largest broken end mill TM-1?

powerglider · Jun 27, 2009

I'm thinking of trying to do some tube bending using my Haas TM-1P, but I'm nervous about the abuse it might have on the machine.

I'm thinking that if I use a relatively small diameter shank to hold anything I'm putting in the tool holder then it will simply break the shank with no damage elsewhere.

So my question is, what is the largest size shank of a tool anybody here has broken off by mistake and never noticed a difference when you just replaced the tool and revised your tool path?

Say you slam a non spinning 3/4" OD end mill with 3/4" OD shank into one of the vise jaws at a feedrate of 30 would it just bust the end mill in half and put a small dent in the vise material? Or would there be permanent damage to either the spindle/quill or the ballscrews on the x or y axis?

ANything else I'm missing?

Hdpg · Jun 27, 2009

Just my opinion but I think this is not a good idea.

Do some Googling using 'brinelling bearings' or 'false brinelling'.

Ball races are intended to carry loads while they are spinning and are seriously derated when stationary.

fmari --MariTool- · Jun 27, 2009

Breaking a tool while the spindle is spinning is very different from breaking a tool while it is stationary. Bearings can take much more abuse and load while in motion than when sitting. Most of the time you can break a 3/4 carbide end mill with no damage to the machine or spindle ( as long as it is rotating). The balls will dent the raceway if you put severe load while bearings are not rotating.

What you plan on doing I would not recommend. If anything I would make a bracket to support a 3/4 rod to the head is such a fashion as not to put any load on the spindle. Maybe you can bore a piece of thick tubing to be a nice slip fit over the spindle cartridge and on one side of this tubing drill and tap a whole bunch of holes to accept this 3/4 mandrel.

AlexBanich · Jun 27, 2009

powerglider said:
Say you slam a non spinning 3/4" OD end mill with 3/4" OD shank into one of the vise jaws at a feedrate of 30 would it just bust the end mill in half and put a small dent in the vise material? Or would there be permanent damage to either the spindle/quill or the ballscrews on the x or y axis?

I'm going to say that you're going to get broken end mill and love mark on the vise. As well you will surely leave some form of scarring on your machine. I know the bearings in a makino edge 2 will quickly develop flat spots from operators slamming the head in to things :rolleyes5:

powerglider · Jun 27, 2009

thanks for the feedback.

Maritool, I guess if I can make and fasten a shaft to the Z column that would eliminate any potential damage to the spindle, but still apply force pulling and pushing it from the linear Z track which probably isn't good.

If it's not a large tubing (like a 1/2" aluminum tube) it probably won't matter, but my main bending is 3/4" OD and 7/8" OD aluminum tubing with .058" wall thickness, and it does take quite a bit to push the arm on my manual Diacro #3 bender. I could measure it by pulling a larger capacity spring scale until it starts the bend to have an idea of the force exerted.

Perry Harrington · Jun 27, 2009

Why the heck do you want to use your $20k+ CNC mill to bend tubing when you have a tubing bender already? Wouldn't it make way more sense to modify the bender to improve usability or production rate?

AF-METALS-TECH · Jun 27, 2009

Load limits

Most machines will alarm out when they hit there load limits, The TM-2 we have is a dog and I dont think it would take a lot of abuse like you are talking about. But if you have to I would go with Mari's advice and save the spindle bearings as much as possible and watch the z load limit while you are doing your op.

powerglider · Jun 28, 2009

Just wanted to say that this is just a thought, I'm not going to try it on my realtively new and expensive machine.

If I do try it I would use an old machine that already has precision issues.

As another member pointed out, why would I put a $20K plus machine at risk to use it for something it wasn't designe for when I have a Diacro bender that works just fine. The answer is that I would only do it if I knew it could take it. Why use it at all if it can? Because it would do a better, more repeatable job at bending than my manual set up as everything about the bend can be controlled and repeatable.

For now, I'll just wait for an opportunity to buy and old cnc machine with a working controller but broken spindle (I can use the column as Mari said), maybe something with a busted tool changer, anyways something that isn't worth fixing is what I'm getting at (but the table moves in x, y within a .01 tolerance). It of course needs to be Cheap.

For the immediate future I'm saving up to buy the probing system for my Tm1P, next is a P cool, then maybe the bending experiment on an old beat up cnc machine.

Thank you for all the inputs.

