Need advice on milling a 1-1/4" wide x 8" long slot into 1/2" mild steel plate.

[dgfoster]

Given your machine limitations and the mess and misery associated with plasma followed by grinding, I would suggest you at least try putting a decent Lennox steel cutting blade in a simple reciprocating saw, drill the end holes, then tilt the work down and away from you, apply some cutting oil, and try the zip saw. I am always surprised at how fast it cuts and how long a blade lasts. Run the saw at medium speed, keep modest pressure on it so the blade cuts and does not rub. You should be able to cut within .060 of the line and the saw job would be done in 15 mins or so. Might require a couple of blades.

If you are a decent welder, you could also drill the holes, start cutting with a vertical bandsaw outside right into the hole and cut out the slugs. Bevel each side of the entry slit, weld it up and grind the weld flat or your belt grinder or mill it flat.

Ya, a bit out of the box, but very possible to do it that way.

Denis

 

[memphisjed]

I am known in these parts for being a bit of a hack so don’t do this but….
The last thing I did was a bunch of 3/8” and 1/2” A36 plate.
I had some bit to do and got tired of it so pulled out the trusty old Sawcat.
It takes care but works fine.
Of course on that same job I ran a bunch of radius work with a standard carbide router bit.
Also took care but also ran fine.
That job was this shop built roll bender I needed at the time.
Plunge cutting 1/2” plate with a Sawcat…
Definitely not for the uninitiated.

View attachment 396697

I am all for crosstraining tools... skill saw and plate, that is pretty brave and cool or stupid and lucky- not sure which yet.
I would cut off disk/ file/ drill ends before that. I would try and fabricate it before that.

 

[WizardOfBoz]

Maybe you said it, but I didn't see how many of these slots you are cutting. Also, what is your time worth? If you are doing multiples of this slot, and your time is valuable, go out and have someone with a proper, beefy mill do this. If you are cutting one or two slots, and are doing this on your own time cuz you like it, there are many ideas above. I would say though, if you plasma cut the plate you are going to introduce warping. Less than flame cut, but still. Is that acceptable for the context of use?

On edit: I read the first page and didn't even see the other three. Sorry if my little post repeats something already said.

 

[jaguar36]

Have some place like SendCutSend with the right tools do it for you. Won't cost you much more than the raw materials.

 

[joe28704]

Need advice on milling a 1-1/4" wide x 8" long thru slot into 1/2" mild steel plate.
Pictured is the Mill-Drill, vise, chuck and end mill ( 3/4" Dia two and four flute, also have smaller Dia end mills ) I have available. My general plan is to make a template to Plasma cut the slot within ( 1/16 or 1/8" ? ) distance from the final machined edge and mill to final size with milling tools shown. The ends of the slot need not be round and can be squared to whatever cutter radius is chosen. Since I've never done this before, my general questions hover around the heat affected zone of the plasma cut and the machining that will be done on it to clean it up. ( I would like as clean a finished cut as this setup will allow as a cam follower bearing will ride in the slot. I have all the time in the world so light passes are just fine with me till I get the width ( 1-1/4") I want.
Also I'd like to find a source or get advice to determine what speed I should run the mill at with chosen cutter. ( I've had the speed set at 315 RPM's for years and its suited me for all my drilling).
Any advice as to how to proceed and specially what not to do would be greatly appreciated.
I'm here primarily to pickup any advise/tips to shorten my learning curve on this.
P.S. On final passes should I do conventional milling or Climb Milling?
Thank you for your consideration.

Yes it is a Thru slot. 2 pieces needed.

 

[joe28704]

Have some place like SendCutSend with the right tools do it for you. Won't cost you much more than the raw materials.
View attachment 396699

Plate size is 5-1/12" X 18". I got the plate from the scrapyard. Need to plasma cut to final size.

 

[joe28704]

there is enough carbon to make cold chisels out of mild steel using soapy brine (super quench). Plasma gets the edge very hot, expanding and contracting it to limits. It is work hardened. Super quenched by thermal mass of parent stock, with the carbon from vaporized metal being sucked in as material is in expanded state, plus nitride, plus work hardened- the haz layer is over 1/32", I find just over a 1/16 in 3/4 stock to get to the nice soft stuff.
torch cutting gives the parent material heat, dispersing the temperature difference. much shallower haz.

