Carbide tip parting on Sieg C3 lathe

[Nyrup BoeghParticipant @nyrupboegh48678]

Hi

Yesterday I ordered some turning tools from Arceurotrade from the "new" cheep series in the catalog. All with the 8mm shank.

I was a bit hesitant in ordering the parting blade (with the 2mm GTN2 insert) and holder, but finally decided to order it.

But the doubt is still nagging me: Does it work on my small Sieg C3 lathe or will the result be chattering away and biting at me… ?

Nyrup

[Nyrup BoeghParticipant @nyrupboegh48678]

[Bob StevensonParticipant @bobstevenson13909]

I part off quite ok on my Chinese mini-lathe byhaving theparting tool upside down and running the lathe in reverse…feed the tool in gently with frequent withdrawlsto clear swarf etc

[john carruthersParticipant @johncarruthers46255]

Do let us know how it goes? I was tempted too.

Cross post; exactly what I do Bob.

Edited By john carruthers on 12/03/2016 08:35:35

[HowiParticipant @howi]

The C3 will be more than capable, be brave allow the tool to cut, you will be surprised just how good they are.

[David ColwillParticipant @davidcolwill19261]

I have a C3 and find it to be a very capable lathe but….. The way the saddle is held to the bed is rubbish. Clearly some are better than others because some people can part off with no problem. I couldn't so replaced the existing arrangement with a tapered gib. this has improved things no end. Also there is no saddle lock as standard and this is another mod well worth doing especially if you want to part off.

A good but not infallible test is to grab the toolpost with one hand the bed with the other and see how much you can move the saddle by pushing in the direction of the cross slide. If you are happy that it is pretty solid you should be good to go.

Regards.

David.

[Ketan SwaliParticipant @ketanswali79440]

Hi Nyrup,

I believe that you ordered 060-325-22208 from this page.

After reading your post, I carried out some rough and ready tests on SC3 – Brushless Motor – belt drive mini-lathe. Usual disclaimers apply. Sorry in advance for failing to follow certain principals.

– Half Nut locked down on leadscrew – lever set to neutral, made sure the top slide was not loose – taking out any slack by adjusting the gib screws. Used the 000 QCTP and holder as it was already in place from another experiment. Adjust the blade to the centre or perhaps just below. 25mm diameter bars stocks used for steel, aluminium, and cast iron.

Parting off steel: Start off speeds needed to be played about with, and initial sounds we not so good.

Speed reads 340 rpm. Picture taken upside down. Coolant applied at various stages with a small paint brush. Probably didn't need it. After getting about 5mm into the cut, the sounds settled and parting got easier.

At this point I got a bit 'over-confident' and luckily the GTN2 insert just fell out of the blade. Couldn't figure out how to put it back in, so asked JS for advice. 'Hit back in' with nylon/rubber mallet:

Job done, back to parting off the remainder. Figured out that I had not quite got the tip to line up with the center. Still parted off:

Aluminium: After conducting above test, proceeded to part off Aluminium, initially at around 1,300 rpm:

Liked the sounds at this speed, no need for coolant, so increased the speed to max. 2500 rpm just to see what would happen:

Confetti time. Not really recommended unless you also wear a face mask, but looks and feels really nice:

Cast Iron: I must have some really dirty stock of this, or, this stuff really behaves badly, or need to play more with this, perhaps adjusting tip height, speed. Proved to be a pig to deal with at around 300rpm, so increased to around 670rpm:

It was going reasonably at this speed, but very slow feed, and then the tip broke, possibly because I was a little nervous and failed to keep constant feed, resulting is some welding:

Didn't have time or chance to play with brass, but I am sure that it will behave similar to aluminium.

In short, was happy with results from first time experimental tests. Results may be different on different mini-lathes which have hi/low gear drives, and speeds will need to be played around with on such machines. Also, experienced users will have their own methods and get their own results. The guard was taken off for the purpose of taking pictures. Short videos were also taken on the phone for own reference. No time at present to put up on You Tube. If people want, will be happy to do so when I have some time.

Ketan at ARC.

[John FieldingParticipant @johnfielding34086]

I am not too familiar with the lathe mentioned but it looks to be a bigger version of the mini-lathes. The limitations will be a) lack of rigidity and twisting of the bed under big cuts, b) insufficient spindle power to drive a tool with big cuts, c) lack of saddle lock is definitely going to be a problem, d) slides are probably not able to resist big cutting forces.

