I need a small slot in my sundial bases. Usually I pre-drill the hole (either 3/16" or 1/4") and then extend by 0.075" (1/4" hole) or 0.50" (3/16" hole) the material is 3/8" key stock, galvanized, made in USA. The mill is a generic X2, the mill bits are Chinese box set.
I have been using the side of the mill doing the full thickness all at once. The slots have been coming out skewed which was visually obvious even at these short distances. The wise was checked and is fine (
I think your problem is that you are not locking the table in the X direction when you are moving in the Y direction.
Dan
Given the result, obviously something is moving.
Since that particular set-up is not giving you the results you want, I would try this.
Center drill and then drill undersize holes at each end of the slot.
Swap to a full size end mill to then size each end of the slot.
Next swap to an under size mill and go between the holes at each end taking passes until you get to full depth.
Now work the edges of the slot to bring it to full width.
By sneaking up on your desired dimension the flex in the cutter or the machine will cause you a lot less mischief and your cutters will last longer.
snip
short answer "no" longer answer - as someone else posted, you need to lock your table in the direction you are not expecting it to move.
I have no problem cutting a 1 inch wide by 1 inch deep slot with a 1 inch end mill on my Abene - it's a bit bigger than your mini, but I don't know that I 'd call it a "beast"
My eyes!! My Eyes!!!
Sigh..you are doing every ..and I mean EVERY newbie error in milling Ive ever seen.
Ill wait and see what the others have to say..maybe Ill not have to write you a chapter on milling.
That cutter btw..should have gone another 50 or 100 of those slots at the very very least. Minimum
Political Correctness is a doctrine fostered by a delusional, illogical liberal minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
[ ... ]
Yes -- and doing it with a four-flute end mill is another bad thing.
While you are cutting, the leading flute in the direction of travel (which is doing most of the work) deflects the end mill to the side opposite of its travel, allowing the next flute back to cut out the one side of the slot. This causes the kind of thing you see -- with the amount you see depending on the rigidity of the entire setup and the length of exposed end-mill. (A longer mill has more flex than a shorter one.
Bad to do more than about half the diameter of the end mill in thickness at a pass.
Even worse to use 4-flute end mills. What you want to use is two-flute ones (often called "slot drills" in the UK I believe because they are so much beter for slotting).
What coolant? What RPM? What feed per tooth? And the galvanized key stock is probably a rather gummy steel. Go for 12L14 (as for turning) to find out how much better things can be.
But yes -- the Chinese origin of the end mill suggests that it could be very poor quality steel.
Buy some *two*-flute end cutting mills by a maker such as Cleveland, check the RPM against the diameter (calculate the SFM (Surface Feet per Minute) and compare it to the tables in books like _Machinery's Handbook_ (pretty much any old edition will do for this). look up the feed per tooth (for a two-flute end mill here), and working with the RPM calculate how many inches per minute you want to feed. You don't want to go faster, but you don't want to go too much slower, either.
Note that some Chinese boxed sets have both two-flute and four-flute in each size, and some of them can be pretty good. It depends on where you get them, among other things. I have a set which I got from MSC, and they are useful for a lot of things, but for serious work I use Cleveland or other US-made mills bought for the task.
Good Luck, DoN.
No, that is not it. I locked the stationary axis every time (I tried this milling along both x and y). I should also add that when I pulled the mill out of the end of the first (banana shaped) slot it would not go down the same hole again and returned to its original position along the (in this case) x-axis. It is apparent in the second pic.
Interesting. Makes me wonder if it is the property of *this particular* mill. As I said, I have not heard anyone mention this phenomenon before and I did a ton of looking and reading before I cut anything.
While its not as tall as a Bridgeport..its far far more rigid than one..and head and hands more rigid than an import minimill.
Crom but I love my Abene!!!!
Gunner
Political Correctness is a doctrine fostered by a delusional, illogical liberal minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
Hm. when I started I was told "two flutes good, four flutes better (for steel)"
It may be even less than that. I have not shown all I have done but when I did 0.100" passes there was a definite tendency for the slot to wander.
Jus Rapid Tap.
I could BS and say 550 rpm but the truth is somewhere between "vroom-vroom" and low pitched "brrr". The regulator is supposed to go from zero to 1100 rpm but I strongly suspect it is not linear. How it holds rpm under load is anyone's guess.
That is even harder to quantify. I follow the Machinery's book advice (see below).
There seems to be a lot of room for interpretation vis-a-vis the steel hardness. I usually take it that I should be OK with 60-90 SFM. At the high end the rpm for 1/4" mill are appx. 1500. I have never got as high as 1100 (nominal) as the machine starts shaking.
As for rough milling the feed should be "all that the machine, work, fixture and tool will withstand". IMHO they should also include operator's nerves.
Right, two flutes it is!
just so you don't get put off by my comment, the Abene mill is pictured under hobbies/tools on my web page wbnoble.com - it has a 6 HP spindle motor and a 2 hp ways motor, which places it in the "bit bigger" category - 'real' mills in production seem to have about 10X that power nowadays, but this is enough for me to break the tool of my choice every time I make a stupid mistake.
I wonder, whether you would be better served with a horizontal mill cutter - hold the work piece vertically
I have no idea what a "generic x2" milling machine is, but these two comments suggest to me that you must be feeding 'way too fast for the stiffness of the setup/machine.
