AL960b metric threads not quite right

[cba_melbourne]

[QUOTE=casjon;1845792.................
Parting off is something I have never managed to do successfully without a hacksaw.[/QUOTE]

I hope you use the hacksaw to part off in a bench vise. Using a hacksaw in the lathe, is exactly how the ways below the chuck get damaged

Seriously, give it a try with the parting blade upside down. It really makes parting much easier on lightweight lathes that lack rigidity. On heavy industrial lathes it will make no difference. But I can guarantee it does work on light lathes. The only downside is, if your lathe has a threaded chuck (like many older designs do) you need to make a rear toolpost, as it is not safe to run the spindle in reverse.

[janvanruth]

Anything that puts side loads onto chuck jaws or chuck key is bad. Chucks are not designed for this. Especially cheaper chucks made of cast iron are at risk of breaking out. Or developing the beginnings of a hair crack... that may then over time grow.... and one day let a chunk go, possibly at high rpm with dire consequences. But also loss of accuracy is a concern. Chuck jaws are very accurate fits to the chuck body - on a new precision chuck, the jaws are actually hard to slide such tight is the fit made. Side loads with a spanner on the jaw will over time loosen that tightness, and what once may have been an expensive precision chuck is reduced to junk status.

It is the first time someone mentions using a lathe tool upside down shall be considered bad practice. Why should that be so? I consider it best practice. It is a very common thing to do when threading to a shoulder. It has the additional benefit that when the tool digs in, it is not pushed deeper into the workpiece but on the contrary it flexes out of it. This is exactly the reason it is also very common practice for parting off, with the lathe in reverse if the lathe has a modern spindle nose, or with the lathe running forwards but the tool in a rear mounted toolpost for lathes that use a threaded spindle nose. It makes parting on not-so-rigid light lathes much easier and safer.

Regarding the VFD, I agree just for threading its overkill. But if you consider all the other benefits, a VFD upgrade is by far the most useful lathe modification of any that I can think of.

I have to disagree

Chucks are designed to have sideloads on the jaws.
How else would they transfer the movement, and thereby the torque, of the chuck onto the workpiece?

[janvanruth]

armstrong.jpg

the answer to parting problems

[casjon]

Since we’re being blunt, your understanding of levers, fulcrums, resistance and effort is a little flawed, not sure if that would make you the fulcrum or not, but, anyway: forces can only be equal when the distance between fulcrum and resistance are identical to distance between fulcrum and effort. The moment one becomes greater or lesser than the other, forces will become unequal. Assuming a square tool post with the tool tip extending beyond the tool post, distances between aforementioned points become unequal.

However none of this really has much to do with this:

A lathe does what it does thanks in large part to it’s size, weight and rigidity, All that brought about by large blocks of metal resting against other larger blocks of metal using smallish fasteners as locators, When turning steel the normal way, forces are transferred through those large blocks of metal: tool, holder, tool post, compound slide, cross slide, bed, stand, concrete floor, think of it as a series of steps, each step becoming progressively larger thereby amplifying size, strength and rigidity.

Or puting it simply, turn the tool upside down and the law of the lever places all of those forces directly onto a single point – the tool post centre bolt!

Obviously I wouldn't expect any agreement whilst your on a roll, but bottom line- who cares!

Other types of parting off tools:

Poverty pack parting off tool – fast:
Top of the line parting off tool – faster

[BaronJ]

Hi Guys,

This is the method that I use for cutting threads, with both dies and single point toolbits. It takes a bit of practice to get it right. From experience. My first machine cut thread was an internal left hand one.

I'll take a photograph of mine tomorrow and post it.

As promised, some pictures of my spindle handle.

21022015-00.JPG 21022015-01.JPG
A couple of pictures showing the handle in use. The wheel is actually a tub pully salvaged from an old washing machine. I did make one using and alloy pully, but found it came with far too many sharp edges to make it clean and safe to use. ( No grit or shot blasting gear ) The hole in the middle is very conveniently rectangular and needed little work to fit a block of steel with a suitable hole drilled in it for a length of tube to pass into the lathe spindle. I made a couple of flats out of some SRBP to stop the block from passing right through the pully and used 4BA countersunk screws to fasten them in place. I could have turned two brass collars and used one to do the same job.

