Damaged Screws & QCTP help!!!

Try holding the dovetailed part, and gently tapping on alternate sides of the ring with a bit of wood, see if the round base will 'walk' off the boss and roll-pin a little at a time..

Although my lathe is larger I went and had a look, after removing the four M6 cap head screws a few taps with a copper hammer had the base ring off, it was just being held by the roll pin. I suspect the pin is only there to make sure the ring goes back in the right place as it carries the angle scale for setting the topslide at an angle.

As for the stud can you post a link to the ebay listing with the videos, I suspect you were looking at ones sold for Mini-lathes which have athreaded hole for the stud, your sis a slightly larger machine.

Given the size of the photo, this is ludicrously ambitious, Margaret … but it will serve as an example of how you can measure the thread

This is a crop of your photo, with point-counts added :

.

Use the vertical dimension to calibrate your Calliper measurement, and then you can see, on the horizontal scale, the distance occupied by five threads.

A brief pause for some arithmetic might soothe the troubled mind !

MichaelG.

Now I feel really guilty! Have you managed to get the remains of the screws out? If they are loctited (and I don't know why anyone would do that), putting the whole thing in the oven might loosen them. Drilling them out would require a degree of skill. Perhaps someone near you might offer to help if you tell us roughly where you are located (not an exact address)

Hi all,

No need for anyone to feel bad. It is part of my learning curve - proving to be costly and a headache but I guess that's how we learn.

Update: Everything is now apart - thanks Jason for your suggestion and input. I heated the ring a little and tapped it and again, it came apart.

I just need to find a way now to get those damaged screws out - otherwise that part is scrap.

For the toolpost stud, I just don't know what to do. I am not sufficiently experienced to make my own (as I am sure a lot of you guys are able to) nor do I have the tapping equipment etc. I have emailed both Amadeal and Arceuro to see if they can help. It seems the CJ0623b is slightly larger than a mini-lathe. I have nothing to compare so I don't know.

It's such a headache.

Thanks again for all your input and help, it is very much appreciated.

Margaret

My guess for the countersunk screws is that they would be M6. (6 x 1 mm pitch )

The screws that you get in this country might very well be better quality than those that you have removed.

With regard nto the stud for the QCTP being threaded at both ends, obviously, the longer thread is intended for the locking handle.

You need to measure diameters and lengths of all the parts.

This leaves the question of the shorter thread at the bottom end.

What size is the serrated part of the original bolt?

If it is smaller than the stud, you may be able to tap out the hole.

MAY is the operative word. Hopefully the new stud is M8 or M10., (Check with a nut ), and the serrated portion of the original bolt is smaller, 6.8mm will allow the hole to be tapped out to M8, or 8.5 mm to tap out to M10.

If this is not possible, you are looking to open up the hol;e and then bush it, so that it can be tapped to suit the thread on the bottom end of the stud.,

This puts you into the Catch 22, of needing a lathe to make the bushing. And to open up the bore in the baseplate.

So the original set up will need to be reinstated for some of this work.

The alternative would be to turn up a bush with a bnore to match the existing bolt, and an OD to match the bore of the QCTP. But it might be a very thin wall, and the lengths may not be suitable..

Don't go past the point of no return, until you are certain of what you are doing

Do NOT rush!

Howard

If the worst comes to the worst, and you cannot sirt the problem, where are you located?

You might need to take the bits to some kind soul, relatively near, who will use their lathe to put you back on track.

Having bitten off a bit more than you can presently chew, you will still have learned, and having someone else help you will extend your knowledge even further.

No experience is ever wasted. Although buying some books and reading them will be money and time well spent.

If you want some suggestions, PM me.

You are almost certainly going to need Zeus Charts, drills (To tap threads, you will almost certainly need some Metric drills incrementing by 0.1 mm. Or buy one othe Sets of Taps and Tapping drills. Not as good as having the correct size of drill, and a First cut, Second cut and Bottoming (or Plug ) Tap.

Howard

I doubt the part with the sheared screws is scrap. Worst case is you drill them out and re-tap for M8. The corresponding holes and countersinks in the other part would have to be enlarged as well. Another, possibly better option is a helicoil type repair. A couple of random examples:
https://www.engineeringsupplies.co.uk/m6-x-10-metric-coarse-thread-repair-kit.html
https://www.amazon.co.uk/DAYUAN-M6x1-0mm-Restoring-Compatible-Repairing/dp/B0B48NK2SC/
https://www.machinemart.co.uk/p/040216677/

You drill out with the supplied drill. Tap with the supplied special tap and fit the spring like repair insert.

