Question about maximizing cutting efficiency on an old Cincinnati horizontal mill

Hello friends,

So, for years, my only milling machine has been an old 1HP step-pulley Bridgeport. I do a lot of heavy material removal so I was always pushing the machine as hard as it could go. It was pretty easy to determine how hard I could go, because the machine would just start chattering and making an awful ruckus if I went too hard. I'd generally keep pushing my cuts until this would start happening, then back off a bit. Simple methodology that has served me well for a long time. Have never broken anything (too badly).

Nowadays, as some forum members know, I've got a beefy dial-type Cincinnati horizontal. I'm just starting to explore the limits of this machine and I suspect that I'm not even close. However, is there anything different I should be doing in my approach? I realize that a horizontal mill that weighs over 3x what my BP weighs is likely going to be insanely rigid in comparison. So I suspect I won't really get much chatter, if any. So, how do you know when you're pushing a cut too hard? Too much vibration? Too much noise? Surface finish starts to go bad?

I guess I'm worried about breaking something in the machine by pushing it too hard and not getting any early warning signs. I'm taking cuts that I'd never dream about on the BP and the machine seems happy, but I don't know how far I should go. I use a phone app to calculate feeds and speeds and I don't think any of my cuts have calculated out to over .6HP which seems sad compared to the machine's 5HP motor. I've done 1"x1" cuts with HSS roughing end mills in mild steel, and roughly .300DOC x 3" WOC with an inserted face mill in the same material and the machine didn't even whimper. How far can I really go, is the question.

Thanks in advance!

Find the 1950s copy of A Treatise on Milling and Milling Machines by Cincinnati - a big hard bound RED book on slick paper

Here is a competitor (K&T)

Dope,
Horizontal Mills are awesome. They eat material all day long. Make sure she's oiling good and tighten the gibs if they need it. Not only do they hog well, milling to size is easily accomplished. An assortment of stagger tooth cutters will compliment your hog mills and give you some nice options. Like 3/4" wide slot 1.5" deep 8" long no problem. If your at the max RPM on a cut usually the cutter overheats, feeding to fast the cutter will break. A five HP motor through the gear train gives you gobs of power to the cutter. 50 Taper holds big cutters too. Mine is a lightweight compared to yours, B&S No.2 Light, here's a couple pics of some cool jobs. You'll like the Cinnci.
spaeth

we have a couple of Cincinnati mills, I doubt you'll be able to accomplish such a feat as overloading that machine. you'd have to have some monstrous tooling and very well secured large chunk of iron to push it that hard. that being said your tools will usually be the weak link, so next step is to get some good tooling. a little practice will tell you a lot about what you can and can't do. The tool you use and your clamping abilities dictate when you are pushing it too hard. The last thing you want to be doing is a 2" slot cut 2" deep and have that 250 lb. block of steel start sneaking down the table. Use that flood coolant to keep your cutters cool and chips flushed, we use oil to keep it cool, if it's smoking, it's too hot. still cuts 6-8 in. per min. 2" deep, just did it last week on a rush job. Containing the coolant and metal chips becomes the hard part.

Securing the workpiece will be your biggest problem. You now have axis power feeds that are stronger than the grip of a standard smooth jaw vise. In addition to the clamping of the vise or strap clamps, use a hard stop to resist the feed forces.

Great info in here guys, thanks. I've already experienced my workpiece moving (very slightly) even with 6 clamps on it so it sounds like that's the biggest thing I have to worry about now. It was never a concern before so that's good to know. 2"x2" slot though, DAMN! What size machine was that on? I've just got a #2 dial-type.

Dope Sir,
Here's a few things that may be of use to you. Always consider the 'direction of force' when milling. If your 'up milling' ( feeding the work piece into the work whilst cutter is exiting the top ) the part is going to want to kick forward. Put a kicker or a stop to keep it from moving forward. ( also known as 'conventional' milling )
If you are 'down milling' ( sometimes called 'climb milling', feeding the work in to the cutter and exiting on the down end of the cutter rotation) then your part is going to want to kick back so you need a kicker at the back of the part. Plus if you don't have a 'anti backlash' device it will be hard to keep the cutter from trying to 'grab' the part.. Can lead to spectacular crashes..
Rule of thumb is to keep at least two teeth in the part.. more are/is better.
If things keep slipping use a piece of paper between the part and table. The paper will take up all the little oddities in the table and the part and when strapped down will makes things really solid.
Just an aside.. I run cutting oil and mostly high speed steel tooling and when everything is 'right' it sounds like frying bacon.. I have taken facing cuts .750 deep on 2 inch 4140 plate for hours on end with no real issues of straining the machine ( 2L cinci 1937 )
Hope this helps
Stay safe
Calvin B

Dope said:

So, for years, my only milling machine has been an old 1HP step-pulley Bridgeport. I do a lot of heavy material removal so I was always pushing the machine as hard as it could go. It was pretty easy to determine how hard I could go, because the machine would just start chattering and making an awful ruckus if I went too hard. .....
Nowadays, as some forum members know, I've got a beefy dial-type Cincinnati horizontal. I'm just starting to explore the limits of this machine and I suspect that I'm not even close......
I guess I'm worried about breaking something in the machine by pushing it too hard and not getting any early warning signs. I'm taking cuts that I'd never dream about on the BP and the machine seems happy, but I don't know how far I should go..... How far can I really go, is the question.

Click to expand...

Very different machines.
As far as breaking it you I assure you it will take a licking and keep on ticking.
Same deal as the B-port for too much work . It will talk to you when it not happy or upset with what you are doing.
Every machine tool manual or cnc talks as it runs. Sometimes the message is I am bored, sometimes it is I'm not gonna do this for very long.
Think the 1 hp BP as a willys jeep and do all, this is a full on tank.
Push that tank until it says no-no-no. Back off 25-30 percent.
Bob