21022015-02.jpg 21022015-03.JPG21022015-04.jpg21022015-05.JPG21022015-07.JPG21022015-08.JPG

These are some general views showing the collet end which is used to secure the handle in the lathe spindle bore. It should be a good sliding fit. I used an approximately 30 degree angle on the taper, which requires a light tap on the shaft to loosen it. The handle is the one that became redundant from the mill when I made the table traverse for it. It simply uses the existing M8 bolt to hold it in place. I deliberately drilled and threaded through one of the webs in the pully, in the belief that it would be more secure. In use it waggles loose and has to be retightened after use. When I get a round tuit, I will redrill and thread in one of the flat parts, then use a nut and washer to secure the handle.

Just a quick note on the danger of the chuck becoming unscrewed. I've never had this happen to me, however if it did whilst using the handle, you would instantly know. The other thing is do make sure that the lathe is NOT started whilst the handle is in place.

[bwal74]

Hi Baron J,

Nice photo's and a good simple solution to threading on small lathes.

Those Super 7's and Myford 7's really are a useful tool. The Super 7's good for a pretty penny here:

http://www.ebay.com.au/itm/321675310...%3AMEBIDX%3AIT

this one didn't even last 24 hrs on ebay. A very similar one went for $5700 yesterday in Sydney.

I think I would turn the lathe off at the power source when using the spindle wheel.

Cheer Ben.

[casjon]

That's a lot of money for such a small lathe. They are a nice looking lathe though, how about some pictures BJ

Most of the older lathes: Hardinge, Hercus, Myford, all are exceptional looking machines, must be all those curves and levers.

[cba_melbourne]

I have to disagree

Chucks are designed to have sideloads on the jaws.
How else would they transfer the movement, and thereby the torque, of the chuck onto the workpiece?

Yes, but
- it makes a difference if the torque is applied to only one or all three jaws
- it makes a difference if the jaw is fully inserted or 2/3 outside of the chuck body
- it makes a differece if the jaw is wiggled back/forth with a shifter or similar
- even a very small shifter can be forgotten attached to a jaw - more so than the chuck key that everyone is always made very aware of. Either of the two will cause damage to the bedways and the chuck when forgotten. Many chucks have been damaged or destroyed exactly in this way.

At the end of the day, it is like with many other things a matter of good judgement / common sense. But can you already expect that from someone still afraid of parting off? So in this case the recommendation has to be against challenging luck, and give safe alternatives instead.

[Gavin Newman]

This thread, while interesting and entertaining in places, seems to have strayed somewhat from the original post. I'd still be interested in seeing Anthony's gear-train and QCGB set up so we can solve his issue.

[sacc51]

Interesting? you betcha.

Some people can't help but entertain. I thank them for that, that's what made me sign up. That and the fact I couldn't see the pictures.

Back on track though, I'd also be interested in a resolution to Anthony's problem, seems odd, must be method rather than machine.?

[Big Shed]

Any further off-topic posts will be deleted, as the last one was.

[janvanruth]

my guess is the qcgb wasnt set correctly
there is nothing wrong with the way of threading used

[pipeclay]

How did you come to that opinion,a detailed description of the method used is still waiting to be seen.

[Stustoys]

my guess is the qcgb wasnt set correctly
there is nothing wrong with the way of threading used

Thats a big call.
I'm not ever sure it's an imp leadscrew yet.

But it would seem the OP is busy with other things............ as happens in my shed all the time

Stuart

[Machtool]

But it would seem the OP is busy with other things............

Dr. Google tells me Tieri Qld is 220Km inland - West of Rockhampton. He might have bigger issues to deal with at the moment.

I still havn't been able to get R.C on the phone, but I did get an SMS from him, about this time last night. 9" of rain in the lead up. One shed floaded, and a yard like a river. Not sure if the shed that went under contained "Pinky"

Regards Phil.