Lathe cross-feed drive?

[Jerry WrayParticipant @jerrywray14030]

Thanks for all the contributions, most encouraging when the spend approaches £2000 !

Andrew, Glad you pointed out my conflicting statement about fun. I had not thought of it that way.

I have never had a machine of my own with PXF but it seems it's the way to go; I don't have a lot of patience now I'm near retiring and 'twiddling' the feed may just drive me mad.

George; Thanks for the pointers, I'll have to check those things, and of course all the bits that might be less than perfect,

and Jason I am even more encouraged that your experience with the 280 has been good,.

When I get it I'll try to remember to post some pictures.

Jerry

[JasonBModerator @jasonb]

Well I did have one motor brush wear quickly, the 60p replacement set have lasted 4 years.

One head bearing dried out so I replaced the pair with better FAG ones

And the speed control pot on the front of the machine went, few quid to replace.

It has done a lot of work, half a 2" traction engine, one IC aero engine, one vee twin 4 stroke,two large stationary steam engines and three hit & miss engines

Edited By JasonB on 27/08/2013 21:10:15

[Anonymous]

Jerry: It was, of course, a tongue in cheek comment. It's an interesting debate as to where 'manual' ends and 'machine' starts. I wonder if there was a heated debate in the past when the transition was made from treadle lathes to the new fangled electric motors. Were there dark mumblings about not being able to 'feel' the cut if using a motor?

Parting off under power is a controversial subject. A few weeks ago I was talking to a couple of professional machinists. One always parted off under power, the other always parted off manually.

I don't have direct experience of Warco machines, but in my experience most far east tooling uses very soft SHCS. This includes 'professional' tooling, as well as ME. I don't manage to strip the threads, but I find that the hexagon sockets tend to 'round' very quickly. I normally replace the screws as a matter of course on new tooling.

Regards,

Andrew

[Russell EberhardtParticipant @russelleberhardt48058]

Thought I'd give parting off under power another go while making a batch of screws from 5/8 in bar. I had been parting off by hand using a 1.5 mm HSS blade. Tried under power with a 3 thou/rev feed and the first one worked perfectly with a nice finish. Tried second one, it got halfway then bang! A chunk came off the tip of the tool.

Back to parting by hand winding to finish the batch. I can hear and feel what's going on and control the rate of feed accordingly.

Maybe power Xfeed is better for parting larger components with a wider tool? I'll give it another go. Any pointers from those who regularly do this?

Russell.

[Another JohnSParticipant @anotherjohns]

re: power cross feed. I've two manual lathes; one full blown with all the knobs and gadgets, a smaller one with change wheels for the lead screw, and no power cross feed.

The smaller one – I've never missed having power cross feed, and have never used the leadscrew for power feeding for turning.

The larger one – use both feeds all the time!

I think that the reason is that I do small things on the smaller machine, so the machining goes quickly by hand twiddling.

Another JohnS

[BazyleParticipant @bazyle]

Jason, Have you identified a Grizzly equivalent manual for this lathe?

Jerry, You don't have to post pictures – we don't ask for proof of lathe ownership however as I'm sure you will have been frustrated by the poor pictures on the vendors site, and have searched a lot for relevant information I suggest when you do post some pictures you a) caption them including the lathe name, and b) post pictures that fill in the details you couldn't find when searching.

[JasonBModerator @jasonb]

Russell I tend to part at a much slower feed rate, usually finest on the machine which is 0.00075"/rev so about 1/4 of what you tried. On small work say 1/2" or less I use a 0.050" blade over that either a 3/32" eclipse in the Dickson holder or one of the Chronos tipped tools which has a 2mm bit.

Bazyle I've not had the need for a Grizzly manual the Warco one has been OK. Though I don't think they do an equivalent anyway

Edited By JasonB on 28/08/2013 12:41:43

[Anonymous]

For parting off on my main centre lathe I normally use insert tooling, 3 mm wide. I lock the saddle at the appropriate point; the top slide is always locked unless actually in use. For low carbon steel I'll run about 3-400rpm and a feedrate of at least 4 thou/rev; below that I find it chatters. I also use flood coolant on everything except those metals that produce fine chips (brass and cast iron), and plastics. The last dig in I had was because I was in a rush and didn't use coolant on a piece of aluminium.

On the repetition lathe, which is all manual and uses 5/16" square HSS, I just pull as hard as I can on the handle! I recently made, and parted off, several hundred aluminium spacers from 8mm diameter stock. I've just measured the thickness of the resulting swarf: 12 thou. I parted off at top speed, about 1000rpm.

