Blog Archives

Index

Current

The CNC Cookbook Blog

3/12/10

Neat Little CNC Toolroom Lathe: Harrison Alpha

Despite my CNC gang lathe fetish, a CNC toolroom lathe would be a more useful thing in my own shop. Here is the sweet little 13" swing Harrison Alpha:

3/10/10

Did a Little Work on the Bandsaw Miter Gage Project

More on the project page:

Shown here reaming all the holes. Center hole is for the dowel pin pivot. The peripheral holes are for a ball detent on the protractor. Detents will be every 10 degrees plus 15 and 45 degrees.

I can't believe how well the Rockwell Delta 20" bandsaw cuts. Like butter through 1" 6061!

3/8/10

Nice German BF20 CNC Conversion

I really liked the integrated belt housings to drive the ballscrews on this German conversion:

Nice clean install, well protected from flying chips...

Plates on the right are pocketed for the reduction timing belt. Plates on the left mount on the machine...

Stepper power connection...

Another view of the guts...

Manipulating the belt onto the big timing gear is going to be a little bit finicky, but not too bad...

Neat little Hall Effect (proximity switch) limit switches...

The World Before DRO's

For those who like machines and mechanisms (and I'll assume that is most of you as it is me), there is a world of interest in learning how things "used to be." How were chronometers made accurate enough for sailing ship navigation well before we could look up the time on our iPhones? One of my favorite topics is all the tooling manual machinists need that CNC doesn't. The electronics and computer software make it superfluous. A rotary table, for example, is unnecessary to the CNC'er (unless you want to turn it into a 4th axis), but quite useful for manul machining. Yet, there are many fascinating ideas one can derive from the old ways of doing things. Ideas that are often useful despite the electronics of today. The old machining books are priceless (though fortunately, often very cheap in used book stores--keep an eye out!). I learn so much from them, and periodically we see something dredged from the past reinvented and made useful to as in the present. The odd conversion of shaper tool to lathe finishing tool (a skivving tool or "shear" bit) is one such example, and there are many more.

HSM has a fascinating thread going about how machinists got by without DRO's back in the day. I plucked two pictures that tell of one machine's abilities in this respect:

The venerable Kearney and Trecker 2D was a very sophisticated mill in its day...

Note the dial indicator with grooved trough. One inserted either precision rods or gage blocks into the trough. The table then "bumped into" that stack which would register very accurately on the indicator.

While we're on the subject of how old machines worked, how about Constant Surface Speed? As you go to smaller and smaller diameters while facing (or turning) on a lathe, you need to speed up the spindle to maintain a constant SFM. This results in a nicer finish. The feature is common on CNC's. Monarch had a version of the 10EE that could do it (Monarch's motor drive electronics were one of its most innovative features, and most difficult now that the world has moved on to VFD's and such). But how about a much older lathe?

This is how Cunliffe & Croom did it in 1914:

The clockwork mechanism apparently adjusted a potentiometer that varied the speed of the DC motor...

3/3/10

Rigging: Moving the Mountain to Mohammed

It's probably a personal limitation, but I absolutely dread rigging heavy machinery. It's really the logistics of getting it into place, and particularly off the truck. I have a home shop, it's up a hill, a big tractor rig can't come up, and I have no loading dock. Shippers all want to charge a fortune to provide a truck with a liftgate, and for many things you just can't get it done without a lot of finagling.

Recently, I saw a great solution, or at least a piece of the solution, while looking through some old posts on the PM boards. Instead of a loading dock, convert a scissor lift:

The scissor lift gets it off the truck, and the palette jack moves it into the shop. The lift has a 3 ton capacity. This is going to be much easier to get past the finance department (SWMBO) than a forklift!

2/25/10

New Project: A Miter Gage for the 20" Rockwell Delta Bandsaw

With the bandsaw now nominally running on its new VFD, its time to finish the details. Here is what's left to do:

- Mount the VFD in the power cabinet. It's wired, but sitting atop.

- Make the stock On/Off switch for the motor work with the VFD.

- Mount and wire the blade welder I purchased from Harbor Freight.

- Make a miter gage.

I had a little time last night, so I did a design drawing for the miter gage:

Pretty straightforward sort of thing to CNC. It incorporates a ball detent system, which allows quick selection of 10 degree angle increments plus 15 and 45 degrees. The project build page is here. Still a little design work to do.

