[upnorth]

Hello again:

I'm now moving up from cutting aluminum to cutting steel. I was wondering if you guys could give me some ideas as to what you consider an acceptable depth and width of cut? I'm going to be cutting some .5 inch thick cold rolled steel. I need to remove a lot of material. Can I cut full depth and if so what width of cut can I get away with. I wish I could just trace around the profile but the material being removed would likely trash the cutter when it broke free. I have for roughing a .375" Cobalt four flute rougher. To finish I was planning on using one of my 3 flute end mills I use for aluminum. I know the finisher is not ideal but its what I have.

I know there are online calculators but I have not had much luck with those. I find if I play with the numbers to maximize the cut I end up with a chattering end mill. Anyway just looking for some rough idea about where to start. I can optimize things later.

Thanks

Tom

[dharmic]

^^ yep, HSMAdvisor or the phone app FSWizard from the same guy. Even then, when you bang your "1018" into it you wanna start at maybe 50% of its recommended load and then work up just in case it's "1018, but a bit harder" or those HRC60 end mills from eBay are more like HRC45...

[kvom]

Roughing endmill followed by finish pass may be an option.

[upnorth]

Ok got the prototype done. No Broken cutters and they seem to have survived it ok. I played around with many different cuts. They all worked for the most part although things were very noisy.I guess I was spoiled from all the aluminum I was cutting previously. I did use a carbide 3 flute that is designed for aluminum as a finisher. It left a great looking finish. I think I'm going to try a carbide rougher next time.

Thanks for the earlier replies.

Tom

[upnorth]

Ok today I tried to run the parts. To say it went poorly was an understatement. The holder pulled out of the collet and went down into the vise. So damaged vise jaws and a broken end mill. It got worse from there the tool holders started getting stuck in the collet after that. I had to remove the power draw bar and tap the top of the drawbar to release the tool holders. That happened three times.

Ok so had to shut down for the day and have a beer. I'm now calmed down. Plan for tomorrow is to change the collet although I'm not sure if that has anything to do with it. The cuts I was using were conservative according to HSMadvisor. However chatter was a constant problem.

Can someone tell me where you would start width and depth of cut and rpm to cut cold rolled mild steel? I'm using a 4 flute cobalt corn cob rougher. Anything else I might be doing wrong? I have cut a lot of aluminum and always breezed right through it. I'm mostly thinking I was using to deep of a cut. I was a bit over .3". I'm also going to reduce the stickout of the now trashed end mill. New end mill going in tomorrow. According to HSMadvisor horse power was not an issue. The mill never bogged or anything like that.

Thanks

Tom

[Eldon_Joh]

I had to remove the power draw bar and tap the top of the drawbar to release the tool holders. That happened three times.

With an R8 collet, that's how it should be. the taper is borderline self locking. the angle is only 2.5 degrees more than what is considered self holding.

as for depth of cut, unless you have a depth of cut such that the end mill has two flutes in contact at any given time, then the forces exerted on the work by the end mill are not constant. so as far as peak force goes, it doesn't matter how deep it is until there are two flutes in contact at one time. and then again it won't increase till three flutes start to be in contact. hp will increase linearly of course. the cutting forces will be the smoothest when the next flute engages at the instant the last one left the cut. so try setting the depth of cut to that..

If your machine has a very lightweight spindle then adding rotating mass to the spindle will help it. my lightweight milling machine can't cut a 3/4th-3/8th-60 degree dovetail in steel, but i can tilt the work piece at 30 degrees and cut the dovetail with a 1/4th inch end mill. i would be able to use a dovetail cutter if i could find a helical one!

[SCzEngrgGroup]

Are you using a Torus Pro, or Pulsar? In either case, if the R8 collet is sticking, then you are not properly maintaining/cleaning/lubricating it. If properly maintained, I've never had mine stick. and, lack of lubrication will greatly reduce the drawbar tension applied by the PDB, which would explain why you're having pull-out. I've NEVER had pull-out, even doing aggressive cutting on stainless.

Regards,
Ray L.

[upnorth]

Hi Ray: Somehow I knew you would be here for this one. Its a Torus Pro. My first thought was maybe the collet needed to be cleaned and lubricated so I did that. I did get a mix of the collet getting stuck and pullout after that. The only thing I can think of is maybe because I have greatly increased the coolant flow maybe some got up inside the collet and made it slippery. I'm going to try a new end mill, Holder and collet tomorrow. As for it sticking I'm wondering if the chatter could have made the collet stick? I guess I'm a bit confused because its a mix of things getting stuck and slipping.

[SCzEngrgGroup]

That is very odd. I've actually dipped the toolholder shank in oil-based coolant, stuck it in the spindle, and done aggressive cutting with no problems. I'd suggest you get some Machinist Blue and look at the contact patterns between the collet taper and spindle taper, and between the toolholder and collet. Something must be very wrong somewhere in there. I'd guess the collet is either out of spec or worn.

