Trying to cut steel on Homemade Milling Machine

[engineer steve]

I tried to cut some steel on my homemade milling machine, as you can see it doesn't like that very much. Some things I want to change are: better milling table with dovetails, more powerfull motor and bigger spindle(with standard taper and bigger bearings).

If you have more ideas that will improve this build, let me know, Thanks!

[Frank S]

Your mill looks like a regular drill press with a 30 taper. A fixed head and a standard spindle pull down as nearly all drill presses have.
Your 2 main problems are not your x y table or motor HP. The XY table can usually be tightened up even though it was made for a drill press.
Your ER collet adapter is way too long placing the end mill very far from the bottom quill bearing. Not sure if you can even install a larger diameter spindle in the quill.
From the video it looked like you were taking a fairly deep cut these machines don't do well with deep cuts because the head has a short distance between the bottom and the top spindle bearings, also the column does not have the mass to prevent flex.
If you will focus on limiting the depth of cut per pass and always feed into the cut, get some tooling to place the end mill closer to the bottom of the spindle you should notice better results. It will never be able to make large deep cuts, but even a 3 HP a J head Bridgeport pattern mill has its limitations as well

[thehomeengineer]

I completely agree with Frank
There are three things that a machinist must consider
1 Work Holding ( How ridged the machine is and how ridged the work piece is being held)
2 Tool holding ( How ridged the tool is supported/overhang)
3 Speeds and feed ( correct RPM for material being cut, correct feed rate and direction of cut)

1 The machine setup is ok vice is clamped to the table and the work piece is held in the vice. However the machine is a light weight construction so again not an issue but lighter cuts will need to be taken 0.040” 1mm on steel

2 Frank has covered the tool holding issue

3 This is where I personally think is your main issue. I am guessing that the table has standard nut and lead screws? If this is the case conventional machining will be a lot better and safer than climb milling. Also again I might be wrong but the spindle speed looked the same for both the aluminium and steel. Mild steel is generally cut in the regain of 20-30 meters/ minute and aluminium is 120-180 meters/ minute. So a considerable difference in spindle speed.

One further point a coolant system will prolong the life of your cutting tools.

As Frank also pointed out even commercially made machines have there limitations as a home made tool I think this will work with a little fine adjustment to your expectations on the size of cuts you are able to make and I am sure you will get over these issues.

Good luck
The Home Engineer

[engineer steve]

Your mill looks like a regular drill press with a 30 taper. A fixed head and a standard spindle pull down as nearly all drill presses have.
Your 2 main problems are not your x y table or motor HP. The XY table can usually be tightened up even though it was made for a drill press.
Your ER collet adapter is way too long placing the end mill very far from the bottom quill bearing. Not sure if you can even install a larger diameter spindle in the quill.
From the video it looked like you were taking a fairly deep cut these machines don't do well with deep cuts because the head has a short distance between the bottom and the top spindle bearings, also the column does not have the mass to prevent flex.
If you will focus on limiting the depth of cut per pass and always feed into the cut, get some tooling to place the end mill closer to the bottom of the spindle you should notice better results. It will never be able to make large deep cuts, but even a 3 HP a J head Bridgeport pattern mill has its limitations as well

Yeah the cut was relatively deep but I wanted to test is the rough way. As for the spindle, I want to replace the entire quill and spindle assembly with a much bigger quill and a standard milling taper, as I said. Besides the spindle I might remake the head just like you see on the cheap milling machines with dovetails and rack and pinion (maybe making a quill somewhat obsolete ?). Thanks for the feedback!

[engineer steve]

I completely agree with Frank
There are three things that a machinist must consider
1 Work Holding ( How ridged the machine is and how ridged the work piece is being held)
2 Tool holding ( How ridged the tool is supported/overhang)
3 Speeds and feed ( correct RPM for material being cut, correct feed rate and direction of cut)

1 The machine setup is ok vice is clamped to the table and the work piece is held in the vice. However the machine is a light weight construction so again not an issue but lighter cuts will need to be taken 0.040” 1mm on steel

2 Frank has covered the tool holding issue

3 This is where I personally think is your main issue. I am guessing that the table has standard nut and lead screws? If this is the case conventional machining will be a lot better and safer than climb milling. Also again I might be wrong but the spindle speed looked the same for both the aluminium and steel. Mild steel is generally cut in the regain of 20-30 meters/ minute and aluminium is 120-180 meters/ minute. So a considerable difference in spindle speed.

