Full convex radius grooving

Dakotahm88 · Jan 7, 2023

New to machining. Still learning. I was wondering, because I can’t find a full convex radius radius cutter larger than 1/2”.

What is the easiest way to put a 9/16 full radius convex Groove in a 18” diameter sheave?!?

M. Moore · Jan 7, 2023

Dakotahm88,
Welcome to the forum. This is the “tooling andparts for sale” area and is not for general questions.
Post your question in the general area and you will get some responses.

eKretz · Jan 7, 2023

Generally you either grind them yourself or get it done at a tool grinding shop.

michiganbuck · Jan 7, 2023

With a 1/2" bit lathe one can grind two halves of a radius checking with a radius gauge, and turning 1/2 at a time. Sometimes one might tickle the last touches with a file.

L Vanice · Jan 7, 2023

Dakotahm88 said:
New to machining. Still learning. I was wondering, because I can’t find a full convex radius radius cutter larger than 1/2”.

What is the easiest way to put a 9/16 full radius convex Groove in a 18” diameter sheave?!?

Convex groove? Did you mean concave? A CNC lathe makes it easy to machine a radius, so that may be the simplest answer.

On a manual machine, it probably needs a custom tool. A grinding shop could make a 1-1/8" wide 9/16" radius nose form turning tool in HS or carbide. I would not try to plunge cut the whole groove with that wide a tool. Rough out the groove with a parting tool making a series of near adjacent grooves of varying depth to get most of the iron cut out of the way and then carefully plunge the form tool in to finish the groove.

Shaplane or Holdridge made radius turning tools that could do a 9/16" concave radius. Holdridge is out of business, but used ones are around. Shaplane is still made and they have one model that can do a 9/16" inside radius on a lathe that swings 18 inches or more.

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Larry

Dakotahm88 · Jan 7, 2023

I need to cut the groove that the cable lays in on sheave.
I was looking for something similar to this, but 9/16”, and as you stated, I’d do the majority of the work with parting tool then shape it with this tool.

Dakotahm88 · Jan 7, 2023

Ohhh I see how that works. Never seen one of those before. Pretty darn cool.

L Vanice · Jan 7, 2023

I am still wondering if you want a groove to fit a 1-1/8" (9/16" radius) cable or a 9/16" cable.

Whichever, there is another (and cheaper) way to turn a concave groove. After roughing it out with the parting tool, use a round nose carbide wood lathe tool on a T-rest. You can use a radius gage or cut a piece of thin sheet metal to the desired shape to use as a guide to get pretty close to the desired shape.The T-rest can be as simple as the end of a lathe tool held parallel with the lathe bed. I have been turning metal with hand held tools since I got my first lathe in 1953. It is the easy way to do curved surfaces without fancy equipment.

https://www.amazon.com/dp/B07S8XBW2H/ref=sspa_dk_detail_0?psc=1&pd_rd_i=B07S8XBW2H&pd_rd_w=bNxkX&content-id=amzn1.sym.4d0fffec-3aba-4480-8fad-c6bd8f7f6b41&pf_rd_p=4d0fffec-3aba-4480-8fad-c6bd8f7f6b41&pf_rd_r=M8CVE1AFHRFT7D40AEQY&pd_rd_wg=d4VBj&pd_rd_r=3560dd4d-d269-4cdc-b731-125cd144d9e1&s=hi&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWxfdGhlbWF0aWM&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExUUxYOFk4VlRFV0hNJmVuY3J5cHRlZElkPUEwMjc0NTY3WDBGU1VBNlRSNzhIJmVuY3J5cHRlZEFkSWQ9QTA5NzI3MDMxOEk1N0NYM1BQQ0hVJndpZGdldE5hbWU9c3BfZGV0YWlsX3RoZW1hdGljJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

I do not have the above tool, so I cannot say whether the geometry of the insert is suited to steel or cast iron. But they might work. I use old Craftsman brand wood turning tools that are no longer sold.

Larry

Dakotahm88 · Jan 7, 2023

Sorry for confusing everyone, and posting in wrong forum lol.

It’s for a 9/16” cable. While that method sounds like loads of fun, I’d probably hurt myself. I should probably get a little more experience under my belt first.

L Vanice said:
I am still wondering if you want a groove to fit a 1-1/8" (9/16" radius) cable or a 9/16" cable.

Whichever, there is another (and cheaper) way to turn a concave groove. After roughing it out with the parting tool, use a round nose carbide wood lathe tool on a T-rest. You can use a radius gage or cut a piece of thin sheet metal to the desired shape to use as a guide to get pretty close to the desired shape.The T-rest can be as simple as the end of a lathe tool held parallel with the lathe bed. I have been turning metal with hand held tools since I got my first lathe in 1953. It is the easy way to do curved surfaces without fancy equipment.

https://www.amazon.com/dp/B07S8XBW2H/ref=sspa_dk_detail_0?psc=1&pd_rd_i=B07S8XBW2H&pd_rd_w=bNxkX&content-id=amzn1.sym.4d0fffec-3aba-4480-8fad-c6bd8f7f6b41&pf_rd_p=4d0fffec-3aba-4480-8fad-c6bd8f7f6b41&pf_rd_r=M8CVE1AFHRFT7D40AEQY&pd_rd_wg=d4VBj&pd_rd_r=3560dd4d-d269-4cdc-b731-125cd144d9e1&s=hi&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWxfdGhlbWF0aWM&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExUUxYOFk4VlRFV0hNJmVuY3J5cHRlZElkPUEwMjc0NTY3WDBGU1VBNlRSNzhIJmVuY3J5cHRlZEFkSWQ9QTA5NzI3MDMxOEk1N0NYM1BQQ0hVJndpZGdldE5hbWU9c3BfZGV0YWlsX3RoZW1hdGljJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

I do not have the above tool, so I cannot say whether the geometry of the insert is suited to steel or cast iron. But they might work. I use old Craftsman brand wood turning tools that are no longer sold.

