How To Mill Small Long Sections

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kwilliam

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How do you mill long 1m sections like 10mmx10mm (thats 3ft of 3/8 x 3/8)

First problem is the stock I get is bent, sometimes badly.
Second problem is - you can't take anything but a very small cut - the stock flexes.
Third problem is - if it is slightly bent clamping it straightens it - so how do you machine it true.
Fourth problem is - you can only machine a small section - it flexes.

How do others tackle it?
 
Bent stock is a problem in itself. Frequently stock is not straight to begin with through simple handling, especially with long pieces. Straightening can be done in several ways, the method you choose will depend on the equipment you have a available.

Myself, I would try this to make the actual cut once I have a piece of straight stock:
  1. Set up the vise with a set of parallels in the vise. The parallels need to high enough to support the work so that the upper surface is far enough above the vise jaws to prevent any damage.
  2. Set up simple wood block supports out away from the vise to provide support further out on the table.
  3. Make sure to have at least one roller stand available to support the long end when you are just starting with one end in the vise. This is especially true if you have a smaller mill like I do, with only a 24" table.
  4. Start with one end in the vise and make the first cut.
  5. Adjust the height of the table as necessary to get the cut where you want it.
  6. After each cut, return the table to the starting position, then open the vise so that you can advance the workpiece.
Once the first cut is made, five repeats should get you to the end of the workpiece if you have a six inch vise.
 
Here's a suggestion that sometimes work.
Take a piece of aluminum flat bar, say a section of 1" x 3" x 4 foot long or 1M long. mill a slot about 1-1/4" wide, maybe a little less, and about say 3/16" deep. If you could find a dovetail end mill with about a 10-15 deg back rake, mill one side of the slot with this. The other side leave straight up and down. Set the square bar in the slot against the one side of the slot. Get a piece of flat bar say 1/8" to 3/16" thick by 1M long. Drill some holes for a screw size around 1/4" or M6 on a 3" to 4" spacing for the length of the flat bar. Along with this drill and tap corresponding holes in the 1 x 3 flat bar. The trick to this is the make the thin flat bar a tight fit against the square bar when secured down to the aluminum bar. Doing this will give you a way to machine the entire length of the square bar in one setup.

You still going to deal with warpage. It's just going to happen. You can stress relieve the material, but it going to bend the moment you take a cut across the square bar. I would suggest to machine a little off one surface and rotate the stock 180 degrees and machine the rest off of the opposite side. This should keep the warpage to a minimum.

Ken
 
I can't help but only can ask a question
If you are milling cold rolled steel, isn't it going to go "banana" on you from internal stresses?
 
terrywerm said:
Bent stock is a problem in itself. Frequently stock is not straight to begin with through simple handling, especially with long pieces. Straightening can be done in several ways, the method you choose will depend on the equipment you have a available.

Myself, I would try this to make the actual cut once I have a piece of straight stock:
  1. Set up the vise with a set of parallels in the vise. The parallels need to high enough to support the work so that the upper surface is far enough above the vise jaws to prevent any damage.
  2. Set up simple wood block supports out away from the vise to provide support further out on the table.
  3. Make sure to have at least one roller stand available to support the long end when you are just starting with one end in the vise. This is especially true if you have a smaller mill like I do, with only a 24" table.
  4. Start with one end in the vise and make the first cut.
  5. Adjust the height of the table as necessary to get the cut where you want it.
  6. After each cut, return the table to the starting position, then open the vise so that you can advance the workpiece.
Once the first cut is made, five repeats should get you to the end of the workpiece if you have a six inch vise.
Click to expand...


I actually tried this method and gave up.
The 3/8squ was so floppy that no matter how I supported it, it moved, vibrated, just would not consistently sit right. Between supports it would sag. When milling the ends - the other end would be off the table unsuported putting bending loads on it.
Thats when I started to clamp to the table.
I even tried clamping some lower stock each side, with machinist clamps - that didn't seem to make any difference.
The best method I have so far is - to have some thinner stock on one side acting as a fence. But still clamping the 3/8 direct to table. Milling a small section at a time.
Surprisingly it doesn't seem to be doing the banana too much by milling one side then milling the opposite side.
 
4gsr said:
Here's a suggestion that sometimes work.
Take a piece of aluminum flat bar, say a section of 1" x 3" x 4 foot long or 1M long. mill a slot about 1-1/4" wide, maybe a little less, and about say 3/16" deep. If you could find a dovetail end mill with about a 10-15 deg back rake, mill one side of the slot with this. The other side leave straight up and down. Set the square bar in the slot against the one side of the slot. Get a piece of flat bar say 1/8" to 3/16" thick by 1M long. Drill some holes for a screw size around 1/4" or M6 on a 3" to 4" spacing for the length of the flat bar. Along with this drill and tap corresponding holes in the 1 x 3 flat bar. The trick to this is the make the thin flat bar a tight fit against the square bar when secured down to the aluminum bar. Doing this will give you a way to machine the entire length of the square bar in one setup.

You still going to deal with warpage. It's just going to happen. You can stress relieve the material, but it going to bend the moment you take a cut across the square bar. I would suggest to machine a little off one surface and rotate the stock 180 degrees and machine the rest off of the opposite side. This should keep the warpage to a minimum.

Ken
Click to expand...

This method looks like it might be worth trying.

Thanks Malcolm
 
I would remove the vice and clamp it to the table. Moving the clamps as I come to them. Take half from one side then flip it and take the rest off.


Sent from my SM-G530T using Tapatalk
 
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