Is the machine bolted down? If not, do it.
Pete Stanaitis
------------------
Michael Koblic wrote:
---- I have never got as high as 1100
----- IMHO they should also include operator's nerves.
Sieg X2, also known as mini-mill. See
or
...
That is only 18x more powerful than mine...Bet you cannot throw yours across the room in a fit of rage!
It is a thought but I doubt that. Usually I feed slowly so that neither the machine nor myself are shaking.
It is.
Ah, nostalgia........................
I posted a similar query (almost identical, really)ages ago and DON Nichols kind response was that I was trying to do several years of shop in 20 minutes (or something to that effect) and he was right. Thanks DON. Went and enrolled at a apprentice level course , still there, still finding creative ways of stuffing things up...
My mill is an X2 - and does the same as yours - what I have found is:- vibration is the killer - it will do God knows what if its not rigidly, VERY rigidly bolted down. And even then, its really only good for plastic/aluminium, its design limitations are that its a cheap Chinese mill. If its vibrating, or the bench its on is vibrating, then its too much. You will break cutters through vibration - think about it, the thing is being bounced around like blazes, no wonder their wearing out fast. Your expecting a bit too much from it - I would suggest cutting multiple small slots, creeping up on the final size. Speed? - almost irrelevant here as the thing doesnt have a tachometer, or a power feed
- you have to go by ear, and you will develop this in time. What sort of vise are you using? - if its one of the ones that can swivel on its base, take off the base and mount it directly on the table. It helps. Are you using the proper sized holder for the bit, not just the Jacobs chuck you use for drilling?. Have you set up the mill properly (or at least tried to) - out of the box, their pretty shocking, play in the gibs, out of plump, lotsa backlash. The belt drive conversion helps too - makes them a lot smoother, you have probably broken a tooth in the gearbox by now (stick it in low range, manually turn the spindle - it should be smooth ALL the way round, if there's a "click at one spot, then a (plastic) gear is broken. Google X2, there's HEAPS of information/mods for the things....
AND - finally - yes, if you have a decent industrial machine, (and you have 3-phase power and a BIG workshop) as mentioned, then these problems dont exist - any machine that takes a forklift or trained riggers to move it is going to be more rigid, with more power, and built to tighter tolerances so things like you describe are ho-hum, run of the mill sort of thing. But, when you do make a mistake, 5hp will throw something a lot further and with greater terminal velocity than the X2... when and if you can, upgrade to the X3, its significantly better, or take the industrial machine route if you so desire and can get it past SWMBO.....
Good luck - it will drive you absolutely NUTS, the learning curve is near vertical to start with, but after a while things start to get better/easier ...which means you start trying to do more complex things, so its a lifelong process.
Andrew VK3BFA.
It would seem to me that if the cutting path errors aren't caused by unintended table movement, then the wandering path is likely to be caused by flexing of the endmill.
It's not easy to see the length of the endmill, or just the cutting section of it, from the photo.
Another significant problem that happens when a small endmill is used to cut the full width of a slot, is chip evacuation, or lack of it.
With cut chips present in the cutting area, the endmill is frequently jamming as it's rotating, causing the endmill to try to cut fresh material, plus the thickness of the chip(s) passing by the flute on the opposite side of the endmill. Chip interference can be heard as clicking or crunching sounds as the endmill is cutting. Some erratic table movement can probably be detected by placing a finger at the point where the table dovetails meet.
The two conditions will lead to a wandering cutting path. The limited rigidity of the minimill may also be a contributing factor.
Using a cutting tool lubricant in a squirt bottle, to constantly flush the chips out of the cut should improve the results, but the sides of the slot probably still won't be perfectly straight. The spiral of the flutes will help carry chips away, but only to a limited degree (less at lower RPMs). Using a medium viscosity cutting lubricant will help the chips flow outward from the cut.
The other recommendation of drilling the ends of the slot location with a rigid drill, followed by material removal with a smaller diameter endmill would likely be the best procedure, especially with a light duty machine.
Flooding a cutting tool lubricant to flush chips away can obviously be fairly messy, so coming up with a method to recover and contain the lube might be worthwhile. A small endmill isn't going to be slinging much lube, but the flooding action should be constrained to the table area.
It might be possible to retrofit a gutter system around the edge of the table, or the workpiece clamping methods might need to be reconsidered, to allow the small parts to be cut with them sitting in a shallow pan on the table.
The type of dispenser bottle I prefer for cutting lube is the wash bottle with 90 degree spout shown near the bottom of this page (but in a 6oz version)
The simple answer is to rough out the slot with a smaller end mill and then finish each side separately.
jsw
Very very well said! Kudos!!
Political Correctness is a doctrine fostered by a delusional, illogical liberal minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
"Wild_Bill" wrote in news:pKEym.1$ snipped-for-privacy@en-nntp-02.dc.easynews.com:
If you can get away without coolant, you can keep the chips out of the slot with a vacuum cleaner. I had to mill some ~ 5/8" diameter holes in some aluminum extrusions, where the hole intersected several cutouts. I had a good stiff end mill, but a not absolutely rigid Clausing 8520 mill. Chips would constantly get caught between the end mill flutes and the interrupted cuts, and cause momentary jams & lots of vibration. You could hear & feel the machine jumping around. I set up my shop vac with a nozzle to keep the chips clear, and it worked MUCH better.
Doug White
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.