How to get a perfect radius

[kwb]

Have a 1/2" plate that I want to put a radii on the edge of. I am not set up to mill the edge of plate. How can I put a consistent radius on about 12' of edge.

If I was working in wood it would be easy with a roundover bit in the router.

 

[nine4gmc]

lots of hand grinding and a contour gauge?

 

[kwb]

lots of hand grinding and a contour gauge?

I am hoping to find something a bit better than that but it might come down to exactly that.

 

[ClintNZ]

How about roughing it out with the grinder then making some sort of adjustable jig to hold a file so you can take off progressively narrower & more numerous strips until you get close enough to your curve?

Cheers
Clint

 

[BJ42LX]

For just $20 this may be worth a try.

http://www.toolocity.com/316-inch-radius-brazed-diamond-router-bit.aspx

I'd do some manual grinding first to minimize the work necessary with the router bit.

 

[JCByrd24]

I'm assuming steel is the material. A carbide router bit would work in aluminum, and might even work in steel. You could also try to shape a stone wheel for a die grinder with a single point diamond dresser, then run that in a router with fence or other guide.

 

[racingtadpole]

If you have a Dremel tool you could fashion a guide for it out of timber or Al and use that with the baseplate and steel engraving bit. Be a bit slow but it should give you consistency. Could probably do something similar with a die grinder if you have one.

 

[4xdog]

Weld or fillet braze a 1/2" round rod to the edge, and file/grind smooth the surfaces where the bead was laid in between the plate and the rod?

 

[IronCleveland]

Do you have a torch. If so I can post some pictures of the circle burner I made.

Sent from my SCH-I545 using Tapatalk

 

[ZRX61]

If you have a Dremel tool you could fashion a guide for it out of timber or Al and use that with the baseplate and steel engraving bit. Be a bit slow but it should give you consistency.

On 1/2in steel plate? LMFAO!!!!

 

[bimmer1980]

http://www.globalindustrial.com/p/m...gclid=CIi6ps7fl78CFUwV7Aod62EAWg&gclsrc=aw.ds

Now you just need a router big enough to handle this cutter......

Just curious--what is the application? how critical is the radius on the plate?

I could get pretty close with a 36 grit disc on a grinder and then switch over to a flap disc for the final shaping....

 

[Kevin54]

Have a 1/2" plate that I want to put a radii on the edge of. I am not set up to mill the edge of plate. How can I put a consistent radius on about 12' of edge.

If I was working in wood it would be easy with a roundover bit in the router.

Get a belt sander and go at it. It will not be precise consistent, but it will be consistent enough that if you are doing this for someone else, they won't ever know. Precision takes precision tools, but if you are not set up to do that, then you have to go with the next best thing and trust your eye. Knock it down with a belt sander, and if necessary, get a large ******* file, use it like a drawknife, and go by feel, plus eyeing it in.

 

[dr_clyde]

I do know with a proper setup, a carbide tipped router bit will cut mild steel. I have never tried it personally, but I have seen it done in a milling machine. I bet if you took enough passes with a guide, a 1/2" shank high horsepower router would do the trick. I'd be super careful and wear all the PPE I could get my hands on, though.

I would just get a corner rounding endmill and a case of beer and head for a machine shop, though, because routers and steel make me nervous about flying carbide if something goes south.

 

[ranger302]

I do know with a proper setup, a carbide tipped router bit will cut mild steel. I have never tried it personally, but I have seen it done in a milling machine. I bet if you took enough passes with a guide, a 1/2" shank high horsepower router would do the trick. I'd be super careful and wear all the PPE I could get my hands on, though.

^ This, i have done this with a 2 hp router and a cheep round over bit from the Depot. Was LOUD, it worked and very fast compared to hand filing.

 

[383 240z]

Why not chuck one of these

with a 1/2 shank, in a regular router, use a speed controller, to set the RPM, and make a BUNCH of light passes, very light since most routers are only 1/4 HP, using a guide clamped to the steel? Keith

 

[RoosterBooster]

... I would just get a corner rounding endmill and a case of beer and head for a machine shop, though, because routers and steel make me nervous about flying carbide if something goes south.

best advise yet

yeah i use the router on aluminum, but steel ??? ... no thanks

 

[nine4gmc]

Weld or fillet braze a 1/2" round rod to the edge, and file/grind smooth the surfaces where it starts to roll over?

This is another good idea

 

[RoosterBooster]

Why not chuck one of these

with a 1/2 shank, in a regular router, use a speed controller, to set the RPM, and make a BUNCH of light passes, very light since most routers are only 1/4 HP, using a guide clamped to the steel? Keith

controlling the vibration (chatter) will be a *****

 

[kazlx]

Is it for looks or serve a purpose? If it needs to be dead nuts, you have to machine it, unless you want to be there all year with a file or belt sander.

 

[Justanoldguy]

Do you have a torch. If so I can post some pictures of the circle burner I made.

Sent from my SCH-I545 using Tapatalk

I think you totally missed the question.
Go back to step 1 and start again.

 

[JonnyMac]

My guess is your local machine shop would do it for $20.
I debate things like this in my head regularly (most recent was how to cut rail track to an anvil shape) its so much quicker and easier to let someone with a tool to handle it do it..
Jonny

 

[kwb]

My guess is your local machine shop would do it for $20.
I debate things like this in my head regularly (most recent was how to cut rail track to an anvil shape) its so much quicker and easier to let someone with a tool to handle it do it..
Jonny

$20 won't make anyone bat an eye around here.

The PNW is one of the most expensive places in the US to do anything and aside from aerospace we have very little industrial base to draw from for this sort of thing.