Thank you for this info. Yes, this is just what I discovered after plasma cutting this 1/2"plate, it took about 1/32 of grinding to get into something cuttable. Will try torch cut next.

 

[implmex]

Hi again joe28704:
This little project is turning into an epic saga...there's been more hand-wringing dialogue that it would take to just mill the bloody thing.
I'll bet, despite all its shortcomings that your mill-drill will do the job just fine if you plunge rough it as I recommended, or if you prefer, plunge rough around the periphery.

So have you tried to mill one?
Have you even tried to mill a test slot?

Don't turn this into the defining project of your life...it's not that complicated.
Even if you laid the slots out with a template, chain drilled them, smacked out the slugs with a big hammer, and kissed the edges with a 3/8" cutter, you'd be done by now.

So I encourage you to learn what you can and cannot do with that mill-drill...it's kinda the obvious way forward.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[dgfoster]

there is enough carbon to make cold chisels out of mild steel using soapy brine (super quench). Plasma gets the edge very hot, expanding and contracting it to limits. It is work hardened. Super quenched by thermal mass of parent stock, with the carbon from vaporized metal being sucked in as material is in expanded state, plus nitride, plus work hardened- the haz layer is over 1/32", I find just over a 1/16 in 3/4 stock to get to the nice soft stuff.
torch cutting gives the parent material heat, dispersing the temperature difference. much shallower haz.

Can you show us any reference to making a cold chisel from low-carbon steel by simple heating and quenching? I ask because I doubt it can be done.

I do know that something like 1018 can be very slightly hardened by heating and quenching—-barely noticeable. And it is well known that it can be carburized (pack hardened as an example) or nitrided to harden it. But plain common low carbon steel getting into the Rc 40’s let alone 50 or 60 by simple heating and quenching? I don’t think so.

I am willing to learn if it is true but it sure is contrary to all my experience and to the experience of a blacksmith friend of mine.

 

[memphisjed]

Superquench Hardening Mild Steel | PDF | Sodium Hydroxide | Surfactant

superquench_-_hardening_mild_steel.pdf

www.scribd.com

Developed by government money and osha. Simple green works instead of Shaklee. Jet dri also works.

You have to really keep your part moving in quench to get cold chisel hard. It really works for need a tool right now quick and dirty.

 

[dgfoster]

Superquench Hardening Mild Steel | PDF | Sodium Hydroxide | Surfactant

superquench_-_hardening_mild_steel.pdf

www.scribd.com

Developed by government money and osha. Simple green works instead of Shaklee. Jet dri also works.

You have to really keep your part moving in quench to get cold chisel hard. It really works for need a tool right now quick and dirty.

OK, I did some searching on super quench and found a couple blacksmith forums discussing it reporting they could get up to something like 45 Rc using the method (that is consistent with the linked article as well.) One did make a cold chisel that he reported to be good for a few cuts "But, so as not to mislead us, Robb said that a chisel of this type might be good for 7 or 8 cuts maximum" That was new information for me and I thank you for pointing it out. It evidently does have good application for things like non-cutting fullering tooling and similar.

An common commercial cold chisel will have hardness around 55-58 in the cutting end and will be through-hardened and the struck end will be about 35-40.

So, the conclusion is that using a mix of equal parts salt and water plus dishwashing detergent and rinse aid moderate hardening could be acheived.

But that does not answer the question of why air/plasma leaves a black glassy glass-hard surface (reported by Miller and Hypertherm to be nitride) and oxygen/plasma leaves a soft surface. Both are heated the same and cooled the same with the quench in this case being the cold mass of the rest of the part.


Denis

 

[jaguar36]

But that does not answer the question of why air/plasma leaves a black glassy glass-hard surface (reported by Miller and Hypertherm to be nitride) and oxygen/plasma leaves a soft surface. Both are heated the same and cooled the same with the quench in this case being the cold mass of the rest of the part.

I'm no expert, but I would guess the plasma causes the iron to react with the nitrogen in the air and form Iron Nitride which is super hard (in the low 70s) while oxygen would just form iron oxide in the mid 50s.

 

[dgfoster]

I'm no expert, but I would guess the plasma causes the iron to react with the nitrogen in the air and form Iron Nitride which is super hard (in the low 70s) while oxygen would just form iron oxide in the mid 50s.

