[Newbie] Drill chuck or boring head? vs endmill?

[pVAnyxi]

I'm getting ready to buy a Taig cnc mill and am at the top end of my budget, nit-picking the last couple of add-ons. My last decision is whether to get one of the drill chucks or the boring bar head, but I'm missing information in the decision making process.

First, my understanding is that the reason to use a drill chuck on a mill is that drilling with a drill bit is faster than endmill or boring bar. It's not as accurate, but the hole is drilled undersize and then finished with a reamer. But is the taig mill strong enough to use anything larger than a little pcb drill in steel or aluminum?

And where does the boring bar become advantageous? Is it back to size of the hole and torque on the spindle? And why not just use a long-reach endmill? Are they still just not as long as a boring bar? Or is the issue more that an endmill on a manual machine would require a rotary table, so the boring bar makes more sense, whereas a CNC could use the endmill in a circle without the trouble? And in the particular boring bar head offered by taig, there's no screw adjustment or anything, it seems to be "tap it, cut a hole, measure the hole". That seems annoying to me; I do enough "cut twice, measure once, repeat" in my woodworking as it is already.

For background, I like to pretend I'll eventually do really accurate stuff, and hole size accuracy will matter, but I'm upgrading from a 3d printer as far as cnc goes, with any metal working done by hand, maybe with a harbor freight drill press for trying to drill holes, so it wouldn't take much to outdo what I'm currently working with anyway. Short term, especially until I build an enclosure and figure out what what coolant pump and such to get, I'll be cutting plastic and wood, and maybe jewelers wax. Medium term, I'll be cutting whatever it is jewelers make duplicatable blanks from (my son does that, but I forget what he said; aluminum maybe?) and small aluminum and hopefully steel parts structural parts. Maybe some one-off finished jewelry pieces. Most of my 3d printed stuff has been functional parts, like doorknob mounting plates, latches, shelving brackets, tablet mounting arms, etc. and I'm tired of engineering around the weak layer boundaries of 3d printed parts. And not being able to use anything outside in the summer or in an engine compartment without worrying about it melting.

 

[Winegrower]

You need a boring head when the hole diameter is bigger than your biggest drill bit.
Edit: oh, sorry...I missed the CNC part. Disregard.

 

[mikey]

I'm getting ready to buy a Taig cnc mill and am at the top end of my budget, nit-picking the last couple of add-ons. My last decision is whether to get one of the drill chucks or the boring bar head, but I'm missing information in the decision making process.

First, my understanding is that the reason to use a drill chuck on a mill is that drilling with a drill bit is faster than endmill or boring bar. It's not as accurate, but the hole is drilled undersize and then finished with a reamer. But is the taig mill strong enough to use anything larger than a little pcb drill in steel or aluminum?

A Taig is more than capable of drilling a decent hole. I would guess max capacity would be somewhere near 1/2" or so. A drill is definitely faster than an end mill or boring. You can bring it to size with a reamer but how accurate it is depends on how well you choose the drill that is used before the reamer, the speeds used with that drill, the size and quality of the reamer and your skill in using it. A boring head, on the other hand, is capable of making very accurate holes. It can cut a hole to any size within its range so that a reamer is not necessary. Done well, a boring bar is capable of finishing as well or better than a reamer. Bottom line is that if you own a mill, you should own a boring head and a drill chuck. You do not have to use the drill chuck or boring head from Taig; there are many other options of higher quality.

And where does the boring bar become advantageous? Is it back to size of the hole and torque on the spindle? And why not just use a long-reach endmill? Are they still just not as long as a boring bar? Or is the issue more that an endmill on a manual machine would require a rotary table, so the boring bar makes more sense, whereas a CNC could use the endmill in a circle without the trouble? And in the particular boring bar head offered by taig, there's no screw adjustment or anything, it seems to be "tap it, cut a hole, measure the hole". That seems annoying to me; I do enough "cut twice, measure once, repeat" in my woodworking as it is already.

A key advantage of a boring head is that the center of the hole it cuts is on the exact centerline of the spindle so you can locate the hole in the part exactly where you need it. It is also capable of cutting holes with straight sides, and while deflection can happen with any tool, a boring bar used with skill will cut very, very accurate holes. An end mill in a CNC mill can do much of the same things that a boring bar can so you don't have to buy a boring head but personally, I would not want to be without one. In fact, I own five of them.