Hdpg · Jun 28, 2009

powerglider said:
For now, I'll just wait for an opportunity to buy and old cnc machine with a working controller but broken spindle (I can use the column as Mari said), maybe something with a busted tool changer, anyways something that isn't worth fixing is what I'm getting at (but the table moves in x, y within a .01 tolerance). It of course needs to be Cheap.
.....

If you do use an old busted machine that isn't worth fixing why go to the bother of making an attachment for the column; you don't care if you brinell the bearings.

But before spending any money you should figure out the force you need to do the bending; most small to medium size machine servos peak out at around 2000lb thrust which is the TM1 limit on X and Y, even a VF4 is only 2550lb.

powerglider · Jun 28, 2009

hdpg,

That's the kind of information I was looking for, thank you.

Not that I'm going to try it on the TM-1P first but it's that figure I wanted to understand.

So if a shaft was bolted/fastened to the colum and I pushed against it until it broke, then so long as I don't push more than say 1/2 the peak thrust (say 1000 lbs) before it broke the table wouldn't care right?

I'll measure the lbs needed to bend the 2 size tubes I use on my manual bender. Since I don't own a large capacity fish scale, I'll turn the bender 90 degrees somehow and then suspend more and more weight on the arm to measure when it starts moving.

powerglider · Jun 28, 2009

you're right about the beat up machine for the test, it wouldn't matter if I put the shaft on a tool holder if the spindle is screwed up anyways.

Hdpg · Jun 28, 2009

The table, more correctly the servo and ballscrew, don't care if you reach the overload limit so long as you do it slowly which is what you will be doing.

You should be able to get an estimate of the forces needed even without the fish scale. Unless you are a real gorilla it is not likely you can pull the lever on your bender at greater than about 100lbs, it is almost certain you cannot pull more than your own weight so that gives you an upper limit.

Then all you need to do is figure out the leverage; length from where you pull to center of rotation divided by distance from center of rotation to where the bender acts on the tube multiplied by the force you apply.

I built a manual bender for 7/8" - 0.062" wall tube that bends around a 3" radius and this needed a lever about 72" long otherwise I simply slid across the floor trying to pull it. The calculation gives a force of about 2400lbs acting on the tube if I am pulling at 100lbs.

This is a really crude way to figure the forces and I would not be surprised if it underestimates by 50% or more.

P.S. Within two weeks of completing it I converted my manual bender to hydraulic. Pulling on that lever was too much like hard work.

powerglider · Jun 28, 2009

hdpg,

you must have been bending chromoly tubing or steel? I bend aluminum 7/8", 0.058" wall with a 2.25" clr (center line radius) and my leverage arm handle is 36" away. I esitmate I'm pulling it at 150 lbs or a touch less. I'll test it sometime with a weight and turned over at 90 degrees, let gravity do the test for me.

I hear you on the physical part of bending. The other difficulty is repeatability with a hand bender, you really need to slam it into a stop at a constant stroke for the last 10 inches of stroke or more to get a fairly accurate bend. Those ring angle things they sell on some benders are a waste of money!

Hdpg · Jun 28, 2009

Stainless steel 316.

Do my calculation with your numbers and you come out fairly close to my bending force.

I guess your alloy is T0 or a very low temper.

You are quite correct about the need to have a constant speed into the stop so the bends are consistent. My shop-built one has a microswitch on the hydraulic ram which turns off the pump and vents the cylinder instead of a mechanical stop and it gives very reproducible bends.

rawen2 · Jun 29, 2009

powerglider said:
I'll measure the lbs needed to bend the 2 size tubes I use on my manual bender. Since I don't own a large capacity fish scale, I'll turn the bender 90 degrees somehow and then suspend more and more weight on the arm to measure when it starts moving.

You might be able to get a rough bending force reading if you can push the handle instead of pulling it. Put a bathroom scale between your hands and the handle. I know it sounds kinda mickey mouse but it might just work.
Ralph

g-coder05 · Jun 29, 2009

perhaps puting a cam follower in the spindle and turning it on before bending the part so the load would be somewhat equal.

agertool · Oct 8, 2009

Ok, I hate bump old threads but....

If you want to bend tubes, instead of using your expensive piece of precision equiptment, why not make a fixture you can bolt to the front bumper of your vehicle and find a bar that is stationary in the ground. Then just ease your vehicle, while it is drive slowly till you get the desired result. You don't want to go to fast when doing this process for you may not stop in time and bend your tubes too far. As far as any scratches and dents in your bumper, well I am sure that it is cheaper than rebuilding your spindle

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largest broken end mill TM-1?

powerglider

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