Ok, Rookie Here-- What Am I Doing Wrong?

[Bob V]

Thanks again to everyone- great forum!

 

[barrydc1]

Where did you get the SFM of 90. That seems a bit high for most steel except the most mild. I would go with 50 as and SFM and same formula, so your RPM should be 400, but as others have said, if you are side milling it often needs to be much less in my experience, but that may the the approach to the work on the tool (see this link: http://www.abtoolsinc.com/pdf/AB_Tools_Inc_Catalog_2012.pdf ) They have some opinions on this, but pretty complex if you're new to this. If you are slotting or faceing, then definitely go with the calculated RPM. Smoke is okay unless your chips are turning blue or purple. Chatter and squeal are not okay and indicate too high a feed rate (not too high RPM). You'll eventually break a cutter if you continue to force a vertical endmill. I don't to any horizontal milling, so if none of this pertains, good luck! Find a good chart online or in Machinery Handbook for the SFM of all the materials you're cutting, and apply that formula until you get a really good feel for it all.

 

[jaded13640]

All I can do is echo what others have already said. What a machine or it's cutter is "supposed" to be able to handle and what it can actually handle are two different things. On a light machine, especially an older, well used machine, you really have to go by feel. Start out with about half the speed that's recommended and feed it based on what it will "handle". Gradually pick up the pace on feed and the same with feed until you get a feel for what your machine will handle. Your situation may be a dull cutter or any number of minor wear issues with your machine. Once you get a feel for your machine you'll just know what to set it at without calculating the "correct" speed and feed.

Good luck and enjoy your new machine.

Wayne

 

[jaded13640]

All I can do is echo what others have already said. What a machine or it's cutter is "supposed" to be able to handle and what it can actually handle are two different things. On a light machine, especially an older, well used machine, you really have to go by feel. Start out with about half the speed that's recommended and feed it based on what it will "handle". Gradually pick up the pace on feed and the same with feed until you get a feel for what your machine will handle. Your situation may be a dull cutter or any number of minor wear issues with your machine. Once you get a feel for your machine you'll just know what to set it at without calculating the "correct" speed and feed.

Good luck and enjoy your new machine.

Wayne

 

[Bob V]

Thanks again! I think I need to just make some chips and get more experience with the machine, but I would have been really puzzled about the speed issue if you guys hadn't helped--much appreciated.

 

[Ropetangler]

Basic rule of thumb, High Speed Steel shouldn't be run faster than 90 surface feet a minute. Sure you can get away with 120, if you're cutting Ledloy, or brass, but for steel, 90 surface (of the cutter) feet per minute is good. A half inch tool then is turning 180 RPM.

Sorry buddy but your maths don't add up here. By my calculations 90 surface feet per minute is 687 rpm for a 1/2" diameter end mill, I'm not sure where you get 180 rpm from, but Vanderlinde was pretty well on the mark with his spindle speed. I would also agree with him that his Van Norman is a pretty substantial mill by home shop standards, much stiffer than a Bridgeport if properly adjusted, and not like some of the more low end Asian machines in regard to machine rigidity.
I'm not a machinist , just a wanna be, but my suggestion would be to ask a local machinist if you know any to come to your place and look over your setup. You may have some part out of adjustment, a loose gib or similar, and you don't have the experience yet, to know if your cutters are sharp or not, so perhaps you could purchase a new one and make sure that you haven't toasted your collet, by spinning your old cutter. They definitely should be run dry, but scrupulously clean, check for any burs in the collet or on any cutter shanks.
Apologies for pointing out the mistake in the calculations, - I've just realised that there is a second page to this thread, and others have pointed out the mistake already. I still stand by my comments on the Van Norman however, if that machine is adjusted up correctly, even if well worn, I would expect it to be far more rigid than the usual Asian machines found in home shops, but in view of the lack of experience of Vanderlinde, it may well need to be tweeked up in some areas to realise its full potential. Good luck, and you have already found plenty of helpful blokes on this forum to help you get started.
Rob

 

[scrdmgl]

Hi,
I got my old Van Norman Mill about a week ago and have spent time until today cleaning it, changing sump oils, reducing backlash etc. Basically getting accustomed to the machine and tuning it up per the Manuel.

