Thread: QCTP Question

Leave it.

First off welcome, and as you have probably already seen we have a good bunch of guys here.
As Pipeclay said just leave it, it will be fine. They usually come soft so not sure why yours didn't. The standard piece in my lathe T slot is soft.

What sort of lathe is yours, any pictures? It also sounds like you have a mill.

Dave

Agree.
Leave it.
regards
Bruce

Thanks guys, guess I'll leave it soft then.
Dave J no mill, just figured out how to put on the 4 jaw, centered it and turned away the major diameter and left the minor at full height to shoulder it on the T-slot.
Piece was pretty hard a file wouldnt touch it. Trying to machine it looked like an F1 disc pad at full braking
I wasnt allowed to do metalwork at highschool.Had a bad reputation so when it was time to do metalwork, the teacher marched me off to home-ec saying "here you deal with him" and yet a year later I did jewellery making with him and he was fine.

ps my lathe is the standard green one I see in all the forums, 95 vintage

Jim

Originally Posted by jimmyratsbreath

Hi all,
First I want to say this is a fantastic website.I have learnt a lot already. I have a generic 12x36 chinese lathe.Bought a AXA toolpost from CDCO (another great find from this website.
The t-slot on my cross slide was narrower than the base plate of the tool holder. I tried to machine it but the base plate was hardened. I then lit the bbq and chucked in the base plate and let it cool slowly.this did the trick and the machining went well.
So now do leave the piece unhardened and use the toolpost as is or do I get it hot and quench it before use?

Jim

Hi there,

Hi Jim, Welcome. There is a lot of experience here on this forum and I have found the guys on here extremely helpful and willing to share their knowledge. This is especially encouraging when, like me you are relatively new and inexperienced in metal working. I have a generic 12x36 chinese lathe too. I would love to hear what you have done with it or improvements you have made.

Cheers,

Simon

Jim & Simon,
are you guys members of the Yahoo 12x36 lathe discussion group?

12x36importlathes : 12x36 IMPORT LATHES

It's for Chinese/Taiwanese 12x36 lathes only. It seems to be very active.

Originally Posted by jack620

Jim & Simon,
are you guys members of the Yahoo 12x36 lathe discussion group?

12x36importlathes : 12x36 IMPORT LATHES

It's for Chinese/Taiwanese 12x36 lathes only. It seems to be very active.

I'm not actually. I will definitely have a look at that. I was never really into forums all that much as many of the ones I have looked into have not been very friendly or accommodating for inexperienced operators like myself.

Cheers,

Simon

Hi Jim,

I bought the same QCTP from CDCO for my Gasweld 12x36 and turned the baseplate down the same as you. I really struggled with that job, it was one of my first. I didn't realise how hard the baseplate was until I got more experience later. At the time I thought all my difficulties were due to the intermittent cut, my noobie ground tools, and my speeds and feeds. Later I realised that the plate was just hard and that conspired with all the other factors

I should of asked for help here.... lesson learned!
Darren.

That's very strange that it was hardened, they are normally sent out soft as they need to be machined down to fit the T-slot.

For others who may read this in the future, there's no need for a 4 jaw to turn a piece like this down, it will fit just as well in a 3 jaw (I mention all this as it's often the only chuck a used lathe comes with), and will simply be turning off centre. Since it's an interrupted cut anyway, and you're simply reducing the width, it won't make one iota of difference.

Pete

I understand that it doesn't matter about centering the job to reduce the baseplate thickness, that's a very good point. You can just rotate about any point.

... but what I did (and what I think Jim did) is to leave the centre as shown in the picture. I found it easiest (as a beginner) to use the 3 jaw chuck to clamp the bolt and then screw on the baseplate so it tightened on to the face of the chuck jaws.

If this is a bad method please say.

Hi Darren,
As you already know it works that way, but it is a lot more rigid if you set it up in the 4 jaw, or even have it on a face plate with a thread rod going through the head stock with a nut and washer at the other end. If you did it this way you would have a bolt on one of the face plate slots to stop it rotating. But the 4 jaw is the easiest if you have one like you do.

On my lathe with my H&F's Dickson style tool post I found I could leave the original stud in and think the stud is a good design the way it locks in their.

