Practical approach to milling sheet metal 

You taught me a new technique! The few stainless sheet jobs I have done were a nightmare like your dramatized beginning. Never to old to learn something new and thanks for your great content. ATB, Robin

Stefan you’re a brilliant teacher. I finished my apprenticeship a decade ago and still learn something new every time you post a video. Thank you!

At 12:45, my hand was throwing away my cup of coffee and reaching for the E-Stop.... I broke more than one endmill milling flat sheets like this, held down by clamps not modeled in CAD. Personally, i love those kant-twist clamps. Problem is, my endmills hate running into them at G0🤣Also, at 15:50, i would highly recommend using two clamps. Otherwise, the cut off piece tends to rotate below the clamp, getting pulled into the cutter.

Another masterclass from Stefan, but the "neglectable" at the end puts a smile on my face

Great advise on using chamfered corner endmills. I recall you mentioning those before and I really need to order some. In addition to clamping the waste stock, using tabs helps keep off cuts from getting thrown around and jamming. I do a lot of milling of ~1mm (.040) aluminum sheet on a small router. Using the tool probing and material mapping helps with the initial cut on GRBL based CNC routers. It helps to use a sharp pointer to do the mapping with a slow Z feed to avoid deflection on thin sheets. The control then compensates for the height variations and it really cuts down on burrs. I have not seen this feature in real CNC machines, but i assume anyone running those has a better processor for cutting sheet metal.

This is a lucky coincidence. I have to do this exact thing Monday morning. Same material and all.

I wish you would have shown this technique a week ago would have saved me a lot of heart ache. Never mind I’ll start again and put your info to good use. Many thanks.

Excellent video Stefan, as always. Thanks for sharing your knowledge and expertise with us.

Depending on the size of my raw material and the size of the finished part, I will use a spray mount adhesive to mount the metal to the wood. The adhesive is gives an extremely strong bond so you can clamp the material much farther away from the cut path which means it's less likely to bow. Also, I will sometimes use Medium Density Fiberboard (MDF, AKA Medite) as it is usually far flatter than your average piece of plywood. If you use coolant it will pretty much destroy the MDF but that's a small loss. To remove your part from the MDF, apply a bit of heat from a heat gun and the glue will soften and release the part.

Excellent video, answers a lot of problems I've had with sheet metal milling looking like someone chewed it off ! You know I'm going to learn somethng when Stefan gets the pen and paper out ! Thankyou !

Thank you Stefan for the masterclass. Interesting and informative from beginning to end. 👏👏👍😀

Thank you Stefan, for this lesson. As you explained it, it became obvious that your approach is how it should be done.

Absolute wonderful video! I have never given this process any thought and would have done this machining operation in one pass. Thankyou for sending me on the right path1

Very useful. I just milled some stainless sheet and the end mill (about 6 mm dia) was fine for the first 20mm. Then it got red hot and end of cutting. I was cutting full sheet metail thickness. Then I swapped to another cutter and used very small DOC as Stefan describes. OK job. Great to see Stefan is describing exactly what worked for me. Thank you Stfan - pity I didn't see you video before I started my job!

I guess this is the closest thing to an April Fool's joke that we're gonna get on this channel.

Stefan, I've been dealing with this very issue today trying to get a good clean cut on a customer's part. God bless you! I changed my approach as you suggested, and i am now going to be able to deliver descent parts. Cutting .8mm 316L Stainless Sheet using 1/16 inch diameter end mill. Now my cut matches the mirror finish on the material! Beautiful!

We do quite some stainless sheetmetal (13-8PH) and to be honest never had issues with just going full slot and as fast as possible. Key is the fixturing imho. I only use precision milled aluminium plates as a backer and drill a bunch of holes to really clamp down the sheet. Think this also helps with getting the heat out of the sheet and into the aluminium. All roughing is done with a 6 mm 3-flute from Garant and finishing with a 4mm 6-flute. And a VMC with TSC to get the chips out of the slot also helps..😅

The one thing I learned about drilling/milling/turning stainless is to use water. Basically flooding it with water keeps the temperature low and prevents stainless from hardening. At work we use cheap hole saws in stainless and they last a long time as long as you cool them with water

Another great video Stefan. The chamfer on the end mill at high feed is forcing the material down into the spoil board. I wonder if the edge finish improves with a aluminium spoil board so there is less micro material movement. Maybe the spindle bearings are loaded up just a little more with the chamfer cutter also. All these small things that make a difference are long in the learning, but with the help of your excellent videos, im sure most of your viewers are getting bettrr results more often. Thanks again.

as always Mr. Stefan you educate us with another informative video ! thank you for all you do and taking the time to show us.

