Safety Turning

[Kpar]

I need some help, Whenever I'm machining High Tensile or S/Steel I get long strings of metal from the cutting tool. A couple of times they have wrapped around my leg if I don't keep pulling them off with long pliers.
Stainless is a real worry as it doesn't break away very easy.
I've tried different spindle speeds, feed speeds and several types of tool inserts. I do get better results if I grind up Hi Speed tools. Is there a trick in using insert type tools or is it the angle of cutting.
I'm always concerned that one will wrap around my arm or wrist causing seriously injury.
Kp

ar

 

[rklopp]

Sometimes it is impossible to break chips. Usually the best success can be had with aggressive feed per revolution and depth of cut about equal to the tool nose radius. The surface speed should be optimal for the material and tool. This is probably >300 feet/minute for most cases. Trouble is, home shop lathes have issues with rigidity and horsepower achieving these conditions. In addition, workpiece deflection can cause taper and difficulties hitting size. Stay away from moving chips or chips apt to be grabbed by the spinning things.

 

[Kpar]

So is this normal for home machining ?. Obviously I've got a lot to learn.
Kpar

 

[stevehuckss396]

On your roughing cuts, stop when the string gets to be excessive in length like a foot or so. then just continue for the next foot of swarf until you get to the end of the cut. Of course you will want to make the finishing cut continuous for a good finish. I just catch the end of the string and steer it down to the floor. My concern is keeping strings from getting grabbed by the chuck and wildly whipped around. As long as I can get them heading to the floor they are pretty harmless. The CNC lathe doesn't stop to clean up after itself so stringer management can be challenging but not impossible.

 

[goldstar31]

From the home lathe, the question does arise on how does one grind a kerf to make a chipbreaker.
There is little information for how it can be done in the average home workshop. Possibly the obvious purchase of inserted tool with moulded in chipbreakers moulded in.

I think that I will not be alone in trying to get an answer

Norm

 

[swood1]

I just stop and let the swarf break then continue cutting. Dont all people do this??

Steve

 

[k2steve]

I just stop and let the swarf break then continue cutting. Dont all people do this??

Only in the drill press

 

[XD351]

I have in the past used a piece of flat bar or an old rule as a chip breaker , i hold onto this with one hand and sit the end of the bar or rule on top of the cutting tool and i find if i use a sort of stabbing motion i can break the chip off at short lengths - most of the time !
Just be mindful of the chuck and any part of the workpiece that can catch the rule or flat bar and if you are in anyway concerned about safety don’t do it .

 

[goldstar31]

Apologies but I was referring to grinding a chipbreaker on the lathe tool which should avoid a long length of razor sharp metal.

Might I add that I have over the years bought unwanted lathe tools- from industry which have this ground in. These are of various metals i.e. hss or carbide. Again, I was at the Doncaster Show in the UK and came back with a 'presentation box' of assorted 8mm lathe tools with this feature. The Supplier was RDG Tools, the successor to Myfords.

I must mention that in all my years, I have never seen anything in relation to what I am mentioning now.

Regards

Norm

 

[swood1]

Hi Norm,

If I remember right it's quite hard to grind a chip breaker yourself on a standard grinder as generally the wheels are rounded off. When I was an apprentice the older boys used to grind them by hand on a surface grinding wheel if this helps..

Steve

 

[Ozwes007]

Stringing with Stainless steel is common as it is a malleable metal unless it’s overheated. Increasing speed with light cuts(remember your cut needs to be at least the radius of your tool plus a bit) ensuring that it remains cool helps. Stringing is common in steels that are not designed for cutting. Similarly super soft grade aluminium has similar issues, turns like std S/steel. When machining in industry we use grades designed for machining, there are excellent grades of machinable s/steel , aluminium and steel that produce chips not strings. However these will still string or curly grub if they are not cut at the right speed, feed and depth of cut combination. One of the most significant issue is the depth of cut. Make sure if you have a .4mm radius tool your cut is at least .4mm and your feed is at least .2mm per rev. (Good rule of thumb) small machines use .2mm radius, because of lack of power. Once you have that you can move your speed up or down to give the chip you want. Using HSS I always use a chip breaker cut in with a 1mm cut of wheel or a small diamond drill(3mm glass drills are excellent for this and cheap) if using a radius tip to put a small dimple inside the radius of the tool.

Hope this helps. Btw, try using 1045 or 1040 grade steel for bar stock, cuts well, is hardenable. Use t4 and above grade aluminium to control chip(don’t use t3 grades, way to soft)

 

[holmes_ca]

If you have a Dremel tool and some diamond shank bits, and if you are careful, it is possible to grind a chip breaker on a hss or carbide toolbit,

 

[Andy Munns]

When I did this at tech college (40 years ago at TAFE in Oz) they supplied hand made hook tools in 6 mm. rod to hook out the spirals and direct them away. We train never to use fingers for this task, but see it a lot. Again, the trainers with a lifetime in industry and training told us to stand clear and hit remote stop switches when things went wrong. Need to make the tool first and not rely on something makeshift second. The other rule is never start a machine unless you can stop it - Mainly applies to diesel engines, but before starting, ask "how do I stop the lathe if I can't get near it?"

