Damaged Screws & QCTP help!!!

There are indeed plenty of ways to fit the new stud. I screwed mine in and used the recess for a washer and lock screw.

The new post threaded into top-slide M10 thread

Underneath, centre of the post tapped M5 and washer fills the old recess.

Fitted together.

The end result on my WM250 with the 100 size version (AXA) wedge type QCTP fitted. See my webpage for more info.

John

Edited By Journeyman on 01/08/2023 09:14:32

Very nice solution John - thanks for sharing.

Just as an aside - and I hesitate to post this on an engineer's forum - but the original damage to the tops of the screw heads looks as if a Phillips driver has been used on Pozidrive heads.

And I also noted a reference to cross-head screws, without specifying whether they were Phillips or Pozidrive.

We do all know the difference don't we? (My supervisor at one place didn't.........)

The Pozidrive has parallel driving flanks, the Phillips has curved driving flanks. So using the wrong driver for the screw will potentially cause damage to the screwhead or driver, and won't impart the full torque to the screw.

Puts tin hat on and runs away............

PS, did anyone mention left handed drill bits? Many videos showing broken screw extraction use these to good effect, as they don't expand the bolt as easy-outs can do.

PPS, It can be worth giving a stuck screw a couple of medium taps of the impact driver in a clockwise direction before trying to undo it in the anticlockwise direction. This action might break the rust or loctite bond, and by bearing on the doing-up flanks of the screw/bolt, will leave the undoing flanks fresh and undamaged to give maximum chance of undoing it. 

.

Edited By John Doe 2 on 01/08/2023 10:56:44

Don't be disheartened Margaret! I'm 8 years into the hobby, and - so far - haven't felt the need for a QCTP.

As you've found fitting a QCTP can turn awkward, and when this happens a beginner might not have the skills needed. So step one is to build skills, basically starting by making very simple objects, and gradually tackling more difficult parts.

I'm self-taught. I started by reading Sparey's "The Amateur's Lathe", which I found excellent. The book's only fault is not covering later technology like carbide inserts and DROs; not surprising - it was written in 1948! Next step was to collect a stock of scrap metal, then buy a lathe and start using it. I almost came unstuck at this stage because, by pure bad luck my entire collection of scrap was unsuitable - I'd picked up a range of alloys that were all difficult to machine - soft Aluminium, gritty Brass, hardened steels, and work-hardening Stainless. Driven by a beginner with hazy ideas about cutters, RPM, depth-of-cut, feed-rate and everything else, the mini-lathe didn't perform well. I was well out of my depth. Luckily, I was given a length of EN1A, which machines well, and that saved the day. Having made a start, stuff started making sense. I got a lot of help from the forum and still do. Many gaps in my understanding because I've learned haphazardly, not benefiting from an apprenticeship or mentor. (I suspect many internet videos are made by people like me because so many contain strange mixtures of good and bad practice. Watch them critically!)

Though I'm not a model maker, I found building a few engines extraordinarily valuable. They exercise:

• Reading drawings
• Planning work - which parts should be made first, and what sequence of cuts is needed to shape them
• Preparing stock - bandsawing to approximate size, removing scale from castings, marking up etc
• Setting up the lathe:
  • Oiling and cleaning the slides
  • Holding the job securely in the correct position: mandrels, glue, faceplate clamps, chucks, collets, steadies, centres etc
  • Choosing a cutter suited to the metal and to the operation - saws, files, drills, knives, boring bars, taps, dies, etc
  • Selecting and adjusting RPM, DOC and Feed-rate to suit the metal and operation
  • Locking unused axes,
  • Removing loose swarf, oil-cans and wandering tools away from the action
  • Asking 'what could possibly go wrong?', especially checking that nothing will collide whilst the machine is cutting
• Driving the machine - a combination of managing sequences of roughing and finishing cuts, removing metal in a sensible order to get accurately sized parts, with an acceptable finish. Achieving the correct size requires understanding lathe dials, calipers, micrometers, DTI and gauges. Driving a lathe requires understanding the various controls, and being able to engage and disengage them at the right times. A 'feel' develops with practice: the optimum work rate is a balance between operator actions, machine capability, the metal, and the cutter.
• Dealing with Failure. As there's a lot to learn, most of us have junk boxes full of rejects. Very upsetting! It's all part of the game. If metal-work was easy it wouldn't be an interesting hobby.

My all time favourite learning engine is Stewart Hart's PottyMill. Neither too simple or too complicated. The finished engine works, and there are no mistakes in the plans. Though all the parts are within beginner range you have to think, apply various techniques, and maybe take a couple of goes to certain parts right. The engine does not require super-accuracy, and is fabricated from stock metal. As a learning project it offers the opportunity to make a crudely finished but working engine, then to develop the skills needed to produce a finely finished well-made version, and then to move on to smart paint-work, in a realistic historic mill setting, with Lancashire boiler, figurines, and factory chimney made of individual scale accurate bricks.

After making a PottyMill, the acquired skills make fitting a QCTP rather easier!

The reason I don't have a QCTP is I find carbide inserts pre-shimmed to height don't take long to swap in and out of a 4 way tool post. I think pre-shimmed inserts in a 4-way are nearly as fast as a QCTP.

QCTPs pay off when the operator favours HSS tooling (which have to come off for resharpening), or their particular work involves a lot of rapid tool swaps, which isn't typical of beginner workshops! There's another trade-off too - though tool changes are faster, QCTP are less rigid than a 4-way. I decided to spend my money on other tools, and have never regretted it. Has to be said though, that I work rather slowly.

As Margaret made good progress with a nasty tool-post problem, I say 'keep going'. Once a few basic skills are acquired, I'm sure a second attempt will succeed.

Dave

HSS tool bits do not have to come out to be resharpened.

You don't think they could have been JIS then?

Oeer, Mark! Am I doing it wrong again?

Do you mean 'HSS tool bits do not have to come out of toolpost whilst they are being sharpened'?

I thought 'HSS has to be removed from a 4-way tool-post for resharpening and then be re-shimmed to height.', that is blunt HSS always has to be removed and taken to a grinder for sharpening? In that case, quick removal of HSS tools for sharpening without disturbing the cartridge means a QCTP is faster than a 4-way, where shims have to be adjusted.

However, carbide inserts are different. They're replaced without disturbing the tool-holder, which means a 4-way tool-post with pre-shimmed carbide holders is pretty much as fast as a QCTP. Fast because only the insert changes, the tool post isn't touched, and no time is wasted at the grinder. To my mind carbide inserts do away with much of the need for a QCTP, unless that is, the workshop uses HSS most of the time.

Dave

Perhaps you could show us what you have in mind.

with a QCTP and a DRO, you can swap tools around and then when you put (say) your plain turning tool back, the diameter display is still correct (assuming it was before you took it off). You get the same with a good ( and I mean good) indexing 4 way as long as you don't take the tools out. With inserts you can even swap the tips, but for fine work I'd check after swapping. If you understand the Chinglish you can even set up tool offsets so you get the right diameter with several tools. Having said that I still use HSS quite a lot, they don't need sharpening all that often in hobby use. For me the downside of 4 way tool posts is the forest of sharp bits sticking out right where your hands are. However, to make good use of a QCTP you need a lot of holders, so it gets expensive. Until you get more experienced I'd stick with the 4 way, buy a bench grinder with the money, and a good book on tool sharpening and learn to grind HSS. Chip a carbide insert and your quids down, blunt a bit of HSS and it takes you a few minutes to regrind