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how many holes should I get out of this end mill?

I'm making cable railing stair balusters again. 20 balusters (posts) each with 8
holes drilled at approximately a 36° angle in particular. On each of top and
bottom, so that makes 16x20 = 320 holes. I bought a 5/16" solid carbide end
mill, US made, and I've been running it at 1100 rpm dry into .120" wall mild
steel tube. I'm getting just a little chatter at the beginning & end of the
plunge. The end mill is double-ended, and I found I got through both ends,
barely, in drilling these 320 holes.
Flood coolant is out of the question here because I'm not set up for it and
can't handle the mess.
I've never worked with solid carbide end mills before. Should I have expected
more than 160 holes per end, or is that about right?
Grant
Reply to
Grant Erwin
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I think you did good for your situation. They don't like chatter and I bet there was foreign material where you busted though the tubing in a lot of spots. Now put that same EM in a solid chunk of steel with coolant and it will run WAY WAY longer.
Reply to
Karl Townsend
What about mist spray ??? Even a small squirt of WD-40 makes a huge difference...
Grant Erw> I'm making cable railing stair balusters again. 20 balusters (posts) each= with 8
Reply to
kbeitz
[snip]
Carbide doesn't like an overload. I think your speed may have been a bit slow and if you are feeding in with the quill, you likely took too big a bite at one or more times.
Wes S
Reply to
clutch
I use a small shampoo bottle with coolant and just spot cool as I drill but that would get old doing the number of holes you are doing, plus you would use a few bottles doing that many. I do find the coolant makes a standard drill last a whole lot longer, things heat up a good deal as you start to break though the back side, thats when I see the coolant doing most of the work.
Reply to
wayne mak
Possibly a dumb question, but why are you drilling with an end mill instead of a proper drill? Even plungeable center cutting end mills aren't really intended for drilling holes, just getting to a given depth before doing the side cutting thing that end mills are intended for.
I'd expect that you'd get vastly better performance and life if you used a drill. If the issue is getting started on the rounded tubing surface I'd think you could fab a quick guide bushing of sorts to prevent the bit from wandering to the side.
Pete C.
Reply to
Pete C.
The chatter is the killer
Gunner
Political Correctness
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.
Reply to
Gunner
I'll bet the corners of the flutes were chipped off as a result of plunging= the=20 cut on an angle. If the broken edges are small it may not be obvious withou= t a=20 microscope. If you want to stick with carbide, I'd try endmills with a corn= er=20 radius, if you haven't already.
FWIW, I've been using TiAlN coated carbide endmills for a couple years and= =20 haven't managed to wear any out before accidentally chipping the edges, exc= ept=20 when cutting molybdenum. Moly cuts much like cast iron, but is horribly=20 abrasive - it'll dull uncoated carbide very quickly. If you find you actual= ly=20 have dulled your cutters, try some TiAlN coated endmills.
Ned Simmons
Reply to
Ned Simmons
Good point, Pete. Last time around I did use a screw machine-length drill, but it wandered and gave me an element of randomness in the hole placement that was cosmetically detectible. I decided to try an end mill this time. One problem is that I am drilling 3 different angles, one 36°20', one 36°30', and one 36°40'. It would be painful to make one angled jig, but to make 3 would almost certainly not have been cost efficient.
One $12 end mill per $7200 job is completely acceptable to me. Next time I'm going to look for a 1/2" shank 5/16" end mill with really short length of cut; i.e. a stub end mill. Which I might have to get custom-ground, don't know. And I might try one of those Trico mist systems, think I have one of those gathering dust somewhere never used.
Grant
Reply to
Grant Erwin
Ever look at the Kregg pocket hole jigs for wood? I'm thinking you could fab something along the same lines with several guide bushings at the various angles you need. I'd think perhaps a day in the shop and $50 in materials would net you a much easier process for the next railing.
If you're using the same dia tubing all the time, a piece of tubing that is a slip fit for it, welded to a base plate and with a piece of 3/4" plate welded to it vertically would be a good start at a jig. Drill your various angle holes in the plate "shark fin" and weld a nut on the tube for a lock screw. Scribe a few reference lines on the jig and you should be able to very quickly position the target tubing, lock it down and drill whichever angle hole you need.
