldn’t strip a ML 7 top slide apart, clean, lube and re assemble without difficulty. You just need a bit of confidence in yourself. Trust me, your going to learn to solve far more complex problems than this. 😀

 

[Dennis RParticipant @dennisr]

Many years ago when first using an ML7 I had a similar problem with the compound slide being very stiff to operate at times, this was caused by over tightening the tool post, which distorted the compound slide .

Dennis

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