Today I bit the bullet and made my first cuts. I clamped down a piece of 1/2 inch steel bar stock (mild steel, I don't know the exact number or hardness). The Speed and Feed, as best I could tell, suggested an RPM of about 650 for the 1/2 inch 4 flute HHS end cutter I had in a collett in the spindle. The feed rate was hard for me to deal with since the machine is currently pure manuel-- no motor feed--so I just tried to "make chips".
My first two cuts across this 4" steel bar were only about 1/16 inch deep and seemed to go fine.
So I cranked the table up for a 1/8 inch depth cut and this went pretty well, but the tool started 'smoking" a bit-- so I used a little foaming cutting oil-- but this didn't seem to stick around long enough to help-- I made it across the 4 inches OK.
I had read that a cutter should be able to cut about half of the cutter diameter-- so I cranked the table up so the cut would be about 1/4 inch deep. This didn't go very well. I made it about a half inch into the material and the tool was smoking quite a bit and intermittently was spinning inside the collett--so I stopped. I tightened the draw bar to incease the collett hold on the tool, but it was already prettty tight- so I didn't think this was the problem.

What am I doing wrong. Is the tool dull (got it with the mill-- no visible chips under magnification. It's hard to say how fast I'm feeding the table. I don't want to go to slow (read that this make the tool "rub and overheat") and don't know if I was going to fast. Why is the tool spinning inside the collett-- I did clean light surface rust out of the collett then coated with WD40-- maybe too slippery? What's with this "smoking" is that expected if I don't have a high volume cooling system?

Sorry about the long post but I wanted to give as much info as possible.
Thanks in advance,
Bob

Hi Bob:
Congratulations on your new mill. If you have a chance send us a picture of your mill because I'm sure that most of us would love to see it.

Regards

Jorge

 

[larryr]

Thanks, Tom.
I'll try running the 1/2 inch tool at 180 RPM.
I certainly believe you guys-- you have the hands on experience-- I obviously don't.

I used an online Speed and Feed Calculator at "Daycounter Engineering Services" web site, and plugged in the cutter diameter (.0.5"), and a SFM of 90, and it gives me a spindle speed of 687 RPM.

Also using the formula:
RPM = (Cutting Speed x 4)/Diameter
RPM=90*4/.5=720 RPM

Question: these tables/calculators give speed rates roughly 4 times faster than what is being recommended by you and others.--Can you please tell me why there is such a difference between the RPM's recommended by the tables and the 180 RPM you recommend?

Once again-- having tried the 600+ RPM yesterday with lots of problems-- I certainly appreciate your help and am going to try all your recommendations today.
Thanks!
Bob

Hi Bob:
Congratulations on your new mill. If you have a chance send us a picture of your mill because I'm sure that most of us would love to see it.

Regards

Jorge

jorge if you want a quick ballpark spindle speed calculator multiply 4x the sfpm and divide by the cutter diameter. for a 1/2 endmill at 100 sfpm this works out to 800rpm. this would be max speed. i have a van norman 12 and i regularly run 1/2 endmills at about 600 rpm with no trouble. you need to slow down and get to know your machine. the depth of cuts you were taking sound excessive to me. i usually start with .050 depth of cut and work my way up from there. use your hand feed and you will be able to feel the cut. you are looking for straw colored chips and a fairly light resistance on the feed handle. i use some brush on cutting oil. the coolant system tends to make a mess and you need to maintain it to prevent bacteria growth and the stink. you mentioned your cutter slipping in the collet. van norman collets use i peculiar looking key in the spindle to locate the collet. if this is missing it could allow the cutter to spin. i have also seen some collets that wouldn't draw up properly on the key causing the same problem. bottom line is make sure you have a sharp cutter and start slow with your feeds and speeds. you can only feed as fast as your tool can cut so if your spindle speed is low the feed has to slow down . van norman mills are fun machines, good luck. check out utube , there are a lot of good machine shop videos to watch.

 

[Bob V]

Thanks Ropetangler (what gave you that handle!), T Bredehoft, larryr, and everyone else.