Ich nutze meistens meine Vakuumspannplatte für Blech. Dadurch ist es von der Höhe her sehr gleichmäßig. Ab und zu nutze ich auch die Technik wie du sie hier zeigst. Das Abfallstück sichere ich mithilfe von 2-3 schnellen Bohrungen mit dem Akkuschrauber und ein paar kleinen Spaxschrauben. Dadurch hat man auch keine Störkontur durch eine Klemme.

Always learn something new watching your videos. Thanks.

Stefan, this is a great video. I have liked milling cutters with a chamfer for a long time. I even "save" the ones that get their corners worn by hand-stoning a chamfer on them. But I have never thought that a chamfered end mill would be good for thin/sheet metal. Along with taking shallow cuts and using a high feed rate, I have really learned something today. Thanks for a great video!

Thanks for sharing. Today was the first time I successfully used a self-made 1-tooth cutter to cut a 'Simmerring'-seat 4 mm deeper into cast iron. Having watched over your shoulder over all those years was all it took. Thanks.

It's very rare that I cnc sheet, but sometimes I have to do 1.7mm cold-rolled. I picked up a couple of cutters the same as I use on my wood router at home - downcut spirals that tend to push the work down. (The sheet has a wood backer the same as you showed).

Very well explained,Stefan.Thank you.

Thanks Stefan you're brilliant. This will help me a lot. I'm planning to make kant twist clamps. And that's a lot of cutting in sheet metal.

Actually this is very helpful to me, as I've just had a nightmare in the workshop trying to mill stainless sheet, so this video is timely, albeit a bit late for me, I could have done with seeing this before I ruined my cutters! but now I'm a bit wiser, so thanks for this.cheers, Dave

Great video and very informative. I’ve been using the super glue and painters tape hold down method like NY CNC on an aluminum plate for thin stuff and it works great. Actually, not just thin stuff. It works great at anything I want to get around without worrying about the clamps. If I don’t hold it in the vise, I’m probably gluing it to a plate. I even glue pieces of aluminum scrap to the top of the vise hard jaws to make soft jaws out of for smallish parts. You’d be surprised how much force it takes to break them loose. For really thin material, you need to use heat or solvent to break the bond because prying them apart will actually bend the part

Danke für den Tipp und die ausführliche Erklärung! 👍

Stefan thanks for another very helpful in depth tip/trick. Always enjoy your tips and musings, First Rate Stuff!

Thx for sharing this tip, very useful. I also (sometimes) hava to fiddle around with sheet metal, and in stainless you have to watch out for workhardening. Gruß aus dem Badischen, from another Stefan :)

I will be trying this approach on cuts that need it. This, id scribe, band saw, one rough and one finish pass at full depth.

Another aspect: For slotting (on home shop/less rigid machines) the 3 flute endmills work better than 4 flute ones. Which kinda makes sense with lower cutting and pulling forces (from flute helix). The surprising bit is that 3 flutes also work better than 2 flutes. With 3 flutes the load (both magnitude and direction) on the cutter varies less whereas with 2 flutes when one flute starts disengaging the other starts engaging. This results in the cutter forces making an almost 180 deg switch, producing bad vibrations. Worse, because the shock loads happen when the flutes are engaging the sides of the slot, overall the slot will end up oversized. Actually, the same shock loading will happen when slotting with endmills with any even-number of flutes though the shock will be less for 4+ flutes and expensive variable flute geometry cutters. But don't just take my word, make similar slots with 2, 3 then 4 flute endmills at the same chip load (or less scientifically same feed) and listen for vibrations and measure the slot width. Do check the runout (on the flutes) of each cutter beforehand as that can easily be bad enough (from bad collet, spindle, debris or wear) to invalidate the test.

Really enjoy your vids Stefan. I’ve been a hobby machinist for 20 years (stress on ‘hobby’) and i always enjoy how you break down details so i can not only learn how but why. Thank you

Thank You Stefan for this very useful advice! I have used MDF board similarly, find it much flatter than plywood. Usually glue a piece of hardwood to the back for quickly putting it in the vice for less critical stuff. Easy to attach clamps around the sides.

