Need suggestions on how to cut discs to diameter on mill

Clodbuster · Jun 12, 2020

Hi All,

So I have a project where I'm trying to use a disc & bearing assembly to make some other parts. These are worn tillage discs, so higher grade wear steel, I don't know the spec but they don't drill or mill easy at all. They are about 15" diameter and 1/8" thick, with a 5/8 bearing. I'm trying to turn them down to 12" diameter, need to do 18 of them.

Now for the tricky part. I don't have a lathe, nor space for one currently. I have a Bridgeport mill, no rotary table. I tried to machine an arc with the setup shown. It's not rigid enough for the plunge with a mill, nor for the arc, wants to grab and break end mills.

Thoughts on how to set this up as a repeatable task with machines I currently have? What kind of tooling? Parting tool held in mill vise? Drill mills? Open to all suggestions.

Thanks

L Vanice · Jun 12, 2020

"It's not rigid enough for the plunge with a mill, nor for the arc, wants to grab and break end mills"

Use a bigger ( 1 inch, for instance) and shorter end mill with six or eight flutes running at a speed appropriate to the material of the cutter and the work. Start the cut on a radial line from the edge with the work locked down before rotating the work. A six or eight flute end mill will not drill its own hole by plunging. Cutting oil or Tapmatic Edge stick lube will help tool life.

Larry

dana gear · Jun 12, 2020

Build your self a 5/8" pilot pin measure out the distance you would need for the diameter your looking for, example center of 5/8" pin to center of plasma cutting head and fab a arm that welds to the pilot pin and would encompass a plasma torch on the other end and cut away. Or take them to someone with a CNC plasma cutting table, once easily set up these would cut out in about 1 minute each on a CNC table.

Illinoyance · Jun 13, 2020

Forget the mill. Make a template that locates on the center hole. Cut with plasma.

Limy Sami · Jun 13, 2020

Plus another on plasma, or OA torch, …….if they're still going to be cultivation etc discs - it won't matter a damn.

Scruffy887 · Jun 13, 2020

I'm surprised you got that far with the bit hanging that far out of the collet. With that much stickout there is a good chance you are going to bellmouth the collet making it useless.

Larry Dickman · Jun 13, 2020

trepan it.

michiganbuck · Jun 13, 2020

Stout brace the underside near the cutting even made of wood and pressing up a little, and a roller on the top side pushing down. Both at very close to the machining action. A short stub end mill 3/4 or better.

Uhe helix of the end mill has to have s brace/support in the pull up direction(with a right hand EM)very close to the cutting action.

*Agree it might be a good job to send out.

You might run a stack of them, 6 at a time to make a stronger part. clamp a paralell top and under at close to the cut ..and move that along close to the cutting..with a 3/4" 4 flute end mill..Likely still need a top side brace.

If saw able you could get it/them closer with sawing to a 1/16 close.

if you could saw to 1/32 close you could use such a rotating set-up to bench grind them.

Chop saw slices to rough in may harden them so making milling difficule..but could try a chop away from finish size to see if it did/would harden.

Limy Sami · Jun 13, 2020

For those who don't know, …..the steels generally used for making harrow discs, is best described as ''not made for machining'' and that's before the work hardened skin is formed.

Carry on machining if you like, but I'd liken it to asking to be repeatedly kicked in the bollox

MattiJ · Jun 13, 2020

Farmhouse bodge: spinning disk on spindle and large angle grinder. Wood block under the outer edge to provide some braking.

Clodbuster · Jun 13, 2020

I already tried it with an OA torch setup. It makes the cut fine, but the heat warps the discs into a bell shape which makes them no good as parts. I need a cooler process.

Also, the first pic is just mocking up what I did, that end mill isn't even snugged down, nor is the lever bolted on. In use everything was held tight.

Clodbuster · Jun 13, 2020

Trepan it?

Can you elaborate - this is new to me.

Clodbuster · Jun 13, 2020

And I have a large vertical bandsaw - that's a good idea... but it is too hard to saw also.

bhigdog · Jun 13, 2020

Clodbuster said:
And I have a large vertical bandsaw - that's a good idea... but it is too hard to saw also.

Friction saw them...........Bob

Richard Winn · Jun 13, 2020

stack a bunch on the table

and do the etch a sketch

Ray Behner · Jun 13, 2020

Clodbuster said:
Trepan it?

Can you elaborate - this is new to me.

YouTube

I'm with the plasma bunch however.

OCTANE WORKHOLD · Jun 13, 2020

Water-Jet, keeps it cool and doesn't care what material it is.

ripperj · Jun 13, 2020

OCTANE WORKHOLD said:
Water-Jet, keeps it cool and doesn't care what material it is.

Pretty sure if the OP had a water jet we would not be having this conversation

About all I can come up with is agreeing with some hack of a chop saw or angle grinder with cutoff wheels to make them sorta round , then mount them on a pivot and grind them true.
I’d have nightmares if I ground them on my mill

I’m a bit curious as to what the end result is for ?

Sent from my iPhone using Tapatalk Pro

Limy Sami · Jun 13, 2020

Clodbuster said:
I already tried it with an OA torch setup. It makes the cut fine, but the heat warps the discs into a bell shape which makes them no good as parts. I need a cooler process..

Sounds like you're putting far too much heat in to it ( a common error when OA cutting) so may I suggest you sharpen your cutting torch act

Make a simple jig so the torch can be held at the right radius and distance from the plate.

Clean (with a flap disc etc) no rust and no paint, both sides of where you are going to cut, and a ''lead in track'' from the rim.

By T&E (trial and error), use the smallest nozzle possible - which for 1/8'' would be the smallest available.

Set the smallest preheat flame possible (again by T&E) then move in quickly from the edge and begin rotating as quick as you can and still cut

A bit of practice will soon have the job right.

On Edit. For the record, I have done the self same job, many dozens if not hundreds of parts, ……..over 40 years ago and with only an OA torch and angle grinder.

triumph406 · Jun 13, 2020

Use the smallest endmill you can get away with.

So if it grabs etc, it will break the endmill.

If you do it with a large end mill, the endmill will not break but could hurt you depending on how your holding the disk

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