Running a mill takes a bit of experience and skill. In my opinion, a hobby guy should learn to manually use a lathe or mill before stepping into CNC so he knows how metal likes to be cut and how to respond when there is a problem. Then again, I'm a strictly manual guy so what do I know?

 

[pVAnyxi]

Running a mill takes a bit of experience and skill. In my opinion, a hobby guy should learn to manually use a lathe or mill before stepping into CNC so he knows how metal likes to be cut and how to respond when there is a problem. Then again, I'm a strictly manual guy so what do I know?

Honestly, I'd rather have a large manual mill and lathe, but I don't think I could do a lot of the projects on my plate with manual, and definitely not as fast (even considering how slow the desktop mill will be). And those projects are what got the "accountant's" approval to buy it in the first place. Not to mention that my garage floor wouldn't handle a large knee mill or engine lathe anyway. I fully expect to break endmills and screw up finishes and such, but I'm a programmer by trade and have written g-code from scratch before for milling aluminum. So once I get the proper feedrate and depth of cut dialed in, the cnc side will serve as an easy crutch to do the actual cutting.

There shouldn't be anything stopping me, as far as I can tell, from using the cnc mill like a manual by just jogging it where I need to go, it just won't have the same tactile feedback as turning wheels, but I'm hoping I'll still be able to get an understanding of the sounds of good vs bad cutting and such. At the same time, a manual machine isn't going to have a higher feedrate than the cnc version of the same machine, and cnc will save me a lot of time standing around. It would be nice to slap a piece of steel plate down and cut a slot in a couple of passes with a bridgeport, but I wouldn't look forward to standing there for 14 hours cranking mini wheels to do the same thing at the low max feedrate these desktop machines seem to have.

 

[mikey]

I totally get the "accountant's approval" part, trust me.

I wonder if you might be underestimating what a Taig or Sherline mill is capable of, though. For example, you said this:

It would be nice to slap a piece of steel plate down and cut a slot in a couple of passes with a bridgeport, but I wouldn't look forward to standing there for 14 hours cranking mini wheels to do the same thing at the low max feedrate these desktop machines seem to have.

A Sherline mill, and I suspect a Taig mill, can do everything a larger mill can do but in smaller bites. I said smaller, not tiny. For example, a Sherline mill will cut a 1/4" wide slot in 1/4" deep mild steel plate in a single pass and I think a Taig will do the same. Either should be able to mill a 3/8" slot in aluminum in a single pass with a roughing end mill. What these mills will not do is the complicated profiling and ramping cuts a CNC mill will do so I'm not trying to dissuade you in any way.

All of this is beside the point. You need a drill chuck and you probably will need a boring head to get deep enough. You also need a good tool holding system to hold your cutters and this should probably be your first purchase. I would suggest an ER chuck of some size, depending on the size of cutters you expect to use. For a small lathe like a Taig, ER 16 or ER 20 would work fine.

Anyway, good luck with your purchase. Given your background, CNC sure sounds like the way to go.

 

[pVAnyxi]

I hope I am underestimating it. I'm basing it so far on guestimates from the time taken for sample images that are on the microproto site, like a very rough 4"x2" car body in aluminum that took 8 hours. I haven't actually done any math to estimate what feedrate that would be, and I'm REALLY bad at doing that stuff in my head. (My teachers always hated all of the tick marks all over my math tests.)

I believe it comes with an ER16 collet, but I still have to verify that for sure. I also need to check what size the collet is, or whether it comes with more than one or what. The taig site says a six-piece set, but this distributor site says 2 and even that is only listed on one with upgraded encoders. And being a total noob, I don't know yet what size cutters I'll need. The site I'm planning on ordering from has a set of 5 double-ended ones I'll get. The largest in the set is 3/16". And it doesn't say what the shank size is on them, so I still need to ask that as well. I'm trying to get as much as I can fit in my budget just added to this bundle so I'll have enough stuff that I can work on something and then I'll expand from there as I find things I need.

 

[mikey]

Do yourself a big favor and buy decent collets and a good nut for the ER chuck. These can make a difference in the accuracy of your cutters and that has a big impact on accuracy, finishes and tool life. I would not use the cheap import collets if I were you.

The best bang for the buck for collets is the Techniks brand. Their set goes from 3/32 to 3/8" in 32nds. For a Taig, 3/8" shanked tools is probably a good maximum size.

For nuts, Techniks, Rego-Fix and ETM make good ones. Their coated nuts are very accurate and their ball bearing ones require less torque; either type will work.