Machining Question

[lbc_PSI]

OK, I've got a sherline mini lathe and I'd like to machine some o-ring grooves.

What type tool is best for cutting an o-ring groove in aluminum or delrin?

Are there specialized tools or cutters?

Could a thread-cutter be used?

Right-Hand Internal Threading Tool - Sherline Products

www.sherline.com

ANd lastly, hat is the depth the groove should be cut..is it a percentage of the o-ring cross-section(thickness) measurement?

 

[Vetmx]

I use a parting blade ground to width for outside orings. For internal orings I use specific tools for cutting them.

 

[ChrisS]

Yup, what Vetmx said. I even dress them round on the cutting edge.
Chris

 

[HogKiller]

OK, I've got a sherline mini lathe and I'd like to machine some o-ring grooves.

What type tool is best for cutting an o-ring groove in aluminum or delrin?

Are there specialized tools or cutters?

Could a thread-cutter be used?

Right-Hand Internal Threading Tool - Sherline Products

www.sherline.com

ANd lastly, hat is the depth the groove should be cut..is it a percentage of the o-ring cross-section(thickness) measurement?

You have the ID and the Cross section x2 there is your diameter, less a tiny bit if you want it a touch snugger.

 

[Metalmaniac]

I use cobalt high speed tool steel. Sometimes a parting tool. Use a radius gauge to check profile to grind proper radius on tool.
Hold tool and gauge up to a light source. Grind or hone on a stone until you see no light. Break sharp edges on part machined.
Taper tool a few thousandths front to back and top to bottom for clearance of tool to part so it want chatter on larger O rings.

MM

 

[KWK]

You need to learn to grind HSS tool bits to get the most out of that lathe. Form bits and parting tools are prone to chatter. You might have to slow it down some. I recommend 0 top rake for form bits, parting tools, and threading bits.

 

[KWK]

Form bit cutting grooves. Like parting

No safety glasses! Only posed for a picture. A young man in my shop that day.

Not polished. This is the finish obtained with properly ground HSS. A nice machined finish is better than polished.

 

[lbc_PSI]

Thanks folks!! Sometimes the answer is already in your toolbox.

The tip on grinding the HSS tool bits to create custom shapes is a great idea.

 

[thomasair]

Fwiw….lighter machines do better with the parting tool below centerline. With the tool below center….it will take a smaller bite when things flex rather than a bigger one.

 

[KWK]

WD 40 is a good lubricant for form cutting or parting aluminum. Prevents it from welding to your cutter. Don't be sloppy and pour it on. An acid brush with little oil held in the groove is all you need. It only takes a thin film. It ain't coolant!
The proper feed rate can also be essential to avoid chatter. Practice on a scrap. Then you know exactly what your depth setting should be

 

[Vetmx]

Fwiw….lighter machines do better with the parting tool below centerline. With the tool below center….it will take a smaller bite when things flex rather than a bigger one.

Thank you for this. I’ve noticed a difference between when I’m working on a big South Bend compared to a mini. Now I know. I’ll build the majority of a barrel on a big mega dollar lathe then finish some things on a mini or when I have to make adjustments. I’ve questioned some of the things I’ve experienced. I just never understood it.

 

[thomasair]

I hope it helps.

A simple way to gauge below or above center on a standard lathe (not slant bed) is to place your 6” machinist scale between the part and tool and bring the tool into contact with it while the lathe is not turning. If the scale is leaning with the top away from you, it’s above center. If it’s leaning with the top toward you it’s below center.

Mike

 

[Vetmx]

Yep, but I have my mini lathe set to center and it seems to want to take bites when parting or cutting a groove. I will set the blade slightly below center the next time and see how it goes.

 

[KWK]

Could be: Rigidity issue, or feed speed, or surface speed, or lubricant, or too much rake, or gibbs not adjusted right. Some like to keep the compound slide gibbs a little snug unless you're feeding with it like cutting a taper. Once you find the right surface speed and feed rate parting works best under power feed. Some operators find that a little intimidating. It takes practice. If your tool post holds the bit too far to the side, that can cause twisting. No good. Big tool posts on tiny lathes may not carry the cutting load straight down through rhe compound and cross slide and into the saddle.

 

[Sergey1972]

Parker handbook for oring gland dimensions.