Proper mill cutter and technique

[Megar arc 5040dd]

No, not all two-flute are centre cutting. Why do you especially care? Do you plunge for the corners of the cutout and similar?

I was wondering because of the 2 counter bored slots. In this case I did predrill the start and stop points. But It made me wonder if that had just been a key way and not a though slot then I would have needed to plunge with a 2 flute end mill. And then that thought led to the question. My mind is a maze of rabbit holes.

Did you snug up your locks? That can make a difference.

They were. when travelling in x the y lock was tight and the x lock just a little snug and the opposite when travelling in y.

 

[Susquatch]

That said I am still a sucker for good old fashion books.

Me too. Although there are a few Youtube Artists that really do know what they are filming, most are just people earning an income getting you to watch them.

On the other hand nobody who doesn't know what they are talking about writes books about it. A book is a virtual guarantee of material worth reading.

A book can also be read anyplace anytime and won't annoy anyone around you.

 

[ChazzC]

For smaller mills, does anyone have a rule of thumb for the maximum amount of metal to remove in a single pass?


Craig

I have an LMS 3990 Mini-Mill, and have successfully used 3/4", 1" and 1-1/14" end mills, albeit with moderate DOC. I used the 1-1/4" end mill to create a fluted knob out of 2" 6061, "nibbling" away at the perimeter with 0.1", 0.065" & 0.019" deep x 0.56" long plunge cuts:

First pass (0.1" DOC)

2nd pass completed (0.065" DOC):

Before attempting these cuts, I ran the project past LMS since the Mini-Mill is only rated for up to Ø0.6" end mill capacity.

 

[mbond]

Me too. Although there are a few Youtube Artists that really do know what they are filming, most are just people earning an income getting you to watch them.

On the other hand nobody who doesn't know what they are talking about writes books about it. A book is a virtual guarantee of material worth reading.

A book can also be read anyplace anytime and won't annoy anyone around you.

Many centuries ago, the transition from written to printed books happened. This seems like a similar kind in both the increase in fidelity from what the author meant, and a decrease in the barrier to access information.

but anything that you can get easily is necessarily less valued than something hard come by. In those days written books were extremely valuable. today most books are cheap. youtube videos are even cheaper

and colour me old and grumpy too

 

[Susquatch]

I used the 1-1/4" end mill to create a fluted knob out of 2" 6061, "nibbling" away at the perimeter with 0.1", 0.065" & 0.019" deep x 0.56" long plunge cuts:

Nice knob Charlie.

I want to make some very similar knobs for an adjustable Equatorial Wedge for my telescope (project isn't on my list cuz it's not shop related). I don't suppose you have a drawing I could scale?

I see what appears to be a non-scalloped base on the knob. Is that going to be removed at some point, or was it left for a particular reason?

 

[Downwindtracker2]

I have six textbooks on general machine tools sitting beside me, but they are more of what than how-to. I tied looking up set up of rotary tables and had to resort to google and YouTube. And unlike the current generation, I have excellent reading skills.

 

[Downwindtracker2]

I have made knobs out hardwood with a router . For us hobbyists and our mills, they have more in common with a router than a machine tool , like say a metal shaper.

 

[Susquatch]

I have six textbooks on general machine tools sitting beside me, but they are more of what than how-to. I tied looking up set up of rotary tables and had to resort to google and YouTube. And unlike the current generation, I have excellent reading skills.

I understand. That's not likely to be in a book. But I'd still be very leery of what I see on YouTube.

Personally, I like to ask questions like that right here on our forum. There is something about knowing the source, their credibility, and the ability to ask additional questions that gives me considerable confidence in their advice.

I have not asked a question yet that has not been answered to my complete satisfaction.

I have made knobs out hardwood with a router . For us hobbyists and our mills, they have more in common with a router than a machine tool , like say a metal shaper.

Yes, wood would be nice too. Maybe part wood and part metal.

FWIW, I have done a fair bit of woodwork in my day too. For me, it was a somewhat cruder activity. Today, I'm not above working with wood on my metal machines. Not so much the other way around though.

In fact, I am looking at some Walnut slabs right now that I might use to make some tool holders and collet racks.

