Author Topic: EN8 problems  (Read 8581 times)

Offline Farmboy

  • Full Member
  • ****
  • Posts: 121
  • England
EN8 problems
« on: October 04, 2013, 02:11:03 PM »
More kindergarten stuff!

With the long summer days rapidly shortening and the first of the autumn rains I finally got back to my lathe.

I'm working on the barrel for a milling spindle of my own design. The material is 4" of 2" round bar that claims to be EN8, bought from a well-known auction website, and I am having great difficulty getting a decent finish. The metal seems to tear rather than cut in some places and appears to have random harder areas.

The boring bar is a DCMT carbide type with a new tip, set to dead centre height. On my last cut I raised the tool with an extra shim (tin can) and there was a slight improvement to the finish. I have tried various speeds and settled on 1,000rpm as the best, which works out to around 250-300ft/min.

I am currently boring the seat for a taper roller bearing using a fixed steady and minimum tool overhang so vibration is minimised, and I am hand feeding as I don't trust my ability to disconnect the power feed fast enough to avoid crashing into the shoulder. I did power feed when truing the outside of the barrel, with both carbide and HSS tools, and had no greater success with the finish so I don't think hand-feeding is the problem.

Is EN8 normally this difficult to machine? Any tips on improving the finish as I get close to a fit on the bearing?

Mike.

Online Jasonb

  • Full Member
  • *****
  • Posts: 9463
  • Surrey, UK
Re: EN8 problems
« Reply #1 on: October 04, 2013, 04:29:16 PM »
I must admit I've not machined EN8 that much and when I did it was a bit harder to get the same sort of finish as EN1A. I did use some cutting fluid applied with a brush which helped and got a decent finish in the end.

Offline DaveH

  • Full Member
  • ****
  • Posts: 188
  • Kempton Park. RSA
Re: EN8 problems
« Reply #2 on: October 04, 2013, 05:05:10 PM »
EN8 is noted for not getting a nice shiny finish.
Gets worse with smaller depths of cut. One way is to use at least a .020" cut with lots of cutting fluid with a high rotational speed and high feed rate. Try .010" see what happens.
Or do what I do and 'hit' it with emery cloth and cutting fluid, and finish with dry emery.
 :cheers:
DaveH

Offline Farmboy

  • Full Member
  • ****
  • Posts: 121
  • England
Re: EN8 problems
« Reply #3 on: October 04, 2013, 09:15:01 PM »
Thanks for the tips. Looks like EN8 was not a great choice for a beginner, but you live and learn. And the finish on those shafts looks a lot better than mine, Jason, so maybe I'll try some fluid tomorrow.

Dave, I certainly found a heavier cut and higher speed gave a better result. The last few cuts were about .010" at 1,000rpm. I even tried one cut at 2,000 which is the next available speed on my lathe but it seemed insanely fast and made sparks so I gave up on that, although the finish was even better. Maybe I should use it for the final stages, bearing in mind I've got to get a nice fit for the bearing shell. It's going to be tricky sneakin' up on a press fit with a 20 thou cut, being a novice and all . . .  :-\

Mike.

Offline DaveH

  • Full Member
  • ****
  • Posts: 188
  • Kempton Park. RSA
Re: EN8 problems
« Reply #4 on: October 04, 2013, 10:27:11 PM »
Mike,
I would just sneak up on it (when it ain't looking  :LittleDevil: ) and give it a final clean up with some emery cloth   :ThumbsUp:
 :cheers:
DaveH

Offline derekwarner

  • Full Member
  • ****
  • Posts: 833
  • Wollongong ...... Australia
Re: EN8 problems
« Reply #5 on: October 05, 2013, 05:57:28 AM »
Guys....there is nothing exotic about EN 8  :Mad:....it's chemistry is not much better than Grade 250 plate & provides similar resultant poor machinability  :cussing:

When we look backwards.........our metallurgist's created endless varieties of grades of steel :facepalm:... however I think for the sake of science & not for use by engineers or machinists

In todays world........why go past a steel with a higher sulphur content for free machinability?...or

Your garden variety BS EN43B would provide a technically sound material for your application and also being able to be machined with a reasonable water washed surface finish......Derek  :cheers:



 
Derek L Warner - Honorary Secretary [Retired]
Illawarra Live Steamers Co-op - Australia
www.ils.org.au

Offline Kim

  • Global Moderator
  • Full Member
  • *****
  • Posts: 7860
  • Portland, Oregon, USA
Re: EN8 problems
« Reply #6 on: October 05, 2013, 04:26:32 PM »
So, if you don't mind another newbie question, how does this compare to the common Mild Steel (1018) or the Free Machining Steel 12L14 that I've heard in the past is a good choice for this kind of machining?

Thanks,
Kim



Offline Dan Rowe

  • Full Member
  • ****
  • Posts: 1170
  • Dripping Springs TX USA
Re: EN8 problems
« Reply #7 on: October 05, 2013, 04:33:54 PM »
Kim, I checked for the US equivalent of EN8 steel and it is 1045. Here is what Speedy Metals has to say about 1045.
http://www.speedymetals.com/information/material30.html

I have not used 1045 for anything but maybe some one else has some experience.

