Spindle speed

Nice links Mikey thanks. A little confusing as I'll have to study those. Axial depth radial depth /2,3,8 etc.
 
Geerbangr said:
Thanks for the replies fellas. I have not yet purchased the cutter I’ll use to do the job. I’m sure you guys can tell I’m pretty green at machining. I do have a dro and I do have auto feed that I will install for the x axis. So with those file links Mikey that should help with the process.

My plan is to use a roughing bit to hog out the heavy stuff then complete the job with a finishing bit.
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2" deep means a long end mill, and a long end mill is going to deflect. If the sides of the slot must be accurate then consider a carbide end mill; it will deflect less. Carbide is not mandatory but if you opt for HSS then lighten your cuts accordingly. The flute length must be long enough to span the depth of the cut and it would be wise to use an end mill diameter that will handle that length; I should think that a minimum diameter would be 3/8", no less. Ideally, you want to use a High Helix end mill to pull chips out of the cut.

If this is to be a through slot and you can accept radiused corners then I would drill holes at all four corners and saw out as much of the slot as you can. Then use a rougher to bring it close to size, maybe 0.050" of material to finish up. This gives you enough meat to remove the serrated marks left by a roughing end mill. Then take light finishing passes to bring the slot to final size. You may be able to get away without the rougher but 2" is a deep cut, deep enough that deflection is a real concern so I would personally use the finisher to finish only.

If the cut is a pocket then you have no choice but to hog it out with end mills. I would use a rougher to debulk the pocket and finish with high helix end mills.

I wanted to remind you that long end mills deflect less when held solidly in an accurate collet. Not many hobby guys can afford shrink fit tooling so an ER collet is the most affordable option. If you don't have an ER chuck for your mill then I suggest you consider one, along with high quality collets.

You can do this. Just take your time, think things through, buy the right tooling and you'll do fine.
 
Mikey, I’ve chose to use a 3/4” cutter because I can get closer to the correct bit speed with my machine. I’ve been contemplating using a saw like you mentioned for cropping out the bulk of the material so I don’t have to wear my bits out.

I only have hss bits so I’ll use a roughing bit to remove any bulk, then finish the cut with the finishing bit.

Once again thanks a million for sharing your wealth of knowledge.
 
Mikey I did not see the last part of your post on ER collets until I posted above. Care to educate me on what a ER collet is/does?

I’m going to go out on a limb and say extended reach is what the ER represents?
 
The "ER" collet system, developed and patented by Rego-Fix in 1973, is the most widely used clamping system in the world[3] and today available from many companies worldwide. The standard sizes are: ER-8, ER-11, ER-16, ER-20, ER-25, ER-32, ER-40, and ER-50. "ER" came from an existing "E" collet which Rego-Fix modified and appended "R" for "Rego-Fix". The number is the cavity opening diameter in millimetres. ER collets contract over a range of 1mm and are available in 1mm or 0.5mm steps, so a range of ER collets can hold any cylindrical shank, metric or imperial. ER collets may also be used on a lathe to hold work pieces.[4]

From Wikipedia.
 
Geerbangr, what were you planning to hold your cutter in? Hoping you weren't planning to use a drill chuck, Please don't even think about . it.
A drill chuck is not rigid enough, they tend not to run very true, nor do they have sufficient clamping force to hold a milling cutter, the cutter wil most likely walk out and ruin your work piece, probably break your cutter and damage the chuck, and maybe damage your mill.

The ER collet system is the best one to use. Assuming your mill spindle has a morse taper, what size us it? If not an MT what does it have? And what size is the spindle bore hole for the draw bolt? Always best to use the largest that will fit.
 
Geerbangr said:
Care to educate me on what a ER collet is/does?
Click to expand...

The ER system is the most commonly used method of holding an end mill in a milling spindle. It uses a chuck with a special nut at the front that compresses a slotted ER collet circumferentially to rigidly hold the shank of a milling cutter. A good collet will hold an end mill quite accurately, with run out within 0.0001" or less. While it is not the most accurate way of holding tooling, it is the most effective way that is within financial reach of most hobby guys. A search on HM will turn up gobs of discussions about ER chucks and collets.

I raised the suggestion because of the longish cutters you will need to use. All end mills deflect all by themselves, especially longer ones, but you can minimize it by holding it solidly and accurately; an ER chuck is the most effective way to do that in light of cost. End mill accuracy and tool life will be enhanced, and this holds true for any cutter you use so it is a wise investment when tooling up your mill.

I suggest you educate yourself about these chucks and collets. I assume your mill has an R8 spindle bore and chucks are readily available to fit it. It is a simple matter of choosing one and then choosing decent collets to fit it. If I were to buy one today, I would be looking for an ETM or Glacern ER-32 chuck. Why ER-32 and not a smaller or larger size? Because it will allow you to use cutters of a size that your mill can handle. An ER-40 will go larger (up to 1" shanks) but that would really push the rigidity limits of your mill. The collets you choose greatly affect accuracy so research this before purchasing. I would suggest Techniks collets as a reasonable option.

I should mention one tooling system that you might consider - the TTS system from Tormach. This is Chinese stuff and not of the quality of makers like ETM, Rego-Fix or Glacern. The big advantage is that it allows you to use different tooling options that are reasonable in cost. Their ER-32 chuck is less than $40.00 and is more than accurate enough for most hobby guys when good collets are used. There are many adapters for tools that fit their system so its worth a look.
 
Thanks fellas for replying. My mill uses R8 collets currently. I would not use a drill chick to hold the cutter. So what you guys are saying is the standard R8 collet isn’t really sufficient enough for my mill and I should step up to the ER cutter? Or is the ER collets just needed for long reach applications?
 
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