How to make best use of your milling machine. Tips and techniques

[Chuck Seiler]

How about mill bits like this?

[Modeler12]

Chuck, I ran a quick experiment with those 'diamond coated bits' versus a real end-mill bit.

 

The wood was a piece of bloodwood and the 'bits' included a short 1/8 inch diameter drill bit (just for fun, but not recommended with tiny drills because of breakage). The ball 'cut' through after two passed, but the T-slot bit just burnt and created some smoke. Same with the drill bit. The end-mill bit clearly made some chips.

All were run at about 4000 rpm. The results are shown below.

 

I still want to grind one of those old drill bits and see if I can make it work (make chips).

[Chuck Seiler]

Jay,

 

    Thanks.  I will have to do some experimentation.

[Mahuna]

There is a very wide variety of bits in 3/32 shanks.  This appears to be the shank most often used in the jewelry and dental tools.  As a bird carver I accumulated quite a number of 3/32 bits.  Most of them are diamond or ruby coated, but I also have some HSS bits that will also work on the milling machine.  The best way to mount them is with a milling collet for 3/32 shanks.  I'll try to put together some photos in the next day or so.

[Modeler12]

The topic is about tips and techniques. So here are a couple ideas about using the four jaw chuck (on the rotary table in this case).

 

The question was raised about reversing the jaws on the chuck. On mine you can do that by unscrewing the jaw until you can lift it off the saddle in the crew. Don't take the screw out all the way and try to reverse the whole thing. Most likely the other end of the screw does not have a hole for the handle/key. After turning the jaw around, screw it back into the slot.

  

The four jaws don't necessarily have to be all in the same position. Below are a couple examples how I mounted a long dowel so I could mill a slot down its center line.
I am using only three of the jaws in this case.

The second one uses all four jaws to hold a flat piece so I can machine a circular groove towards the tip.

I only use this for light passes on wood. You might think of this as using the chuck as a vise.

Edited September 4, 2015 by Modeler12

[Mahuna]

I needed to mill a slot for the centerboard in a keel for a Skipjack.  I have two milling vises, so I used the two vises in tandem to hold the keel.

 

First I held a couple of parallel bars in both vises, with the vises loosely attached to the table.  I indicated in the vises so that they were in the same plane.

 

          

 

Then I was able to mount the keel across the vises and mill the slot parallel to the sides and along the centerline.

 

             

 

         

 

I have a tooling plate for my mill, which allows me to mount different pieces to the mill and save the x-table from inadvertent cuts.

 

          

 

I borrowed this idea to make a ‘router table’ for the mill, using a thick piece of plywood that is perfectly flat.  I drilled holes for cap screws and t-nuts to fit the channels in the x-table, and made a fence from an angled piece of aluminum.

 

          

 

          

 

I also use this table when I’m drilling multiple holes that may sometimes drill through the stock – this saves the x-table.

 

          

 

As for the bits I mentioned, this is part of my collection of 3/32 bits from my bird carving days.  I accumulated this hoard over 15 years of carving.

 

                    

 

The bits in the photos below are very useful on the mill.

 

          

 

          

 

I also recently received the bits in the attached photos from a friend of mine who owned a jewelry store and was retiring.  I’m sure there are some bits in this treasure trove that will be very useful on the mill, and I don’t think I’ll be needing to buy more bits for the foreseeable future!

 

         

 

          

 

 

[Modeler12]

Frank, your are lucky to have friends in the jewelry business and get all those nice bits.  

Have you used any of them on wood? Any suggestions about cutting details (speed and feed) to minimize the burning?
I am sure those bits were designed for cutting metal.

 

I really like the way you milled the slot/groove in the keel as you showed very clearly in those pictures.

It is nice to be able to use all the tools you have available. Two vises for the mill is certainly helpful.

Most of the time we need to improvise with what we have on hand and figure out a way to go from there.
You showed us a nice adaptation.

[gjdale]

Frank,

 

Do you have any more pics of your 'router table' in action? I've been wondering how this might be possible and clearly you've solved the problem.

[Mahuna]

Hi Jay:

 

A good way to minimize burning when milling wood is to upgrade the mill with the 10,000 RPM pulley set.  On a recent trip to Carlsbad, CA for a little vacation I brought the headstock and motor to Sherline and they upgraded the pulley set.  All it cost was the price of the parts (I'm still not comfortable taking the mill apart to that extent).  So now my mill and lathe can run at high speeds.  By the way, every time I deal with Sherline I come away impressed with their customer focus.