Dan
ShaylocoDan

Offline Kim

  • Global Moderator
  • Full Member
  • *****
  • Posts: 7860
  • Portland, Oregon, USA
Re: EN8 problems
« Reply #8 on: October 05, 2013, 04:52:35 PM »
Thanks Dan,
So essentially its a higher strength steel.  Interestingly, it says in that link that machinability is good, but its "welding qualities are limited". Something else to keep in mind if you'd planed to weld.

Kim

Bluechip

  • Guest
Re: EN8 problems
« Reply #9 on: October 05, 2013, 05:44:19 PM »
Farmboy

Alloy steels are obtainable in various states of 'temper'.

Some readily machinable by the bloke in his shed, some probably not so.

http://www.roymechx.co.uk/Useful_Tables/Matter/Strength_st.htm

En16T is not too bad, although I used a HSS tool-bit, not a carbide insert. Another bit of known En16, of unknown temper though, well, the Myford just bounced off it ...  :disappointed:

So, En8 it may well be, but not normalised.

Wait until Nov. 5th, and chuck it in the bonfire overnight ...  :)

Dave BC

Offline Farmboy

  • Full Member
  • ****
  • Posts: 121
  • England
Re: EN8 problems
« Reply #10 on: October 05, 2013, 08:27:47 PM »
The only reason I got EN8 was that it was the nearest size to what I wanted and a reasonable price, I didn't go looking for it especially. As far as machining goes, it doesn't seem particularly hard but seems prone to tear rather than shear with the tool, hence the poor finish.

Having said that I have now followed yesterday's advice from Jasonb and DaveH and found that a 0.5mm/.020" cut at about 300ft/min with a carbide tip and a little oil left a far superior finish to my previous, more timid efforts. So I bored to 1mm undersize then set up for a .45mm cut (still feeling a little timid) and let rip with pretty good results, and lots of pretty blue swarf. I then took another cut on the same setting, which found a little metal it had missed the first time, possibly due to tool flexing? After that I took another very light shave with oil at a very slow feedrate, at which point the bearing shell would just begin to enter the opening, so I think I should be able to refine it a little with Dave's suggested emery cloth to achieve a nice press fit.

To summarise, the best finish came from raising the tool just a smidgin above centre height, cranking up the lathe speed and taking a heavy cut with lubrication.

Incidentally, I just found one chart that recommends 670 - 970ft/min with carbide on EN8 so maybe I should have stayed with 2,000rpm  :-\

As for welding, on one site it says that EN8 is not readily welded, while another source says it welds easily . . . you can find pretty much any answer you want on the interweb if you look hard enough . . . which is why it's best to come here to the experts . . . thanks chaps   :praise2:

Mike

Offline Trevorc

  • Full Member
  • ****
  • Posts: 134
Re: EN8 problems
« Reply #11 on: October 27, 2020, 07:04:37 PM »
I know this topic is 7 years old but to me it is very topical. I am using EN8 for crankshaft and was using carbide insert tooling- result was absolute rubbish finish- instead of cutting metal it looked like it was being torn from the bar. Using Google found this thread.
I can personally vouch for the advice given- ditch the inset tooling and use HSS bit instead.
I ground a piece of HSS steel  with generous top rake angle and very small nose radius.
It worked like a charm, a0.020 inch  cut at 100 surface feet per minute speed gave a dull grey smooth finish with or without coolant. :pinkelephant:
I have now rediscovered the home ground HSS tool bit! I will now delete those carbide inserts from my Santa list!!
Trevorc

Offline jadge

  • Full Member
  • ****
  • Posts: 503
  • Cambridge, UK
Re: EN8 problems
« Reply #12 on: October 27, 2020, 10:29:15 PM »
It's perfectly possible to machine EN8 with insert tooling and get a good finish. But, unlike some carbon steels, you need to run at a high surface speed. Have a look at this thread, towards the bottom of the first page:

https://www.model-engineer.co.uk/forums/postings.asp?th=51900&p=1

Andrew


Online Jasonb

  • Full Member
  • *****
  • Posts: 9463
  • Surrey, UK
Re: EN8 problems
« Reply #13 on: October 28, 2020, 07:10:14 AM »
I've turned a few more bits of EN8 since I last replied to this thread, for what are often long and whippy parts like crankshafts that we often use EN8 for I swap over to a **GT insert for finish cuts, as you can see they cut well though I don't have the test gear that Andrew has to quantify "well"

<a href="https://www.youtube.com/watch?v=LpVtM35GFtM" target="_blank">http://www.youtube.com/watch?v=LpVtM35GFtM</a>

Offline steve-de24

  • Full Member
  • ****
  • Posts: 141
Re: EN8 problems
« Reply #14 on: October 29, 2020, 11:38:06 AM »
Whilst looking at a catalogue of materials I noticed that leaded EN8 seems to be available, see page 29 of   http://preview.m-machine.co.uk/CATALOGUES/metals%20catalogue.pdf  anyone tried it?


 

SimplePortal 2.3.5 © 2008-2012, SimplePortal