One further point a coolant system will prolong the life of your cutting tools.

As Frank also pointed out even commercially made machines have there limitations as a home made tool I think this will work with a little fine adjustment to your expectations on the size of cuts you are able to make and I am sure you will get over these issues.

Good luck
The Home Engineer

Good point about the feeds and speeds, I did use higher RPM on the aluminium but still not exactly right. I want to replace the motor with a 1200W router + gearbox, this will alow me to controll the RPM much better. This project really is a learning curve for me, I figured buying a cheap mill wouldn't make me a better machinist, (trying to) make a mill gives me a greater understanding of things. Thanks for your feedback!

[KustomsbyKent]

Having been down this path before, I'll add my 2 cents worth.
I have tried using an x-y table on a drill press, and it just isn't stiff enough for any serious milling work, particularly in steel.
You will always be struggling with flex due to the column of the drill press that just isn't stiff enough, and will flex.
I have used small mill/drills, and while better than a drill press with x-y table, they still want to flex and move.
Before you stick further money into this setup, consider looking for a small vertical mill... even a well used and sloppy one will still be a much better platform, and will be worth putting money into. Depending on where you are, used mills can be quite easy to find, or not so easy. In South Dakota, they fairly scarce. My big mill came from PA, and was definitely worth the shipping hassle. I recently added a much newer/smaller mill, but paid much more for it, as it was a retired guy selling out. It has been very handy for the work I do on it.

An x-y table on a drill press is really only useful for drilling holes in accurate positions on small workpieces.

[Toolmaker51]

I rarely post addresses to sites/ forums that cut into ours. I'm on a lot of them and none have depth of constructive help you'll get here.
That said, I refer to one often because it'll run tables on my phone while out on the floor.
This link is their "Calculator Menu" https://littlemachineshop.com/mobile/menu.php
While drill sizes can be adhered to, I'd use the Speed/ Feed menu at maybe 50-60% the calculations with your current machine.

[wizard69]

Unless you enjoy the process and experimentation that modifyiing drill presses involves, I'd suggest that modifying this machine will be a waste of time. Like "KustomebyKent" above I've been down this road, in one case because I don't have a mill and needed to get something done. In a nut shell it never works out well and can actually be dangerous if you don't have a draw bar in the spindle. A lot of your issues will start with the basic frame of the machine which as has been noted will flex significantly. There is not good way to rectify that.

Now I'm not saying abandon the DIY route, being a DIY type person my self that is why I'm here. From my perspective you will be far better off designing your own machine and building it from the ground up. Here are some suggestions that you might want to consider:
1. Consider profile rail for linear motion. In a modest home shop they should be easier to do than a cobbled together plain bearing (box or dovetails). Yes it adds expense but it also simplifies what you need tooling wise to get to an end result.
2. To go along with the linear bearings, aluminum tooling plate or ground steel plate can save you a lot of grief for some parts of the machine. Again the assumption here is that your home shop does not have large scale machining capabilities.
3. The vertical column and the base it is bolted to is critical to the machines ultimate machining capabilities. The higher your expectations the more robust these need to be. Expectations are everything here, People buy and use Sherline and Taig tools and are perfectly happy with them (some even CNC them). However most of use expect a bit more, the trick is to figure out how much more you need and to design for it.
4. The need for a stiff vertical column in most cases dictates use of steel tubing in DIY designs. This means it is really handy to have a welder or a friend with one. It might be possible to come up with a weld free design but butting something as simple as a flange on the end of a tube is dramatically easier via welding. On the flip side, understanding where to avoid welding, due to distortion, is also important.
5. One interesting reality is that CNC'ing a small machine can actually make a lot of sense as you can get the machine to operate in a repetitive manner respecting the machines mechanical capability. In other words CNC allows you to use smaller tools and chip loads to achieve a result that does not become tedious if attempted manually. An example might be cutting a slot, if it takes a CNC a half hour and many passes to get to a result, it isn't a problem.
6 Now that you have this "mill" you have enabled yourself to build a better mill. So don't knock this machine you have, just work within its capability to get you do a more robust machine.
7. Machining requires a wide range of spindle speeds. The easier it is to achieve speed changes the better but variable speed motors are not a complete solution. You really need to have a the ability to achieve a significant reduction ratio. This might be in the range of 60 to a 100 to 1 if you are running a 3400 RPM motor. Torque is an issue but some cutting operations simply need lower speeds for the tool or the part to survive. One common example is running a large hole saw or Forstner bit in wood, you need to keep speeds low to prevent heat build up burning the wood or in some cases pulling temper from a cutter. For metals, Stainless is a good example of where you often need spindles speeds well below half used for mild steel to avoid work hardening and the evils there. Sometimes you need the torque too, I'm just trying to point out that a machine can really benefit from a transmission that offers a significant speed reduction in some form. In low end machines that usually means multi reduction belt drives.

