First time using mini-mill

[jhanko]

Hey guys, long time-no see. I recently made some titanium Nitecore D10's. They turned out great, but I'd like to make a couple of them really special. I ordered some 1.55mm x 5mm trit from Bart that I want to put in these. The area that I want to put them in has ~.080" wall, so I'm fine there. I got a mini-mill that mounts to my lathe. I wish I would have got a seperate machine instead. It seem to always be in the way when I'm working on the lathe. Oh well, too late now. I also ordered some .0625", 4 flute carbide end mills. I never used a mill before and was wondering the best way to cut these slots. Plunge to desired depth, then cut to length or make several small cuts? How can I get all the slots the same length? Any way to divide the slots with equal spacing without buying a rotary table or something like that? How do I chamfer the edges of the slots when I'm done? Sorry for so many questions, but I nervous about destroying any of these. I photoshop'd a picture of what I want to do. Thanks!

 

[G1K]

To get the slots evenly spaced (3, 4, or 6 slots) you can get a collet block set. Usually they contain a square one and a hex one. If the part you have will fit inside a 5c collet your golden, 5c collets are cheap and so are the collet blocks.

Here's an example (no affiliation)
http://www.penntoolco.com/catalog/products/products.cfm?categoryID=836

I've seen these much cheaper on ebay, but not sure of the quality.

FWIW, you won't be able to get 90 degree inside corners like the rendition above, the slots will have the radius of the cutter in each corner, or 1/16".

With a 1/16 endmill, you want to take shallow cuts and you also want the cutter RPM fairly high. Make sure the feed direction for the rectangle is opposite the rotation of the cutter, you don't want to climb cut, it may deflect the small cutter and break it. Keep the cutter and slot free of chips and keep it cool.

If it's a center cutting end mill you can plunge with it, otherwise drill a small pilot hole somewhere in the slot location as a starting point.

As for controlling lenght, use the handle scales or a DRO if so equipped. Maybe a picture or two of you lathe/mill?

R

 

[jhanko]

To get the slots evenly spaced (3, 4, or 6 slots) you can get a collet block set.

Those are neat. Never seen those before. Sounds like a cheap solution.

FWIW, you won't be able to get 90 degree inside corners like the rendition above, the slots will have the radius of the cutter in each corner, or 1/16".

I was aware of that.

With a 1/16 endmill, you want to take shallow cuts and you also want the cutter RPM fairly high. Make sure the feed direction for the rectangle is opposite the rotation of the cutter, you don't want to climb cut, it may deflect the small cutter and break it.

Well, I think I screwed up then. I ordered end mills that are .002" larger than the trit OD. I though I could cut both sides of the slot at the same time.

If it's a center cutting end mill you can plunge with it, otherwise drill a small pilot hole somewhere in the slot location as a starting point.

That I can handle...

As for controlling lenght, use the handle scales or a DRO if so equipped.

I don't have DRO's and my handles have enough backlash to cause considerable inconsistancies

Maybe a picture or two of you lathe/mill?

I'll get one up in a few minutes.

Thanks for the info. I love learning!

 

[G1K]

Well, I think I screwed up then. I ordered end mills that are .002" larger than the trit OD. I though I could cut both sides of the slot at the same time.

You can do both at the same time, just be careful of the end mill loading up and the tool deflection. Go slow with the feeds and keep it cool and well lubricated.

R

 

[gadget_lover]

A few other thoughts...

1) You have the mill head mounted on the lathe? There's a good chance you can use the lathe spindle as an indexer by chucking the light in the lathe, then spin the chuck X number of teeth, mark the cut, go onto the next.


2) If the light is mounted on the table, then you can clamp stops to the ways to limit the travel. This will assure all are the same length. The exact length is not as important as the fact that they look the same length.

3) Add a stop the vise that will hold your light so that it goes back to the same relative position each time it is moved.

4) based on the size of the bit (1/16 inches = 1.5875 millimeters) and the width of the trit vials, (1.55mm), you will only have to move the light in one direction. This means you will have full engagement of the cutters so climb milling is not an issue.

5) Use a collet designed for small cutters. A drill chuck is likely to have a lot of runout (many thousandths of an inch) which may cause the carbide to shatter.

6) Check with one of the folks here about the right RPM for 1/16 inch carbide in titanium. You really need to get close to the right speed, probably above 2000 rpm.

7) If only two vials are visble at a time, then any deviation in the spacing is not apparent. I think you can do 5 vials and not notice if they are off.

