Thread: QCTP Question

So now where talking about truing the plate to suit crook hole by facing the chuck side of the plate, instead of just reducing it in thickness.
I wouldn't want to do it that way without centre drilling the stud and using a centre in the tailstock to support it. It's not something I would recommend to someone starting out either. Facing it from the tailstock side is delicate enough for a beginner with the interrupted cuts, but facing it from the chuck side with no support could end up with a bent stud with one slip up and it is then buggered and who know what other damage could happen.

If the hole was crook I would just make a new one, but for someone that wanted to use it and since there is no real precision needed for this, using a 4 jaw I would chuck up or collet up the stud up in the tailstock with the plate on the end. I would then bring it up to the chuck and bring each jaw in and tighten them taking care to keep it centre.
The stud could then be taken out and the face machined accurately to the hole.

Most guys mill, file, hacksaw, bandsaw the pieces out and leave it square instead of round. Neither has any real advantage over the other in this situation, though technically the square would be stronger, just different ways of doing it. If you only have a lathe a round one is easier

Dave

Originally Posted by Dave J

So now where talking about truing the plate to suit crook hole by facing the chuck side of the plate, instead of just reducing it in thickness.
I wouldn't want to do it that way without centre drilling the stud and using a centre in the tailstock to support it. It's not something I would recommend to someone starting out either. Facing it from the tailstock side is delicate enough for a beginner with the interrupted cuts, but facing it from the chuck side with no support could end up with a bent stud with one slip up and it is then buggered and who know what other damage could happen.

If the hole was crook I would just make a new one, but for someone that wanted to use it and since there is no real precision needed for this, using a 4 jaw I would chuck up or collet up the stud up in the tailstock with the plate on the end. I would then bring it up to the chuck and bring each jaw in and tighten them taking care to keep it centre.
The stud could then be taken out and the face machined accurately to the hole.

Most guys mill, file, hacksaw, bandsaw the pieces out and leave it square instead of round. Neither has any real advantage over the other in this situation, though technically the square would be stronger, just different ways of doing it. If you only have a lathe a round one is easier

Dave

No David, I am talking about reducing the thickness, but doing it in such a way that the nut remains perpendicular to the stud. I am not going to argue with you about this, it is a tool post stud being used as an arbour for goodness sakes, not some 3 mm noodle, light cuts are being used and for these it is quite sufficiently rigid, however you are free to machine any way you wish. If you wouldn't do it this way that's fine, and I happen to feel that your suggestion to also use the tailstock for additional support when facing the "wrong" way is a good one and something I forgot to mention. However given that you initially said you thought the OP used a milling machine machine, and from what you've said since, I get the impression you have not done this type of operation before. Indeed now you're talking about it being round, it seems you are not even aware that 3 jaw chucks are perfectly capable of holding both flat and square stock, it's just that they will be turning off centre. Not a problem if all you're doing is reducing a width, meanwhile there is a perfectly good arbour built right in, in the form of a stud. Facing a piece of MS in the normal manner is not at all difficult (or at least it shouldn't be), whether it is being held by a chuck or in this case an arbour.

Many lathes are sold used without 4 jaw chucks. Many people don't have milling machines. These QCTP are from China and so their quality can be a bit variable. This was something I did years ago and now I think more about how it went I recall that the stud on mine was indeed concentric and so I faced the bottom of the nut (definitely the preferred approach if possible). However I am away at the moment so can't check, but if not that nut, I've certainly faced and trued up in similar circumstances. One way or the other, I can assure you I have a rectangular nut under my QCTP that was reduced in both thickness and width and no files nor hacksaws were harmed in the process; it was all done in the 3 jaw and it didn't take long at all. You want to file and hacksaw it instead, then knock yourself out! I have simply suggested to others the way I tackled the problem when I had nothing more than a bare lathe, a 3 jaw chuck, and a crappy American toolpost that didn't even have a "boat".

Pete

One thing you have to remember on these forums when giving advice, is to think about the safety of someone completely new to the world of machining, as there are a lot of people that read these forums that are not members as well.
We don't want them to end up in hospital or damage their machinery, get disheartened and sell it all before they have even started.
Fair enough a 3 jaw could be used if you don't have a 4 jaw, but it shouldn't be the first choice in this situation if you have a 4 jaw, especially for someone new to using a lathe.



Dave

Originally Posted by Dave J

One thing you have to remember on these forums when giving advice, is to think about the safety of someone completely new to the world of machining, as there are a lot of people that read these forums that are not members as well.
We don't want them to end up in hospital or damage their machinery, get disheartened and sell it all before they have even started.
Fair enough a 3 jaw could be used if you don't have a 4 jaw, but it shouldn't be the first choice in this situation if you have a 4 jaw, especially for someone new to using a lathe.

