Squaring off material in the mill

Added: 2026-05-21

[00:00:00]How guys? Got a little video here today on squaring off a block of aluminium. So hopefully this little video will be useful to those of you with a mini mill that need to square off material. It doesn't really matter what the size is.

[00:00:13]The actual overall process is pretty much identical no matter if you're working with a block like this or a postage stamp little piece. With that said, this is a block of aluminium. It's 6082 T6 aluminium. So, it does cut fairly nice and we need to get it down to these dimensions. So, 480 mm long, 85 mm deep, and then 55 mm wide. I am going to be making a chassis for my Daystate Blackwolf. And this is the external dimensions of it before we start taking some of the faces down. With that said, squaring off a block of material is nice and simple. There's just a few things that we need to do before we start. So, first thing I've gone ahead and done is just break all of the edges with a file so that nothing is going to cut us as we're maneuvering the material and removing the burrs from the edges. Also, make sure that nothing is going to hinder the material when it gets clamped down in the vice. What I mean by that is if you have a rolled over edge and you try to clamp onto it, you're not going to be clamping on the face. you're going to be clamping on the very edge of material that's been rolled over. The other thing I've gone ahead and done is just taken a file and wipe it across the surface to remove any high spots that could cause us problems when we go to lay the material in the vice. We don't want it rocking up and down on a little high point in the material as that will just mean we'll have to remove excess material in order to get it nice and square. The last thing I've gone ahead and done before I get started is use an engineer square to find or pick out the two squarest sides. So, we want the sides that most closely resemble the square in order to get started on this lump of material. It's this face here and this back face here. So, I'm going to be laying the material down in the vice with this side facing the fixture and this side on the base of the vice just like that. Right then, over at the mill. And the first thing you see me doing here is wiping the vice down. We don't want any chips between the material and the vice. This is less important at the moment, but when we get a few faces milled, having chips in the vice will damage the machined faces and make it so that the material is not properly referenced against the vice.

[00:02:36]Next, I'm just using a sacrificial piece of material behind the work so that the back face does not influence the clamping of the material. This is just a round piece of brass, but you can use most soft round metals. Then once the vice is tight, I give everything a little tap to make sure everything is sitting nicely against the vice base.

[00:02:58]With that done, the last thing I'm doing before we get started is just touching off over the material to make sure it's sitting relatively flat. This piece of material has a slight bow in the middle.

[00:03:10]So, it's about 0.4 mm proud in the center and that is reflected in the touch off readings. This process is far more important for longer work pieces as smaller blocks won't have so much variance over the face, but it does give you a good indication of how flat the material is lying in the vice. With all that done, it's time to finally get started. And here I am just using a 50 mm face mill at 1,000 RPM, taking a quarter of a millm cut, running at a little under 100 mm per minute. And at the moment I'm taking a cut of around 40% of the cutter diameter. You don't really need to do this with face mills, but for smaller endmills, sometimes it's better to do deeper cuts using less of the cutter's width rather than doing a full width slotting operation. And then when we get to the end of the part, my step over is about 20 mm. Again, with face mills, you don't really need to do this. I'm simply showing the process for an endmill. and I do do it differently on the other faces. The other thing I'll mention is that every now and again you can see me spray a little WD40 as a cutting lubricant. It's quite good for aluminium as it stops the chips sticking to the carbide inserts, but for steel, you definitely want to use a dedicated cutting oil. Next up, I'm just going to quickly check the flatness of the part.

[00:04:39]And this is done by just placing a straight edge across the material, then trying to fit a feeler gauge under it. I always do this on the first cut just to make sure the mill is set up correctly and that the head is trammed in. It won't show minor misalignment, but if something is majorly wrong, I can pick up on it straight away. With that done, it's just a case of deburring the edges, then flipping the part in the vice. So, we're resting the newly machined face up against the fixed jaw of the vice. We are still using the sacrificial material behind the workpiece. And once everything is clamped up nicely, it's just a case of milling the new top face square to the one we just did.

[00:05:45]Right. Then at this point, we've got two faces that have been milled. So I've got this back edge here and then this top face. At this point, these edges should be fairly square to one another. So we can go ahead and check that. What you would typically do is just use something like an engineer's square. Put that on the side of the work. Then drop it down onto the top. Then shine a light under this edge of the square. Then look from this side to see if you can see any light appearing under the square. If you had light appearing under the square, it would indicate that the material isn't perfectly square. At this point, I do want to make you aware that if you're using a hobby mill, there's probably a 90% chance that you're not going to be working with perfectly square pieces.

