Small mill - reasonable expectations in steel?

[sru_tx]

@bill stupak i felt the conventional cut was beating the machine up much more than the climb cut. After touching up the end mill on a stone and using a different piece of stock, I was getting much better conventional cutting performance (0.020") than before and the climb was good too.

@WCraig work being held by a 4" grizzly milling vise. Piece is secure in the vice and vice is secure to table.

@macardoso that's a distinct possibility regarding material variability. The second piece milled much easier. I'm impressed by your previous post. It's good to know this machine can do more. You said DOC was .125". What was WOC?

I'll double check my table. I'm guessing my problem is/was a dull end mill and too large of a diameter.

 

[macardoso]

@macardoso that's a distinct possibility regarding material variability. The second piece milled much easier. I'm impressed by your previous post. It's good to know this machine can do more. You said DOC was .125". What was WOC?

That was full slotting. Should have clarified that.

I mostly do aluminum and find my best recipe is a 3/8" 3F ALU-Power endmill from YG-1, 20% radial engagement (.075") and 1" DOC. 5000rpm, 60in/min.

These are CNC numbers, a custom high speed 2.3HP spindle (5000rpm vs 2250rpm), and carbide endmills so your manual machining will be a bit of guesswork, but it gives a reference for what this can do. That last cut really throws material across the room. At the end of the day, machine rigidity is the limitation for both of us.

 

[MrWhoopee]

The formula for RPM=(Cutting Speed x 4)/diameter. Cutting speed for mild steel is 80-100 sf/m. I use the low end of the cutting speed range (80) since I pay for my own cutters. For a 1/2 in. cutter, this yields (80x4)/.5 = 640 rpm. Using the high end you get 800 rpm. Depth of cut does not change these numbers.

Memorize the formula. Here's a cutting speed chart. It says for turning, but it's the same for milling.

 

[Cadillac STS]

I have a little Sherline mill that could take that 1/2" axial depth of cut with a 1/4" radial depth of cut in a single pass in mild steel so something is off. SFM for the above cut would be around 120 SFM so RPM should be around 1800 rpm with a 1/2" finishing end mill and about 20% faster with a roughing end mill. It seems to me that there is a dull cutter involved or something is moving. So, I have a few questions:

• Are you using a sharp cutter?
• Are your gibs adjusted well? Did you lock them down before taking your cuts by any chance?
• What kind of tool holder are you using? Is it just an R8 collet? If so, was the drawbar pretty snug? Any chance the tool was slipping?

Just to clarify something. You have a Sherline mill and it can cut a half inch deep slot one quarter of an inch wide in one pass in mild steel? 1/2 inch deep, 1/4 inch wide? Slot, cutter buried? I just must be reading it wrong.

 

[mikey]

Just to clarify something. You have a Sherline mill and it can cut a half inch deep slot one quarter of an inch wide in one pass in mild steel? 1/2 inch deep, 1/4 inch wide? Slot, cutter buried? I just must be reading it wrong.

I said 1/2" axial depth, 1/4" radial depth so clearly I meant a peripheral cut because at the time it was not clear he was making a slotting cut. Yeah, a Sherline mill can make that peripheral cut, maybe not fast but it will do it. I made that cut in steel keystock to make some T-nuts years ago when I didn't know my machine wasn't supposed to be able to do it. My mill has ABEC 3 bearings in it, has around 0.0001" TIR at the spindle and with the belt on the hi-torque setting can actually take deep cuts in steel ... who knew?

I've also taken a 3/8" deep slotting cut in aluminum with a 3/8" rougher to make pockets. Yeah, a full diameter depth of cut on a Sherline mill, and I don't really dawdle around when I feed it, either. I've done this multiple times. I've also done peripheral cuts with that same 3/8" rougher at 1/2 radial depth and full axial depth (3/16" deep cut into the material using 3/8" of the vertical length of the rougher). This little mill will do the same cuts that my larger RF-31 will do, just a little slower.

My little Sherline lathe can take a 0.060" deep cut in mild steel in a single pass, something lathes much larger cannot do. I've not only done that, I've done it in front of other people. In fact, my friend just recently took a 0.050" deep cut (0.100" off the diameter) in stainless steel with a 1/4" HSS tool on his brand new Sherline lathe; he didn't know that lathe wasn't supposed to be able to do it, either. Well, it did and I know because I was standing next to him.

Sherline machines are actually machines so I use them like they're real machines. I don't abuse them but I don't baby them, either.

And just in general, if I say I did something it usually means I did it. Not sure I have a need to prove it to you, though.

 

[macardoso]

I started with a Sherline and they are surprisingly well built machines. I personally used them for 1/4" tools and smaller. Not the most rigid out there but they can do some real work. I'm not surprised by what Mikey said. Travel size was my complaint.

 

[Cadillac STS]

I didn’t mean any disrespect with that question. I just thought it was a big cut for that size machine and I probably read it wrong.

I have a CNC lathe built around a Sherline lathe and am familiar with that.

Lot of nice work can be done with Sherline tools but just taking smaller cuts and taking your time.

I have Joe Martin’s book “Sherline Tabletop Machining” He is the founder of Sherline. Nice read about running a shop and how Sherline came about.

 

[macardoso]

I doubt Mikey took any offense whatsoever! He constantly impresses us here with what he can do with his Sherline!

 

[mikey]

I didn’t mean any disrespect with that question. I just thought it was a big cut for that size machine and I probably read it wrong.

I have a CNC lathe built around a Sherline lathe and am familiar with that.

Lot of nice work can be done with Sherline tools but just taking smaller cuts and taking your time.

I have Joe Martin’s book “Sherline Tabletop Machining” He is the founder of Sherline. Nice read about running a shop and how Sherline came about.

I apologize for the tone of my post. I got up to use the BR and saw your post and should not have responded half asleep.

I view Sherline machines as machines. They can take cuts that larger machines can take, only slower. Note that I said slower, not lesser. I use Niagara Cutter's feed and speed charts where the speed varies with the axial and radial depth of cut. If I want to take an axial cut of 1/2 or 1/4 or 1/16 the diameter of the end mill then there is a speed for that. I set the speed and use whatever manual feed I need to take the cut, and the machine cuts it. I have never had a problem with this. I use a Beall ER32 chuck to enhance rigidity and I think that helps. Quite frankly, the key difference between my Sherline mill and my RF-31 is the feed rates I can take, not so much the depths of cut. Although I have power feed, I usually feed by feel and maybe that's why the machine can do more than it should.

Just about everything I know about machining, I learned on Sherline machines and just transferred that to bigger machines. I stepped up to bigger machines because I needed more capacity, not capability. To be very honest, I actually prefer to work on my Sherline machines and do so when the size of the work allows, especially the lathe.