Shop Floor Talk  

Go Back   Shop Floor Talk > Welding and Metalworking Forums > Blacksmithing & Forming

SFT Search:   
Reply
 
Thread Tools Display Modes
  #1  
Old 06-24-2009, 09:43 PM
OLD MAN's Avatar
OLD MAN OLD MAN is offline

2-3-1940 to 3-8-2011
Nobody was faster
 
Join Date: Apr 2008
Location: TEXAS
Posts: 12,577
Default Hardened By Heat

I bought some 3/4" circles that had been cut out by a torch. They are center spotted and they used a circle cutter to cut them. They are pretty close. I want to mill them but I need to sand or grind some of the edge off to get the hardened metal out of the way. How much has to come off for the mill to not have any trouble? Plain steel from a sheet. They are about 8" across.
__________________
You do the best you can with what you've got.
Reply With Quote
  #2  
Old 06-25-2009, 09:38 AM
digger doug's Avatar
digger doug digger doug is offline
Not to be used as a Flotation Device
 
Join Date: Jan 2008
Location: NW Pa
Posts: 11,628
Default

O.M.
Mild steel really doesn't get hard, but the scale formed
in cutting them with a torch is very hard.

Grinding off that scale is hard to do, can you drop them in
a cement mixer ?

At work we roto-blast, which is an extreme sandlbast
(airless) using steel shot. Unless you've got a line
on one of these, let's see what is avail to you.

Regular sandblasting works, do you have a little
cabinet unit in the shop ? You really only need to
concentrate on that cut edge.

I have machined these before, as an apprentice, and
we just went at them with carbide (negative rake)
in the lathe, scale flying everywhere.
Reply With Quote
  #3  
Old 06-25-2009, 11:01 AM
Ironman's Avatar
Ironman Ironman is offline
Iron Modification Investigator
 
Join Date: Feb 2008
Location: Warburg, Alberta, Canada
Posts: 13,645
Default

If I am correct, mild steel will caseharden in a oxy acetylene flame. The mild stell will absorb carbon from a neutral or fuel rich flame and this skin will be tough on drill bits, but should not affect a good machine tool.
__________________
Gerry
You got freedom of speech, if you don't say too much.
Aaron Neville

"I must abide by my core values, my ethical responsibilities and constitutional obligations. There can be a cost to acting on one’s principles, but there is a bigger cost to abandoning them.” Jane Philpott
Reply With Quote
  #4  
Old 06-25-2009, 11:33 AM
USMCPOP's Avatar
USMCPOP USMCPOP is offline
Gold Star Dad
 
Join Date: Jul 2006
Location: Richmond, VA area
Posts: 11,887
Default

Can you slowly spin them, then hit the edge with an angle grinder?
__________________
USMCPOP
Reply With Quote
  #5  
Old 06-25-2009, 12:15 PM
digger doug's Avatar
digger doug digger doug is offline
Not to be used as a Flotation Device
 
Join Date: Jan 2008
Location: NW Pa
Posts: 11,628
Default

Quote:
Originally Posted by USMCPOP View Post
Can you slowly spin them, then hit the edge with an angle grinder?
It's gonna make allot of dust, I think O.M. would not want allot
of dust.

A cement mixer can be filled with water during the "run"
and there shouldn't be any dust.
Reply With Quote
  #6  
Old 06-26-2009, 11:35 AM
Walker's Avatar
Walker Walker is offline
Standard of Excellence
 
Join Date: Aug 2004
Location: Cave Creek AZ
Posts: 4,386
Default

Just knock the surface off with a sanding disk. My experience has been mostly with a die grinder and I have found that once the scale is ground off it is easy to work.
__________________
Walker
Chief slag chipper and floor sweeper, Ironwood Artistic
Reply With Quote
  #7  
Old 06-26-2009, 05:21 PM
OLD MAN's Avatar
OLD MAN OLD MAN is offline

2-3-1940 to 3-8-2011
Nobody was faster
 
Join Date: Apr 2008
Location: TEXAS
Posts: 12,577
Default

I took a photo of one of the circles, I have several.
Attached Thumbnails
Click image for larger version

Name:	Picture 038.jpg
Views:	224
Size:	58.8 KB
ID:	47599  
__________________
You do the best you can with what you've got.
Reply With Quote
  #8  
Old 06-26-2009, 07:30 PM
Charlie C's Avatar
Charlie C Charlie C is offline
More STEAM!!
 
Join Date: Dec 2006
Location: Southern Oregon
Posts: 6,036
Default

Jerry, I would grind the disk untill I could not see any flame marks from the cutting torch.
Reply With Quote
  #9  
Old 06-26-2009, 08:08 PM
digr's Avatar
digr digr is online now
The Real Deal
 
Join Date: Apr 2005
Location: Duluth MN
Posts: 8,022
Default

I would face off a piece of 2" pipe and tack it to the center of the plate and center it with a four jaw chuck and turn the od on the lathe. I have done it that way and it works good.
__________________
Drawing by Smartdraw
Reply With Quote
  #10  
Old 06-26-2009, 08:21 PM
Barn Owl's Avatar
Barn Owl Barn Owl is offline
Senior Member
 
Join Date: Jun 2009
Location: San Diego California
Posts: 937
Default

If you knock the edge of the circle swinging the hammer toward the center of the disk the dross should pop right off. If it was flame cut right there should be very little. If the travel speed was too slow or the heat was too high it is going to make removal harder. If there is not too much (couldn't tell from the photo) grinding is the best way but if there is a lot that is really stuck then a well placed blow with a hammer and it will come off in chunks.
We don't allow the students to cut their plates with the band saw after it has been flame cut because we have found that it reduces the life of the saw blade exponentially. Milling bits might be a bit tougher than a band saw blade. If you have a big belt sander, that will take most of the hardened surface away and save your bits when on the lathe. I've got a big 4 hp sander and it really eats through rough edges.
__________________
Mike

"Yes, we did produce a near perfect Republic. But will they keep it? Or will they in their enjoyment of plenty, lose the memory of freedom? Material abundance without character is the surest way to destruction. Indeed, I tremble for my country when I reflect that God is just."

Thomas Jefferson



If you spent 1 million dollars every day from the time Christ walked the earth until now, you still would not have spent 1 trillion dollars!

Last edited by Barn Owl; 06-26-2009 at 08:26 PM.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Web Search:

All times are GMT -5. The time now is 07:02 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.