 

http://www.sherline.com/4335inst.pdf

 

Hi Grant:

 

I've been using the table mostly for drilling.  I still need to make a device to stabilize a wood strip against the bit when using the table for routing.  Now this thread will shame me into getting it done!  

[gjdale]

Glad to hear that Frank! I look forward to seeing/reading about your results. It's been one of things I keep thinking, "surely there must be a fairly simple way to do this". I'm just glad that you are a little further down the path with this one. (BTW, I too have the Sherline Mill, upgraded to the 10,000 rpm pulley set).

[Modeler12]

Frank, i just had to find out if the speed of the diamond coated tool has anything to do with cutting clean slots.

I took my old dremmel-like tool, mounted the same diamond coated T-slot cutter, and the same piece of wood, and ran it at about 10,000 rpm or so. 

It burnt a pathway with lots of smoke along the way. The view is of the same piece as before, but form the other side.

  

 

Sorry, but for wood I am still a believer in cutting chips rather than burning my way through.

[Mahuna]

Hi Jay

 

I haven't tried any of my diamond-coated bits on the mill, only HSS and carbide.  After your demo I won't even try the diamond-coated.

 

When carving I always used tupelo, which is a lot like basswood only finer grained.  The diamond and ruby bits only burnt the wood when there was a small knot or other hard area, otherwise the cuts were nice and clean (and lots of dust).  Based on this and your results, I would say the diamond bits aren't good when used in hardwoods.

Edited September 6, 2015 by Mahuna

[lehmann]

I just saw the picture in the first post.  By coincidence, I have the same setup on my mill, but it's on a full size knee mill, not a table-top.   I do research for the sawmill industry on saws, and this setup will be used in an experiment I'm doing.   To give some scale, the saw is 7.25 inches diameter.  

 

I also use it for woodworking - it's a great overhead router, although the spindle speed is a bit low.  Like it for woodworking, because I don't have to build templates to do repeated or precise slots, holes, etc.  On the other end of the scale, I have the "sensitive drill chuck" for drilling a #80 hole.

 

One of the nice things about having full size machines is that I can build the table-top machines myself.  Hopefully, later this week I'll share some pics of a small table saw that fits on a Taig lathe.

 

[Mahuna]

OK – so I finished the parts for the router table.

 

I made the following item on the mill.  It’s brass, and I used the rotary table to cut the arrow shape at the working end.  I used a 1/8” four-flute cutter to cut the slot for the hold-down bolts.  I had to move the y-table about 5 thousandths to make the slot wide enough for a loose fit on a 6-32 socket-head screw.  Then I thinned down most of the body, leaving the arrowhead at the original height.  I filed all of the corners clean with a #4 cut escapement file, then cleaned everything up with fine sandpaper and 0000 steel wool.  I don’t know what to call it, but it functions like a featherboard to keep the work piece tight against the fence, so lets call it a featherboard for the time being.

 

          

 

I used t-nuts installed under the table to hold the socket-head screws (also used for holding the fence).  Here’s a photo of the ‘featherboard’ mounted on the table.

 

           

 

In use, I first make sure that the featherboard is set so that it holds the workpiece against the fence.

 

           

 

I used a carbide cutter that I got from my jeweler friend.

 

           

 

This was mounted using a 3/32 Milling Collet.  It gets mounted directly into the Sherline spindle, then is held fast and tightened around the bit using the drawbolt shown in the photo.

 

           

 

In operation, the wood is fed left-to-right since the cutter is traveling clockwise (right to left).  On a regular router table, since the bit is mounted on the spindle below the table the feed is right to left.  On the mill, the spindle is above the table, hence the difference in feed direction.  I used my right index finger to hold the wood down on the table, and pushed the wood with my left hand.

 

           

 

I ran the mill at about 7500 RPM and got a nice clean cut (I used a piece of pear as the trial wood).  It needed a little cleaning with an old toothbrush, but there was no ripping or burning that I could see.

 

           

 

I then tried one of my diamond bits (I think it’s medium coarseness) to see if there was any burning.

 

                   

 

The only difference I could see was that the cutting tended to peal off, rather than becoming fine dust as with the carbide cutter.  I ran this at the same speed, and there didn’t seem to be any burning.

 

           

 

Thanks to this thread I now have a working 'router table'.  I used 3/32" shank bits for the first test.  I do have the Dremel 1/8" Router Bit set and a 1/8" Collet, so I'll probably try that next.