2/24/10

Tapping Tidbits: Limit for Form Taps + Peck Tapping + Thread Mill When Risk is High

Quick, how do you know whether you can or can't use a forming tap? Forming taps don't create any chips, they cold form the material to form a thread. Forming taps themselves are stronger than cutting taps, so they are less prone to breaking. In addition, they produce stronger threads and you have less concern about whether the hole is going to get jammed up with chips since there are none.

While most machinists may think form taps are only for aluminum, the answer to the quick question is you can form tap materials up until they have a hardness greater than 36 HRC, which is about 340 BHN. That actually covers a surprisingly wide range of materials including a lot of steels. That information comes from tapmaker Titext via the link I've provided.

Second tapping tidbit: you can "peck" tap difficult holes. For the most part, you will need rigid tapping to be able to peck tap because the tap has to get itself synchronized back to the same set of threads as it goes in and out of the hole. Peck tapping is only called for with a cutting tap--no benefit to pecking with a form tap. Peck tapping is also an excellent way of clearing the long stringy chips often found when machining plastics and some other materials .

Last tapping tidbit: For the hardest materials, and especially when the cost of a broken tap is very very high, consider thread milling. You're much less likely to break a thread mill, and if you do, it won't be stuck in the hole the way a tap would be.

2/15/10

Die "Traminator" and Spindle Squeegee

You must have noticed if you've read these pages for very long that I am a consumate gadget collector. A lot of machinists are in the camp of less is more. Why use a Blake Coax if you can just sweep your indicator? I'm in the camp of one more labor saving device that works is one less bit of labor. I need all the productivity help I can get in the shop!

I use the "Traminator" and my Spindle Squeegee for routine house keeping with the mill spindle. These are just a couple of handy gizmos whose jobs can be done with other more general tools, but that I like even so.

First, the spindle squeegee:

It's just a handy way to clean up your spindle taper and make sure there are no chips stuck up there.

Second, the "Traminator" and my collection of tramming accessories:

The Traminator and Case in Back, Pry Bar and Wrench in front...

The Traminator (my name for it), was a gift from my brother for Christmas. This one is made by SPI and its very nicely built. To calibrate, set it on a flat surface and zero the two dials. Insert in your spindle, bring it down in Z until the dials read, and adjust tram until they both read the same value. Super easy and fast! I had been tramming with an Indicol and DTI, but I like this a lot better. It's just faster and easier for me. In this case, I could tell from some face milling I'd been doing I was out of tram in both X and Y. The Traminator made short work of it. I use the pry bar through a hole in the side of the spindle to get a little more leverage, and tap on it with a mallet to tram. It's real important on the IH mill to carefully watch what happens to tram as you tighten the locking bolts too, and that is particularly easy with the Traminator.

Better Vise Mounting Clamps

I had been using the normal clamps that came with my table clamping kit up until I got my new Glacern 6" Premium Vise. It came with a nice clamping kit that I like a lot better:

Old Style...

New Hotness...

The new clamps are simpler and more compact. For example, when I run two vises with my Jaws of Doom between them, it gets hard to swing a wrench in there. It also helps that I switched to a couple of Socket Head Cap Screws to use for these clamps.

I need to make up a couple of sets from some steel to use with my other vises. Incidentally, the Glacern vise has been superb!

First Chips from Rockwell Delta Bandsaw

Finally got a chance to hook up a VFD to my new/old bandsaw so I could see it run. It's set up for 3 phase and the VFD I had laying around for eventual use with my mill was the easy way to fire it up. I made a few chips. Blade needs adjusting, and it also has the wrong blade in it for metal. This 20" bandsaw (Rockwell/Delta 28-365) seems to have been babied in a woodworking shop for years. I have a hunch when I get it all tuned up it will cut through metal like butter, especially aluminum. It's already very strong.

First chips...

I'll need to get busy making some accessories for it too. No form of fence or miter guide came with it, for example.

2/14/10

Quick, What Hole Size for a Reamer?

Reamers are a fast way to finish a hole and very convenient relative to other precision approaches like boring. Reamers are certainly not the be all and end all of hole boring, but if you've never used one, give it a try. One thing to keep in mind when using reamers is hole size guidelines. If you make the hole to large (i.e. to close to the reamer's finished bore size without going over), there isn't enough meat for the reamer to do its job. Too small and you're making the precision reamer work way too hard.

