Full convex radius grooving

eKretz · Jan 8, 2023

Depends on the size of the machine. On smaller machines, yeah, no doubt. You can get away with a lot by barring the chuck around by hand for the finish though - as long as the tool is really sharp. And setting it a smidge below center helps.

L Vanice · Jan 8, 2023

eKretz said:
Depends on the size of the machine. On smaller machines, yeah, no doubt. You can get away with a lot by barring the chuck around by hand for the finish though - as long as the tool is really sharp. And setting it a smidge below center helps.

I think turning a groove on an 18" sheave demands a rather big and likely heavy lathe. There has been no suggestion that the OP was going to use a 12" Atlas with riser blocks or any other such lame thought. My Powermatic wood lathe has a left hand faceplate thread on the left end of the headstock. They sold T-rests with heavy bases that stand freely on the shop floor to allow turning wooden bowls and such of very large diameter, but I class turning 18" iron on that rig with the Atlas and riser blocks method. Probably get some views on Youtube and maybe AFV if it was recorded, though.

The chatter issue was addressed previously with agreement to rough out the shape with a cutoff tool before finishing the final radius contour.

Larry

DDoug · Jan 8, 2023

L Vanice said:
The chatter issue was addressed previously with agreement to rough out the shape with a cutoff tool before finishing the final radius contour.

Larry

I don't think so...I've gotten nasty chatter just touching the cutter in there to take a final little shaving cut.

cyanidekid · Jan 8, 2023

hell yea, a lot of ways... don't even need a lathe. this could even be done with a
rotary table, a die grinder with a carbide bud burr clamped up to a rigid table. sketchy, but possible,

set it up in a drill press first to hog out some metal by drilling radially around... ? pain in the butt, but possible...

eKretz · Jan 8, 2023

Whether the hand turning rest will work is going to be pretty heavily dependent on whether it's really just a single groove in a pulley/sheave or if it's a drum with a spiral groove to wind up the cable. For the former that should work fine. Not so much for the latter. Seeing as how he's had a little difficulty with terminology already, I'm not sure what he's working with exactly.

Dakotahm88 · Jan 8, 2023

I inherited a Kingston HD22-90.
I went by the terminology on the one tool I found that looked like what I needed. A full convex cutter. I’ve been practicing for about 3 months on a 1440 Jet building 2” pins with grease ways through them, etc… I have not used the Kingston yet, but I’ll be grooving, or re-grooving, a lot of these in the near future and wanted the most efficient way to do it without purchasing a CNC lathe.

DrHook · Jan 10, 2023

Dakotahm88 said:
I inherited a Kingston HD22-90.
I went by the terminology on the one tool I found that looked like what I needed. A full convex cutter. I’ve been practicing for about 3 months on a 1440 Jet building 2” pins with grease ways through them, etc… I have not used the Kingston yet, but I’ll be grooving, or re-grooving, a lot of these in the near future and wanted the most efficient way to do it without purchasing a CNC lathe.

Well, your lathe should be plenty capable...

Are you cutting a single groove, or is it a spiral on a drum? Are you starting from scratch on the pulley(s) or are you re-doing an existing groove?

Dakotahm88 · Jan 10, 2023

all just single groove, and mostly re-grooving although there are times I need to start from scratch. I’d never try to do drum grooving

.

guythatbrews · Jan 10, 2023

Lots of chatter possible, especially if this sheave is spoked. Bolting to a face plate would help but that is a big faceplate and maybe tough to fixture.

Another way to do this is by old school methods. Step over the tool and plunge until you hit the part profile. Use and indexable or hand ground tool maybe 1/16 or 1/8 radius. With a spreadsheet, or if you want to go full old school a note pad and pencil, calculate the tool path radius centerline at the stepover you choose, maybe .020 or .030? Then use the dials to make the cuts. You can vary the stepover, less on the sides and more toward the middle.

Or if you have CAD or CAM get the numbers that way.

Much less chance of chatter.

eKretz · Jan 10, 2023

If the chuck has t-slots it can be clamped back against the jaws or parallels, that will help immensely. Stepping out can be a good option but it's a little time consuming.

guythatbrews · Jan 10, 2023

eKretz said:
If the chuck has t-slots it can be clamped back against the jaws or parallels, that will help immensely. Stepping out can be a good option but it's a little time consuming.