I think grinder / belt sander is going to be my best bet. It is pure aesthetic but the edges are long enough that it needs to be good. As long as they don't want a high gloss finish I probably get away with some quality time burning up a couple flap wheels.

 

[J king]

20 bucs for 12 ft? Lol

 

[spooler41]

I think I coud have finished that job, in the time it took to read this post. With a 4.5"
grinder and a good disc it wouldn't take long.

..........................Jack

 

[BigMike782]

Or from the time it was first posted it could have been done with a Dremel

 

[McLean]

4.5" angle grinder w/ a flap disc. Maybe fashion a quick 'n dirty fixture to hold the grinder that locates off the edge and slides on the top?

Doing it by hand would be quite feasible too, esp with a fresh 40 grit flap disc and a contour gauge.

 

[racingtadpole]

Or from the time it was first posted it could have been done with a Dremel

Probably should wear my glasses more regularly what I thought read 12" is in fact 12'.... Metric..one day maybe.

 

[OccupantRJ]

Off topic a little, but I just ground a radius as you describe on a slab of 30 mm granite with a standard flap wheel on a 4-1/2" grinder, if this helps anyone else in a similar situation. A hard wheel followed by a flap wheel should do a suitable job on the steel plate. Trick is to make full passes the length of the plate, adjusting the roll angle with each pass.

 

[IronCleveland]

I think you totally missed the question.
Go back to step 1 and start again.

Sure did, disregard.

 

[JonnyMac]

Ha ha... I read it as 12 inches not feet!!! Metric is where its at!!

 

[bamatj]

If you really have to have a full radius you are going to have to grind awhile. You better plan on buying a 7 inch grinder and the roughest wheel you can find. You will still probably need a 4.5 to rest some. I hope you can flip the plate over because doing the bottom will be rough. It can be done though, not trying to discourage you lol. Knocking the edge off something is one thing, a full 1/2" radius 12' long is a whole different ball game.

 

[bamatj]

Actually I wasn't thinking when I posted that. You will be doing a 1/4" radius. Still a lot of grinding. I was checking out an online surface area calculator. If I punched the numbers in right it would be the same as taking a 6 foot long 1/4" rod and grinding it to dust. That is if you ground a perfect radius. I could be wrong though, I'd like to see if anybody else comes up with the same thing.

 

[bamatj]

If I'm doing the calculator right its also the same as a 2 inch bar, 17" long.

 

[dr_clyde]

No matter how you do this, it's going to be a lot of work.

The cheapest is a big *** grinder and a lot of 36 grit discs. But it's hard work and tricky to get the radius right.

If you have a good size welding shop nearby they may have a line burner that could knock a bevel on the edge that would save a lot of grinding.

They also make small mills that run on a track for beveling large plates. See if you can rent one. Just put a corner rounding mill in instead.

 

[Kevin54]

I'll tell you right now, there is no job shop around that will do that for $20. In todays world, the burden rate for a job shop is probably in the $200/hr. range. Could they do it in an hour.....maybe. It all depends on the setup.

A good coarse grit belt in a belt sander will knock it down, and fairly quickly. It may take an hour or so, but it will do it.

And if this is just for safety and/or aesthetics, you may not even need a 1/2" radius.

 

[Justanoldguy]

I'll tell you right now, there is no job shop around that will do that for $20..

Pretty sure that issue was resolved earlier...

 

[ng8264723]

what about making a jig for an angle grinder? That would allow the lines to stay even. You can cut and move.

 

[PT Doc]

I used a flap disc on -/2" plate and created a bevel on both sides of the plate I believe it's about 20" x 30". A coarse flap disc preferably ceramic will make quick work of it. Get a ceramic belt from lowes for your belt sander. That will allow you to make longer sweeping passes.

I would just put a small 45 on the edge.freehandong a nice looking radius will not be easy without the right equipment.

 

[theknurl]

On 1/2in steel plate? LMFAO!!!!

yes.......12 feet of 1/2" plate

 

[BFBOB]

Actually I wasn't thinking when I posted that. You will be doing a 1/4" radius. Still a lot of grinding. I was checking out an online surface area calculator. If I punched the numbers in right it would be the same as taking a 6 foot long 1/4" rod and grinding it to dust. That is if you ground a perfect radius. I could be wrong though, I'd like to see if anybody else comes up with the same thing.

Okay, you're on! A 1/4" rod has a cross sectional area of pi r^2, or 3.1416 * .125 * .125 = .049 sq". Multiply that by the length, 72" and the result is 3.53 cu".

Figuring how much material is removed doing a 1/4" roundover is a little trickier. Start with a rectangular solid the the thickness of the plate by the thickness by the length, or .5" x .5" x 144". Subtract the volume of the inscribed cylinder, .5" dia x 144". That gives you the volume of material to be removed to turn the rectangular solid into a cylinder. With me so far? Now, since we're only rounding over one edge, the material removed is on fourth of that.

So: Rect.Sol.Vol= .5" x .5" x 144" = 36 cu". Volume of the inscribed cylinder = pi r ^2 = 3.1416 * .25 * .25 = 28.27 cu". Subtract, and you get 7.73 cu". One fourth of that is 1.93 cu". Equal to the volume of a 39" long 1/4" rod. Still a fair amount of material to remove, but not so tough with a belt sander, which would be my choice. I'd make the final run using the free-running section between the front roller and the platen, with a fine grit (120 or so). There, the belt will follow the contour of the roundover and sand off the lateral ridges left by going back and forth. It would take several belts of at least 3 grits, but probably not more than a couple of hours.