On my Myford Super 7 parting off was still an issue even after tinkering with all the slide and bed adjustment to eliminate slack, until I bit the bullet and invested in the optional rear parting tool post. What a revelation! I had promised myself one day I would get one. On a trip to the UK I finally visited the Beeston factory and exchanged a lot of money for the item. Arriving back home I fitted it and I was gobsmacked how easy it was to part off things I would never have thought possible before. Before 1-inch BMS was about the limit, now 2-inch was a walk in the park. On ali bar 4-inches didn't even raise a sweat. The length of the parting tool blade was the final limitation on the diameter for ali bar. I can just manage 6-inch but the blade sticks out a little more than I like, but the blade doesn't seem to mind.

The secret to parting off are to lock the saddle, make sure all the slides are correctly adjusted and to work as close to the head stock chuck as possible. It goes without saying that the work must be held very tightly in the chuck, so a 4-jaw chuck is much better than a 3-jaw chuck. Keep the feed on as hard as possible without crowding the lathe and use floods of coolant, except cast iron which works best when cut dry. Use low speeds when parting off for maximum torque. On a lathe with a fancy variable speed drive I think you will be limited with the torque but on a geared head or belt driven lathe slow speeds are torque multipliers!

In my appie days I spent 3 months at the English Electric Napier Works on the East Lancashire Road in Liverpool at the government training school and I worked on everything from a little Boxford up to a WW2 Dean Smith and Grace monster with a 8-foot long bed and a 18-inch chuck. That lathe would part off 6-inch diameter steel bar like a hot knife through butter, it was, despite its age and hard life in the munitions factory during the war, a very solid machine with a huge motor and it had self act on the cross-slide to boot. So knock the cross slide drive on and stand well back as the blue ribbons of steel came at you at a furious rate of knots.

[Russell EberhardtParticipant @russelleberhardt48058]

Could one of the problems be the overhang caused by the use of the QTP? The cross-slide/top-slide arrangement is designed to take high downward forces, however with the tool much nearer to the chuck than the centre of the cross-slide there is a high twisting moment which isn't well supported.

I have similar problems with heavy parting cuts on my Atlas if using the QTP. I use the QTP for light parting but for heavier parting I use a tool block with little overhang. There were some advantages to the old lantern type toolpost!

Russell.

[John Stevenson 1Participant @johnstevenson1]

Can't comment on using a C3 lathe but I recently bought some of these tools off Ketan to upgrade my parting off tools and have standardised on the 2mm wide blade.

I bought a couple of the blade type holders as shown above and have found them very good. Also bought two 16mm clamp on type holders and a 12mm clamp on type holder for the small CNC lathe which is a bigger than a C3, more Boxford sized.

This has highlighted more what I put in a post previously in that cutting tools are advancing at a rate that machines are not.

We can now use far higher speeds than before but still limited by low speeds on machines and the mangle gears on the end for screwcutting and fine feed.

I chose the clamp on type tool as with the tip securely fixed in all planes you can profile with the same tool, the blade type is limited to do what it says on the tin, part off in one plane.

Even the CAD/CAM people are getting wise to this and making it so certain tools can profile in a groove scenerio.

By next problem is that on small non ferrous materials that the CNC lathe is ideal for, top speed whilst being at 2,400 top is nowhere near fast enough for modern tooling.

According to what the manufacturers say as regards materials and feed per rev I really need about 9,000 revs on this lathe. Even 5 years ago if you said you were parting off at 9,000 you would have been ignored.

But what it means is that a quite complex part that currently takes 2:50 to produce can be done in 0:35

OK I know most are not in a production environment but this is one aspect of modern technology filtering down to normal users, even if you don't get to use the technology you often share in it by buying items at reduced cost due to savings.

One example is that in bulk I am buying laser cut parts cheaper than 5 years ago even though steel, believe it or not has stayed pretty constant for bulk buyers.

[Ketan SwaliParticipant @ketanswali79440]

Few points to make:

– On the SC3, there is plenty of spindle power/torque, and I didnt find this to be a real issue with the 25mm bar stocks.

– Rigidity – mostly reasonable for what it is, but would agree to a point about reduction in rigidity due to lack of saddle lock.

– Overhang due to QCTP is a good point. Would have been a lot better to hold in original tool post. I just used the QCTP as it was already on. Perhaps should have considered removing it and replacing it with the original post which could have improved ridity too with far less overhang.

Still was happy with the results (except for cast iron) on 25mm diamenter.