I believe you mention you have more than one to do over time. Maybe a fixture to the chuck t-slots. Just be sure anything in the t-slots can't sling out. The boss was showing away one day on a 24" American and slung out a standoff about 3" round x 2" thick. It was a killing mistake but luckily nobody got hurt. He was a dangerous guy,

His rpm was high and yours won't be. Just don't mess up and start at high rpm.

DDoug · Jan 10, 2023

I would make a template from 1/4" plate mounted under the tool.
.25 radius button tool, .250 dowel pin press fit in stick holder further "back"
towards operator.

Rough out as above, then go in with the button tool, and the template with hand feeding.

BTW I thought I read somewhere (can't find it now) that wire rope sheaves are not supposed to be a simple radius, more of an ellipse.

eKretz · Jan 10, 2023

guythatbrews said:
I believe you mention you have more than one to do over time. Maybe a fixture to the chuck t-slots. Just be sure anything in the t-slots can't sling out. The boss was showing away one day on a 24" American and slung out a standoff about 3" round x 2" thick. It was a killing mistake but luckily nobody got hurt. He was a dangerous guy,

His rpm was high and yours won't be. Just don't mess up and start at high rpm.

Individual standoffs or parallels should be secured to the chuck with t-nuts and studs. The t-slots on a chuck should also be slightly tapered in depth so that they get tighter if slipping to the outside occurs. A fixture may be difficult if there are varied sizes.

The groove should not be the same diameter as the wire rope, it should be slightly bigger. If actually using 9/16" cable the groove should probably be cut to more like a 5/16" radius. Generally the grooves are also shaped with a slight outward taper (larger to the outside) from the centerline of the radius. I've not seen or made any elliptical ones.

Edit: looked it up, new groove for wire rope should be .303" radius.

EmanuelGoldstein · Jan 10, 2023

At the very least you could do it in halvsies, with two tools. That'd help with the chatter. (Yes he's going to have a problem with chatter).

guythatbrews · Jan 10, 2023

DDoug said:
I would make a template from 1/4" plate mounted under the tool.
.25 radius button tool, .250 dowel pin press fit in stick holder further "back"
towards operator.

Rough out as above, then go in with the button tool, and the template with hand feeding.

BTW I thought I read somewhere (can't find it now) that wire rope sheaves are not supposed to be a simple radius, more of an ellipse.

Of course! I have duplicated handwheel handles this way. Much less prone to mistakes than grooving to a dial number and very much quicker.

Dakotahm88 · Jan 10, 2023

DDoug said:
I would make a template from 1/4" plate mounted under the tool.
.25 radius button tool, .250 dowel pin press fit in stick holder further "back"
towards operator.

Rough out as above, then go in with the button tool, and the template with hand feeding.

BTW I thought I read somewhere (can't find it now) that wire rope sheaves are not supposed to be a simple radius, more of an ellipse.

The very bottom is radius then it slowly tapers up to the edge, starts as a U, then goes to a V if that makes sense.

DDoug · Jan 11, 2023

Dakotahm88 said:
The very bottom is radius then it slowly tapers up to the edge, starts as a U, then goes to a V if that makes sense.

Yes, I think that's just a lead in chamfer to handle any mis-alignment.
However somewhere I was reading how a full radius bottom was not good, as it injured the wire rope.

guythatbrews · Jan 11, 2023

One source for sheave groove profile.

Sheaves and Drums - Python Wire Rope

pythonrope.com

Overland · Jan 11, 2023

A little anecdote, maybe of interest....
Back in the '70's in UK auto industry we used to turn crankshaft forgings on a LeBlonde lathe using form tools.
These were special made auto lathes, turning all the diameters at once.
The tools were vertical HSS form tools with a dovetail on the back for the toolholder. They were set at about 5* off vertical for front clearance, and sharpening was by grinding off the top end of the tool at appropriate rake.
Chatter was never really an issue unless we had to replace all tools at once. We'd change out tools a few at a time as the new sharp edges would cause the chatter.
These cranks were for 4 cylinder, 3 bearing cranks for 1,000 cc motors.
Massively rigid machines, and tool boxes.
Such fun,
Bob

Full convex radius grooving

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