In this thread I have simply described how I machined my QCTP. It was not dangerous and there were no hospital admissions in my name. Just because you clearly don't understand how to machine on an arbour doesn't make the technique wrong, heck you may even like to try it some day it's a very handy technique! Sometimes I'm right, often I'm wrong, but all I can do is try to pass on what I've tried and, heaven forbid, learnt. We're all here for pleasure and I'm quite sure others feel the same way too.

Pete

Keep it nice Kiddies.

This is renowned as a friendly board where ideas and methods can be discussed freely.

You may not agree with the method but there are ways of putting your point across without slagging off the person that posted it.

If this sniping continues a few bannings may take place.

Play nicely.

For those who may be going down this path, here are a couple of photos that may help. It's not intended to be a "blow by blow" description of the process, nor a recommendation that this is the correct or only way. Simply how to get the job done if all you own is a 3 jaw, in my experience not uncommon on used machines. As usual, common sense prevails in terms of the depth of cut used and how rigid the holding opportunities are. If I had to do this job again now I would not do it this way as I have a 4 jaw, milling machine, linisher, surface grinder etc etc that are better suited to the task. Most people starting out don't however have any of that, so this is how to get around that situation.

The OP's situation that generated this thread is somewhat unusual from what I've seen. The nuts that are shipped with these Chinese QCTP are deliberately shipped oversize so they can be machined down to the precise size needed for the lathe they're being mounted on. It doesn't matter whether you choose to reduce the width or thickness first, I chose the width. What some apparently don't understand is that a 3 jaw chuck can be used to hold and face other than round stock. Unfortunately I couldn't show this on the nut as I loctited the stud in, but here is a shot of some scrap brass of around the same size. Facing cuts ONLY are used to reduce the width of the nut. To keep the stud centred obviously you only take half the material off one side before reversing the nut and doing the other side. Again, use common sense with the depth of cut, however the nut I had machined easily.



The next difficulty is to reduce the thickness (if required). For this I chucked the stud in the 3 jaw and used it as an arbour to once again face ONLY the nut. The poor finish is clearly evident as I was struggling with my old toolpost and poor quality tools. However it got the job done and nobody sees it so it really doesn't matter. As I mentioned above, if the stud is not drilled and tapped squarely then it may be worthwhile taking a light facing cut from the other side just to true it up. As David said above, if you do that it would be a good idea to use a tailstock for additional support as the arbour (stud) will be sticking out a long way. Once the upper face is trued up, push the arbour right back into the chuck and face as per normal.

Here is the finished result. Flat sides, and sized to perfectly slide into the T-slot. No hacksawing or filing is required.



Hopefully that helps somebody who is starting out in this area.

Pete

If you use the stud as an arbor mounted in a 3 or 4 jaw chuck I believe its pretty unlikely you'll get a face machined perpendicular to the threaded hole. Much more likely that you will end up with a face machined parallel to the bottom of the plate.

As for mounting things in a 3 jaw like that it always makes me way to run. Yes sure its a method that you will see in books and if I really had to I might do it myself. But 1. its putting a side load on 2 of the jaws, 2. The work becomes a huge single toothed cutter(depending on size), 3. It wont come loose it will come out. If the part NEEDED to be parallel or spot on size or square, then maybe. This part doesn't need to be any of those things so for a beginner maybe a hacksaw would be the way to go, depending, it might be faster anyway. Of course they are free to make up there own mind.

Stuart

Stuart the nut is turning on the stud as an arbour, why do you say it would machine parallel to the bottom of the plate? I can't understand how that is possible. Surely the face will be perpendicular to the rotating stud on which it is mounted?

In what books have you seen this? I was hoping to simply provide a link to this however did quite a search last night and couldn't find one reference. I thought it would save me having to take the toolpost off and take the pictures but alas I couldn't find anything. I've never seen this setup before so I'd be grateful though if you could direct me to the information you've seen.

As far as your points, yes you're quite right, it certainly does put a side load on the jaws and that was something I considered, and indeed looked at again when I took that photo. The chuck I did it on was not the one shown in the photos, it was an old clapped out chuck. Having said that, the jaws run in tight slots in the chuck and are wound almost all the way in so they do get good support. I really don't know what you mean about it being a "toothed cutter", so I'm not sure I can comment on what I found with regard that. Mine machined quite easily with interrupted cuts. Yes if the part had come loose it would come out of the jaws, like I said, common sense is required and the chuck is done up such that the part doesn't come loose! The part is central in the chuck so it's simply rotating about itself and there is no real centrifugal force trying to pull it out of the jaws. A 4 jaw is FAR more secure in this regard as it captures the work, but as I said, if that's not available you can hold work as I showed, it may look somewhat flimsy, but in fact seemed to me to be quite secure. I don't like interrupted cutting if I can avoid it, and these days I'd simply mill it down. But as I said above, mills, 4 jaws and so on may simply not be available.