 

 

[Mahuna]

I couldn't wait, so I tried out one of the Dremel router bits.

 

          

 

It did a great job.

 

          

 

          

 

These bits will be much better than the smaller bits, especially for fancy cuts, but I'm sure the smaller bits will also come in handy.

 

 

[mtaylor]

Frank,

 

You just added more tools to the arsenal...    Thanks.

[gjdale]

Frank,

 

Thanks so much for posting this. You've answered many questions and your pictures illustrate your explanations beautifully. I think I can now follow suit.

 

One question I do have though. Do you think there would be any benefit in using a bearing on the end of your "feather board"? I'm thinking that it would hold the timber against the fence while still allowing to move freely past the end of the feather board (much like in my thin ripping guide for the Byrnes saw). Or would that just be overkill and difficult to make?

[Mahuna]

Hi Grant

 

I thought about using a bearing, but the size of the 'featherboard' (maybe it would be better to call it a guide) is so small that I didn't even try.  I didn't feel any binding when moving the wood through, so I don't think it would be much of an improvement.

 

My next little project will be to make a saw guide similar to yours out of aluminum, and now I don't think I'll use a bearing in that either. 

[gjdale]

Thanks Frank - I suspect you're right on both counts.

[shiloh]

Don't think they are discussing the guidance of a router bit, it is stationary. Moving the stock past the stationary blade, be it a saw blade or router bit, requires a different approach than trimming your Formica.

jud

[Modeler12]

Thanks Frank for your pictures and explanation. Marvelous.

I was not aware that Dremel makes router bits in the various shapes. So, I took a look at what is available and I was surprised.

Dremel, of course, sells their own brand and they look very nice. A set of five runs about $30 US.

But what shocked me were the sets from China, Hong Kong and Malasia for as low as $3 for a set of ten. Now, I grant you that the quality is questionable, but at that price I am going to give it a go. Here are some links:

http://www.ebay.com/sch/i.html?poi=&adpos=1s5&ul_noapp=true&geo_id=10232&MT_ID=70&crlp=79516278875_857&keyword=dremel+router+bits&rlsatarget=aud-150920456644%3Akwd-117020436&_nkw=dremel+router+bits&device=c&crdt=0&treatment_id=7&clk_rvr_id=894839254983

 

http://www.toolbarn.com/dremel-tr770.html?gclid=Cj0KEQjwjrqvBRD6wf2fy-C61PIBEiQAUzKQTrf6ULwRsu1UiUtVU4i5sCh2b8smnM4A5BnUJ2SiN5waAmdZ8P8HAQ&ad=54711642134

 

One more thing about diamond coated bits. My trial run shown above was made with a piece of bloodwood and that may not have been fair. I know that it contains more than the usual amount of oil and tends to burn readily (like oak and other hardwoods). But even running the same tool through a piece of basswood caused some burning (10,000 rpm).

Your pieces look great by comparison. Nice set up, Frank.

[shiloh]

While talking to a machinist several years ago, he mentioned that the Chinese tools seemed to be to hard, especially drill bits. He still uses them, but the new ones go into the kitchen oven at about 400° for 3 or 4 hours, apparently that tempers the bits so they don't break and they stay hard enough to cut.

I need to check the temperature and time for tempering of tool steel.  Check my numbers before using them.

jud

[Modeler12]

Jud, it is my understanding that to change the hardness of these bits you first have to anneal the metal and that is at a temperature well above 400 deg F. Three to four hours in a kitchen oven is not going to do it.

 

I have just ordered some of the 'cheap' bits and will let you know what gives. . . . . Of course, delivery is not going to be quick. They probably ship direct from Asia somewhere. Total cost about four dollars. But now they also have my credit card number . . . .????

[jhearl]

But now they also have my credit card number . . . .????

 

And what makes you think they didn't already have it???

[Mahuna]

Hi Jay

 

Thanks for the links.  I have pretty much all of the shapes shown (I guess the real cheap ones are all knockoffs, so I shouldn't expect anything different).  I may buy one of the cheaper sets anyway, and experiment with altering the tool shapes to match typical molding shapes.  If that works, that would be great.  I don't think tempering (or even the level of sharpness) is a big deal when shaping wood.  I've shaped and sharpened pieces of hacksaw blades for hand shaping with no big problems.

 

As for the credit card, I think you'd be safer using PayPal.

Edited September 9, 2015 by Mahuna

[Modeler12]

And what makes you think they didn't already have it???