Larry

Dakotahm88 · Jan 7, 2023

So I need one of these, 9/32 radius.
Which I don’t see available either. Or buy that fancy thing, which I’ll probably end up doing just to have it.

sfriedberg · Jan 7, 2023

Get yourself a HSS blank, either square or rectangular with a width at least 9/16". A 5/8" blank is probably 4.5 or 5" long, and will mount in a toolpost toolblock with no need for a separate bit holder. Use a bench grinder to put the desired 9/16" diameter profile on the blank. For simplicity, leave the top of the blank unground and mount it as a zero-rake cutter. (Top of the blank at lathe centerline.)
Or, get yourself a sufficiently large brazed carbide cutter with a rectangular profile, say 5/8" wide. Using diamond wheels (rather than green silicon carbide wheels), and preferably using something like a Baldor 500, put the desired 9/16" diameter profile on it. You should rough away the steel shank using normal grinding wheels, before switching to the diamond wheels, as the diamond may be slowly consumed by iron/steel.
Or, get a slightly smaller HSS blank and grind left-hand and right-hand quarter circle profiles on opposite ends of the blank. Or buy two brazed carbide blanks and grind quarter circle profiles on each.

michiganbuck · Jan 7, 2023

For a one-up?..for a 9/16 cable?
Still another option might be to take a 9/16 HSS drill (or a 5/8 to 1" drill) and cut it off near the end of the flutes, and toss the drill flute end in the dumpster. Grind it just about halfway through at the out end to 5/8 back, and grind the shank/but end to fit your tool holder...and grind the out end to a 9/16 nose (or what) with clearance below the cutting edge. But full-round 9/16 is a huge bite to take, and likely to have a ton of chatter cutting in one shot.
*RE: Yes just using a scrap any size drill for the HSS material source... and run on a beach grinder/or a surface grinder.

As you mentioned, may have to notch it out with a tool bit of sorts like a 1/4 to1/2" tool bit with a 9/16 nose.

Yes, a 9/16 drill cut short will be a tad under 9/16 but that may help you to take a little from one side and then the other, so you do not have a 9/16 wide chip. Breaking strength will be a little less than a 1/2 " tool bit with using a 9/16 drill.
Perhaps go in with a parting tool with a 9/16 nose to make almost depth ar a rougher.
For a
9/16 cable you may want a .600 groove ..I dont know how much bigger it should be

L Vanice · Jan 7, 2023

Dakotahm88 said:
So I need one of these, 9/32 radius.
Which I don’t see available either. Or buy that fancy thing, which I’ll probably end up doing just to have it.

If by fancy thing you mean a Shaplane, they do not sell one that does a 9/32" radius The smallest is for 3/8" or larger radius. In the first post, you asked for a 9/16" radius and got answers based upon that request.

Another cheap way to finish a 9/32" radius groove is to take a 9/16" HS drill blank and grind the end square across. Feeding the sharp end into the groove tangentially will produce the desired radius groove.

https://www.msdiscounttool.com/catalog/product_info.php?products_id=25920 Only $15 each for a cheap import.

Larry

EmanuelGoldstein · Jan 8, 2023

L Vanice said:
Another cheap way to finish a 9/32" radius groove is to take a 9/16" HS drill blank and grind the end square across. Feeding the sharp end into the groove tangentially will produce the desired radius groove.

Stand it up on end, weld/braze/silver solder onto a piece of 1" square steel of any type ? You could even drill a flat-faced hole vertically a little less than halfway into the end of the toolholder bar if you can't weld, braze, or silver solder.

Mucho ways to skin the kitty.

DDoug · Jan 8, 2023

Who here thinks cutting a full diameter in one plunge cut is going to chatter ?

Overland · Jan 8, 2023

This might work, then move it side to side etc, to get the form you need, that you could check with a 9/16" drill.
Bob

edit: well it might chatter like the ex, but hopefully a stout lathe and some care, and maybe a round file to clean up.

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mjk · Jan 8, 2023

Am I the only one that would be concerned with someone new to machining taking on an 18" diam sheeve?
If you have a lathe large enough to handle one, either you should know what to do or have someone who does

Firstram · Jan 8, 2023

Use the mill, I just did this yesterday to convert a V-belt pulley to 1/2" rope. Obviously, the setup would be a little more involved with a disc that large. A rotary table with a horizontal cutter or a dividing head off the back of the table with a 9/16 end mill would do it.

richard newman · Jan 8, 2023

Dakotahm88 - you will get much more useful advice if you tell us what machines you have at your disposal, how many you need to do, what material, and for what use.

And for the experts out there, how accurate does the groove need to be for cable?

SIP6A · Jan 8, 2023

DDoug said:
Who here thinks cutting a full diameter in one plunge cut is going to chatter ?

Anybody that has done it

Full convex radius grooving

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