Trouble cutting splines in stainless steel

[AndyStobbs]

Could use some advice regarding the above. Couple of pictures will speak a thousand words...

Using this


To cut splines in a replacement driveshaft for my jetski. The cutter is a HSS brown and sharpe, which I have ground to the correct profile for what I need. It was 1/4" wide previously and I have knocked 0.100" off each side to give a point thickness of 0.050" at an angle of 18 degrees (per side).

A test cut on alloy went well


But I have barely eeked out one full spline on the 316 blank and the cutter is now blunt. Splines are 0.050" deep and have been taking cuts of 0.010" (on both the alloy and the stainless).

I had plenty of cutting oil in the picture, and was traversing the carriage by hand at what felt like a nice feed.
Re-sharpening this cutter is an option, but I don't want to do it for every spline, I have got 18 to cut on this end, and 20 to cut on the other end - same profile.

Removing the blank is possible but will have to be very careful to not lose the indexing of the splines.

I think ideally I need a carbide tipped tool, what say you?

 

[mike os]

Has does not last long in stainless. .. hssc ( cobalt) would last longer but I suspect that a tipped tool will be required if you don't want to resharpen during the job

 

[I'm getting on a bit]

You should take the cut at full depth once you are happy with the profile on Ali.

Speed of cutter is critical as well as chip load.

Stainless is prone to work hardening and I think that is what happened in this case.

 

[AndyStobbs]

running at 350ish rpm, 20T cutter

 

[I'm getting on a bit]

I will check my cam software later if no one beats me to it

 

[lchris21]

loving the ingenuity of your "horizontal" mill

 

[I'm getting on a bit]

Hi Andy what is the diameter of the cutter?

 

[penfold]

You should take the cut at full depth once you are happy with the profile on Ali.

Speed of cutter is critical as well as chip load.

Stainless is prone to work hardening and I think that is what happened in this case.

What he said; SS is a fatherless for workhardening and knackering your cutting edge.

 

[Rocketman]

Can't you use FC3 throw away solid carbide cutters to cut them out to say 0.1-0.2mm left on and then finish off with your drafting cutting if you need draft on them. FC3's are dirt cheap these days.

 

[AndyStobbs]

Hi Andy what is the diameter of the cutter?

3"give or take. Can measure tomorrow.

loving the ingenuity of your "horizontal" mill

I actually have a massive horizontal mill but haven't wired it up yet, and don't have any dividing gear for it (not that the dividing set up on the lathe is off the shelf either - but I had started making bits and formulating ideas long before the mill came along in easter).

I don't know what an fc3 cutter is but will research it. FWIW I don't think its the stainless work hardening, I think its just too much for HSS in a bodged set up. I could only just take 50thou pass turning, let alone trying to use a lathe to mill.

Had made a few enquiries today about an indexable cutter, Chester machine tools had trouble understanding me, RDG directed me to HPC who said they needed all parts to match the cutter profile.

 

[penfold]

I don't know what an fc3 cutter is but will research it. FWIW I don't think its the stainless work hardening, I think its just too much for HSS in a bodged set up. I could only just take 50thou pass turning, let alone trying to use a lathe to mill.

You may be right; a notching apparatus might be a better bet than a rotary cutter.

 

[Woody.v8]

Break out the shaper

 

[I'm getting on a bit]

HSS tool cutting Austenitic SS 12MPM
Martensitic SS 18MPM

75 x 3.142 = 236 mm so 12mtr / 236 = 51 RPM

18 MPM = 76 RPM

0.08 mm per tooth feed rate

So you were cutting way too fast and probably feeding too slow

Before carbide was HSS only so no excuses

 

[AndyStobbs]

Thanks for working out the speed, will mess with the pulleys and try again.

 

[brightspark]

i think u need 3 step pullys on your cutting atachment. it looks a nice job

 

[AndyStobbs]

I've just bought that VFD from Roofman, might look for a small 3 phase motor and mount that with the vfd remote.
Was after a smaller motor anyway, but that motor on there now was all I had to hand, been making that attachment in fits and starts for months.

 

[AndyStobbs]

Have't had time to sort this all out yet. Did speak to hpc about a gear cutter. On the cusp of buying a small 3 phase motor to try again. But will have to dismount the job to re-sharpen the cutter.
Anyway, is it bad practice to use the cutter to plunge - should it always start from an edge strictly speaking?

The jetski is running now after I straightened and repaired the original driveshaft - so the shaft project has kind of slowed... to a stop.