Because for this purchase I used a card that was never used on-line. But then again . . . .????

[shiloh]

Jud, it is my understanding that to change the hardness of these bits you first have to anneal the metal and that is at a temperature well above 400 deg F. Three to four hours in a kitchen oven is not going to do it.

 

I have just ordered some of the 'cheap' bits and will let you know what gives. . . . . Of course, delivery is not going to be quick. They probably ship direct from Asia somewhere. Total cost about four dollars. But now they also have my credit card number . . . .????

not talking about hardining the bits only tempering.

Tempering colors

 

Pieces of through-tempered steel flatbar. The first one, on the left, is normalized steel. The second is quenched, untempered martensite. The remaining pieces have been tempered in an oven to their corresponding temperature, for an hour each. "Tempering standards" like these are sometimes used by blacksmiths for comparison, ensuring that the work is tempered to the proper color.

If steel has been freshly ground, sanded, or polished, it will form an oxide layer on its surface when heated. As the temperature of the steel is increased, the thickness of the iron oxide will also increase. Although iron oxide is not normally transparent, such thin layers do allow light to pass through, reflecting off both the upper and lower surfaces of the layer. This causes a phenomenon called thin-film interference, which produces colors on the surface. As the thickness of this layer increases with temperature, it causes the colors to change from a very light yellow, to brown, then purple, then blue. These colors appear at very precise temperatures, and provide the blacksmith with a very accurate gauge for measuring the temperature. The various colors, their corresponding temperatures, and some of their uses are:

• Faint-yellow – 176 °C (349 °F) – engravers, razors, scrapers
• Light-straw – 205 °C (401 °F) – rock drills, reamers, metal-cutting saws
• Dark-straw – 226 °C (439 °F) – scribers, planer blades
• Brown – 260 °C (500 °F) – taps, dies, drill bits, hammers, cold chisels
• Purple – 282 °C (540 °F) – surgical tools, punches, stone carving tools
• Dark blue – 310 °C (590 °F) – screwdrivers, wrenches
• Light blue – 337 °C (639 °F) – springs, wood-cutting saws
• Grey-blue – 371 °C (700 °F) and higher – structural steel

Beyond the grey-blue color, the iron oxide loses its transparency, and the temperature can no longer be judged in this way. The layer will also increase in thickness as time passes, which is another reason overheating and immediate cooling is used. Steel in a tempering oven, held at 205 °C (401 °F) for a long time, will begin to turn brown, purple or blue, even though the temperature did not exceed that needed to produce a light-straw color. Oxidizing or carburizing heat sources may also affect the final result. The iron oxide layer, unlike rust, also protects the steel from corrosion through passivation.^[12]

jud

Edited September 10, 2015 by shiloh

[Canute]

Nice metallurgy primer. Thanks.

[mtaylor]

Learning something new everyday... metallurgy here today.   Drill sharpening on another topic.  Wonderful stuff for the brain.

[Modeler12]

Frank, I liked your idea for the router table enough to jump in and make me one.

I adapted it to my mill where I try to keep the 4 inch vise and rotary table mounted on the bed as much as possible. For that reason I raised my router table on a block of wood which can then be clamped in the vise.

I wasn't sure how you hold your guide with the two cap screws, but in my case I routed a slot underneath just wide enough for two hex nuts to slide back and forth. The brown spots you see in the picture is some paste wax.

 
This allows me to route planks from zero to 3/4 inch wide. Anything wider can be done without the guide.

I have not yet cut the fence for cutter clearance and will wait until I get some cutters.

 

Meanwhile I tried to route a piece of basswood (1/8 x 5/32 inch) using a 1/16 inch diameter end mill and another diamond coated bit. 

Going with the grain helps to reduce burning, but when I stopped too long there was some darkening of the wood. The edges of both cuts were a bit fuzzy. And I need to do some fine tuning. For sure, I want to add a feather board to hold the work piece down (maybe one on each side). The sample was too flexible and had a tendency to lift up. 

 

I want to thank you, Frank, for sharing this nice idea.

 

One more comment about the 'fuzzy edge' etc. 

When I looked at the slot cut by the end-mill, I noticed there was a visible difference between the two edges. The one towards the picture was sharp and very thin and clear. The other side was not so. 

The direction of the router bit rotation (and work-piece movement) have a lot to do with this. Climb cutting gives a smoother edge because the wood is sheared and the chips pulled around and away. Perhaps the picture below explains it better:

Edited September 12, 2015 by Modeler12