8) make some test pieces to practice on. A groove 0.061 (1.55mm) deep in a .080 thick curved wall may give you a surprise, depending on the curve, how much deeper you want to go to protect the vial, etc. I'm no good with trigonometry, but I can envision the arc on the outside, the arc on the inside and the width of the cut. That image says that to get the vial below the surface of the curve you will be cutting deeper than .061, and that the thickness at the outsides of that 1/16 wide slot will be less than .080.

8) Use a good indicator, center finder, etc to make sure you are centered over the tube. You can use the 6 inch ruler trick for that.


Good luck

Daniel

 

[jhanko]

Wow, great info here! Keep it coming!

1) You have the mill head mounted on the lathe? There's a good chance you can use the lathe spindle as an indexer by chucking the light in the lathe.

When I bought the mill, I thought it mounted to the carriage and wanted to do that exact thing. When it arrived, I found it mounted to the bed.:shakehead

If the light is mounted on the table, then you can clamp stops to the ways to limit the travel.

That's a good idea. I should be able to come up with some simple stops.

Add a stop the vise that will hold your light so that it goes back to the same relative position each time it is moved.

Another good idea.

Based on the size of the bit (1/16 inches = 1.5875 millimeters) and the width of the trit vials, (1.55mm), you will only have to move the light in one direction. This means you will have full engagement of the cutters so climb milling is not an issue.

That's great news!

Use a collet designed for small cutters. A drill chuck is likely to have a lot of runout (many thousandths of an inch) which may cause the carbide to shatter.

Unfortunately, I'm stuck with the chuck. The good news is that I have checked the runout repeatedly at <.001".

Check with one of the folks here about the right RPM for 1/16 inch carbide in titanium. You really need to get close to the right speed, probably above 2000 rpm.

My mill goes from 0-2500 rpm, so I'm good there...

If only two vials are visble at a time, then any deviation in the spacing is not apparent. I think you can do 5 vials and not notice if they are off.

That's good news, but I think I'm too anal to accept the deviation. It would drive me crazy...

Make some test pieces to practice on. A groove 0.061 (1.55mm) deep in a .080 thick curved wall may give you a surprise, depending on the curve, how much deeper you want to go to protect the vial, etc. I'm no good with trigonometry, but I can envision the arc on the outside, the arc on the inside and the width of the cut. That image says that to get the vial below the surface of the curve you will be cutting deeper than .061, and that the thickness at the outsides of that 1/16 wide slot will be less than .080.

Good info...

Use a good indicator, center finder, etc to make sure you are centered over the tube. You can use the 6 inch ruler trick for that.

Dont mean to sound stupid, but what is the "6 inch ruler trick"?

Good luck.

Thanks, I'm going to need it!

Here's a picture of my rig...

 

[StrikerDown]

If the chuck it held in the spindle with a taper like a MT-2 you can get holders that have an MT-2 arbor. If that works it should be more secure and accurate for the small end mill.

Lower the spindle and see if there is a slot through the spindle. If there is your mill drill probably came with a drift (tapered wedge) that is used to remove the the tapered arbor from the spindle.

 

[jhanko]

If the chuck it held in the spindle with a taper like a MT-2 you can get holders that have an MT-2 arbor. If that works it should be more secure and accurate for the small end mill.

Lower the spindle and see if there is a slot through the spindle. If there is your mill drill probably came with a drift (tapered wedge) that is used to remove the the tapered arbor from the spindle.

The mill does have an MT-2 taper with a drawbar to hold it in place. So, I should look for a 1/8" (the end mill shank size) holder with an MT-2 drawbar arbor? It doesn't sound easy to find or cheap...

 

[gadget_lover]

The ruler trick is the same one you use to get the lathe tool's tip exactly on center.


Put a sharp tool in the mill chuck. Center it over the tube you are going to work on. Set a thin stiff piece of metal on the tube. I use a 6 inch metal ruler.

When you pinch the ruler between the sharp point and the circumference of the tube, it will tilt left or right unless the tip is right over the center.

The first picture shows the tip too far to the right. The second is fairly well centered.

 

[StrikerDown]

The mill does have an MT-2 taper with a drawbar to hold it in place. So, I should look for a 1/8" (the end mill shank size) holder with an MT-2 drawbar arbor? It doesn't sound easy to find or cheap...

