New to Practical Machinist

[ThisOldEnco]

Howdy everyone, I am new to the Practical Machinist forum and wanted to introduce myself and explain a few of my interests/current machining predicaments.

Originally I took to machining as a hobbyist, with access to a shop on the weekends where I could tinker with different machines that always interested me as a kid. Now I am a mechanical engineering student, and I find myself in the shop machining parts for mask-making lines (thanks to this pandemic). The shop I have acquired was equipped with a brandless import style mill as far as I can tell, a wobbly drill press, some miscellaneous presses/torches, and an Enco lathe that is in surprisingly good condition. I have had great success with machining parts on this lathe, though primarily in aluminum and occasionally mild steel. I have not acquired many new tools, as a large amount of tooling for the mill and lathe was left behind when the shop was abandoned before me. This is mostly high speed steel cutting tools, which are the tools for the job because they are the tools I have.

Almost all of my parts are designed and simulated in Solidworks, before being made in the shop, and I am wanting to experiment with different materials. Due to the requirements of the companies I am working with, I am trying to make parts from 4140 alloy steel. I have never worked with this material, though I have some samples that I would like to experiment with. Have people had good results with high speed steel on this material? Or should I invest in some carbide insert tooling? Looking for some general advice and recommendations on how to approach this forum.

Glad to be here,
ThisOldEnco

 

[Milland]

Get some carbide tooling, but given that you're likely horsepower and machine stiffness limited, don't expect miracles. Try starting out with faster RPM and feeds, but lower depth of cut to get performance from carbide.

As you get some experience you can increase depth of cut, but try not to start slowing the machine due to load - back off depth if this happens, or if chatter results from the cut.

Good to hear you're working on mask production, now all you have to do is convince a large part of the country that they should wear them...

 

[ThisOldEnco]

Good to hear you're working on mask production, now all you have to do is convince a large part of the country that they should wear them...

That does seem to be the only issue doesn’t it... and thank you for the input! I will let you know how my experience goes after playing with the machine speeds and feeds a little.

 

[wippin' boy]

soon the haters will show up and do there thing because you don't already know the answer to the questions you ask
try to ignore them, there are many helpful and highly skilled people here.

 

[dgfoster]

. Due to the requirements of the companies I am working with, I am trying to make parts from 4140 alloy steel. I have never worked with this material, though I have some samples that I would like to experiment with. Have people had good results with high speed steel on this material? Or should I invest in some carbide insert tooling? Looking for some general advice and recommendations on how to approach this forum.

Glad to be here,
ThisOldEnco

There is one more choice you did not mention—-brazed carbide cutters. If you are doing simple facing and turning, a sharp carbide tool will outlast a HSS cutter and will allow much higher SFM. Simple brazed cutters available from various “cheap” suppliers may often be made from decent carbide but will arrive in a not actually sharp condition so they will not perform nearly as well as they might. If you get a decent diamond wheel to sharpen them on and a set of diamond files, you”be able to make them work a lot better. The difference between a sharp brazed carbide and an as-supplied cutter is significant.

4140 PH is probably what you are using. It cuts beautifully with a sharp cutter, a moderate nose, a fairly high speed. In the annealed condition it cuts OK but you’ll like cutting it prehard at around 28 to 32 Rc. Prehard can also be cut just fine with HSS, just considerably slower.

Flood coolant or a mister can also make life a lot easier. There are folks who tout mist and those who hate it. It works, is non-toxic, and not messy. Cooling options have been discussed many time at lengthen this forum. Searching via Google will turn up some interesting thread. There are also drip lubricant adherents. All have pluses and minuses.

Good luck with your masks. You will be providing a very useful product.

Denis

 

[ThisOldEnco]

There is one more choice you did not mention—-brazed carbide cutters. If you are doing simple facing and turning, a sharp carbide tool will outlast a HSS cutter and will allow much higher SFM. Simple brazed cutters available from various “cheap” suppliers may often be made from decent carbide but will arrive in a not actually sharp condition so they will not perform nearly as well as they might. If you get a decent diamond wheel to sharpen them on and a set of diamond files, you”be able to make them work a lot better. The difference between a sharp brazed carbide and an as-supplied cutter is significant.

4140 PH is probably what you are using. It cuts beautifully with a sharp cutter, a moderate nose, a fairly high speed. In the annealed condition it cuts OK but you’ll like cutting it prehard at around 28 to 32 Rc. Prehard can also be cut just fine with HSS, just considerably slower.

Flood coolant or a mister can also make life a lot easier. There are folks who tout mist and those who hate it. It works, is non-toxic, and not messy. Cooling options have been discussed many time at lengthen this forum. Searching via Google will turn up some interesting thread. There are also drip lubricant adherents. All have pluses and minuses.

Good luck with your masks. You will be providing a very useful product.

Denis

Thanks for the info. Is there a big difference in performance with brazed carbide as opposed to insert tooling other than cost?


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[Mike1974]

Thanks for the info. Is there a big difference in performance with brazed carbide as opposed to insert tooling other than cost?


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Probably not on a manual lathe. On a cnc lathe, yes, worlds!

 

[dgfoster]

Even on a manual, insert cutters can, for example, allow me to rip off a lot more metal with better chip control than a brazed cutter. So, inserted cutters can be very advantageous. I am not putting brazed over inserts. But brazed cutters have a place and I use them half the time and inserts half the time. If I knew more about inserts (there are mind-boggling variations suited for endless material types, finish requirements, variations in basic lathe reigidity and power) I would porbably use them more and to better advantage. My main point was to try brazed carbide and learn to sharpen it well. I have had occasion to modify brazed cutters to do some oddball cuts quite handily.

The main way I sharpen and shape brazed carbide is offhand on a diamond wheel mounted on my surface grinder. Where angles are more critical, I mount the cutters in a smallish tilting vise and use the surface grinder as intended. A good diamond wheel eats carbide pretty fast and leaves a very fine finish. (Green wheels are the absolute pits, literally and figuratively---do not even think about using one)

Denis

 

[CarbideBob]

Yea 4140.
Love it and come in flavors , dead soft and PHT or 4142 .
HSS works all fine in dead soft, Carbide in the harder but HSS will work if you back way off the speed.
In carbide, chip color, comes off clean and goes to straw and blue as it sits once cut.
HSS stay away from color in the chips, Straw is okay.
Hot roll of course some rock hard scale skin and that dealt with in many ways.
Dead soft Hot 4140 my favorite stock. Predictable and stable. It goes where it should go and takes heat treat nicely.
Bob