Ketan at ARC.

[Neil WyattModerator @neilwyatt]

My mini-lathe is happy parting, or at least grooving, up to 2" diameter – I suspect a full 1" tool overhang might be a bit too much. I think the stock in the image below is 1 1/2".

Problem with your approach, John, is I can't wind the cross-slide handle fast enough!

Neil

[John FieldingParticipant @johnfielding34086]

Hi Neil,

Buy yourself a cordless drill and make an adapter to fit the cross-slide handle

Ketan,

I am surprised you are having difficulty with CI, it is one of the easiest metals to groove and part off.  Maybe the top rake isn't suitable on that carbide insert?

Edited By John Fielding on 14/03/2016 12:19:07

[JasonBModerator @jasonb]

Ketan, you may want to check that the tool blade is at right angles to the lathe axis, that penultimate photo shows a badly marked side to the blade holder which could be due to it rubbing. All the photos look like it is pointing in towards the headstock, maybe the forces have pushed the toolpost round.

 I have a similar tool from another supplier that is 3-4 years old at least, often used and the black coating is barely marked.

J

Edited By JasonB on 14/03/2016 12:41:40

[Ketan SwaliParticipant @ketanswali79440]

You are right Jason…. It was rough and ready testing securing of the QC Tool post. Didn't use a square to square it up properly.

Ketan at ARC.

[AjohnwParticipant @ajohnw51620]

Personally I suspect that problems people have with parting off are often down to themselves. I'll even throw in Myford owners that have to use a rear parting off tool into that. I didn't need one on a well worn ML7. I wonder why.

John

–

[John Stevenson 1Participant @johnstevenson1]

Posted by Ajohnw on 15/03/2016 10:55:41:

I didn't need one on a well worn ML7. I wonder why.

John

–

You never used it ???

[AjohnwParticipant @ajohnw51620]

Posted by John Stevenson on 15/03/2016 11:00:12:

Posted by Ajohnw on 15/03/2016 10:55:41:

I didn't need one on a well worn ML7. I wonder why.

John

–

You never used it ???

A fair amount actually John. I do remember shortening a couple of bolts where I had to accept that it was going to be noisy.

John

–

[John FieldingParticipant @johnfielding34086]

Hi Ajohnw,

The rear tool post was also to speed up work. With the old 4-way Myford tool post it made things slower to have to change tools before parting off. With the rear parting tool post it was always ready and if it got in the way I just remove the QCTP slide bit and popped it back on when I needed it. Now I have a QCTP for the front I probably wouldn't buy one for the rear. The parting off nightmare was also to do with the saddle slides. I didn't realise at the time the real problem was the previous owner had the bed ground and didn't get the saddle done to suit, so it was real rattle and clank. The rear tool post hid that error but now it is fixed properly so no more dramas!

Having a 4-way front tool post on a small lathe is often too clumsy when working on small stuff, the unused tools always seem to get in the way, so the new front QCTP is a much better option.

[AjohnwParticipant @ajohnw51620]

The rear parting off tool has been used on lots of lathes. Convenience especially for batch type work.

The slides are the problem on Myford 7's. The rear tool causes the saddle to lift up and there is usually less wear on the underside of the rear rail which helps but it also pulls up the dovetails which helps even more. Keep an even feed at a sensible rate and all's ok. Personally I feel some of this is down to how people set them up and on other lathes as well. The main problem when parting off with my ML7 was headstock bearing wear as I more or less fixed the rails problem but the feed had to be enough to keep the spindle up and hard into the wear.

I also had a Raglan. Same design of bed, some wear, enough to cause a bothersome taper and not so critical. I suspect that may be down to the width of the rails especially when Myford used the front rail as a narrow guide. Raglans are rather good lathes and well worth restoring. I did get as far as finding some one to regrind the bed strips but hadn't replaced the headstock bearing and one was scored. I assume that they would be a standard sizes. It's hard to be sure. Boxford for instance have used odd ball sizes on some lathes but it's possible to fit a standard one.

Lathes co reckon the detachable bed strip grinding isn't on. Some people clocked up the unworn part for me on a grinder for zero error, sub a 1/10 thou from measuring them and cleaned up the outer edge. The lathe lined up perfectly when I knocked the existing dowels back in. Damp and cold moved me into the house so it had to go.

Atlas is another one. I did buy some bits of an Atlas owner and he didn't have myford problems and pointed out that he could replace the bearings and had. He did very good work. I'm not sure how available bearings are now. I think lathe co give numbers.