How old is the battery in your PDB? A weak/tired battery will reduce the torque.

Regards,
Ray L.

[newman55598]

Is it a high quality corn cob end mill? How aggressive are the teeth on the end mill? I used a none brand name end mill that caused crazy chatter. Changed to a new brand name end mill and problem solved.

[LeeWay]

On my Pulsar, the tools just drop out. We use a butterfly impact to tighten the drawbar with. When a tool starts to stick, we know it is time to clean them.
We clean them with acetone. Tool shanks and collet inside and out.
Then we use this stuff. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

We use it on the drawbar threads and the taper being careful not to get it in the slits of the collet.
We can go between 2 to 3 weeks like this before we get another tool sticking in the collet. We do not have tool pullout from the collet either.

[upnorth]

I mistyped in an earlier post. To be clear the tool holders are pulling out and the collet is getting stuck in the spindle. When I said the tool holder was stuck its stuck because the collet is jammed. I'm going to try the suggestions from here either today or tomorrow and will let you guys know what happens. I don't think the issue is with the power drawbar. The collet is pulled in nicely. When I push the down button it takes the torque off the collet but it just does not drop out of the spindle taper.

More to follow.

Tom

[AUSTINMACHINING]

I mistyped in an earlier post. To be clear the tool holders are pulling out and the collet is getting stuck in the spindle. When I said the tool holder was stuck its stuck because the collet is jammed. I'm going to try the suggestions from here either today or tomorrow and will let you guys know what happens. I don't think the issue is with the power drawbar. The collet is pulled in nicely. When I push the down button it takes the torque off the collet but it just does not drop out of the spindle taper.

More to follow.

Tom

I have the same problem from time to time. A light tap on the side of the spindle flat is enough for the R8 collet to drop the tool. This seems to be highly dependent on the type of grease used on the R8 taper and how often you maintain it. I tried some anti seize grease which did not work well at all. I got some heavy greenish colored Greas from home depot that works much better, but you do need to stay on top of keeping it lubricated or the collet will stick in the spindle. Since using the better grease I also have not had the tool holder pull out of the R8 shank, even under deep axial cuts that would stall the spindle.

[LeeWay]

Yeah you do not want any grease that will crawl. I think that and only applying a very thin layer of lube are key to getting best results.

[upnorth]

Ok I got the parts all done. I put in a higher quality rougher and it was in poor shape after 3 parts.

For Ray: The power draw bar is less than a year old so its not likely a battery problem.

I did have some more trouble with the collet sticking. I had been using anti seize on the outside of the collet. I think it has been washing out. It may also have been washing in and coating the tool holder shank. I switched from anti seize to some synthetic bicycle grease on the collet so I'll see how that works out.

I was able to rough out the last parts using a weldon shank indexable end mill. I did about 10 of them without changing inserts. The parts are about 2"x 6" .5" thick with about 40% of the material being machined away. I have a few ideas about what I was doing wrong with the last set up so I'll run it a bit different next time. Inserts were quite chipped by the end. I finished same as before with a carbide end mill and the end result was good. I quit experimenting because I just wanted to get the job done.

[MBViklund]

Ok I got the parts all done. I put in a higher quality rougher and it was in poor shape after 3 parts.

For Ray: The power draw bar is less than a year old so its not likely a battery problem.

I did have some more trouble with the collet sticking. I had been using anti seize on the outside of the collet. I think it has been washing out. It may also have been washing in and coating the tool holder shank. I switched from anti seize to some synthetic bicycle grease on the collet so I'll see how that works out.

I was able to rough out the last parts using a weldon shank indexable end mill. I did about 10 of them without changing inserts. The parts are about 2"x 6" .5" thick with about 40% of the material being machined away. I have a few ideas about what I was doing wrong with the last set up so I'll run it a bit different next time. Inserts were quite chipped by the end. I finished same as before with a carbide end mill and the end result was good. I quit experimenting because I just wanted to get the job done.

I have good experience with indexable mills in steel as well. Bought the 16mm indexable from tormach with their inserts. Funny enough some cheap probably copy Mitsubishi inserts lasted longer than the oem ones.

https://youtu.be/D_HhUJehptc

[upnorth]

I have good experience with indexable mills in steel as well. Bought the 16mm indexable from tormach with their inserts. Funny enough some cheap probably copy Mitsubishi inserts lasted longer than the oem ones.

https://youtu.be/D_HhUJehptc

I think I'll invest in some indexable tooling as well. I'm a bit nervous about using it in a quick change tool holder though. I have found some for a decent price that go directly into the R8 taper. I think I may go with something like that.