Anybody have any pointers on machining keyways in 304 stainless?

machineshaft · Feb 2, 2020

Currently I machine a lot of fully keyed shafts out of mostly 1045 with the occasional request for 4140ht. I do it on a K&T horizontal and it works great. However, lately I have had people asking me if I would make these shafts out of 304 stainless.
I know nothing about doing such an operation, coolant %, speeds, feeds or whether to do it in one pass like the 1045 or not. My sense tells me 2 passes but before I go scrapping cutters I thought I would ask the experts.

Thanks in advance , Jaeson

MrWhoopee · Feb 2, 2020

The first thing I would do is ask if 303 is acceptable.

machineshaft · Feb 3, 2020

Yeah I agree but this particular customer told me they wanted 304 due to outdoor operation of some sort of conveyor system, and the additional sulfur content would decrease its resistance to corrosion. So I am kind of stuck with it unfortunately.

They were talking about ordering a pretty good quantity and they are not afraid to pay for them , and i would like to open a new door.
My steel supplier wants anywhere from $6.75- $7.00 per pound. Wow am used to buying 1045 at about $1.10.

Hardplates · Feb 3, 2020

Rigid set-up, sharp tool, slow speeds, highish feeds. Get in and get out, do not rub or take a dinky cut as it will work harden and all head downhill from there.

Unlike many people I like working with stainless. It's pretty easy to get a really nice finish. It's not very forgiving but if you have everything set-up correctly its easy to work with.

machineshaft · Feb 3, 2020

I definitely have the rigidity am using a pair of 8" vises side by side with V blocks in each one of them.

I will make a mental note of the cutting situation that you mentioned thanks so much for that. Does the cutter need to be carbide tipped? Or will steel cutters work with coolant?

cyanidekid · Feb 3, 2020

machineshaft said:
Yeah I agree but this particular customer told me they wanted 304 due to outdoor operation of some sort of conveyor system, and the additional sulfur content would decrease its resistance to corrosion. So I am kind of stuck with it unfortunately.

They were talking about ordering a pretty good quantity and they are not afraid to pay for them , and i would like to open a new door.
My steel supplier wants anywhere from $6.75- $7.00 per pound. Wow am used to buying 1045 at about $1.10.

wow indeed. is that for ground and polished shafting? 304L? as to the need for carbide, id say IF your stainless is of consistent and proper analysis and free of nasties like carbide and AlO2 inclusions it would probably be fine, but if you really have the volume why not just invest in carbide? maybe start at 50% of 1045 steel speeds?

Gordon Heaton · Feb 3, 2020

I don't mind working with 304, and I always use carbide. I do a fair amount of single-pointing and cutting flats and keyways in rounds (304L for me). The worst thing about it is deburring. It isn't hard, but there's always a burr. For coolant I use Rustlik WS-5050 @ 1:14 mix through a mister. Watch out for stringers, they're sharp and strong! Even the thin ones will cut you before they break.

MrWhoopee · Feb 3, 2020

If I understood correctly, these are keyed full length. If so, I would do a trial piece before investing in a lot of material. It may end up looking like a banana.

machineshaft · Feb 3, 2020

Gordon Heaton said:
I don't mind working with 304, and I always use carbide. I do a fair amount of single-pointing and cutting flats and keyways in rounds (304L for me). The worst thing about it is deburring. It isn't hard, but there's always a burr. For coolant I use Rustlik WS-5050 @ 1:14 mix through a mister. Watch out for stringers, they're sharp and strong! Even the thin ones will cut you before they break.

1:14 noted thank you

These will be fully keyed rounds of 304L and I am doing them on a horizontal. My question would be do the indexable cutters hold size well enough for one pass and not go O.S. I use the steel ones now and usually stone down the sides of them about .0005 so they wont go more that .002 O.S. when machining 1045.

machineshaft · Feb 3, 2020

MrWhoopee said:
If I understood correctly, these are keyed full length. If so, I would do a trial piece before investing in a lot of material. It may end up looking like a banana.

Yes I was going to pick up a 1" x 24" as they want a sample part before they start talking quantity with me.

Good input thank you

machineshaft · Feb 3, 2020

cyanidekid said:
wow indeed. is that for ground and polished shafting? 304L? as to the need for carbide, id say IF your stainless is of consistent and proper analysis and free of nasties like carbide and AlO2 inclusions it would probably be fine, but if you really have the volume why not just invest in carbide? maybe start at 50% of 1045 steel speeds?

Yeah will be 304L but is listed as 304/304L stainless steel cold finished annealed round.
50% of 1045 speeds noted thank you

jim rozen · Feb 3, 2020

Cutter speed: slower than you think.

Feed rate: faster than you think.

Cutting fluid: you cannot go wrong with black sulfurized cutting oil.

Do NOT let the cutter dwell in the cut or the part will work harden badly.

Cole2534 · Feb 3, 2020

Gordon Heaton said:
Watch out for stringers, they're sharp and strong! Even the thin ones will cut you before they break.

Yet still I think, I can just peel this one away...and it never works.

Gordon Heaton · Feb 3, 2020

machineshaft said:
. . .do the indexable cutters hold size well enough for one pass and not go O.S. I use the steel ones now and usually stone down the sides of them about .0005 so they wont go more that .002 O.S. when machining 1045.

I would think 304 would be the same in that regard. Best bet is to run a test cut and see what it yields. As for repeatability the carbide (indexable or solid) should be very consistent.

MrWhoopee · Feb 3, 2020

machineshaft said:
Yeah will be 304L but is listed as 304/304L stainless steel cold finished annealed round.

Watch out for this material. The straightening rollers create a very subtle tri-lobed shape. It will mic on size but won't pass a ring gage or close tolerance bored hole. We ended up keeping centerless ground 303 in stock to save the aggravation.

Gordon Heaton · Feb 3, 2020

MrWhoopee said:
Watch out for this material. The straightening rollers create a very subtle tri-lobed shape. . .

Excellent point! In the larger sizes, up around 3" the effect is not so subtle. Easily seen with the naked eye in the right light, and it can take from 5-15 thousandths to clean up.

machineshaft · Feb 3, 2020

Thats good to know thanks

thermite · Feb 4, 2020

machineshaft said:
... before I go scrapping cutters I thought I would ask the experts.

Thanks in advance , Jaeson

My "experts", and since forever-ago:

RoundRail Shafting | Thomson | Find a Product

Same-day / next day shipping, 440C or 316 Stainless.

Full-length keyways are a standard option.

Most recent order was for a mere 36" of 1 1/2" OD full-length keyway, ignorant 1556. Not even CLOSE to my "first ever" order. Shafting is what they do. See also "Grob spline". Both have competition. It's an industry.

If you are going to compete on commodity items with the "Big Boys"? What does your client know that they do NOT know?

Seems the least you could do is copy their use of 316?

machineshaft · Feb 4, 2020

Yeah I see your point, looks like 316 meets all aircraft industry requirements and a boatload of other things.

Is it more machinable that 304?

kenton · Feb 4, 2020

304 has better machinability than 316 but 316 is more corrosion resistant. The machinability difference between the 2 may not make much difference but given the choice I would choose to cut 304L.

Anybody have any pointers on machining keyways in 304 stainless?

Plastic

Hot Rolled

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Stainless

Plastic

Titanium

Titanium

Hot Rolled

Plastic

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Diamond

Diamond

Titanium

Hot Rolled

Titanium

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