And I am pretty sure that is the answer to my rhetorical question. My question was really why, if "super quenching" was causing air/plasma edge hardening, did the same hardening not occur with oxygen/plasma cutting. You are exactly correct, because it is not super quenching (which could cause at most a 45Rc edge---easily machinable) causing glass hardness but rather nitiridiing.

Denis

 

[TaperPin]

In the time it took to read this thread, the poor guy could have had the parts dikym-sharpied,clamped down and been through the first cutoff blade and first cut in a big angle grinder!

Know what tool you need based on requirements. Milling a cam follower slot sounds great, but for a slot loaded on only one side for a car hood, nobody will ever know if you have milled it or carefully cut and filed it. If you can’t file a straight slot, get it close so you just skim off the side the cam is riding on.

So it’s been a month - fill us in on the fun you had cleaning up the plasma cut and how the milling machine worked!

 

[D Nelson]

Need advice on milling a 1-1/4" wide x 8" long thru slot into 1/2" mild steel plate.
Pictured is the Mill-Drill, vise, chuck and end mill ( 3/4" Dia two and four flute, also have smaller Dia end mills ) I have available. My general plan is to make a template to Plasma cut the slot within ( 1/16 or 1/8" ? ) distance from the final machined edge and mill to final size with milling tools shown. The ends of the slot need not be round and can be squared to whatever cutter radius is chosen. Since I've never done this before, my general questions hover around the heat affected zone of the plasma cut and the machining that will be done on it to clean it up. ( I would like as clean a finished cut as this setup will allow as a cam follower bearing will ride in the slot. I have all the time in the world so light passes are just fine with me till I get the width ( 1-1/4") I want.
Also I'd like to find a source or get advice to determine what speed I should run the mill at with chosen cutter. ( I've had the speed set at 315 RPM's for years and its suited me for all my drilling).
Any advice as to how to proceed and specially what not to do would be greatly appreciated.
I'm here primarily to pickup any advise/tips to shorten my learning curve on this.
P.S. On final passes should I do conventional milling or Climb Milling?
Thank you for your consideration.

Yes it is a Thru slot. 2 pieces needed.

Waterjet it to size and forget about it

 

[mike44]

Thank you for your thoughts. Yes it is a thru slot Thats why I was going to plasma cut the majority of it out. I guessed 3/4 because it being stouter than 3/8 then run it slower? I have all sizes end mills up to 3/4. What speed would you run the 3/8? Thank you. By changing pulleys the mill/drill can go up to 2500 Rpm. Posted new picture of chuck. Your point B) is well taken thank you.

Chain drill as been posted. You will be left with points if done correctly. Install a milling adaptor and an endmill. Do not climb cut. Do not use a chuck and an endmill together.
If you have at least 1 HP you could just mill the slot using cutting fluid and light cuts.
I have a mill-drill but only used for milling. Weighs almost 900 lbs and has a powerrfeed on the X axis. I could mill a slot like yours easily.

 

[surplusjohn]

Need advice on milling a 1-1/4" wide x 8" long thru slot into 1/2" mild steel plate.
Pictured is the Mill-Drill, vise, chuck and end mill ( 3/4" Dia two and four flute, also have smaller Dia end mills ) I have available. My general plan is to make a template to Plasma cut the slot within ( 1/16 or 1/8" ? ) distance from the final machined edge and mill to final size with milling tools shown. The ends of the slot need not be round and can be squared to whatever cutter radius is chosen. Since I've never done this before, my general questions hover around the heat affected zone of the plasma cut and the machining that will be done on it to clean it up. ( I would like as clean a finished cut as this setup will allow as a cam follower bearing will ride in the slot. I have all the time in the world so light passes are just fine with me till I get the width ( 1-1/4") I want.
Also I'd like to find a source or get advice to determine what speed I should run the mill at with chosen cutter. ( I've had the speed set at 315 RPM's for years and its suited me for all my drilling).
Any advice as to how to proceed and specially what not to do would be greatly appreciated.
I'm here primarily to pickup any advise/tips to shorten my learning curve on this.
P.S. On final passes should I do conventional milling or Climb Milling?
Thank you for your consideration.

Yes it is a Thru slot. 2 pieces needed.

Instead of milling a slot can you screw on a channel or guide rails? Or make two plates with a recessed separator, thus creating your channel . A cam follower may or may not require alot of guidance.