There was recently some back and forth on CNCZone about reamer hole sizes, and I felt like it would be a good time to throw out that G-Wizard now tells you the recommended guidelines for how far undersized to make your holes before reaming:

G-Wizard says to make the hole 0.010 - 0.025" undersized for a 1/2" reamer...

Fastest Way to Center a 4-Jaw, By David Lemereis

Got a nice note from David Lemereis this morning directing me to some YouTube videos of some of his latest projects. He's built a powered drawbar he says was inspired by mine that has some great improvements as well as some other mods for his BF-series mill (I can't tell the different sizes apart, but it is a really nice looking mill). By all means, go check out his videos as they show some very nice work. But, what really caught my eye here was his video of how to center a 4-jaw very quickly:

This is the method I've been using since I first learned about it from Jack Burns on the HSM boards. I really do think it is the fastest way, and it has worked like a charm for me ever since I discovered it. Now David makes it look even easier with his video. Newcomers need not be afraid of the 4-jaw once you've watched the video!

2/13/10

Brian Rupnow Shows How to Turn Tapers With a Boring Head in Your Tailstock

A picture from this HSM thread is worth a thousand words:

It's a "dead" center, so you'll have to work accordingly!

Feeds and Speeds for Micro-Machining with G-Wizard

I have a G-Wizard user who makes wrist watches for a hobby. Needless to say, he works with some very small tools! He wanted me to check into more specifics so G-Wizard could make better recommendations for micro-machining. I liked this article written by the head of the micro-machining group for Makino:

How Do You Get The Cutting Parameters Right For Small End Mills?

He raises a number of excellent points.

The number one enemy of tools for these tiny operations is runout. For most ordinary machining, 0.0005" of runout would be fine, but for micro-machining, you will break a lot of tools with that much runout. As he says, when people are breaking tools, they slow down their feedrates. That works, but it doesn't address the real problem of the runout. Most authorities will suggest no more than 10% of your tool's diameter is acceptible for runout. That 0.0005" runout therefore translates to a requirement to run tools larger than 0.005" in diameter. He goes on to say that 0.0005" is about the limit in runout accuracy for ER collets, and that assumes the errors in the collet system do not stack up unhappily with any spindle runout. Lastly, it is also possible to have runout on these smalls tools themselves. In other words, the flutes are not concentric with the shank.

In terms of suggesting what type of tooling, he recommends carbide coated with TiAlN or TiCN. Interestingly, he also recommends 2 flute cutters for this small work to provide more gullet area to clear the chips.

Lastly, he provides recommendations for the specific cutting conditions.

Maximum Depths of cut:

30-40Hrc Materials—50% radial / 10% axial

41-50Hrc Materials—45% radial / 6% axial

51-60Hrc Materials—40% radial / 5% axial

Chiploads are figured generically as follows:

Above 55Hrc Roughing: 3% of cutter diameter Semi: 2% Finishing: 1%

Below 55Hrc Rough: 5% Semi: 3% Finish: 1-2%

With the latest release of G-Wizard, I have incorporated these chipload guidelines in when working with tools smaller than 1/16" in diameter.

Looking at my friend's watchmaking example, he was still not confident of the feedrates predicted. I suspect he has some runout that requires a further slowdown to ameliorate. This is very easy to do with G-Wizard using the machine profile's feature.

Let's create a special profile for "Watchwork" that runs at 1/10 the chipload:

Set the Chipload Adjustment to 10% for Watchwork...

Now the profile will take whatever chipload G-Wizard would normally compute and apply the 10% factor to it, resulting in 1/10 the chipload and therefore 1/10 the feedrate. Go back to the Feeds and Speeds calculator and select the "Watchwork" machine profile at the top left. Now the numbers are right in line with what our watchmaker reports he has discovered empirically when drilling brass:

2/9/10

Homann ModIO Pendant Kit for the IH CNC Mill

I started building my Homann ModIO Pendant Kit for my IH Mill this evening. Very nice kit, I think I will like it a lot! You can follow my build progress on my pendant page. Here are a couple of pix of progress so far:

I'm planning a leisurely pace with this kit, so I'm not in a rush to stuff it together. I want it to come out nice and work well.

2/9/10

G-Wizard Gets a Tool Crib

G-Wizard now has a Tool Crib. What that means is you can create a table of exactly the tools you own, or that are in your machine's toolchanger, and you can select those tools for the feeds and speeds calculator instead of having to fill out all the parameters every time. For example, here is the Feeds and Speeds calculator with the "Crib" box checked and a list of the current tooling defined in the Tool Crib:

Picking tools from the Tool Crib...