Regarding the speed, even my bandsaw wouldn't have cut that as fast as machining the part down on the lathe. It was very fast, no more than a few minutes to do each side, so I'd certainly be up for a race with somebody wielding a hacksaw Sure if somebody wants to hacksaw it out then they can knock themselves out. I guess the same can be said for machining in general. I am very conscious about putting experiences up here that may be unsafe but I am quite comfortable putting this information up.

Pete

Because the nut will pull up against the jaws of the chuck so the faces of the nut will be aligned with them, not the thread.

"The Amateur's Lathe" L.H.Sparey. I'm pretty sure there are others but luckily his was the second book I picked up.

So a beginner needs to find a balance between damaging his chuck and the work piece coming out. That's a pretty steep learning curve. Who knows what his chuck is like. Who knows what speed he will pick. Who knows what his tooling and doc are like. If you look at the leading corner of the "nut" and think about what its doing when rotating you may see what I mean about single toothed cutter. As for centrifugal force, sure there isn't any unless the part starts to slip in the jaws. Once it starts to move off center there will be plenty and nothing to stop it getting worse. Personally I haven't had something throw out of a lathe chuck, but I know someone that has, it missed, but he didn't enjoy the experience. I'm not really sure where "common sense" comes into chuck tightening. Best to avoid where possible, a setup that will throw the work should things not go exactly as planned.

Which is why I said "depending". Depending on how much has to come off. Depending how long it takes you to set it up in the lathe. Depending on how big a cut you are game to take. Depending how fast you are game to run the lathe. A race? sure, my price for loosing is coming second and maybe being a little out of breath, you're price for loosing is coming second and maybe wearing said nut on your face.

Stuart

Ok, thanks. I would have thought half a poofteen gap would have taken care of the chuck knocking anything off concentric, if that's what was happening, but obviously not. To be honest I now wish I had never brought this up it. I thought it would help other members who weren't fortunate enough to yet have a 4 jaw. My mistake.

Sorry for the OT, again.
The message has served it's purpose.

Dave

Dave that's fine. I thought about whether to reply and bump this thread, but decided that indeed I will say a few words here.

I'll be perfectly honest and say that you weren't exactly on the top of my Christmas card list, in fact what you probably didn't know is, for the second time, as a result I'd basically decided to withdraw from the forum and not post any more. Indeed ALL forums unless it was me who was asking for help. I was happy to "take", but I wasn't going to "give" anymore. It was taking a HUGE chunk of my time and I just seemed to be getting crap in return. When I decide not to participate anymore I don't make a big deal and throw a song and dance routine, I just pick up my bat and ball and go play elsewhere. I'm sure many people are very happy when that happens too, though most probably don't even know, never mind care. Unfortunately the above events happened to coincide with some other things that were happening, both in the virtual and my real world and I was simply sick of the number of people who seem to take some form of pleasure in trying to bring others down. It happens everywhere and it's a real shame. Today, after lunch, I'll wheel my bicycle out and go for a ride for a couple of hours, riding in the National Park or on bike lanes, not hurting or inconveniencing anyone, just trying to stay fit and enjoy life. Yet I know that there is about a 50:50 chance (literally) that I will get abused, have bottles thrown at me, get tooted, and so on; I'm not making one iota of difference to their life, yet they're trying to bring mine down. I simply don't understand that thinking. I didn't want to turn on my computer and see the same thing happening on that. I don't think anyone does.

Having said all that, I am no saint. So while I have the floor, if anyone else reads this, it's my turn to say that many MANY times I've read back through my own posts and thought how ugly they read. I can only assure others that there is normally no malice intended, and if there is I will make it quite clear Often I'm posting while tired after work (36-48 hours between beds is quite typical), sometimes I use a really lousy choice of words, and sometimes ... well, sometimes I'm just plain cranky! But the intent is generally to help others where I can. You're right Dave, I haven't been at this game long, but in that short space of time I've learnt a lot, an amazing amount when I think back, but I STILL know sweet FA, and as long as I keep that attitude I'm hoping the learning curve will keep at the same steep pace! I try to pass what I've learnt on to others, hopefully I've made the mistakes for them (I tend not to publish them! ) and I'd hope they'd do the same for me. Sometimes it may sound like it, but I'm not trying to impress anyone, I'm pretty happy with my lot in life and the reality is my feeble machining skills wouldn't impress anyone ... well ok, my 2 year old is impressed when I use the "sparky-sparky machine" (surface grinder, what else would you call it!).

It takes balls to swallow one's pride and make not only a public apology, but also contact a person in private and send the same heartfelt message. So to say I'm impressed is an understatement Dave. Yes I'm sure we'll find plenty to disagree on in the future, but let's hope it's now from a position of a clean slate and mutual respect.

Pete