I also bought some bits of a Super 7 owner who did very good work. The machine was carefully selected from several when he parted company with the people he worked for. Same some one else with this amazing colchester triumph. Even if well made people should realise that they vary.

John

–

[John FieldingParticipant @johnfielding34086]

Hi Ajohnw,

Yes I agree, it is largely down to getting the machine fettled to near perfection.

One benefit of the rear tool post for parting is the way the cross slide dynamics come into play. With a front parting tool if the cut starts to dig in the tool gets dragged a little lower and aggravates the problem. This means if the tool is even a fraction high of the centre line it increases the depth of cut and then things can happen very quickly. If the parting tool is smack on the centre line or a td lower than the problem isn't as severe. It is better to set the tool a fraction lower so if it does start to dig in then it deflects away from the material and reduces the depth of cut enough to continue. The problem is that the tool can spring a bit, you cannot have an absolutely rigid tool!

On the rear tool post the dynamics are reversed. The material is now rotating away from the parting tool tip and if the tool starts to dig in it gets pushed away (upwards) so reducing the depth of cut. As you mentioned the way the slides react to different directions of thrust have a lot to do with it, but generally with a rear parting tool even a fair bit of slop isn't as serious as when using a front parting tool.

Many years ago I helped a friend sort out a real basket case lathe he had purchased. It was a toy really, tiny with not much cast iron in the bed and I didn't expect it to be great. We devised a method of measuring the twist in the bed with a couple of DTIs and a hefty piece of steel bar bolted across the top of bed and used it as a lever to twist the bed using a spring balance to measure the pull applied. Torsional stiffness measurement the textbooks call it. With only 30kg pull on the lever of one foot the bed twisted 20-thou! But I would expect that as the lathe was a baby and not well endowed in the metal thickness.

[Neil WyattModerator @neilwyatt]

> With only 30kg pull on the lever of one foot the bed twisted 20-thou!

So that's 2.2×30 x 12 = 792 lb.ins of torque

I assume your lever was attached near the tailstock end?

Torque (lb.in) = 63,025 x Power (HP) / Speed (RPM)

So a typical small lathe with a 0.5hp motor working hard at 500 rpm:

63,025 x 0.5 /500 = 63 lb.ins of torque MAX.

Assuming a liner deflection to torque relationship that means less than a thou movement at full power and the cut being taken art the far end of an unsupported workpiece. 2.5 kilos would have been a more realistic test than 30.

In the real world finishing cuts are taken at well below the rated power (reducing torque) and long work is likely to be supported with a steady or a tailstock centre (reducing the distance . over which twisting forces can act, reducing the deflection).

I doubt that the user of that small lathe would notice any effects caused by twisting of the bed under a cut.

[Nyrup BoeghParticipant @nyrupboegh48678]

Hi

Thank you to all participants in the debate of the subject.

I have now managed to get a little time in my own workshop and tried the tools I ordered from Arceurotrade.
They worked very well indeed.
Yes, there were some chatter from the 2mm parting tool, but it realy didn't matter.
The small aluminium thread-bushings I was making parted off verry well.

When I part off on lager lathes (Colchester, Victor, Weiler and Haas CNC) I keep the rpm in the range of 300-800rpm. I did the same on the Sieg C3 minilathe.
Also – as mentioned by an other participant – the tip should not be above center hight
but rather a bit below centerhight.

Regards,
Nyrup

[AjohnwParticipant @ajohnw51620]

I've been playing with a mini lathe recently. One factor I have noticed is that even when turning once chatter starts it may not be possible to get it to go away. The reason for that chatter was too deep a cut for the style of tip that was on but I doubt if my boxford would notice as it was only a little too deep. Just spoil the finish.

It has a saddle lock, I suspect that the chatter is mostly down to the whole saddle bouncing around. The main problem is likely to be the fit of the guides on the underside of the rear rail as the front prismatic V should look after itself. That''s the whole idea of the arrangement plus that it can give generous wear areas.

John

–

Edited By Ajohnw on 03/04/2016 11:09:57

Edited By Ajohnw on 03/04/2016 11:10:29

[HopperParticipant @hopper]

A mate of mine uses carbide parting tool in his generic C3 mini-lathe to turn 2mm wide and 2mm deep grooves in the outer race of 50mm OD roller bearings. Seems to have no problems with it.

[Author]

Posts