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Capacity and realistic use question

Cookbot

Plastic
Joined
Jul 23, 2014
Location
United Kingdom
Hey, new user, first question and all.

I run a small website making custom car parts and I'm working on a new project using 304 stainless. Many of the parts are too complicated to make by hand and being done by CNC, but one part is very simple. It's basically a M16 stud connector, turned round for about half of its length. I'm looking at getting my own lathe to do this, but need to know if a lathe of the size below could realistically cut stainless and do it at a speed where I can do runs of 100 pieces without wishing I hadn't bothered starting! I'm looking at the lathe pictured below and will only have to do 3 batches of 100 to recoup its costs. Is this likely to be a suitable lathe for my needs or will I have to go larger (and thus cost more)?

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It's made by a UK company called Chester if anyone has heard of it before.

Thanks, Paul
 
Yes, and no.
The lathe is not the limiting factor.

For 100 pcs runs, a good collet chuck setup (lever collet) will be needed.
AFAIK, Chester and no-one else has anythign like that typically available.

Then you will need a turret setup, or something you bodged up to face turn and cut off effectively.
After which You have a too-small lathe (power and rigidity), making ok-looking parts to ok-accuracy.
Slowly, manually, and inefficiently. IMHO.

Plus the lathe is far underpowered to do anything remotely profitably.

Look at it this way:
The tiny lathe, can produce the turned off piece in say 4 passes (0.15 mm per pass radial, 100 mm long, 1000 rpm) of 1.5 min each, plus face, cut off, say about 8 mins each cykle.
The incremental value of the piece is maybe 3€. (Your margin per piece, retail not wholesale. Maybe).
If you are very lucky, you can make 7x3 == 21 € gross per hour. Maybe.

Option 2.
Any suitable turret lathe can do this in one pass, at 30%-50% faster speeds (-200%), at around 2 min cycle time (down to 1 min) including a finish pass.
At 30 pieces / hr == 90€ / hr.
Turret lathes in the 1000kg mass/1.5-2 kW range.

Option3.
Any nr of jobshops will be happy to make the pieces for You at 50€/hr or so.

Only options 2 and stand to make you any money.

The buy-in to make you own pieces start at around 4000€ without sawing.
Thats your rock bottom price to make parts well, and profitably.

(1000€ beater lathe,
1000€ collet chuck and collets,
1000€ turret setup and tooling,
1000€ toolholders, inserts, odds and sods and bits to fix and setup all above,
minimal metrologoy (electronics mics, thread gages, sundries).
Add 100+ hours of work, if you are experienced and capable.

I have a Chester Craftsman, a 2800£ light industrial lathe.
Very good lathe, and could do the above, not especially well.

Set up with 5k$ worth of (extremely good) CNC setup, and I have bought 2 lever collect setups to make my own as samples.
One 3AT one, and one 5C one.

FWIW..
Good luck.
 
Small repetition lathe like a Britan or capstan e.g. Smart & Brown model L is the correct weapon for that sort of job. Just need to make sure the collets go up big enough. Correctly set-up a Britan will chomp those parts off about as fast as you can pull the handles and an L with lever op collets won't be that far behind. E-Bay is your friend, couple of Smart & Browns up right now that should do fine. Simple lever cut off slide is sufficient for your job but arguably its worth getting the normal cross and top slides too as then you can do a good deal of ordinary turning work.

Thing is your picture is a modellers lathe, a waste of time. You will die of boredom trying to do what you plan and it has essentially zilch capacity for 12" to the foot scale work.

Clive
 
Thanks for the quick replies. Ones in the £££'s of pounds are prohibitive, so a simple well built (old?) lathe would probably be more suitable for me. The machine shop I use currently is after £1 per part, which isn't too bad I guess, but when you start multiplying this by hundreds, it soon adds up.

The part in question is only 24mm A/F and getting turned to 20mm round, but as it's stainless, to do little passes like that would take forever!

I'll give the hobby lathe a miss I think and I'll have a look at the Britan or Captstan you mention.

I also want one for doing prototypes, so guess the hobby machine would be ok for that, then leave the mass runs to the machine shop.

The one pictured is only £250 second hand and £700 new.
 
Why 304? Do the parts need to be 304? My experience with 304 has been horrible. I have machined few materials that were less cooperative. If possible, I would find a different ss grade.
 
Why 304? Do the parts need to be 304? My experience with 304 has been horrible. I have machined few materials that were less cooperative. If possible, I would find a different ss grade.

yea, the tube they're getting welded to is 304, so want to keep it the same throughout.