Given the simplicity of the jig it should be cost effective to make more if needed. For that matter you could have several fins on the same jig. Just seems a lot easier than messing with end mills designed for side cuts when you aren't side cutting, or custom ground bits for a simple 5/16" hole.
Pete C.
Reply to
Pete C.
Good Morning Grant :) I'm not set up for flood coolant either, and I'm not doing the type of production work your are, but I've had good luck using the 'stick' type of BoeLube. (called Boelube Solid) (Boeing #7020, MSC# 61232567 $11.11 on the 2004/05 big book) Comes in a container that looks similar to a caulking tube but it's like a hard wax. I just chip off a chunk and touch it to the mill prior to starting a cut. As the cut proceeds the lube melts (smokes a little). Seems to cut down on the chattering and chipping. Works well on metal band saw blades also. Bob rgentry at oz dot net
Reply to
Bob Gentry
So, you save yourself an end mill. My bet is that you'll end up working awfully hard for your twelve bucks...
But mist coolers and carbide don't mix very well. The same is true of giving it a squirt of something now and then. While carbide in a CNC work center with "firehose" flood cooling and carefully calculated speeds and feeds will outlast what we get in a conventional mill, such luxuries are usually limited to high production operations. Carbide is perfectly happy running hot. The problem comes from the sharp temperature differentials that occur with any form of "part time" cooling.
HSS is much softer and can tolerate the stresses that result from somewhat uneven expansion and contraction, the much harder (and more brittle) carbide simply will crack, usually little pieces off the cutting edge.
I think you have the recipie about right and would suggest you quit while you're ahead.
Jerry
Reply to
Jerry Foster
Since nobody else mentioned it, you might try M-42 or M-57 HSS end mills. I use these and carbide almost exclusively, now. They are vastly tougher than HSS, and less prone to chipping than carbide. You can usually get these cobalt HSS tools for a couple cents more than plain HSS.
Jon
Reply to
Jon Elson
Grant, those sound like mighty accurate angles. Are you sure they aren't all the same?
Steve
Reply to
Steve Smith
I am, Steve. I measured them myself with a precision inclinometer. The idea is to cut the end of the square tube and weld a foot on it such that when you set the foot solidly on the stringer beam the tube will be vertical, or close enough so the bubble on a good level doesn't touch the line on either side. I've done this a coupla times now, and to get to that level of quality you have to really pay attention to the angles.
To be honest, the holes I drill I do all drill at the same angle, though. I drill 5/16" holes to pass 1/8" stainless cable through, so if there's an angular error involving half a degree nobody could tell. Here's a pic:
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That was the first one I did, the builder & real estate guys liked it so well they ordered 2 more sets for the other 2 matching townhouses.
Grant
Reply to
Grant Erwin
That's good looking. Nice job!
Peter
Reply to
Peter Grey
Great looking job Grant but at the same time OT ... I have a feeling that that SS wire could be a death trap to kids.
I don't know how but kids always find a way. IE lean over the rail to far, fall forward driving head between wires, continue falling forward and end by being asphyxiated while hanging by head between wires.
Shit happens!
Reply to
Jake
There are very strict building codes relating to allowable openings in railings for just this reason. The spacing between the cables is just over 3", and the "baby's head" rule allows 4". The railing is designed and built to code.
There are many stainless cable railings in existence in the area I live in. I don't recall ever hearing of such a tragedy in my area.
Grant
Reply to
Grant Erwin
OK good! I am happy that everything meets code, it is a beautiful piece of construction.
At the same time I hope the code takes into account the flexibility (deflection) of the "non rigid" wire components being employed in the construction. In my heart I seriously doubt that the 4" baby's head rule has any real value when applied to non rigid components who's tension degrades over time with the normal wear and tear in such common areas as stair wells.
I by no means want to make mountains out of mole hills. Having said my piece I will shut up and drop the subject.
Reply to
Jake
On Tue, 02 Jan 2007 21:25:14 -0500, with neither quill nor qualm, Jake quickly quoth:
So are heights, electricity, water, stairs, cement, asphalt, bicycles, cars, pointy sticks, kitchen knives, forks, pipes, small objects, other kids, etc.
Precisely. Why worry? It'll happen (or not) without your worry. (See sig. READ sig., UNDERSTAND SIG! She knew of what she spoke.)
Reply to
Larry Jaques

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