You define your Tool Crib on this page:

You can enter any description you'd like to help you remember what the tool is. All the parameters are stored in the table so you don't have to tell the Feeds and Speeds calculator the diameter, type of tool, number of flutes, and all that other jazz every time you want to do a feeds and speeds calculation.

Should save a lot of steps and make the calculator even nicer to use.

The Beta Test is still under way and still free. Details on how to join may be found here:

http://www.cnccookbook.com/CCGWizard.html

2/8/10

Flycutters Can Give Better Finish than Face Mills, But Why?

I've heard fly cutters can give the best possible finishes (albeit at slower speeds), but why? I found the answer in some Ingersoll literature where they suggest removing all but one cutter from a face mill if finish is of paramount performance because this converts the facemill to a flycutter which has no runout. Interesting!

How Much Feed is Too Little Feed?

Tool manufacturers will tell you that too little feed is just as bad for tool life as too much feed (or too much spindle rpm). But how little is too little? That part is seemingly hard to find out. I went fishing around with Google to try to find what speeds and feeds result in a "burnishing" effect with tools. Here is what I found:

- Article on hard milling: 0.0008" per tooth is definitely burnishing because it is "less than the edge hone typically applied to the insert."

- De-Classified 1961 Batelle Institute report on aerospacing machining of super-alloys says an IPR greater than 0.0035 will result in burnishing and likely work hardening of these alloys. Interesting how well this number agrees with the one above for a 4 flute cutter. 8 tenths times for would be 32 tenths.

- Kennemetal says the "highest possible feed per tooth will usually provide longer tool life. However, excessive feeds may overload the tool and cause the cutting edges to chip or break." So feed as fast as you can until you start to chip or break edges. They reiterate this under work hardening. One wonders whether rubbing leading to work hardening isn't the principal risk of cutting with too-low chiploads with respect to tool life.

- Another reference, like the first, to keeping chiploads higher than tool edge radius. In this case, IPT should be greater than 0.001". This is once again an article on hard machining where work hardening may be a factor.

- Minimum chip thickness is 5-20% of the cutting edge radius. Below that level, chips will not form and the cutter will "plow" across the workpiece causing plastic deformation and considerable heat.

- Ingersoll says that as a general rule carbide chiploads should not be less than 0.004" or you run the risk of rubbing which reduces tool life and causes chatter.

Use a calculator with all the right compensation like chip thinning to make sure you're not reducing tool life!

Neat Bandsaw Tricks

Cleaned out some of my notes and consolidated them onto my mini-bandsaw page. There's some good tricks in there to get more from your mini-bandsaw. Every time I think mine is done because I got some better saw, I wind up making a little mod to it and bringing it back into service. The last rumor of its demise was due to my DeWalt Multicutter carbide chop saw. I will admit, it took me a couple years to bring it back, but I finally did. I mounted it on a nice cart so it was more stable and at a better work height, and I added a little table to it. I used it mostly in vertical mode at that stage. Handy to pop it on to cut little pieces quickly. A lot less drama than the chop saw too.

The latest rumor of its demise is due to the hulking big 20" (thought it was an 18", but got to doing some research and checking the nameplates and it is a model 28-365 Delta/rockwell 20" Bandsaw, woohoo!) bandsaw I got. It is not yet operational. Spent some time tinkering this weekend to get it going. Motor just hums, so I'll have to suss that out. My brother will likely be invaluable as he helped me get my big compressor with a similar issue going.

We'll see whether I can come up with a good use for the little guy, but meanwhile, the updated page should help others with a saw like this.

At the moment, the other tool I almost never use and need to upgrade to make it more useful or get rid of is my drill press. Of course I have a drill press page full of potential upgades too!

2/6/10

Try a Corncob Rougher to Stop Chatter

Corncob roughers are great. They're those endmills that have the serrated edges. They cut through most materials much more freely than conventional endmills, but my friend Pete says they are da bomb when dealing with chatter, and particularly if you're fighting a small machine's rigidity limitations.

I'll have to try one out the next time I'm having a problem.

Making Cool Fasteners

I like cool and offbeat fasteners. Call it a fetish, but I got hooked on weird fasteners working on cars. They can be very decorative and aesthetically pleasing. Take this shopmade example for a folding knife that I saw recently on the awesome HSM Shopmade Tooling thread:

The "bolt" looks great on the knife, doesn't it? The tool would be a real nuisance to make manually, but very straightforward with CNC. I'll have to try something like this at some point. It needs to wait for my CNC lathe to be finished though.

