Thread: Chip control in stringy material with HSS

Hi Bryan
Have you tried clamping an interrupter on the tool post. The best way to describe it is another bit of high speed steel to act as a chip breaker on top of your turning tool.

Phil

Phil, no I haven't, but I like the idea. Will think about how to implement it if I tackle this material again. I did grab a fresh stick and make a more serious effort to copy the tool shown here: Easy HSS chip breaker - Practical Machinist. Still no breakage, but coiling in a much more predictable way, and I was able to get the job done with a lot less stress. I found it would coil away cleanly until the end caught on something so it couldn't spin anymore. Then it would start to wrap around the tool. By letting it get to 6" or so then pausing the feed to force a break the snarls were kept to a minimum. The stop-start feed didn't do a lot for the finish though, so a self-breaking chip would still be preferable.

My brother in law brought me a slab of 6 inch round bar to machine a trolley jack saddle. He bought the jack cheap as a second from super cheap and then got the slab cut from work but didn't know what it was as it had been there for years. I only did it because he had done me a few favors in the past but it really wasn't worth the effort. I think he thought it would be an easy job to machine 150mm down to 30mm.

It took me hours to machine because of the stringy chips like you have and I ended up only just fitting them in a wiz bin because they where so long and thick. From memory I ended up holding a screw driver behind the tool to help curl them and had to interrupt the cut constantly. I also had a pair of wire snippers in the other hand to pull and cut them off. I ended up with swarf all over the floor behind me by the end.
Not much help but at least you know your not the only one that goes though this. LOL

A few months latter there was a recall on his model jack so I told him, but he kept it. The saddle was worth more than the whole jack with the time I put into it.

Dave

Bryan,

A short while ago I made a couple of drawbars from 4140 which involved reducing a 150mm long section of 38mm bar to 13mm. I used a Kennametal insert suited to low powered turning and was able to turn off 3mm per pass at about 1500 rpm and wth a moderate feed. The swarf was a continous wire, close to lethal in nature. Easily cut down to the bone. It didn't break and to prevent it balling up and jamming I donned rigger's gloves and reeled it in like a fisherman into a bin. The gloves were covered in myriad slashes and I was soaked in sweat. Not an experience I wish to repeat in a hurry. Great finish on the bar though. The topic of inserts and their suitability has been discussed ad infinitum and won't be here.

Can you please post details of any progress you do make with an add on chip breaker or ground groove? I am keen to find an alternative to the above.

BT

Bob what sort of chip did you get when you reduced your DOC and increased your feed rate?

Originally Posted by pipeclay

Bob what sort of chip did you get when you reduced your DOC and increased your feed rate?

A thinner, still lethal wire and a sh...y finish Peter. I fooled around with different speeds and feed rates. I have the high speed pulleys on the little Hercus and the thing whips along but so do all the feed rates. I tried hand feeding, backing off as Bryan did to break the wire, but with the amount of metal I had to remove I would have been there all day. The 4140 was coming off blue, melting the paint on the saddle and burning my hand.

I need to pull my finger out and grind some HSS cutters to limit the variables. Carbide geometry and grades are a minefield.

BT

Bob that sounds like a barrel of laughs. Hate to think what would have happened if the wire had somehow snagged on the chuck.

Pipeclay, with the first tool, increasing feed, regardless of cut, seemed to thicken and straighten the chip out, which was worse. The second tool was much more forgiving, tending to coil regardless. I will get a pic later of that tool.

Edit: Sorry, I thought that question was for me.

I can think of more relaxing hobbies!!

I reckon my adrenal gland gets more of a hammering now than when I was a young bloke with 9 motorbikes.

Maybe you should have treaded the swarf through the runners on a fishing rod and wound it onto the reel.
Imagine what your other half would think if she walked in the shed at the time.
Then her telling your friends that you don't even go out to go fishing, and do that in the shed as well.

Dave

Originally Posted by Dave J

Maybe you should have treaded the swarf through the runners on a fishing rod and wound it onto the reel.
Imagine what your other half would think if she walked in the shed at the time.
Then her telling your friends that you don't even go out to go fishing, and do that in the shed as well.

Dave

I don't reckon I could have wound the reel quick enough Dave.
The only satisfaction I derived from that stunt was using the finished product .

After reading about some of the problems associated with long & dangerous curly chips, I just set up a piece of 3/4 " dia mild steel & did a few trials.
The speed was 530 RPM the depth of cut 3/16' & feed rate .004" per revolution.
The toolbit was HSS & one I have used succesfuly for eliminating long stringy chips.
The photos describe the toolbit,& the short curly chips produced, no problems.
More details on the grinding of these types of toolbits are shown on page 21 of The Textbook of Turning by P.F Hercus.
I did not have any 4140 steel to evaluate, & it would be interesting to try it.
regards
Bruce

Hi Bruce,
I don't have any problems turning mild steel, but what ever that stuff was my brother in law brought me was a mystery, which sounds like the stuff Bryan is machining.
To get it down I was taking 3mm deep cuts and a few times at the start I had to get out of the way and shut the machine down so I didn't get cut up by the thick ribbons. By the time I had the tooling and technique down the job was almost finished.

Dave

Originally Posted by Abratool

After reading about some of the problems associated with long & dangerous curly chips, I just set up a piece of 3/4 " dia mild steel & did a few trials.
The speed was 530 RPM the depth of cut 3/16' & feed rate .004" per revolution.
The toolbit was HSS & one I have used succesfuly for eliminating long stringy chips.
The photos describe the toolbit,& the short curly chips produced, no problems.
More details on the grinding of these types of toolbits are shown on page 21 of The Textbook of Turning by P.F Hercus.
I did not have any 4140 steel to evaluate, & it would be interesting to try it.
regards
Bruce

Would you like me to post you some Bruce?

Originally Posted by Anorak Bob

Would you like me to post you some Bruce?

Thanks for the offer Bob.
Yes, I would be pleased to get a piece so that I could run a few trials.
I just read about your very testing job on the dividing head, & perhaps if all else fails it might be worth following what Stuart suggested, in setting the head up in the same position each time. Years back an old Toolmaker, said to me "Son, you will spend your life chasing the flowers on these micrometers" I have often thought how true that can be.
Some of these jobs just increase the frustration, & blood pressure to an undesirable limit.
Sounds hot over in your part of the world.
regards
Bruce