Well done in all aspects. I have a few projects using thin metals I've been putting off for lack of knowledge/expetience. I feel much more confident I can take them on, now. Close to 10 yrs ago, I was in the market for my 1st lathe or mill. Looking for a machine, I saw an ad for end mills, '40 pounds of end mills, $35.00'. Knowing nothing about end mills other than they aren't cheap, I went to look at them. 95% were brand new, some still in the rubberized protective coating. Got them home & was looking at one, to chk the cost on the 'net. My heart sunk when I saw the corner of the flute chipped off. Being ignorant of something, the 1st thought is, 'No wonder they were cheap. They're effed up.' Started looking at each end mill. At the 3rd-4th, I realized they were all 'chipped'. By then, I began to get familiar w/ them & realized the 'chips' were very uniform. It was then I understood they weren't ruined & it was a great deal, after all. I got a lathe that same day, but it wasn't until last year before I got a mill, (cancer detoured me for 4+ yrs) & I've been able to put the 40# to some use. I've read a lot & watched a lot of vids about end mills & milling in the intervening years. You are the 1st to discuss anything about chamfered flute ends, their use or even their existance. Thanks. GeoD

Thanks for sharing your knowledge and experience. I'm a little wiser today 👍 🇬🇧

Very helpful. Air starting/wood thickness variance and end mill discussion are my takeways. Thanks from Colorado.

Very informative and helpful video. Thanks for posting, I know it's a lot of work to make these videos so please know it is appreciated!

I use that technique in wood or plastic or metal cutting.... it takes a little longer but usually it is almost as fast..taking deep cuts heats up your blades / tool and is harder on your Power tool too... shallow multiple cuts are going to be easier on your tools ..reducing the heat and force needed to make the cut depth.. . it is something i learned about 40 years ago and i find it the best way to do cuts.... i don't care if it " seems " to take longer because i know it is going to allow me to do the cuts without problems every time....especially when using Piwer tools that are just powerful enough but doing long cuts it is going to overwork your tool and the cutting tools too... you can relax and get alot done if you are patient.... 🇨🇦🤓🤟

Many thanks once again. Very concise presentation, valuable information.

Great info Stefan . saved in the grey matter for reference . Cheers Ade.

As always, excellent description and discussion, understandable and convincing. Thanks for continuing to share your experience and expertise!

Another excellent tutorial Stefan. Hope all is good in the land of precision machining and Black Forest cuckoo clocks. Cheers!

Indeed, that works way better. It's all in the details. This is something I think I would never have figured out myself.

Thanks Stefan, I think I have learned a lot here. 👍

This is a great tip. Thanks! My last low precision sheet metal project I glued a 1:1 scale drawing to it and cut it on the bandsaw

That is one to remember for sure . Even for large cuts on my other mill ( 4 1/4 ton Stanko ) with a face mill i often go the multiple lighter cuts, high reed & rpm . Seems quicker & less load on the machine . 👍

Thanks Stefan! You never disappoint! You're always on your game! It's such a treat to be able to freely benefit from your knowledge and experience! I'm so glad you choose to share all of this great info with the rest of us!❤ 😊

I use double stick tape and leave two tabs to keep things from flying on the cnc.

My endmills usually develop an edge chamfer after I try to use them.

Brilliant as always and many thanks for this machining tip. I have a somewhat tricky project coming up where I have to cut square windows out of a curved piece of aluminum. I better come up with a way to clamp the center part so it doesn't jam or ruin the cutter. Obviously clamps won't work as the cutter will pass through its position. But, at least this vid has made me think about it.

Great tips Stefan. I have had some very ugly results trying to make cuts in sheet metal, both aluminium and stainless so thank you very much for sharing your expertise.

Excellent and really useful tips. Thanks!

Thank you Stefan. I run a CNC Router on Aluminum and Hard plastics. This information will serve me well

Massively helpful! Sehr hilfreich. I wish I'd known this, two years ago, when I tried to make myself an instrument panel by milling sheet steel clamped to plywood. It was a total dog's breakfast. (Früstück des Hundes?) I concluded that a Bridgeport was not a sensible machine to use on thin sheets... but you have shown me that it can be done, if one knows how. Thank you.

Thanks Stefan. That was very interesting. I was an expecting an April Fools joke but I'm glad I watched. All the best, Mart in England.

Hello Stefan! I have been watching your channel for a long time and thanks to you I receive a lot of useful information. Thank you so much for sharing information with us. Big greetings from Belarus, Minsk!

Thanks for the tips and demo Stefan, always fun to learn a little something looking over your shoulder. Thanks!

Thanks for the excellent tip! That's one kind of cut I've done from time to time and it's nice to learn a better way.

I only have a small horizontal Atlas Milling machine. If you ever get the time, I hope to see a video for doing this on a similar machine. I have so much to learn, and work-holding is my biggest weakness. Thanks for sharing.

I learn a boat load here. Stephan, you’re the best!