2/4/10

Armadillo Way Covers

Or at least that's what someone called this style and I liked it:

Cutting Steel on a Sieg X2

I recently had a G-Wizard user contact me about cutting steel on his Sieg X2. He was not happy with the results he was getting and couldn't go near as fast as G-Wizard was telling him to. I wanted to pen some thoughts for this fellow and others who are in the same boat. Sorry for the long post, but it touches on some of the seminal issues that have to be understood right from the start of your machining learning curve.

First, the difference between working steel and aluminum is almost like night and day. Hoss remarked recently on CNCZone that he bought an RF-45 mill so he could work steel and that he had only really been happy working Aluminum on his Sieg X2. I can tell you that even with the RF-45, steel is more challenging to get good results with.

This fellow was trying to square some ¼" angle iron to make some vise clamps. As he put it:

The angle iron was very wavy and needed some squaring. But when cutting, the mill sounded like I was shaking it to pieces if I tried side milling at .030 DOC and around 800 RPM using a 1/2" HSS endmill. The faster I fed the more it shook.

What's up with that?

I remember manual milling steel on my RF-45, a much stouter mill, before I CNC'd it and got G-Wizard. At the time, it would've been rare for me to take more than about 40 thousandths depth of cut turning the handwheels in steel. It just seemed too gnarly and I was in no great hurry. Trying to cut 30 thou on a much lighter mill might be the issue right there. I've since gotten a lot bolder with the CNC, but let's look this situation over carefully.

First up, there are actually three issues to be concerned with. One is what the recommended feeds and speeds might be and how to go about administering those manually. Two is what the machine can actually handle. Three is the possibility of chatter. Let's consider each one in turn.

What are the Recommended Feeds and Speeds?

For a side milling cut of ¼" angle iron at 0.030 depth of cut with a ½" 4 flute HSS Endmill, G-Wizard gives back 1015 rpm @ 37.278 IPM. For a gearbox machine, you'll have to take the nearest spindle rpm and override G-Wizard with that value. In this case, he says 800 rpm, which drops the feed to 29.394 IPM. Keep in mind that recommendations are just the starting point. It's up to the skills of the machinist to take it forward from there.

Next problem is how to manually feed at such a rate? I always converted to handscrew turns/second or seconds/handscrew turn (if it was a slow feed) and then just counted them off-it'll be close enough. In this case, the handscrews are likely 100 thousandths per turn, 10 turns an inch, so we need 290 turns a minute. That's about 5 turns a second, pretty quick!. Faster than a manual machinist will likely be comfortable feeding.

But in this case, the mill is shaking like crazy with a feed that is probably much slower. Let's say 1/5 of that (1 turn a second). So he was going maybe 5 or 6 IPM at best and no way would the mill go faster without shaking apart. Time to consider:

What Can the Mill Actually Handle?

This brings us to issue number two: can this mill actually handle the recommended feeds and speeds? Note that this is a fairly complex question. A less than completely rigid setup, a small mill, and a cheap cutter can combine to make it really hard to hit recommended feeds and speeds.

Let's analyze the symptoms of two problem areas:

- Cutter is getting burned and dulled very rapidly. Lots of heat in the cut. The cutter may be discolored. This is a sign of too much SFM. Need to cut back spindle rpms. Many hobby mills have such low maximum spindle rpm we don't see this one too much. Look at the chip color on steel. Blue will kill HSS cutters. Straw is about right, and silver will give you longest life. Carbide is capable of amazingly faster spindle rpms.

- You are breaking endmills. This can be the sign of too much chipload. Need to feed more slowly. OTOH, this can also be a sign of inadequate chip clearance too. If chips are packing into the cut the endmill's job is tremendously more difficult. Make sure they're being rapidly cleared.

This individual reports the cutter is raising a burr and acting dull as well as there being a ton of vibration. The cutter may have started out pretty dull or low quality, so that is something to keep in mind. The vibration may be chatter, which is a harmonic vibration affected by speeds and feeds, but not a feeds and speeds problem per se. I lean to the theory that this is chatter, BTW. Chatter is a bad combination of rigidity and resonances in the machine.

Let's put the chatter theory aside for later and look at whether the mill can handle the cut.