 

[nel2lar]

I'm in with holmes_ca , I use my dremel tool to cut a straight line about .250 long and about .125 deep, then angle toward the cutting edge. As the metal goes down it hit a stop and as small as it is usually breaks. I would rather get sprayed with brass the stringy chips.
Nelson

 

[blanik]

I have a small Sieg (SC4-550) Lathe, which, as mentioned elsewhere in this thread, is typical of most small lathes in not having the power or rigidity to run a sufficiently high feed rate to chip break stainless steel and similar troublesome materials. In an effort to improve this situation, I borrowed a technique used by Keith Fenner (https://www.youtube.com/user/KEF791/videos). When Keith machines cast iron, in order to prevent the chips from spraying all over the place, he inverts the cutting tool, and runs the lathe spindle in reverse. This results in a nice stream of cast iron chips going straight down into the chip tray.

So, I thought I'd try this technique when machining stainless. Inverting the cutting tool also means raising the tool up in the tool post to get the tool back on centre. I used an appropriate sized piece of key steel sitting on top of the QCTP to hold the tool holder high enough. Running the lathe spindle in reverse, also requires fiddling with the lead screw gearing (no tumbler on this lathe) to reverse the direction of lead screw operation.

The result is still long nasty lengths of stainless steel swarf - but at least the swarf is directed down into the chip tray.

You'll find Keith Fenner's explanation and demonstration of this technique (on cast iron) at , commencing at the 17 minute mark, if you don't want to watch the whole lot. Unfortunately, I don't have any video of the technique in use on my lathe machining stainless - if I get time when I get home from holidays, I'll chuck up a bit of stainless and record a demo video.

Regards,

RoyG

 

[john_reese]

If using carbide inserts purchase those with a chipbreaker for light finishing. Attempt to run them at the manufacturers suggested feed rate. Depth of cut should be no less than the nose radius. If the chips do not break try a higher feed rate. Most hobby lathes probably lack the power or rigidity to pull this off.
If all else fails do what swood1 said and interrupt the feed periodically to break the long string.

It takes a bit of trial and error to find the sweet spot, even on a lathe large as my 16". Even then, changing the diameter you are cutting can knock you out of that sweet spot.

 

[BIGTREV]

I have a small Sieg (SC4-550) Lathe, which, as mentioned elsewhere in this thread, is typical of most small lathes in not having the power or rigidity to run a sufficiently high feed rate to chip break stainless steel and similar troublesome materials. In an effort to improve this situation, I borrowed a technique used by Keith Fenner (https://www.youtube.com/user/KEF791/videos). When Keith machines cast iron, in order to prevent the chips from spraying all over the place, he inverts the cutting tool, and runs the lathe spindle in reverse. This results in a nice stream of cast iron chips going straight down into the chip tray.

So, I thought I'd try this technique when machining stainless. Inverting the cutting tool also means raising the tool up in the tool post to get the tool back on centre. I used an appropriate sized piece of key steel sitting on top of the QCTP to hold the tool holder high enough. Running the lathe spindle in reverse, also requires fiddling with the lead screw gearing (no tumbler on this lathe) to reverse the direction of lead screw operation.

The result is still long nasty lengths of stainless steel swarf - but at least the swarf is directed down into the chip tray.

You'll find Keith Fenner's explanation and demonstration of this technique (on cast iron) at , commencing at the 17 minute mark, if you don't want to watch the whole lot. Unfortunately, I don't have any video of the technique in use on my lathe machining stainless - if I get time when I get home from holidays, I'll chuck up a bit of stainless and record a demo video.

Regards,

RoyG

 

[BIGTREV]

Lots of great practices to be learnt from Kieth Fenner

 

[doc1955]

Even with a proper ground chip breaker tool you need to keep the feed rate up and most likely if you are going for a finish cut you will not achieve it. On heavy cuts with the proper feed no problem so on the finish cuts you just need to be careful. I keep a chip hook handy and a pliers to direct the chip as Steve mentioned to the floor (and nice chip nest Steve lol).

 

[Wizard69]

Your concerns about the safety issues with stainless are right on but this can also happen with other alloys of steel. These long length of dwarf can mutilate a hand in a milli second. The worse is catching you in such a way that you get pulled into the lathe and die a very painful death! So do experiment with various chip breaker approaches. If they don’t work you have to manage breaking the chips your self. The most common ways have already been covered but the over riding safety principal is never to put your hands or other body parts in harms way. Further always stop the lathe to remove large build ups of stringy dwarf. Always!

By the way this stuff if it gets caught by the chuck can fly around and do a number on your face or neck. You need to worry about all parts of your body.