Did it chip or or just overheat and harden?
 
yea, the tube they're getting welded to is 304, so want to keep it the same throughout.

Did it chip or or just overheat and harden?

My experience was 20+ years ago with 304. As I recall, it work hardened easily, inserts chipped, drills burned up and taps broke. I will admit.....at that point in my machining career I may not have been using as good tools as are now available. I also may not have been experienced with speeds / feeds as I am now. However, it was such a nightmare I have avoided it ever since.
 
How about a Smart & Brown 1024?

One of the best small toolroom lathes ever made. I have one and am just a bit biased. However I wouldn't want to be making batches of hundreds on it. Not that you couldn't do it, it is just not suited to the job. A small reasonably tooled capstan would eat this job for breakfast and you could continue to make money with it on other similar work.
 
Small repetition lathe like a Britan or capstan e.g. Smart & Brown model L is the correct weapon for that sort of job. Just need to make sure the collets go up big enough. Correctly set-up a Britan will chomp those parts off about as fast as you can pull the handles and an L with lever op collets won't be that far behind. E-Bay is your friend, couple of Smart & Browns up right now that should do fine. Simple lever cut off slide is sufficient for your job but arguably its worth getting the normal cross and top slides too as then you can do a good deal of ordinary turning work.

Thing is your picture is a modellers lathe, a waste of time. You will die of boredom trying to do what you plan and it has essentially zilch capacity for 12" to the foot scale work.

Clive

M16 in S304 on a model L Clive ,are you sure? I've got one and although I haven't tried I would expect something to break ,perhaps yours is lower geared than mine.

To the OP If your supplier is doing a good job I would leave them to it but a S+B 1024 would make an excellent lathe for general use and prototypes.
 
Another vote for the capstan lathe, but in all honesty we would set up the screw machine for a parts run that size.

If you can find one at a fair price it is going to save you a lot of man hours if this is on going work.
 
Another vote for the capstan lathe, but in all honesty we would set up the screw machine for a parts run that size.

If you can find one at a fair price it is going to save you a lot of man hours if this is on going work.

If he's posing the question of whether or not that little thing is suitable for turning 304 (or anything really) I think there's some black bread to be eaten before he's ready to buy and set up screw machines ;).
 
If he's posing the question of whether or not that little thing is suitable for turning 304 (or anything really) I think there's some black bread to be eaten before he's ready to buy and set up screw machines ;).

Ya, but it is a far better tool for the job. I watched an acme gridley sell off for scrap price last week, prolly cheaper than his toy lathe would be new.
 
Well I've seen it all now

Q Should I buy this little Chinese POS

A No ,what you need is an Acme Gridley

Let's just hope he has a big garage.
 
That lathe is harbor freight...

I had one picked up for 299 on sale.

Chuck was repeatable and it was okay but lors of plastic.

It IS A TOY and it will do what you need this time but you will wish for something better.

The speed control is nice but the rest not so much
 
i'll make assumptions because i don't know exactly the operations....but basically you need to outsource the 100 pieces to someone with a real cnc lathe

1) that lathe is a POS that will make you mental

2) parts don't have to be complicated for cnc to make sense, production speed and the volume you need is why you want to cnc it

3) time = money. a proper cnc lathe will make in minutes what will take you an hour on that machine. removal rate depends on rigidity and HP

4) cutting 304 on that? hehehehe

5) making 100 of anything on that? you'll want to open a vein before you get to 50.

The real decision making isn't the cost of the machine vs cost of outsourcing, its the cost the machine + the time to make 100 vs outsourcing. I emphasize that a proper production cnc lathe might be 50x faster per part. ie cnc shop might charge you $70 an hour but it will take them 1/50th of time it'll take you on that lathe.
 
M16 in S304 on a model L Clive ,are you sure? I've got one and although I haven't tried I would expect something to break.

Frankly no I'm not sure of Model L capabilities as I don't have one myself and my only experience was in checking out and setting up one bought by a now deceased friend. It certainly seemed sturdy enough on test cuts and not uber fast but it was a chuck machine with no collets which may or may not make a difference. One things for sure there isn't enough money in the world to persuade me to pull and put back the countershaft and motor unit again. 'kin heavy and no space. Bleugh! However its irrelevant now I see that the OP needs to deal with 24 mm A/F material which is, I think beyond the collet capacity of all the small repetition lathes and bench lathe derived capstans.