In this case, G-Wizard assumes a chipload of 0.0022. We may want to take that down some if dealing with cutters that are well used and/or not name brand. A low end value might be as low as say 6 or 7 tenths of chipload. FWIW, that's actually 6.5 IPM on the handle. Too little chipload, BTW, can lead to as much trouble as too much, so don't arbitrarily assume you want to always crank it down. If you want to always reduce it, you can always enter a chipload adjustment in G-Wizard's machine profile. For a Sieg X2, I would be tempted to enter at least some reduction in chipload from the recommended values.

In terms of how difficult that cut is, I like to use HP as a measure. G-Wizard tells us this cut is 0.15 HP if you follow recommended feeds and speeds. So 0.15HP is being fed into the workpiece, your setup, and the mill, and it must resist that force successfully to do the job. FWIW, the same feedrate in 6061 aluminum requires about 1/3 as much HP. That's a decent rule of thumb-the same cuts in steel are 3x more demanding than aluminum. Put another way, whatever your mill could do in aluminum, you can do 1/3 that much in steel, and we're talking the mildest steel, not tool steel or stainless!

Let's turn it around. Is the desired cut, 1/4" deep, 0.030" wide, the sort of cut one would make in aluminum on this machine? I suspect it is. But if steel is 3x more difficult, would the machine be happy cutting say 0.090" wide? Probably a lot less happy.

On my IH mill, I set a 1 HP limit on G-Wizard that I've learned from experience is a good number. That's half the rated 2 HP of the motor because I know if I start to get north of 1 HP I am working my mill pretty hard. I can do it, but I need to take extra care with every aspect of the setup. That's not to say the mill is incapable of doing more, just that I, as the machinist, will have to work harder to ensure success above that level.

I don't know the limits of the Sieg, but I wouldn't be surprised if 0.15HP are very close to equivalent to 1HP on my mill. So, we have both a chatter-prone situation as I will discuss shortly, and we are at the edge of prudence.

What about Chatter?

Okay, let's now go back and focus on chatter. Since it is a resonant effect, you can change feeds and speeds to get away from it or you can increase the rigidity of your machine, tooling, or setup to help resist the vibration.

I said before I suspect chatter, but why? First, one of the big symptoms is lots of vibration and often a sharp sound (hence the name "chatter"). Second, The X2's have a notoriously weak column, which will be prone to chatter. Think attaching your spindle to a tuning fork. Making one of the column mods to stiffen it would really help a lot. Also, the writer mentions that the part was in the vise and "sticking out like a diving board." That's a sure recipe for chatter and low rigidity. Thin plates love to vibrate like tuning forks, which makes me lean even harder to the theory this problem is chatter.

What to do about the chatter? If you want to vary feed or speed, try faster first according to a lot of the sources I have read (Kennametal, for example). In fact, you can systematically map the resonance character of your machine with each cutter, but that's a topic for another post.

Changing feeds and speeds is quick and easy, but it won't always work. The next step would be to find ways to hold the angle iron much more securely and with as little sticking out as possible. I recently built a very stout set of vise jaws (my Vise Jaws of "Doom") to get away from some chatter problems in surface finish. This was while trying to engrave ¼" 6061 aluminimum in a 6" vise. I had maybe 2" sticking out on either side of the vise and no chatter was audible, but you sure could see it in the cut with even the lightest face milling passes.

Here are some ideas for how to systematically deal with chatter:

1) Vary speed and/or feed to get outside the resonance zone. Try increasing feed, then decreasing, then try increasing followed by decreasing speed.

2) Change axial or radial depth of cut. There is a large body of literature on chatter that suggests the resonant frequency of chatter varies with axial and radial depth of cut for a given machine and tool, but regardless of material or workpiece. Changing the axial or radial depth of cut may move you out of the zone of resonance.

3) Make the setup more rigid. Leave as little of the workpiece as possible unsupported. Add more clamps. Etc.

4) Make the tooling more rigid. Use a larger diameter endmill. Reduce the length and "stick out" of the cutter.

5) Make the mill more rigid: Lock every axis but the one that has to move. Tighten the gibs as tight as you can while still being able to move the handwheels smoothly. Make sure the ways are well lubed so you can run your gibs even tighter. I even went to the trouble of doing an epoxy/granite fill on my machine's base and part of the column. I estimate an increase of 15-20% in the rigidity as a result. I have already mentioned making the column to base connection stouter and there are many other's postings on places like CNCZone to help with ideas there.