How is that new lathe of yours going, we haven't heard anything about it yet.
With your 3 jaw, are they still coming back plate mounted?
If they are, what I did with mine was to machine down the register on the back plate a few thou. This lets you true the chuck up by loosening the bolts on the chuck while you indicate the job in by giving it a bump with a dead blow hammer, then re tightening them. After this you will find it runs true at this diameter for repeated jobs and is pretty good at other diameters.

Also have you found the 2 grub screw for cross slide back lash adjustment? They can be gotten to from the back of the cross slide.
I have still had no problems with mine after nearly 8 years and I have found they wear very little if kept oiled.

Dave

Darren, I understood the OP was talking about the width of the nut and not the thickness, however maybe I misunderstood that. No there is nothing wrong with what you did, but it will require light cuts and can obviously only be in a direction that causes the nut to tighten. Indeed the advantage in what you have done is the face that is pulled up against the top of the T-slot will now be perfectly perpendicular to the stud, clearly a desirable situation. If you mount it independently in chuck jaws then there is absolutely no guarantee that would be the case and you're instead replying on the stud being accurately drilled and tapped from manufacture. So the end result is, whether you knew it or not at the time, you actually did the job perfectly

Pete

Hi guys,
Simon, havent made any improvements yet.The lathe was from a printing plant,bought for $1000.00 with the 3 &4 jaw chucks 2 live centres & drill chuck tail piece tool box change gears,heaps of cutters and boring bars,books etc. Actually went to the auction to buy a mill R-30 clone,which went for $1400 ! thats new price! then this lathe was going to be sold at about $700 before I jumped in.

Pete F I did the same as Darren.However as you stated using the bolt held by the 3 jaw showed a horrendous amount of run-out (tapped out of square) hence the 4 jaw.Like I said earlier she was proper hard,files just slid off.Tempted to reharden and temper just for the experience.I was well chuffed when the hillbilly anealling actually worked.
Dave J my original bolt was thicker, so would have involved a lot more work.This way I can always substitute either depending on the job.
Jim

Originally Posted by Pete F

Indeed the advantage in what you have done is the face that is pulled up against the top of the T-slot will now be perfectly perpendicular to the stud, clearly a desirable situation. If you mount it independently in chuck jaws then there is absolutely no guarantee that would be the case and you're instead replying on the stud being accurately drilled and tapped from manufacture. So the end result is, whether you knew it or not at the time, you actually did the job perfectly

Pete

Mounting it by the stud in a 3 jaw would be (relying) on the hole being accurately drilled and tapped square from the manufacturer.

If you did it in a 4 jaw, you would indicate the face of the plate and indicate the hole by putting the stud in, and then indicating it as close as possible to the plate, which would help cancel any errors if it was drilled and tapped out of square.

It would end up being more accurate than holding it in the 3 jaw if the hole was drilled and tapped out of square from factory as Jim was, and is why he went that way.
Not that it is really needed for this job, but the 3 jaw chucks are not that accurate unless you have a good one, but the contact area on the ends of the chuck jaws is only small for a piece this size to sit on.

Especially with it being a interrupted cut there is also the chance of someone new to machining to take too big of a cut and spin the stud in the chuck, which could damage it.
Sure it can be done in a 3 jaw if the thread is true and you only take small cuts, but a 4 jaw would be clearly desirable in this situation if there is one available.

Hi Jim,
Sorry about that, the reply was directed at Darren as he has the same lathe as me, I will edit it to say so.
It sounds like you got a great deal with that lathe, tooling and books etc. It's amazing how people go stupid on prices at auction like with that mill, but you where lucky with that lathe.
It's also good to here you have a bit of experience in annealing now with this job, and when something else comes along you will know what to do to get it machinable. I still find it strange it came hard as they are meant to be machined to suit the lathe.
It wouldn't hurt to re harden it if you wanted to. You could dunk it in oil to cool it, then have the best of both worlds with it being black and rust resistant.

You bring up a good point about keeping the old stud so you can use either tool post. I was lucky that my standard stud fitted the QC tool post, which I thought was strange as I bought the lathe and tool post from 2 different places. I doubt you will ever change the tool post back unless you need it for a big boring bar or something, but it would make a good rear tool post as a future project.

Dave