[00:06:33]So, there's a good chance that you will be able to see a small amount of daylight underneath the square. However, it's important to remember that we are working with material and we do need to have tolerances. We can't make everything absolutely 100% perfectly.

[00:06:49]So, a good way to quantify the amount of outer square your work is, if it is indeed outer square, is by using a feeler gauge. So, this is the thinnest feeler gauge in my collection, and it's 0.02 mm, which is just under 1,000th of an inch. What we're going to do is use our square, put that on the side of the material like so. Then try and get the feeler gauge underneath there. So, as you can see there, the feeler gauge doesn't want to go under the square. So, we can at least assume that the work is square to within 0.02 mm. For this project and for my machine, I'm perfectly happy with that. I know my machine isn't perfect. As you can see here, we do have these ridges. If I take my finger now, running across them, I can just about feel them. They're not super pronounced. I can't grip onto them, but I can feel that they're there.

[00:07:58]Now, the reason that happens is because my mill head isn't perfectly straight or perfectly square to the table. It's actually lent forward very slightly.

[00:08:09]What this means is the cutter cuts very slightly more on one edge than it does the other. It's not a lot by any means.

[00:08:17]I think last time I mentioned it over 200 mm. There was about a 0.03 mm difference between the two edges, which is about a thousandth of an inch.

[00:08:29]Now, I'm not typically too worried about that because again, that's over 200 mm.

[00:08:34]So, pretty much double the width of this piece of work here. It would really be nice to have a much nicer machine like something like Bridgeport, something like that where I could tram the head absolutely perfectly and get it spot on each and every time. But again, we live in the real world and not everything is going to be able to be manufactured absolutely perfectly. For now, I'm happy everything's in my tolerances. If at this point you checked your block and it was majorly out, so 0.1 of a millimeter outer square, you would have to double check your setup. Make sure you didn't have a chip under any of the sides and also make sure that you're using your sacrificial material behind the workpiece as you clamp it up. With that said though, we can move on to our next face. So, we did this one last. So, we're going to rotate the part 90° and start work on the other face. So, this face here, we do need to take a fair amount of material off here. At the moment, it's about 63 mm wide.

[00:09:40]So, just under 63, 62.76.

[00:09:44]And we need to take it down to 55 mm.

[00:09:47]So, we've got about 7 mil of material to remove. With that all said, that's pretty much the process. It's not terribly difficult to do. The key things are to make sure that your mill is trammed in correctly and that there is no debris between your material and your vice. If you can do both of those things, it's pretty easy to get square material. And as I show the other two sides being milled, I do want to go over a few more things. So, to start off with, we have a little bit of material to remove here. So I'm taking 2 mm passes at full cutter width, then doing a full step over. So I'm pretty much taking the top layer of material off in two passes. So one from right to left, the other from left to right. Once I get down to near my final dimension, I'll take a quarter of a mm skim cut off the top. Then measure the thickness of the material for the final few passes.

[00:10:46]Having said that, the next thing we'll do is just go over a few things, then I'll give some troubleshooting tips. So, first thing I'll mention is that if you have a fair amount of material that you need to remove, it's best to take it from both sides rather than all off one.

[00:11:02]The reason for this is that the material that you're working on will generally have some internal stresses and as you machine material away, you may allow the part to warp when it's taken out of the vice. Not something you need to worry about if you're working with smaller parts. But if you have a part with thin walls or you need to take more than 10 mm off one side, it may be worth keeping that in mind. Another thing I'll mention is that for making some parts, you don't need to fully square the block off. It's sometimes quicker and easier to get a couple of reference faces milled in, then do your machining from them. This part will be machined on all sides, so it makes sense to square the block off fully. But that's not always the case.

[00:11:51]If you were making a small part that's tricky to hold in the vice, then milling the profile from a solid block and cutting it off using a parting saw is sometimes easier than squaring off a block the right size, then milling each side individually. It all comes down to what you're making. And to be honest with you, it's something that you pick up after you've done a few projects. The next thing I'll mention is that your cut depth and feed rate will be determined by your mill. Hobby machines will bog down in heavy cuts, so it's often better to run lighter cuts and higher feed rates, although you will need to experiment with your machine to get the best out of it. My machine will take a 2 mil cut with a 50 mil face mill at around 100 mm per minute fairly happily.

[00:12:42]I could probably push it a little harder, but it does tend to start to sound a little unhappy. You finish in the part starts to look a little choppy.

[00:12:52]So, I keep it at around those settings, and I'm quite happy with my results.

