Milling advice wanted - new to milling

[cederholm]

Thank you - that makes sense.
My spindle is 2mt. While digging through the tools left to me I found two Bridgeport (so labeled) 2mt collets. They seem to fit the machine and draw bar, but they won't bite down and hold the tool. Any thoughts?

There is a lot of tool/holder sticking out from the spindle, if you have a collet that will hold the endmill in the spindle then that would help the setup. It's OK to use it that way, but it is less ridged than having a shorter setup. You just have to compensate by taking lighter cuts.

It looks like the width of the cut is greater than 1/2 the diameter of the end mill, that can tend to pull the tool into the work. This may be why the endmill is chipping. I would make that cut in 2 passes on the width with a springy setup, maybe 1/4 the diameter of the endmill.

 

[Jim2]

I am using one of those holders, am I not? I understand that my tool might be set to low but is it okay to use the holder shown?

I'm not sure what you've got there. It may have it's uses, but I don't think it's a very good tool in this application. I don't have anything similar myself. I rely upon r8 collets primarily when milling, though I have added a couple of the end mill holders like



See how much shorter the stickout is here? Maybe you're running a different taper (not r8)? A smaller endmill would reduce chatter, and likely have less stickout. . . . It may help by reducing sfpm also--something is wrong when you're losing the corners off the endmill that fast.

Jim

 

[cederholm]

Thanks Jim, I'll do more research. You're photo is very helpful.

- Carl

I'm not sure what you've got there. It may have it's uses, but I don't think it's a very good tool in this application. I don't have anything similar myself. I rely upon r8 collets primarily when milling, though I have added a couple of the end mill holders like



See how much shorter the stickout is here? Maybe you're running a different taper (not r8)? A smaller endmill would reduce chatter, and likely have less stickout. . . . It may help by reducing sfpm also--something is wrong when you're losing the corners off the endmill that fast.

Jim

 

[JimDawson]

Thank you - that makes sense.
My spindle is 2mt. While digging through the tools left to me I found two Bridgeport (so labeled) 2mt collets. They seem to fit the machine and draw bar, but they won't bite down and hold the tool. Any thoughts?

The only thing I can think of is the collets are not the correct size for the shank of the end mill. The fit should be a tight slip fit with the collet in your hand, if the shank of the endmill is loose in the bore of the collet, then the collet is the wrong size. The other possibility is that the collet is not drawing up tight, try it without the end mill in it and see if it will draw up more. You may have to shorten the collet a bit on the back end.

 

[John Hasler]

T Bredehoft,

I am using one of those holders, am I not? I understand that my tool might be set to low but is it okay to use the holder shown?

I'm not very knowledgeable about mills but that looks like an extension holder for reaching down into deep holes where the spindle won't fit. It appears to me to be at least four times as long as it needs to be to do your job. When milling as when turning length is your enemy.

Also, could you change your setup to cut with the side of the tool? I find that gives better results and doesn't use up the tool as fast. Cutting with the end makes the tips do almost all the work.

 

[cederholm]

That makes sense John. I'm not sure if I understand about cutting with the side. Are suggesting a deeper cut with less width? Of course cutting in the correct direction as noted above.

Btw - using the advice above I did finish my tool holders, now I'm taking notes to learn and inprove. I'm very gratefull to everyone for their insight and advice.

I'm not very knowledgeable about mills but that looks like an extension holder for reaching down into deep holes where the spindle won't fit. It appears to me to be at least four times as long as it needs to be to do your job. When milling as when turning length is your enemy.

Also, could you change your setup to cut with the side of the tool? I find that gives better results and doesn't use up the tool as fast. Cutting with the end makes the tips do almost all the work.

 

[John Hasler]

That makes sense John. I'm not sure if I understand about cutting with the side. Are suggesting a deeper cut with less width? Of course cutting in the correct direction as noted above.

Btw - using the advice above I did finish my tool holders, now I'm taking notes to learn and inprove. I'm very gratefull to everyone for their insight and advice.

I'm suggesting rotating the workpiece 90 degrees so that the dovetail is horizontal and cutting with the side of the mill instead of with the end. You'd lock the quill and the knee and feed only with the table so that the flutes do the cutting.

Again, I'm not an expert at this. My milling experience is with my own rather odd machine.

 

[mikey]

I agree with all the above, especially the climb milling and the need to choke up on the end mill to reduce extension beyond the holder. It does look like that holder is a bit long for this job. I did not see any mention of cutting speed but in carbon steel cutting at the full diameter of the cutter your SFM will only be about 35. That gives you a speed of only about 280 rpm with a 1/2" dia. cutter. If you cannot get down this low then take the width in multiple passes at the lowest speed your machine can manage.

 

[herbet999]

reverse spindle motor?

What was I thinking... I'll keep my mouth shut

 

[barrydc1]

A couple things that haven't been mentioned. I stilll new at this too, and have learned a lot here and now by experience too. If you are cutting a hardened steel. You'll go through endmill pretty fast if they are HSS (high speed steel). They don't chip as easily as Carbide endmills do, so I assume you are using carbide. A formula to use to find the RPM to use is this. Look up in a Feed/Speed Chart the Square Feet per Minute (SFM) chart the kind of steel you have and it's hardness (the hardness you may have to guess at if you don't know). Do a little research if you know where you bought the QCTP holder. When you know that SFM value, multiply it by 4 and divide by the endmill (or other cutting tool/part on the lathe) diameter you are using. This will give you a ball park RPM to start from. When I was new at milling, I was afraid to hurt things, so I typically went way too slow or sometimes way too fast feeding the part, and often too shallow a cut. Also if you are using carbide, then double that SFM value before you multiply by 4 and divide by the diameter. Once you get this ball park RPM listen to the cut and make sure there is no chatter, or other "BAD" sounds. This is part of experience, as there will be rattling and shaking of a sort. You will have to know what is okay for your machine. The rigidity of the set-up is important, and less leverage is the idea, so no long stick-outs when you don't absolutely need it. I would watch a bunch of Tom Techniques videos and then go try things and that has helped me a great deal. Good luck as you learn and have fun with this new and expensive addiction!