I might add that a lot of modern drill presses do not offer the speed reductions that you may need. This is a pet peeve of mine.

Yeah the cut was relatively deep but I wanted to test is the rough way. As for the spindle, I want to replace the entire quill and spindle assembly with a much bigger quill and a standard milling taper, as I said. Besides the spindle I might remake the head just like you see on the cheap milling machines with dovetails and rack and pinion (maybe making a quill somewhat obsolete ?). Thanks for the feedback!

Some other things related to the above;

A quill is extremely useful on a Mill (just look at the common Bridgeport) but it is an implementation headache on a DIY mill. This is again where CNC or motor driven feeds, can be a big win on a DIY mill, a motorized linear axis can in many cases make up for the lack of a quill, Depending upon how deep you go down the rabbit hole you can do linear feeds that are in sync with the spindle. Even if you don't go that deep it is often fairly easy to get a decent feed rate manually setting the speed.

In other words they quill can go away no problem but you really will want a way to feed the Z axis precisely. You don't even need to build this capability in at first, just make the mill so that it is easy to add later.

As for the spindle itself a standard taper implies pretty big bearings and thus a fairly large machine right from the start. I'd suggest looking at just how large an 40 taper spindle is in cartridge form. Even a 30 taper can be large. In all honestly I'd consider a smallish taper until you have a more robust shop. R8 or even an ER spindle would be good enough in a home built machine of this class. The exception would be if you have the equipment or access to equipment, to build up a very robust machine. This quickly can become the difference between a machine that weighs a few hundred pounds assembled and one that weighs several thousand pounds assembled. I can not see a reason to built a 40 taper machine that can't take advantage of the taper to even a limited degree.

I'm not a big fan of dovetails on DIY unless you have the tools to pull it off. As for Rack and pinion I really believe that a lead screw is better even if it might be more complicated to implement. The primary issue with rack and pinion is backlash and how you deal with it. Leadscrews have their issues too but I just see the implementation as being easier.

Before going too far I'd take a look at TAIG Tools and their Micro Mill and then look at all the DIY mills on the internet and try to come up with a size that makes sense to you. Then take the time to figure out how you make a mill of that size as stiff as possible. If you are looking for a bench top machine also figure out how much weight the bench can support. You can do a decent bench top mill but I really doubt it will be much lighter than 300 pounds to get decent results and likely a bit more.

Lastly what ever you build operate it within its capabilities!!!! ANY mill can be operated beyond its capability leading to finish or dimensional failures or in some cases a broken machine.

[Toolmaker51]

I'm thanking Wizard69 for Post *8; an excellent description of general machining parameters and threshold faced by DIY to accomplish it by milling. Terrific!

Taking some liberties now with machine tool engineering, physics, mechanics, with a bit of 'apples and oranges'.........

There's a reason lathes were the first machine tools; and historical samples emphasize hurdles faced developing a mechanically simpler machine. There are complexities in milling completely different than turning. However, one set of elements they share with mills, is two-fold. 1. Spindle rigidity/ distance between bearings and 2. Maintaining that alignment to cutting axis.
Lathes and drill presses direct force along the spindle axis, mills introduce additional loads across it.

Compare resistance offered by mass [width & depth] of a lathe bed (12" machine for example) to it's cross-slide, against column necessary for a mill to do same (say a Bridgeport pattern = 12" X axis).

Next might envision a heavy Monarch or American Pacemaker turning along a cylinder 1/2" deep; few operators attempt facing off very same material and DOC (depth of cut).
Compare that to size mill required to push a decent 1" or 2" endmill same 1/2" deep.

[engineer steve]

Thanks for the helpfull tips and trick, for me it is mainly about the process of creating this thing and trying to get it to work. Small milling machines are relatively cheap so when I feel like I really need a machine, I would buy one for sure. As I said, this really is a hobby project/ experiment and I am learning a lot.