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Milling Thin and Deep Channel on Vertical Mill

Just a small update. I am not too worried about the part collapsing on the blade as there is still a significant amount of meat at the bottom of the part, and we raised the whole works on parallels so the pressure is concentrated at the bottom where there is less leverage. (See diagram)
vice bite cross section.png
Splitting the part in two is not out of the question. A flat section that mates to a "L" shaped section could reduce machining time and complications despite the need for more hardware.

We will continue our endeavors tomorrow.

Thanks,
Justin
 
Hi Justin:
You remarked:
"despite the need for more hardware."

May I assume you propose to bolt it together?
Have you considered brazing or silver soldering it instead?

What about TIG welding it?
The bottom is skinny enough you can probably get a full penetration weld easily without even having to bevel it much.
If you use stress relieved or hot rolled stock, and if you clamp it to a heavy backing plate you can probably keep it very straight too.
Kiss over the bottom outside and the ends with a cutter after welding and nobody will even know it is welded.
Put a copper chill bar in the gap to keep it from collapsing, and you may well find you're done and moving on to the next job before a guy with a slitting saw has even really gotten started on it.
Just make sure the chill bar is longer than the part...long enough that you can knock it or press it back out of the slot

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 
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Hi Justin:
You remarked:
"despite the need for more hardware."

May I assume you propose to bolt it together?
Have you considered brazing or silver soldering it instead?

What about TIG welding it?
The bottom is skinny enough you can probably get a full penetration weld easily without even having to bevel it much.
If you use stress relieved or hot rolled stock, and if you clamp it to a heavy backing plate you can probably keep it very straight too.
Kiss over the bottom outside and the ends with a cutter after welding and nobody will even know it is welded.
Put a copper chill bar in the gap to keep it from collapsing, and you may well find you're done and moving on to the next job before a guy with a slitting saw has even really gotten started on it.
Just make sure the chill bar is longer than the part...long enough that you can knock it or press it back out of the slot

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
Thank you for the input, seems like excellent options for this op. We have plans to try and split the channels in two for another design revision in the future. Bolts, solder, or welding are all viable options. Out of curiosity, why do you specify TIG over MIG or stick?

Unfortunately it is a bit late for that as we just finished cutting the part yesterday. I should have checked this forum earlier but I was in class all week. Everything came out okay, but we do have one issue.

As some mentioned, making this cut in the way we outlined earlier could cause the forks to spread outwards, and that is exactly what happened. The channel is now .040" wider on top than on the bottom.
attachment.jpg
My plan now is to use some beam clamps and a feeler gauge to press the forks back into place. I can do this along the whole length of the channels to try and close the gap. Do you think this is the best way to fix the issue? For context, the channels are to be filled with copper bars and soldered in place with solder paste to create a composite bar. One of our guys suggested clamping down on the top while the solder solidifies, holding the forks straight.

Justin
 
Hi WakelessFoil:
Heat will be your friend when you try to bend the legs of the channel back where they belong.
Those bars look like cold rolled mild steel...the stress release caused that spread as I and others predicted.
So pinch a bar the size of the slot you want and get a rosebud on the back of it.
Bring it up to dull red and you'll probably have it hot enough to move pretty freely.
You may have to go a twitch smaller with your bar if there is still springback.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 
Hi WakelessFoil:
Heat will be your friend when you try to bend the legs of the channel back where they belong.
Those bars look like cold rolled mild steel...the stress release caused that spread as I and others predicted.
So pinch a bar the size of the slot you want and get a rosebud on the back of it.
Bring it up to dull red and you'll probably have it hot enough to move pretty freely.
You may have to go a twitch smaller with your bar if there is still springback.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
Sounds like a plan. Being that the channels are about 18" long (and thus hard to heat evenly with a torch), I may opt for using our electric furnace to bring the steel up to temp. Of course this would heat the whole thing and not just the spine. What do you think of this?

Thanks,
Justin
 
I think it's time for the redesign to start now........your wasting more time screwing around fighting too many issues
all hoping it wont go out of spec.
Sometimes you just got to go to Plan B
 
for this its preferable to use a side cutting slitting saw.

if your going to soft solder it in an oven (after bending it straight) my question is if the joint will survive the difference in thermal expansion.
 
What type of solder? Soft (lead or lead free, 80/20 or 60/40?) or hard solder (ez, mid, or hard). Or braze?

All of the above will become a nasty crystalline mush if you move parts while solder solidifies. 60/40 lead will give you the most forgiveness.. the mush is nasty, sometimes reflow will not work after this- then you get to dig all the solder out and try again.

Clamp channel into place around inner section then solder. A hard solder will hold that “composite” straight after unclamping.
 
if your going to soft solder it in an oven (after bending it straight) my question is if the joint will survive the difference in thermal expansion.
We have done this once before (thought with a slightly different design) and it seemed to hold up.

What type of solder?
In an earlier revision of this project we used solder paste, I do not remember the composition of the solder but I do remember it flowed at some 300 F. Painting inner channel with paste, clamping, and baking seemed to produce a good result.
 
UPDATE:
We set the old furnace to 700 C and squeezed the channels in with beam clamps and sheet steel to protect it from oxidation. Got them red-hot then cooled slowly over 24 hours. Though they were a bit dirty coming out of the furnace, a few seconds with a wire wheel shined them up again. They are straight now.

f446d0df6d57cc4d422e9c87b1353bfee100ddcb-1.jpegf446d0df6d57cc4d422e9c87b1353bfee100ddcb-3.jpegf446d0df6d57cc4d422e9c87b1353bfee100ddcb-2.jpeg

Justin
 
I’m in same shop, took the liberty of editing Wakeless’ pic to see the difference in before (left) and after (right) baking. It is easy to see the unwanted V-shape on left and the desired parallel,sides of slot on the right. Unplated sheet steel was cut to cover both long sides of workpiece and placed under the clamps to mostly exclude O2 from attacking the piece during heating because the resulting corrosion is very difficult to remove. IMG_4536.jpeg
 
Shishkabob before baking. Ordinary beam clamps were used to squeeze open end. A shim was placed in the slot to limit the amount it could close.IMG_8709.jpeg
 

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Unless adding a little carbon to the surface of the steel is incompatible with the specs of the product, next time you could add a little charcoal powder, or even pieces of paper inside your wrapped package: they will burn consuming all the available oxygen, reducing therefore any surface oxidation.

Paolo
 








 
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