What is it that you want to know about using a rotary table?

 

[JustaDB]

I used the 1-1/4" end mill to create a fluted knob out of 2" 6061, "nibbling" away at the perimeter with 0.1", 0.065" & 0.019" deep x 0.56" long plunge cuts:

Nice! DRO?

 

[Downwindtracker2]

I hear you about YouTube "experts" . It was around centering, which is now done to my satisfaction., three zeros and a one. (which I think is kinda odd. ) I suspect the machining on the rotary table for that one, as I'm just sweeping the center hole. To do it properly I should be rotating the table and the shaft, keeping the dial test indicator on one point. That would cancel machining errors.

 

[Dabbler]

Your original question is great!! It covers workholding, fixturing, order of operations AND coolant, as well as cutter selection... Ohboy! All of the above suggetions are fantastic!

To cover most of the ways to make this part would take a bunch of pages. I'll limit this to what I would do, scaled down for an RF45 machine...

I'd square the block, then mill the 2 slots. These are slot limited, but I'd use wd40 and high RPM (over 1600). I peck mill slots before finishing them with an undersized cutter. Use only a 2 flute cutter for this operation.

I'd conventionally drill the 2 corners leaving .030 or so for finishing I'd use a drill bit 1/8" larger in diameter than my bandsaw. Off to the bandsaw - leaving at least .030 or .040 to clean up. the size allows you to turn the piece in the bandsaw.

Then I'd take a piece of rigid material, steel aluminum or particle board, and bolt the piece to the board. Having a sacrificial pallet is useful for situations like this. Blondihacks also has a good video on using a pallet on the mill.

On a machine your size, I'd use a 1/2 inch cutter at 800-1000 RPM, using .150 DOC conventional milling with the spine toward the fixed jaw. I'd take most of the excess to the line, leaving .005 or so for clean up. I'd then mill that off full depth. all of this using WD40 and a 2 flute or 3 flute Aluminum cutting end mill. Id ensure the X and Y locks are used appropriately. Climb milling will minimize grab, but the cutter has a tendency to grip in the corners.

I hope this helps...

 

[Megar arc 5040dd]

Here is the final piece. I took advice given earlier and applied it to finishing the part. I was worried that it was doing to take for ever to line up the part but it end up taking maybe 30 seconds to a minute before it was as perfect as my eye can see. With everything it tool to make this part the thing that bugs me most is it being asymmetrical. But I guess that's what happens when you are matching up to a chinese casting. I am glad I did at least have the sense to do the counter bore and screw slots as the first step after squaring the material.

Cuts for the angle were very light since it was only held by one clamp. One tight clamp but still only one.

I checked it out with a dial indicator and it was bang on. The same can not be said for the graduated dial on the quill fine feed. I decided to test that against the dial indicator at the same time and it was out over .001" in the first .010". My dro install is not complete. Tomorrow I start the next project of making hinges, that's being covered in a different thread.

 

[Megar arc 5040dd]

One last question. Ok that's a lie I am sure I will have a million more after this one. Is this a center cutting endmill? I noticed that 2 of the flutes meet in the middle and I haven't seen this before on other 4 flute end mills I own.

 

[Susquatch]

Is this a center cutting endmill? I

Short answer - Yes.

You can plunge cut with that endmill almost like drilling.

 

[Susquatch]

Cuts for the angle were very light since it was only held by one clamp. One tight clamp but still only one.

I "THINK" that you might have a problem with your clamping arrangements. You probably won't find this info in a book or a video. You learn about this by personal experience (to be avoided) or by hearing about the mistakes of others.

1. Never allow the bolt to extend below the T-Nut.

2. Always try to achieve compression (columnar) loading of the T-slot clamping system. Tensile loading should be avoided.

3. Avoid over-torqueing a T-Nut and bolt.

Here is a photo of the Mill table damage you are trying to avoid.