[00:12:57]But, it is just a case of figuring out your machine and working with it to get the results that you want. As for troubleshooting tips, if you find that your top surface is not flat when checked with a straight edge, you do need to check the head alignment or tram. If it's off, your face mill or end mill will create a large radius in the top of your part. Or in other words, the top surface will be slightly dished. It would have to be pretty far out to cause any major problems, but most mills will have some way of aligning the head. So, if you put a straight edge on your part and the two edges are touching but nothing in the middle is, you need to check the tram. The other thing I'll mention is that I'll go over an alternative squaring process at the end of the video that's useful if you are struggling to get the first two faces square to one another. It's just the same process in a slightly different order, but I have found it useful in the past. So, I'll share it at the end of the video.

[00:14:03]Right then, with all four sides done, it is time to work on the two ends. This part is far too long to stand upright in the mill. So, I'm just machining the sides using an endmill. This side I am notching as I don't need the whole face to be square as it will be machined off at a later date, but I'm just machining the end to get it square along with doing a few spring passes to clean up the face. The other side was done in a similar way, but I used a much longer endmill to mill the whole face in one go. And again, I just took that nice and slowly, doing plenty of cuts to make sure that the cutter wasn't being deformed as we worked through the material.

[00:14:54]Right then, so there we have all six sides machined. They're all nicely squared off to one another. I have gone ahead and checked the part over just with a square and a 0.02 mm feeler gauge and everything squared up nicely. So, as you can see there, with just a little bit of pressure on the square back, the feeler gauge is pinched. So, we can assume that all the faces are at least square to 0.02 mm. A better way to check overall squareness would be to be using a surface plate, a squareness comparator, and a master set square.

[00:15:31]However, for this particular project, that is absolutely way too overkill. And to be honest with you, 90% of the time, just holding the part up to a light with a square on one side is perfectly good enough for this end here. So this end on the side. I did have to use a super long 8 mm endmill in order to machine the face up nice and square. It was a little bit bit of a pain as the endmill itself wanted to deflect as it was cutting. So I had to take numerous passes in order to square everything up. If you didn't have a part that was so long, so if you had a more rectangular part just like so, what you could do is just use a square, put the part in the vice, and then square up the block just like so.

[00:16:18]Then take your first cut over the top edge. If you needed things a little more precise, you could obviously indicate along a machined edge, setting it up in your vice, then take the top face off, flip it over, rest it on some parallels or the machine vice base, then just take the top off as well. There's nothing really that complicated about it. It's just a case of following the procedure, making sure everything is nice and clean between setups, as well as making sure that your mill is set up correctly. With that said, there's one more thing I want to show you over at the mill. So, we'll go back over there and I'll talk about the alternative setup for squaring off the block. Right. Then, so last thing we'll do is just run through very briefly an alternative squaring process.

[00:17:06]So, say for example, we have our block of material here and we're struggling to get the first two sides square to one another. Now, there's quite a few reasons why this would happen. It could be that the moving jaw of your vice is lifting slightly as you tighten it and it's just kinking the part in the vice or it's not lying perfectly flat against the back of the vice. Whatever the reason, sometimes it is useful to ignore the square face for now. So, say we're trying to square these two faces. We'll ignore this one for now and focus on getting two parallel sides. So we have our bottom face which has been machined and the unmachined face on the top there. We'd focus on getting those two sides parallel first. And the way we'd go ahead and do that is just lay the work in the material on the primary face. So for now, we'll just put it in the vice base just like that. If I were doing this part for real, I would have to stack it on some parallels, but I'll leave them out just for this demonstration. What I'd go ahead and do then is put a piece of card, just a folded up piece of card behind the work and either use the sacrificial piece of material or another piece of card behind the job. And again, all that does is take out the inconsistencies on either of the two faces, so the front and the back one. Then tighten the vice up and make sure the part is sitting firmly against the vice base. You could do that a number of ways. You could shine a light from one side and then look from the other to see if you can see any light gaps. Alternatively, you could use feno gauges or if you had the par on your parallels, you could just give the parallels a wiggle and see if they were pinched. You shouldn't be able to move them if the part is sitting fully on them. With the vice tightened and the part tapped down, you could then take a nice facing cut, just a very light one, across the face of the material. And what that should give you is two parallel faces that you can then flip in the vice and clamp things up nice and securely. With the two parallel faces, it should be much easier to get the top face square to them as you won't have to worry about the moving jaw of the vice influencing the clamping of the material. It should clamp up nicely and you should be able to machine the top nice and square to the other two sides.

[00:19:27]Then you would just go ahead and flip the part. Do the same thing on the other side. and then clean up the edges any way you see fit. But there you have it.

[00:19:35]There's just an alternative squaring process. And with that said, that's pretty much going to do it for this particular video. So, thank you very much for watching. I hope it's been interesting or useful. and I'll see you in the next