6) Prep the workpiece. The writer mentions the surface of the angle iron was "wavy". Being a resonant phenomenon, chatter can feed off those waves. In fact, a flat surface that has gotten wavy because of a chattery pass is even more chatter prone afterward. Try to break up the waves if you can. I'd be tempted to hit it with my big disc sander if all else failed.

Last thought: this particular poster asks about G-Wizard's climb milling recommendations. As the G-Wizard docs (and many other sources) will say, if your machine has backlash, you'll need to be very very careful climb milling, and unless you have a lot of experience, you should just avoid it altogether. On a real light machine like a Sieg X2, I just wouldn't try it unless I had ballscrews to reduce backlash to a minimum. On my IH, before I had ballscrews, I used to get away with it by taking very light cuts with relatively small tools. A ¼" endmill taking 15 or 20 thousands was the maximum I would attempt. In addition, I used to really tighten up the gibs and lock and unused axes. The handwheels were very hard to turn, and the machine is relatively heavy, so it was tough for the cutter to drag the table into the backlash.

2/1/10

Finished Making the Vise Jaws of "Doom"

More on these handy tooling items on my vise tooling page. Here's the pic:

24" long, 4130 steel, and spanning two 6" Kurt (well one is a Kurt and one is a Glacern) vises to make one Super-Vise. There's the beef!

(In this shot the jaws are clamped on a couple 1-2-3 blocks just so I could indicate them and make sure they were square)

BTW, the handy way to tram two of these vises is to tram one and then clamp my big Brown & Sharpe parallel in it. Clamp the other one on the parallel while lose and then clamp it down. Done!

(I can always indicate them both in for really critical jobs but this gets it pretty darned close!)

Making Some New Way Covers for My IH CNC Mill

I finished this job a few weekends ago, but I'm just now getting around to documenting it. Here is the finished result:

I used some simple aluminum clamps that work using a bunch of neodymium magnets:

Hoss Uses Slot Pins for Big Jobs

What to do when the job is bigger than your mill's capacity? Hoss uses slot pins as an alignment guide:

Once the pins are trammed in properly, and you can design them so the tramming is automatic based on their fit to your table slots, you can be assured that any work you clamp up against them is properly aligned with the table.

Programming a Higbee Thread

The Higbee is a modification to your existing thread that makes it thread much smoother and without possibility of cross threading. A proper Higbee looks like this:

Not how the rough final thread has been smoothed out...

The goal is to remove the final part of the thread which is usually a small fin on the turned 45 degree angle portion of the part blank up to where it is a full profile 60 degree thread form. To do this you use a grooving tool (or a parting tool) after you are done with the threading cycle.

To start, you must calibrate your threading and grooving tools to the face of the part, which will be your zero. The center or tip of the threading tip has to be calibrated so it is equal to the leading edge of the groove tool and the groove insert must be as wide or wider than the base of the thread form. For example, a 1/8" wide insert will work up to 8 TPI because 0.125 is the pitch of an 8 TPI.

OK, let's go through an example. You're doing 10 TPI threads for a 1" thread length. Your threading cycle will give you a full 1 inch of thread, and the length of the first thread is Z minus 0.100" (since it is a 10 TPI). That first thread is the length to deburr. Program your grooving tool using the same threading cycle to a depth of Z minus 0.100". Make a couple of deburring passes and play wit hthe starting X value. Your spindle rpm and the machines rapid traverse rate with determing the amount of angle of ramp on the deburred thread. The rapid rate will stay constant, so for a squarer ramp run slower rpms. For a tapered ramp, run more rpms.

If your controller has G32, tapered threads, then you're really in fat city. Just cut a 45 degree tapered cut for that first thread and you are done.

Also worth noting: the Higbee was invented for fire couplers. A real Higbee would eliminate the first thread entirely and "Higbee" the second thread.

If you have a CNC lathe, it almost makes sense to Higbee every thread. They'll certainly be a lot cleaner and nicer if you can afford the time and the toolchange.

Cool Plasma Table Work from Algeria

DZStar posted a video of his shopmade plasma table and some of the designs he has made with it on CNCZone:

This machine uses a simple spring-loaded Z-axis (no electronic torch height controller) to maintain the torch distance from the workpiece. The torch is an inexpensive ($700) Italian unit. All in all, it shows just how easy and simple it is to create a plasma table that can do some pretty amazing work. Here are some of his designs:

Doors with intricate mosaic patterns...

My personal favorite!

Earlier Entries in the Blog...