So, there we have it. Lower feedrates, higher feedrates, slow speed, high speed; I suspect the answer is that there is no surefire recipe for successful parting off.

Regards,

Andrew

[Sub MandrelParticipant @submandrel]

> surefire recipe for successful parting off.

It's a zen thing.

Neil

[Howard LewisParticipant @howardlewis46836]

Like many others, I have found parting off works better using a back toolpost (which is what is always used on Capstan lathes).

Various explanations have been offered for this, (pressure on dovetails. etc)

This carries a 3/32 blade in a holder which allows a little flexibility. This blade is ground at angle, so that the workpiece should have no central pip, (left on the base stock).

Theoretically, this is bad because the swarf is wider than the slot, but it works OK virtually all the time, maybe the flex in the holder helps

In the Front toolpost, I sometimes use a 2mm replaceable tip tool, and very rarely does it dig in.

[Jerry WrayParticipant @jerrywray14030]

Many thanks to all the contributors to this thread, I've now placed my order with Warco, who expect to deliver it in early October.

Andrew, your comment following my 'fun' and twiddling post was understood in the way you meant it. It's amaxing how easy it is to make a remark without understanding that others might interpret it in a different way! To be honest I had not thought of the boundary between various levels of mechanisation.

I now to think about some of the other issues I might have.. For that I will start a new thread.

Once again many thanks for all the useful information.

Jerry

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Generally speaking the bigger the lathe then the more use power cross feed is .

An important consideration though is the detail design of the cross feed system – some are good and some are very bad .

You need a system where you can select feed rate quickly and then drop in the feed with one simple action – just like engaging the longitudinal feed on most lathes .

Some systems are very cackhanded and some are incomplete – most notably ones where power is only available on the in-feed and requires a disengage before manual out feed . Not always a problem but it is better to have proper choice of powered in feed / powered out feed / manual feed .

Another thing to look for is systems that work intuitively backwards compared to the longitudinal feed – this is a particular problem where feeds all originate from one leadscrew and needs a change over of tumbler setting when changing from long to cross feed .

MikeW

Edited By MICHAEL WILLIAMS on 29/08/2013 13:28:55

[mechman48Participant @mechman48]

As far as parting off under power goes, I have always been reluctant to & always used manual when I’ve had to, mainly due to lack of confidence & not have the correct set up. I think I have now resolved my issue; I needed to have some large washers to replace the ones holding my vice to the mill table as the present ones are the large penny / patch ones, backed up with a couple of 10 mm standard washers. I decided to put my Hemmingway kit (usual disclaimer) constructed rear tool post to the test & part off some 30mm dia. BMS that I had drilled 10.5mm, I have used this tool post before but only on brass as a test after I built it.

Having set it up true& checked centre height I proceeded to part of … manually first, the cut went ok provided I applied plenty of neat cutting oil with one hand & trying to maintain constant feed rate with the other, (really could do with 3 hands here). Two washers were completed ok but the finish wasn’t the best so in for a penny etc. I went for the PXF… I locked everything down & my speed was set at 200 rpm (arbitrarily) & the federate was as set originally from day one…. .03mm per rev. the lowest setting on the machine chart. I set the leadscrew to run in reverse, actuated the crossfeed lever & set to, the cutting action was very smooth but it soon told me when it started to get tight, I could discern the swarf trying to bind in the cut, this was remedied quickly by applying a constant supply of neat cutting oil, by brush (I don’t have a constant supply set up … yet) which made cutting a lot easier. There wasn’t any noticeable loading on the motor & it did the cut well, which has done wonders for my confidence now, also the finish was much better. Still goes to show, you can teach an old dog new tricks!

The blade used was HSS 3/32, I also have a small ¼” HSS tool steel cutter that I have ground to 1mm thick blade for small parting off which I have used without any fear. I am tempted to get one of the indexible insert type parting tools, complete with holder but it’s a bit pricey at £32 (RDG) but do I do enough parting off to warrant the expense… hmmm?

First attempt at PXF parting off in years…

The remaining rag shows parallel cutting…

The two on the left were manual feed, bit of a rough finish, (the dark one is 'cos the flash didn't reach it, it's not heat discolouration)) the one on right is PXF parted off & much better finish…

I shall not now be wary of using PXF with the rear tool post on steel.

George

[JasonBModerator @jasonb]

Mechman, there is nothing to stop you using the "C" position when using cross feed which should give you half what you have now assuming your chart is anything like mine which leaves most of the "C" position blank.

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