Wouldn't write off the 1024 when it comes to this job. I've done a couple of similar jobs on my Mk2 VSL (batch of 20 and the customer paid a hefty quantity surcharge plus treble shop time for Sunday work), something around a couple of minutes per piece should be realistic once he gets into the swing. I gather there is a reasonable 1024 within pick up range for the OP so probably worth going through how I'd set-up to give him an idea of what else is involved beyond the basic lathe to go into "pretending to be a capstan" mode!

Needs Dickson QC tool post with four holders, coventry die head and dies, roughing tool, finishing tool, trimming tool, six position turret bedstop and cross slide setting spacer. Smart and Brown didn't make a 6 position bed stop but ones to fit can be found, no idea what make mine is as it was a no name "found" ages back. My basic setting is with the topside 25° from parallel with the cross slide i.e 75° on the scale and, obviously, the tool post set so one carrier will be perpendicular to the bed and one parallel to it. Cross slide setting spacer drops between the end of the cross slide and the flange on the dial assembly so that the cross slide can be bought back into position after parting off. Position defined by coventry die head which needs to be on centre line. Spacer can be anything roughly right as the topside has plenty of adjustment. Consider bonding a magnet into a recess on the spacer so it stays in place.

Turret bed stop settings give end of cut saddle travel position for :-
1) workpiece length, I usually use the parting tool as a stop to gauge how far to pull the workpiece out from the chuck.
2) roughing tool cut, roughing tool is set to give correct depth of cut in one pass with the cross slide pulled back against the spacer.
3) trim tool position to clean up flat under the AF as the roughing tool will leave a distinct taper
4) finishing tool stop, finishing tool is set to give correct depth of cut in one pass with the cross slide pulled back against the spacer.
5) die head stop
6) parting tool stop

Work sequence assuming starting with rough sawn bar which may not be square ended:-
Mount bar in chuck with sufficient projection to trim square.
Mount parting tool, set stop position 6, part off.
Move saddle back, set stop position 1, bring saddle to stop, loosen chuck, pull work forward to touch parting tool and tighten chuck.
Move saddle for clearance, replace parting tool with roughing tool, fit cross side spacer and pull slide back into position against spacer.
Set bedstop to position 2 and make cut. Either under power or hand feed for saddle, I usually rough by hand. Saves changing feed setting or hanging around at slow finishing feed.
Move tool away from workpiece, run saddle back to access the end and use the side of the roughing tool to put a small chamfer for the thread start.
Bring the cross slide back against the spacer, replace roughing tool with trimming tool.
Set bedstop to position 3, bring saddle up to stop and feed trimming tool in to clean up under the head. Ideally arrange things so that the cross slide spacer can stay in place.
Move saddle for clearance, replace trim tool with finishing tool and bring cross slide back against the spacer if need be.
Set bedstop to position 4, make cut under power with suitably fine feed for good finish. Tool tip radius needs to be such as to make proper blend under the hex head.
Move saddle for clearance, mount coventry die head and select back gear.
Set bedstop to position 5 and make rough threading pass with die head. There is a definite knack to hand feeding the saddle as the die head works to keep things engaged.
Run back, set die head to finishing position and repeat pass.
Move saddle for clearance, remove die head and fit parting tool.
Part off. I use a fine power cross feed setting, back gear with HSS tool or HSS turning speed with carbide tool.
Select direct drive and repeat until all parts done.

This sort of job you need to minimise futzing about so single good enough compromise speed and feed settings always beats shifting for optimum and avoids forgetting a shift when you get into the swing. How do I know!

I'd be using HSS tooling at around 100 rpm direct drive speed and corresponding back gear speeds with mist coolant. If running flood coolant a chuck guard is essential to protect against splatter. Right carbide tooling can probably work dry but I don't know what tools to recommend. Allow time to get all the coolant out from under the saddle when finished. A pain of a job on the 1024 but if left it will wreck the bed. Wipe way oil on after cleaning for protection. I use Hyspin AWS 32 as the basic lathe oil, Magna BD58 as way and drop gear oil and Rocol Ultracut 370 as coolant mainly 'cos RS deliver next day off my credit card. Ultracut is expensive at £100 for 5 litres but at 50:1 dilution is goes a long way and doesn't go stinky in the tank.

Limey and Forrest will now tell me I've been doing it all wrong.

Clive
 
Well I've seen it all now

Q Should I buy this little Chinese POS

A No ,what you need is an Acme Gridley

Let's just hope he has a big garage.


If you are tipping into manufacturing and are making 100 plus simple parts on a manual lathe on a regular basis your a noun from John Weldons lexicon.

Quite frankly I would rather suck start the largest handgun in my possession before I would do such an act.
 








 
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