Sorry buddy but your maths don't add up here. By my calculations 90 surface feet per minute is 687 rpm for a 1/2" diameter end mill, I'm not sure where you get 180 rpm from, but Vanderlinde was pretty well on the mark with his spindle speed. I would also agree with him that his Van Norman is a pretty substantial mill by home shop standards, much stiffer than a Bridgeport if properly adjusted, and not like some of the more low end Asian machines in regard to machine rigidity.
I'm not a machinist , just a wanna be, but my suggestion would be to ask a local machinist if you know any to come to your place and look over your setup. You may have some part out of adjustment, a loose gib or similar, and you don't have the experience yet, to know if your cutters are sharp or not, so perhaps you could purchase a new one and make sure that you haven't toasted your collet, by spinning your old cutter. They definitely should be run dry, but scrupulously clean, check for any burs in the collet or on any cutter shanks.
Apologies for pointing out the mistake in the calculations, - I've just realised that there is a second page to this thread, and others have pointed out the mistake already. I still stand by my comments on the Van Norman however, if that machine is adjusted up correctly, even if well worn, I would expect it to be far more rigid than the usual Asian machines found in home shops, but in view of the lack of experience of Vanderlinde, it may well need to be tweeked up in some areas to realise its full potential. Good luck, and you have already found plenty of helpful blokes on this forum to help you get started.
Rob

Thanks, Ropetangler (how did you get that handle!). Based on all the help on this forum, I think I was doing several things wrong: 1) I don't know whether the 1/2 inch cutter I was using was sharp or not.-- I have bought a 1/4" center cutting end mill from Niagra-- haven't had a chance to try this out, but it at least eliminates that variable-- and I'll run it slowly at first so I don't ruin it. 2) The cutter spinning in the collet: I only hand tightened the drawbar and there was some WD40 on the outside of the collet-- I think both these things allowed the cutter to spin in the collet under load. Also almost all the collets I received with the machine (about 15+ of them) have internal rust and some have burrs-- I am trying to figure out the best way to clean up the inside of these collets to improve runout at the tool. 3) The collet slots -- no problem with the 1/2" collet here, but many of the collets have damaged external key slots-- I plan to clean these up with a dremmel, since guys on this forum tell me that the spring steel collets really can't be remachined with a slot cutter. 4) -Probably the worst thing I did: after about a 10-20 thou cut-- I went straight to a .25" cut-- with all the problems I mentioned in my first post. I went to the .25" cut because I had seen a guy on youtube who said you can cut to a depth=1/2 of the tool diameter-- but as guys here have pointed out-- that's probably under ideal circumstances=coolant, sharp cutter etc.
Right now, the piece of help I could use the most is how to best clean up and deburr the insides of the collets and toolholders I got with the machine without increasing tool runout. I got about 6-7 toolholders (don't even know what tools most of them hold!) and the collets need the insides cleaned. I mentioned that an arbor I bought has a mirror finish-- and (again on this forum) I've learned there should be a mirror finish on the inside of some of the toolholder-- how can I restore this? I bought some fine emery cloth and cleaned up one toolholder with a M2 taper so I could attach my Jacobs chuck-- and the emery cloth reduced runout of the chuck from 35 thou to 2 thou-- but obviously no mirror finish!
--Sorry about running on here--
Bob

 

[Bob V]

jorge if you want a quick ballpark spindle speed calculator multiply 4x the sfpm and divide by the cutter diameter. for a 1/2 endmill at 100 sfpm this works out to 800rpm. this would be max speed. i have a van norman 12 and i regularly run 1/2 endmills at about 600 rpm with no trouble. you need to slow down and get to know your machine. the depth of cuts you were taking sound excessive to me. i usually start with .050 depth of cut and work my way up from there. use your hand feed and you will be able to feel the cut. you are looking for straw colored chips and a fairly light resistance on the feed handle. i use some brush on cutting oil. the coolant system tends to make a mess and you need to maintain it to prevent bacteria growth and the stink. you mentioned your cutter slipping in the collet. van norman collets use i peculiar looking key in the spindle to locate the collet. if this is missing it could allow the cutter to spin. i have also seen some collets that wouldn't draw up properly on the key causing the same problem. bottom line is make sure you have a sharp cutter and start slow with your feeds and speeds. you can only feed as fast as your tool can cut so if your spindle speed is low the feed has to slow down . van norman mills are fun machines, good luck. check out utube , there are a lot of good machine shop videos to watch.

Hi Larry, thanks for your comments.
I figured out the key/slot situation, and I think I have that under control. I'm still working on excessive runout caused by rough internal collets, and internal tool holders- need a way to clean this up.
Speed and feed: I'm going to try starting slow, with a new Niagra cutter and get some experience! (after I get my crops planted).
Bob