Mounting your parts firmly on your milling table is your primary objective. BUT, all of your clamping setups should also be designed to minimize the potential to break the T-Slots in your table. Here are a few thread about T-slots that are worth reading:

Read this entire thread 'T-Slot Size vs Clamp Size?' https://canadianhobbymetalworkers.com/threads/t-slot-size-vs-clamp-size.11754/post-161737

Another nice thorough discussion of the issue. Thread 'Mill hold downs' https://canadianhobbymetalworkers.com/threads/mill-hold-downs.10473/

 

[Megar arc 5040dd]

I "THINK" that you might have a problem with your clamping arrangements. You probably won't find this info in a book or a video. You learn about this by personal experience (to be avoided) or by hearing about the mistakes of others.

1. Never allow the bolt to extend below the T-Nut.

2. Always try to achieve compression (columnar) loading of the T-slot clamping system. Tensile loading should be avoided.

3. Avoid over-torqueing a T-Nut and bolt.

Here is a photo of the Mill table damage you are trying to avoid.

View attachment 58450

Mounting your parts firmly on your milling table is your primary objective. BUT, all of your clamping setups should also be designed to minimize the potential to break the T-Slots in your table. Here are a few thread about T-slots that are worth reading:

Read this entire thread 'T-Slot Size vs Clamp Size?' https://canadianhobbymetalworkers.com/threads/t-slot-size-vs-clamp-size.11754/post-161737

Another nice thorough discussion of the issue. Thread 'Mill hold downs' https://canadianhobbymetalworkers.com/threads/mill-hold-downs.10473/

I'm not quite sure I understand the part you are concerned with? No threads extend past the T-nuts all my T-nuts have rolled over bottom thread in order to prevent screw jacking of the T slot. Is it that there is nothing directly above the T-nut pressing down as the T-nut pulls up? In the second picture this is the case since I needed to use a long strap in order to have the work piece sit along the middle T slot. This was so I could use the middle T slot as a rough guide when lining up the part initially. Even though there is a bit of distance between where the T-nut is applying an upward force on the T slot and where the work piece and packing are applying a downward force. The soft aluminum surface of the part would get marked from the steel strap long before the thick T slot was to ever be damaged. The strap was tight enough for the part to not move by hand and feel secure. The reason for the light cuts was that with only using one clamp, and having only one small point of contact on the work piece, the cutting force on a heavy cut could cause the piece to rotate slightly under the clamp ruining the alignment. The is especially true when the cuts are at the ends furthest form the clamping point.

If you are talking about the clamps on the vise then I understand your concern however that is why there are 4 clamps to spread out the clamping. If I had used 2 then I would have had to really reef them down tight in order to feel like the vise wouldn't move. They are also temporary until I have a chance to make dedicated clamps that take up a lot less space and are more appropriately positioned. I have been waiting on this until I have decided the best location for the vise.

If I am completely missing something please let me know. I am always learning so all advise and feedback is always welcome.

 

[Downwindtracker2]

It might not be for you Megar, rather for others reading this good discussion on aluminum millings, or milling in general . A lot of machining is set ups.

 

[Dabbler]

@Megar arc 5040dd It is 'best practice' to position the threaded rod as close to the point of contact (upward pressure on the clamp) as possible. This minimizes the leverage prying your cast iron table slot *up*. With a wide gap, it is possible to break the cast iron. It also provides some support for the table if the piece to be clamped is solid to the table near the threaded rod.

 

[ChazzC]

Nice! DRO?

Thanks! Yes, TouchDRO: one of my first projects using it.

 

[Megar arc 5040dd]

@Megar arc 5040dd It is 'best practice' to position the threaded rod as close to the point of contact (upward pressure on the clamp) as possible. This minimizes the leverage prying your cast iron table slot *up*. With a wide gap, it is possible to break the cast iron. It also provides some support for the table if the piece to be clamped is solid to the table near the threaded rod.

Thanks for the info this is fascinating to me and brings up many questions that I sure have been previously talked about. Am I correct in assuming that the best ideal placement is to have clamp perpendicular to the T slot with the edge of the work piece right up to the edge of the T slot and the step block of the clamp right up to the other edge of the T slot? Ideally with the stud sticking up in the canter of the clamp so the force is equal on both sides of the T slot? Are T slots on tables generally considered to be weak or is this mostly a problem only on smaller mills?