I did a quick search on the Griz website But you should check around:
$16.
http://www.grizzly.com/catalog/2009/Main/616

Not the problem at hand, just an observation:
That is a large looking drill chuck in your tail stock! much bigger than the mill/drill Almost looks as big as the 3 jaw! Just wondering if it crowds you for space and if you can you use the chuck out of the Mill/drill to gain length between tail and head?

 

[jhanko]

The ruler trick is the same one you use to get the lathe tool's tip exactly on center.


Put a sharp tool in the mill chuck. Center it over the tube you are going to work on. Set a thin stiff piece of metal on the tube. I use a 6 inch metal ruler.

When you pinch the ruler between the sharp point and the circumference of the tube, it will tilt left or right unless the tip is right over the center.

The first picture shows the tip too far to the right. The second is fairly well centered.

Awsome trick! Thank you...

One more thing, Is this what I should be looking for? I'd have to find them with metric drawbar threads though...
http://cgi.ebay.com/7-PC-Morse-Tape...ItemQQimsxZ20090117?IMSfp=TL090117114008r9374

 

[gadget_lover]

Your mill looks a lot like the head from the micro-mill that I have.

You can get 1/8 inch MT2 collets all over the place. LMS has them, so does Enco, etc.

If you really have only .001 runout you will be OK, but beware of the endmill slipping. Check it between cuts to make sure its still the same height.

 

[StrikerDown]

Gadget,

This is how I know if my cutting tool is above, on, or below center on the lathe.
Funny I never thought to use this trick on drilling round work. Thanks!:thumbsup:

 

[gadget_lover]

Awsome trick! Thank you...

One more thing, Is this what I should be looking for? I'd have to find them with metric drawbar threads though...
http://cgi.ebay.com/7-PC-Morse-Tape...ItemQQimsxZ20090117?IMSfp=TL090117114008r9374

Yes, that is what you want. The collet goes most of the way into the spindle, so you lose almost no room between the table and the cutting tool... other than the length of the tool.

Check your drawbar to see what thread you actually have. I have some collets that use a 3/8-16 thread and some that are metric, so I just bought a foot of all-thread and cut it to length.

Daniel

 

[jhanko]

Your mill looks a lot like the head from the micro-mill that I have.

Yep, exact same mill. Mine just came with a cast L-bracket to mount it to the bed instead of a table. How do you like it? Haven't used mine yet...

 

[jhanko]

I have some collets that use a 3/8-16 thread and some that are metric, so I just bought a foot of all-thread and cut it to length.

Daniel

Great idea! Never thought of that trick either... Too much information. My head is about to explode!

 

[StrikerDown]

I did a quick search on the Griz website But you should check around:
$16.
http://www.grizzly.com/catalog/2009/Main/616

Not the problem at hand, just an observation:
That is a large looking drill chuck in your tail stock! much bigger than the mill/drill Almost looks as big as the 3 jaw! Just wondering if it crowds you for space and if you can you use the chuck out of the Mill/drill to gain length between tail and head?

OOps I just noticed the 1/8 shank size, do you already have the end mill?

Drill chucks really aren't designed for much side loading but that is a small end mill that would break before you applied much side load... Give it a try on a sample work piece and go for it if it works to your satisfaction. Make sure to check the run out on the tool shank.

PS: The collets look like a much better idea!

 

[gadget_lover]

Yep, exact same mill. Mine just came with a cast L-bracket to mount it to the bed instead of a table. How do you like it? Haven't used mine yet...

It is remarkably usable. I've had one for 3 years now, and I've done all sorts of things with it. I used it just last night to make a few standoffs for the DRO I'm adding to my bigger mill.

You need to stay within it's envelope. No big (> 3/4 inch) end mills, no 3 inch boring bars, no .250 deep cuts in a single pass. I've milled trit pockets in titanium with it.

BTW, you can get the collets separately from LMS in metric or imperial thread.
http://littlemachineshop.com/products/product_view.php?ProductID=1745&category=

Daniel

 

[jhanko]

Ok, looks like I got everything covered except how to hold the light. I've been looking at collet blocks and don't think they will work. I think I will need to hold the light in the section with the smaller diameter. Is there any way to get this to work? My other option is to cut the trit slots before I turn down that section, but I want to mill a couple of light that are already complete...

 

[G1K]

The light looks like it has a threaded connection between where you want to mill and the head? Make a threaded hole in something that you can grip in your 3 jaw chuck. Screw the light half into that, and your set. For support on the other end, use a live center, or even just some material between the light and the compound, since the light wont be spinning.


R