LBFU School, has always been a solid teaching tool...💯

Exceptional video Stefan. Thank you so much for going the extra effort to show us why.

great tips, great explanation (as always). also some of these tips apply to different areas of crafts too, eg don't clamp bendy wood in multiple places when cutting or resawing. Fortunately I learned that using cheapish wood and not metal :D

Exactly what I needed, as tomorrow i need to millout holes in some electrical panels. Earlier tried full depth and that was not nice. Will try this approach. Thanks for the video 🍺🍺🍺

I have found that using a straight flute solid carbide end mill for sheet metal is the best. The straight flute does not create the lifting forces that a helical flute end mill creates. The cut is more rigid with a better finish.

Awesome demonstration and explanation, as always. Thank you!

Great technique! I’m curious about your thoughts on left-hand helix endmills for sheet metal? Robin has demonstrated this- they apparently push down on the work, eliminating vibration and also reducing burrs. I haven’t tried it, but it seems promising.

Excellent as usual. Glad to see that you do not use some form of super plywood that will make go into depression. :) Very useful technique.,

Thanks again Stefan for the efforts You spend sharing this information. Best Wishes to everyone.

Wow, thank you! Have resorted to my contouring saw and drill. Can overcome the 304 with high speed drills sometimes but sometimes I saw the drill come out of the sheet metal with a reduced drill diameter. Yikes. Tricky for me like an amateur.

I've always had good results using adhesive and sticking it to your backing board.

I love those Uvex safety glasses, look way better than the usual, gonna get some of those.

I learn something new pretty much every video You make, nice trick!

Stefan, you can cut even thinner material this way by sandwiching it between two sacrificial pieces. Also a shaped clamping piece helps enormously

Very interesting. Thanks. I’m sure it going to be very useful.

You can try band sawing the corner out staying about 1/16 away from finish, then put it in the miller and side cut to finish, you will minimize your burr. The other way we did was to take small cuts on the depth, staying away from finish then finishing it off. Please use oil otherwise you will kill the cutter..

Thank you, Stefan; i‘m looking forward for the next hard-to-mill-topic 💪

Sharp edges cut great but are a fragile thing. Radiused or chamfered endmills are much more durable in my experience.

Thanks Stefan! Great tips. Given the minimum chamfer available from your supplier seems to be 1 mm, do you think it would be worthwhile using a tool & cutter grinder to add a custom chamfer on occasion? I'm thinking if someone had quite a few cutouts to make, a smaller chamfer, perhaps also at a higher angle, might allow you to reduce the number of finish passes required, and perhaps a higher angle could increase the downwards force on the work and reduce the tendency for it to be pulled up by the cutter. Edit: perhaps I should have said "lower angle"? I mean one with less Z and more Y.

Fantastic info as always.

Thanks for that information. Thanks for the video keep on keeping on.

I recall from one of your previous videos/lessons that you used a continuous down spiral with low step down from Fusion 360 for pockets in thin materials. Similar to what you are using here. I kept that recipefor futurre use. Thank you

At the end the view reminds me on this old tonys bench, black shirt and way of filming his stuff

Great demo and really good advise. Thanks Stefan!

I believe the aluminum you were referring to, for using as a backer plate, is called MIC 6. :)

I don't know what it might be called in Germany or anywhere in Europe. But in North America, MDF due to how it's manufactured is far flatter than most plywoods for a backing board. It's also a lot cheaper. But it won't tolerate coolant or even cutting oils for very long. The wood fibers begin absorbing the coolant or oil, they start to expand which starts to break up the resin bonding and the piece literally begins to warp and fall apart. It also doesn't hold wood screws as well as plywood for part holding, through bolts with washers and nuts might be better in higher loading situations.

Thanks for sharing, Stefan! I'm going to update my OS to use this technique for sheet metal in the future. Thanks again, and I hope the world is the even better than the best it can be on your end. ^___^

great video Stefan, Another one to go in my apprentice training playlist.

Thank you. Another wonderful and important tutorial 👍🏽

Thanks for the sheet metal tip, I didn't know that!

Thanks. I will give it a try

i saw a video recently about reverse flute end mills and thought they would work nicely in this scenario with light cuts and downward spirals to eliminate the burring. something to look at.

20:28, Weil die spanabhebende Kante von der Oberfläche und dem Rücken her grösser ist als wie bei einem scharfkantigem Schliff. Ja macht Sinn. Guter Tip danke =) Da werden einige Freude haben ^^

Good practical information Stefan,thanks.

Thanks for sharing this approach.

Just what I needed to know! Thanks, Stefan.

I have screwed internal cutouts (countersunk!) to the spoil board to prevent disaster. Often I use superglue, but if you get your part hot enough, the glue will bid you adieu.