Robert.

Hi Howard,

Thanks for your suggestions. I have definitely bitten off more than I can chew, and the disappointing part is that it all looked such a simple swap on the YouTube and ArcEuro videos I watched. Had I known what I was letting myself in for, I wouldn't have attempted it. I am near Coventry.

Unfortunately, the shaft cap and larger diameter part of the original stud is larger than the newer threaded stud.

Stud cap: 15.18mm

Knurled part of stud shaft: 10.37

Fatter part of stud shaft: 10mm

New stud thread: 7.5mm

All the best

Margaret

Margaret,

You will gain experience and confidence from this; daunting as it might seem at present.

I'll PM you

Howard

Hi Robert

Thank you for your suggestion - that is excellent. I didn't realise you could do that. If I can't get the screws out that is my next option.

I appreciate it.

Many thanks

Margaret

Hi Margaret, there are a few different ways of getting the broken threads out, but I doubt you will not have the experience or the gear to do some of them. Easy-outs are one way, but as they have sheared off, these may not work, drilling them to the tapping size, will very often allow the remains to be pulled out with nose pliers, but of course they will need to be drilled on centre, building them up with weld is a very successful way, but will require a good amount of skill on such a small size, but drilling a blind hole about half the diameter a soldering/brazing a rod into the hole, would have a good chance, but again will need an amount of skill. If you have a small engineering firm near you, they may be able to help, but of course that will have a high kind of price, but an ME club might do it for next to nothing.

Regards Nick.

ps: Robert, the M6 repair might be the better option because fortuitously, I found several matching bolts in a drawer which had come as spares with an Ikea kitchen. The are exactly the same and M6!

Hi Nick,

You are right, I don't have the equipment nor the experience to attempt this kind of repair unfortunately. I will likely use the option Robert suggested above with the helicoil system.

I don't know of any ME clubs around me, although I am sure there are some.

Many thanks for your suggestions.

All the best

Margaret

Hi Howard,

It has certainly given me a few grey hairs!

Margaret

Speaking from very extensive experience I strongly suggest that you ask Howard L for his assistance. I have visited him a number of times this year and his help has been invaluable. He is a very knowledgeable and kind man.

You cannot go wrong

Regards

Mickb

Thanks Mickb

Coventry Model Engineers are **LINK**

I'll bet someone there will take pity. Don't go down the helicoil route until you've exhausted all possibilities of getting the existing screws out. We can then look at adapting the existing plate with 3 holes to accept the threaded stud.

Of course the simplest might be to see if the supplier will take back the QCTP. If you bought it mail order (which includes interweb) he is legally obliged to.

Edited By duncan webster on 29/07/2023 21:45:12

Presumably you now have access to the back of the damaged screws. If you can lay hands on small self tapping screws about 3.5mm to 4mm outside diameter, you can drill 3mm holes right through the remains of the headless screws. Try to keep the holes centred, but this does not need to be very good. Then screw in the self tapper from the back, and with a bit of luck this will fetch out the remains, leaving the original thread undamaged. If locktite is suspected, enter the self tappers, then heat the part to 150C and unscrew while hot (hold in a cloth).

In this sort of operation, the danger is that the self tapper (or easyout, or whatever) expends the part being removed, thus wedging it tighter. Therefore if it does not turn at reasonable pressure, quickly resort to heat.

Avoid using Easyouts like the plague. TOTALLY mis named. They are likey to expand the remains of the screw in the hole and make them impossible to remove.

Go and join the Coventry Club, and ask for practical help. Lots, and advice on many subjects should be available.

My preferred method would be to use a 5 mm drill to centre each hole under a drilling machine,

Once centred, clamp in place.

This should just "spot" the screw, so that a centre drill can make a proper centre, to be followed by successively larger drills until 5 mmm is reached. 5 mm is tappoing size for M6 so possibly the threads can be picked out with a scriber, or a first cut tap used to remove metal, as if tapping the thread from virgin.

Mick b may be right, YOU can't go wrong, but I CAN and often do!

Howard