Machining grooves

[itsme]

Hi there,

I've been thinking about how I can machine round grooves into the face of a round piece of stock (either aluminium or iron).

The grooves need to have parallel sides with flat bottoms. They have to be very accurate in terms of roundness and the finish needs to be very good. They will also be quite narrow and fairly deep - about 1mm wide (maybe even less) and perhaps 3 or 4 mm deep. I'm not sure of the diameter of the grooves, but it would probably be greater than about 80mm.

Because of the above criteria, I have pretty much ruled out a milling machine and minute endmills due to accuracy, finish and fiddly-ness problems. I have been thinking about using a lathe with a tool that looks like a parting off tool. The one side of the tool would have to be angled to clear the outside radius of the grooves, but otherwise it could be like a normal parting tool. I have included some simple drawings to try and make myself more clear.

Do you think the above setup would be suitable for this?

Thanks
Warren

[ViperTX]

Yes, that will work. Just make sure that the support for the cutting edge is small enough so you don't get a wider groove...take a look at some of the grooving tools available.

[Geof]

The tool you draw is what is needed but 1mm is very narrow for a depth of 3 or 4 mm. One thing that you may find is needed is to carry your top rake back a bit more than the full cutting depth. This way if the chip curls it will curl outside the groove.

[mrainey]

For Googling purposes, that type of tool is often referred to as a trepanning tool.

[Mcgyver]

what everone else said, thats a tough cut at only 1mm wide. any chance for a design change?

[Verfur]

The tool should have a radial relive to match or be smaller than the radi of the out side of the groove and the in side would have a radial relive same as or larger than the inside of the groove. The hole thing would simaler to a hole saw only with one tooth and it would need to be taller from the top of the tool to the bottom of the tool of the tool bit with little relive from the bottom of the groove. I would try a hole saw and gind all the teeth but one off and sharpen and relive the tooth. Or go with EDM machine $$$$$$$ and lots of TIME.


John

[One of Many]

The only thing I could add, would be to custom grind the radius to maintain as much material in the tool as possible. If you started with a 3/8" blank that is ground to .09 thick for a length of .2, you could then grind the profile of the radius to about .035-.038 thick by swinging it past a small grinding wheel.

Dress the wheel to add relief tip to root and shift the center of the swing radius to add relief top to bottom.

DC

[JPMach]

It's called a face grooving tool. Go to www.iscarmetals.com and search for tool #PICCO R 610.1008-20, it only goes to 1.5 mm deep but it could probably be modified to go deeper. It is made out of solid carbide, so at that width and depth it should give a nice finish.

JP

[itsme]

Hi there,

Thanks for all the replies.

I'm not going to be making this cut any time soon - at least not within the next few months. Sadly, the size can't be changed (well, it could be made smaller, but that doesn't really help). The grooves will be for side seals on a small rotary engine. What I find quite amazing is that Mazda have used side seals on their rotary engines that are only 0.7mm wide. Their grooves are cut about 5mm deep into cast iron .

I might grind some tools up this weekend and have a few test cuts in scrap material. I'll see how many it takes to make one groove. I'll also have a look around at what tools are already available.

Regards
Warren