Stacked Slitting Saws

[Fohrrest]

I’m new to machining but I’ve already got some jobs to do with the old Comet milling machine we just got at our shop. A guy who owned a machine shop two blocks down sold his business and we got the Comet, a surface grinder, and a bunch of end mills.
We’ve got everything set up and I just spent today cutting the 6061 aluminum, 1.25” solid tubing with 5, 3” medium slitting saws stacked 0.125” apart.
The task at hand is making aluminum rungs for a ladder we’re fabricating. There are 20 pieces at 18” and I have to make a pass, flip the work, and make a second pass to cover the entire side of the rung. They have to be 0.125” deep, on all 4 sides. I’ve got the mill in low gear at about 200rpm, compressed air to blow the chips out (no coolant yet), and tap oil on a paint brush.

I did 10 sides today and towards the end of all of them I would get screeching, and sometimes it would almost stall and then cut every 0.020”.
Is the noise from lack of coolant, 0.125” depth of cut, or normal?

 

[f350ca]

Try WD40 or kerosine for a lube.

Greg

 

[brino]

200rpm and 3" saw puts you at about 160 sfpm.
Assuming HSS saws, I'd want to be around 110 sfpm, so ~140 rpm.
That's not very different.....

You might try kerosene as cutting fluid. I use low-odor lamp oil for aluminum.

One other thing.....
It looks like you do five cuts with one side up(red line) and then flip and then three more(green line).


Could you balance it out to four and four to reduce the power required?

-brino

 

[benmychree]

200rpm and 3" saw puts you at about 160 sfpm.
Assuming HSS saws, I'd want to be around 110 sfpm, so ~140 rpm.
That's not very different.....

You might try kerosene as cutting fluid. I use low-odor lamp oil for aluminum.

One other thing.....
It looks like you do five cuts with one side up(red line) and then flip and then three more(green line).
View attachment 351451

Could you balance it out to four and four to reduce the power required?

-brino

For aluminum, the surface speed is quite slow, I'd be at twice that, but perhaps with the lack of rigidity that a vertical mill offers, who knows? Definitely, a coolant of some sort is needed, kerosene is the standard.

 

[Video_man]

I'm thinking that's a pretty deep cut for slitting saws, likely you are loading up the gullets of the blade and not able to clear the chips, particularly with no appropriate lube (kero or WD40, oil probably is too thick). Try cutting about the same depth as the teeth and see if it works better.

 

[brino]

@Fohrrest

Also, Welcome to the group!

-brino

 

[Fohrrest]

@brino Thanks!

 

[BGHansen]

I'm just a hobby machinist but have done some similar work. In my experience, chip clearing is THE biggest factor when using slitting saws. If you start getting hot, the aluminum will stick to the saw teeth making it work even harder and build up even more heat. I did a slitting job on 0.100" thick stainless cutting 0.200" wide strips using 1/16" wide slitting saws on an Atlas horizontal mill. I was drizzling cutting oil before the cuts and fed slowly. Started hearing screeching after 20 or so passes. Looked at the saw teeth and they had bits of stainless welded to them.

I went to cutting oil and a blow gun with a continual blast of air. Cutting went much easier after that. Made a huge mess, but without a full enclosure on any mill it's part of the game.

I think you're on the right track with getting some liquid on the work to cool the chips down so they don't weld in place (specific heat of ANY liquid is much better than air). The blast of air will help get them out of the saw teeth.

For RPM's, I use the simple formula of "400 / D" for steel and "1000 / D" for aluminum. Those numbers came from Tom Griffin's website "Tom's Techniques". He is a wonderful shop teacher. Using the formula, if cutting with a 3" slitting saw in aluminum, starting RPM would be "1000 / 3"" or 333 RPM. I've read that carbide likes to go fast, if your saws are carbide or have carbide teeth, double the speed.

Bruce


Slitting 0.100" thick stainless to 0.200" strips on an Atlas MFB horizontal mill

 

[markba633csi]

Yep aluminum is getting stuck to the teeth- it's a pain. Liquid wrench makes a good substitute if you don't have any WD-40 or kerosene handy
-Mark

 

[Boswell]

If aluminum is welding to the teeth, then at least you know the problem. Too much heat at the cut. lots of options
1. Feed slower
2. reduce Depth of Cut
3. Slower RPM
4. Better chip removal (air, Coolant)
5. Better Heat removal (Coolant)