Cut Quality issues

[letmefixit]

Ok this may be a dumb question. My mill is sitting on my stand. Not bolted down and not on any type of a foot pad... would this cause some of this. I am getting some really great information from all of you. just waiting for the time when i can get back out to the shop to try some of them. I did try an 8 flute mill... much better cut and finish. I was not really taking much material when i was cutting with the 3/4" 4 flute. I did some face milling with a 3" 5 cutter face mill and the cut looked great... its just that side cut that has me But I will keep working with it. I havn't seen a reply back about a different type of bearing on the spindle yet... any takers on that one???

DJ

[BobWarfield]

DJ, the whole trick on something like this is going to be figuring out the weakest link in the chain, fixing that, then finding the next weakest, yada, yada. Otherwise, you try an experiment on a stronger link, and maybe you improved it, but you can't even tell because the weak link is letting you down.

Some of these things are measurable. The runout Pete talks about is a good example. You can take a DTI and your tool in the spindle and just straight up see what the runout is. Post that up hear and you'll get an idea back of what to expact. That finish is showing quite a bit of variation. Looks a lot like what chatter looks like, BTW.

Hard to believe it is due to tool deflection from a 3/4" endmill that was likely not being run all that hard. You got a known bearing problem, though fixed. But do you have enough preload? Do the bearings run a little warm? You want them to run a little warm, but be stable. If they don't get warm at all, you can up the preload.

How are you feeding the cut? By hand? I remember my early hand feeds produced TERRIBLE surface finish seemed like no matter what I did. What a revelation power feed was. Then CNC trumped that by a lot.

Is something, anything loose? Is the machine leveled and firm on its stand? Is the tool tight in the taper? What are you using for a tool holder? A cheap set screw holder has a ton of runout versus a collet chuck. An R8 collet is somewhere in the middle. BTW, if its an R8 collet, is it properly tightened? Tormach has a great white paper on collet pull out. Scary how easy it is to miss a trick and make it easy for your tool to be slipping in an R8 collet.

You improve one thing, then you go around looking for more to improve. Then you come back to what you already improved and improve it some more. Weak link by weak link.

So on, and so forth. It's a methodical trial and error sort of thing. It's harder if you don't have the experience of someone looking over your shoulder to tell you what "right" is. Does that cut sound "right"? Heck, I dunno, just got this darned mill. Sure is noisy!

Cheers,

BW

[Runner4404spd]

I have the angular contact bearings in my spindle. however, i was able to get good results using the tapered roller bearings.

your bad finish is a direct result of the tool not biting into the material enough and skipping over the surface. you need carbide its sharper than hss.

bob is right, make sure your spindle bearings are properly preloaded, i like to see my bearings run about 120F, i could probably get them even a little tighter but its a matter of continual adjustment and at some point i want to make parts.

[Fastest1]

I am not sure what is causing the problem however rigidity is probably not the concern right off. The IH's are pretty massive in regards to the hobby market. I do know that as Bob mentioned above, my first cuts sucked (and I wish there was some documented improvement in my technique and results like Bob's). I do know that my thoughts in general about cutting metal were all flawed. I always thought more spindle speed should smooth the finish, it seems to work in wood. Kind of like needing more HP in the car. The more I learn, the more I get used to this ticking sound of the cutter. I am generally suprised by the finish when the machine is making terrible noises, not straining or choking the motor down just not a smooth cutting sound. Flycutting is really an eye opener on how beneficial slow spindle speeds are. As Bob also mentined above the power feed is a big help if not cnc. No matter what I tried manually it was very hard to achieve an impressive finish. With my cnc machines it is pretty easy but toolpaths, entry, exit and overlaps and other techniques play such a large part. Good luck

[letmefixit]

Wow I sure have allot of work to do. Can someone come lift my mill up so I can slide my 1/4" steel plate under it and then put my foot pads on? Thanks for all your suggestions.

DJ

[Fastest1]

An engine hoist and or a few pieces of pipe can move the world. I moved an old Smithy 3 n 1 years ago, by myself with 4- 2ft long sections of pipe and some cinder blocks and maybe a little bit of patience. Got everythng done and placed where I wanted it. Reached over to remove the last section of pipe I used as a roller (by grabbing the end with a finger inside the pipe. The pipe had a burr that cut the sh!+ out of me. It still gives me shiver if I think about sticking my fingers anywhere near an open pipe end!) My back hurts knowing you have to move the mill. Luck and beer.

Wow I sure have allot of work to do. Can someone come lift my mill up so I can slide my 1/4" steel plate under it and then put my foot pads on? Thanks for all your suggestions.

DJ

[letmefixit]

ya i put the mill in place with my back hoe on my tractor... but the backhoe is off till spring... have to push snow...

[rmarchjr]

Just curious - why use an endmill? When we need real flat surfaces we use a fly cutter.
If the machine lacks the mass or isn't rigid, not sure anything will help.

I would first try the right tool for the job - almost perfect surfaces are way easier with a fly cutter and you won't need to push the machine so hard.

[letmefixit]

faceing is not the problem... Face mill dose a wonderful job on the top... the problem im having is when im side cutting... lots of chatter. The group has given some really good suggestions... they have been a great help.

DJ