I was just wondering if anyone has any tips on making a finishing cut on EN8 alloy steel. I've just made a shaft up and I was not impressed with the finish I was able to get. Initially I thought the new carbide tips I was using were different as I don't remember having this problem last year. I've just stuck a bit of 50mm mild steel in the lathe and while the finish is better it is not as good as previous work done. Do the tips make a significant difference? I am going to try to find a bit of HSS and give that a try.
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Tips and tool types can make a big difference, is centre height ok. Could try reversing the feed towards tailstock, if it cuts theres movement.
For instance when I am idle I can still leave as good a finish as preferred tool and tips even with several decent neutral parting tools on EN8 and harder.
For instance when I am idle I can still leave as good a finish as preferred tool and tips even with several decent neutral parting tools on EN8 and harder.
shenion
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I have several different carbide inserts. There are many factors that effect the finish:
I find inserts with a chip breaker and a relief angle work bets for good finish.
- tip radius
- coated vs uncoated; there are many differnt coatings
- quality of the carbide
- difference in lead, relief, rake and top angles.
- chip breaker (also creates a rake angle.)
I find inserts with a chip breaker and a relief angle work bets for good finish.
BrokenBiker
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I tend to use HSS for anything when I want a really good finish, but I did have some decent carbide inserts with a 0.8mm rad that did a good job on harder stuff.
Pete.
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You're probably running the speed too low and the cut too shallow. What lathe are you using?
With carbide inserts and EN8 I use a relatively high speed (probably 750 - 1000 rpm if not 1200 for your tedder shaft) and make sure that I'm taking quite a large cut as the finishing cut by creeping up, measuring several times before the final cut and keep checking that the DRO still reads correctly. I'm talking at least 25 thou. Poor finish with carbide is often too shallow a cut as well as too low a speed. You can experiment with the speed to get the best finish on your roughing cuts
No, it's mild steel with a higher carbon content.
Thing is this mild steel tends to not have the quality of grain or constancy through the material that EN8 has. This cause more problems machining than it's worth cost wise when machining.
Ask a tool maker what would they rather machine a bolster in and invariably they will opt for EN8 even though it's more expensive. It's not the better mechanical properties they like about EN8 over standard mild steel it's the consistency for machining.
EN8 in general terms sure you can through harden it but it's only really a refined mild steel really all be it with a bit more carbon content.
I've just run a few test cuts on some EN8 and some bright mild steel bar using a freshly ground HSS tool, it is definitely down to these tips - the finish on the EN8 is nice and smooth and as expected not so good on the mild steel but more than acceptable. I will try a few more cuts tomorrow at higher speeds with deeper cuts with the carbide tips. Strange, as I cant remember having any problems last year using tips from the same company. In fact I can remember someone commenting on how good the finish was on a quick knock up slide hammer I made.
doubleboost
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The Harder you work carbide the better the finish
For really light finishing cuts on a small lathe you need high speed steel
For really light finishing cuts on a small lathe you need high speed steel
brightspark
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correct theres 2 much emphasis on using carbide tiptools when theres realy no need on most materials hss tools will do 90 percent of jobs
shenion
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I get better finish and can take lighter cuts with good carbide inserts. My HSS shear bit does not do as well. The cheap ones and and ones without proper angles do only work with heavier cuts. The thing is most what you find have no clearance or rake angles (xNxx inserts.)
Many thanks. Your quite right, I've upped the speed and taking a 40thou cut gives me a nice finish - in fact very nice finish on EN8. Looks like I will have to change the way I work when making finish cuts with carbide tooling.
Does anyone know how to identify EN8, I've just received a fresh length of 25mm and it machines awful - more like mild steel. I thought it was me until I had to use a bit of 40mm over the weekend (yes, another tedder shaft
) and that machines a treat (now I know to take large ish cuts) The end is painted yellow the same as my existing stuff but it doesn't look the same. and it sure doesn't machine the same.
) and that machines a treat (now I know to take large ish cuts) The end is painted yellow the same as my existing stuff but it doesn't look the same. and it sure doesn't machine the same. 