Lath not cutting
Mike Brett | 22/05/2020 17:04:04 |
129 forum posts 18 photos | Hi I purchased some mild steel blanks of E-Bay 60 mm x 10 mm to machine some railway carriage wheels. They where listed as laser cut, and as I am having great difficulty trying to machine them I wondered if the laser cutting is the problem. I have tried different speeds and different tools but all I have managed to do is polish the outer rim which seems to be very hard. Would the process of laser cutting leave a hard skin. Mike |
Alain Foote | 22/05/2020 17:26:16 |
69 forum posts 10 photos | Yes laser cutting can leave a hard skin, suggest you tickle them with an angle grinder first. |
Mike Brett | 22/05/2020 17:35:50 |
129 forum posts 18 photos | I was afraid that would be the answer. If I tried to grind the edges it would no longer be a perfect round and I would never get it back in the chuck. |
John Haine | 22/05/2020 17:46:26 |
5563 forum posts 322 photos | Get them red hot and hold them red for a few minutes, then allow to cool slowly. |
John Baron | 22/05/2020 17:51:54 |
![]() 520 forum posts 194 photos | Hello Mike, Guys, I treat laser cut edges the same, similar to machining cast iron, you have to get under the skin ! Once you do it tends to machine easily. I agree with John Haine, annealing them will work.
|
AdrianR | 22/05/2020 17:52:13 |
613 forum posts 39 photos | Couple of thoughts. The hard skin should be very thin, so you should be able to get under it with a carbide tool.and an aggressive first cut. Are the sides hard too? Can you get under the skin from the side? As it is a wheel wont you need a hole in the middle for the axle?. You could make the hole in the middle on all the wheels. Then make an arbour and with out removing it from the chuck mount the wheels to finish them. You wont need them to be round then, so the angle grinder is an option. Adrian |
Martin Connelly | 22/05/2020 18:23:22 |
![]() 2549 forum posts 235 photos | I thought you could not harden mild steel so is this a scale formed from the gases used in the process? If so I doubt annealing would work but getting under the skin would. Martin C |
Mike Brett | 22/05/2020 18:24:19 |
129 forum posts 18 photos | Many thanks for replies. I will try and anneal them tomorrow, although I only have a small propane torch but I will give it a go. I will also try from the side , might work. The axle hole will only be 8 mm so not a lot to play with. At least they only cost me 10 pounds so not to much of a lose if it ends up in the bin. Mike |
JasonB | 22/05/2020 18:39:32 |
![]() 25215 forum posts 3105 photos 1 articles | If you have enough spar on diameter you can run the edge against a linisher/belt sander or even use an angle grinder. If the flat surfaces have mill scale on them I'd also suggest an acid dip. |
Dave Halford | 22/05/2020 19:05:09 |
2536 forum posts 24 photos | Posted by Martin Connelly on 22/05/2020 18:23:22:
I thought you could not harden mild steel so is this a scale formed from the gases used in the process? If so I doubt annealing would work but getting under the skin would. Martin C It's a bit like case hardening |
Ady1 | 22/05/2020 19:16:02 |
![]() 6137 forum posts 893 photos | If your lathe is up to it, backgear and a 5% cobalt tool (M35) |
John Haine | 23/05/2020 09:59:55 |
5563 forum posts 322 photos | Thay may well not be "mild" steel but some form of structural steel with a higher carbon content. |
Neil Wyatt | 23/05/2020 14:13:47 |
![]() 19226 forum posts 749 photos 86 articles | Although mild steel contains only very small amounts of carbon it is possible to achieve a degree of hardness with very rapid quenching. It is tricky to do but can be done - I was reading about it a few weeks ago. Laser cutting meets these difficult to achieve conditions, unfortunately! I've had to deal with laser cut blanks... Water jet cutting is better from this perspective, especially if you want holes spotted for small drills. Neil |
Phil H1 | 23/05/2020 15:09:39 |
467 forum posts 60 photos | Have you considered some slices of steel bar - they are only 60mm diameter and most of the suppliers will cut 'slices' for you. Put the laser cut stuff in your scrap bin - they will be useful for something else - unless you have 100 of them of course. |
Mike Brett | 23/05/2020 16:58:33 |
129 forum posts 18 photos | Hi all Yes next time I have to make wheels I will buy mild steel bar , but I persevered and have finally got four nice wheels. I think they could indeed have had a higher carbon content , certainly the hardest bit of mild steel I have machined. I finally got there by annealing then using a carbide tipped tool. Took a while to get under the skin though, thicker than I imagined. Tried back gear and slow speed , but while it was cutting through ok ,the finish was poor. In the end I used a medium speed and the finish was much better. Had to keep stopping though because of heat build up. Anyway many thanks for all your help. Stay safe Mike |
John Haine | 23/05/2020 17:13:40 |
5563 forum posts 322 photos | The kit for the Acute tool grinding system I bought contained a number of laser cut items and yes, they were hard to machine, not sure they had hard spots but the material was "sticky", definitely not free-cutting! |
IanT | 23/05/2020 17:44:45 |
2147 forum posts 222 photos | Mike, I purchased some blanks a little while ago that sound very similar (mine are 10mm x 50mm). I've not tried turning them as yet, although I have drilled mounting holes in their centres - which was not a problem. Generally when I turn wheel castings I use an insert tool to get under the surface - and the outer edge of my blanks look like they will need the same treatment. Regards, IanT |
SillyOldDuffer | 23/05/2020 17:51:04 |
10668 forum posts 2415 photos | Posted by Neil Wyatt on 23/05/2020 14:13:47:
Although mild steel contains only very small amounts of carbon it is possible to achieve a degree of hardness with very rapid quenching. It is tricky to do but can be done - I was reading about it a few weeks ago. Laser cutting meets these difficult to achieve conditions, unfortunately! I've had to deal with laser cut blanks... ... Neil Or could it be Nitriding as well as or instead of? The welded join along rolled mild-steel pipe can be very hard too. Maybe a laser generates a plasma like an electric welder and the hardness is Nitrogen ions reacting with Iron to form a thin but tough outer skin. Edited By SillyOldDuffer on 23/05/2020 17:51:20 |
JasonB | 23/05/2020 18:46:40 |
![]() 25215 forum posts 3105 photos 1 articles | A lot of the laser cut stuff is S275 which is not the nicest stuff to machine, better suited to teh welding and fabrication guys than machinists, it also has a slightly higher carbon content (0.25% ) which may be what the heat is affecting. The other downsid eis it is a hot rolled steel and does have a thin smooth coating of mill scale, not so much black but a dark silvery grey which can be hard and abrasive to tools. If getting stuff laser cut then ask for HR4 which is hot rolled so no scale and about 1/3rd the carbon content. Still not a snice as a slice of 230M07 though Edited By JasonB on 23/05/2020 19:01:09 |
Neil Wyatt | 23/05/2020 22:26:52 |
![]() 19226 forum posts 749 photos 86 articles | Took some tracking down to find details! This paper found water quenching actually caused a low carbon steel to be harder (and more brittle) than case hardening it.
International Journal of Advance Research, IJOAR .org
ABSTRACT |
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
Sign up to our newsletter and get a free digital issue.
You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.