Buna Ziua, and welcome to the Forum, Andrei.

I have to admire your ambition to want to build a mill from scratch – but I fear it is not an easy job. You will definitely need a much more rigid arrangement than most pillar drills can provide.

I have sent you a private email – look at the envelope in the green line at the top of the page when you are logged in.

Could you tell us what type of work you intend to do, and this dictates the type of machine you need?

Regards, An

Buna Ziua,

Your setup is not rigid enough for milling steel. But if you use a smaller end mill the cutting forces will be less. This will give better results. Take your time because smaller end mills are brittal.

For a 3 mm HSS end mill in mild steel you can run 3400 RPM. Make sure you make (thin) chips. If you make "dust" you are feeding to slow and this will quickly dull your end mill. If you feed to fast, you make thicker chips but also risk breaking the end mill.

There is no need to start learning milling using expensive end mills. When you no longer break end mills, it is time to move up to a better and more expensive end mill.

Before you go too much further, work out what RPM will be required for the materials / tools you want to use (from published cutting speed information) – High RPM may be more of a curse than a blessing.

For example, if you want to cut steel with a 6mm diameter tool, the maximum spindle speed is ~3000 RPM for HSS and ~8000RPM for carbide. I think that both of these are below the minimum RPM for the first type of spindle.

First off, I would say "just buy a mill". If you ignore that, then I would steer you towards the second type of spindle for a mill.

I built a router type machine (CNC) with a cheap, air-cooled spindle motor, and it was nowhere near rigid enough.  After some re-engineering, it will cut aluminium (fairly happily) and steel (not so happy). It is still not very rigid and I'm in the process of making a new spindle along the lines of your second option.

Cutting test for material removal (it runs a bit happier with lighter cuts):

Good luck

Edited By Andy_G on 11/02/2023 10:01:23

Ady1 mirrors my thoughts perfectly.

I will add that building a conventional milling machine from scratch is substantially more expensive than buying one of an equivalent level of rigidity.

I've helped two friends build custom CNC mills, and even discounting the electrical and control element it's a big undertaking.

For my sins I'm working up the plans for a Horizontal Boring Mill at the moment and even the steel for the frame to hold the (repurposed) bedways comes to more than a second hand bridgeport.

If you are serious then another 'food for thought' item are these pictures & descriptions of the of the origins of the BCA jig-borer; built like the Boley & Leinen with a plain compound table it doesn't get much simpler than this.

Lathes.co.uk – BCA Jig-Borer

Everybody does I think! A pillar drill looks so much like a milling machine that one feels it ought to work after a fashion, even if only light cuts are possible.

The problem is that drills only have to deal with up/down forces, and consequently most of them resist side pressures poorly. Even big chunky pillar drills bend, vibrate, and lose their chucks. Horrible.

The only good news is that vertical milling machines have no trouble with drills. Apart from the cost, milling machines are wonderful!

Dave

Edited By SillyOldDuffer on 11/02/2023 15:51:02

Anything is possible right, and starting with a pretty over-built drill would obviously help… But it may not be easy or cost effective to get the performance desired.

If there's an MT spindle nose and the spindle is bored through (or can be) to accommodate a draw-bar then that gets over one of the two big issues.

You could probably even turn down and bore out a solid spindle with an external screwed or JT nose to fit an internal MT2/3 ISO20/30, or ER32 taper, provided it has enough "meat" to it.

There's also the consideration of how rigid the bearings are with respect to side-loading, most cheaper drills will use one thrust bearing at the bottom and one or more deep groove bearings further up, that will result in deflection during side loading and quickly destroy the bearings.

High-end drills sometimes use angular contact ball bearings instead which may be able to cope with milling forces depending on their arrangement in the spindle and pre-load forces.

Depending on the existing bearing seat sizes and how they're pre-loaded one could fit angular contact or taper roller bearings to improve a spindle for milling.

That leaves five issues left to to overcome:

• Rigidity of the body/table itself,
• The rigidity of the quill within the body,
• Precise z-axis adjustment,
• Secure locking of the quill to prevent z-axis creep, and
• Rigidity of mounting the x-y sub-table to the main drill table.

All solvable (for a given level of solved), but some more easily than others.

Edited By Jelly on 11/02/2023 16:47:12

Edited By Jelly on 11/02/2023 16:51:45

The Fobco is built very solidly, out of substantial castings, and uses a very rigid spindle design, which includes a pair of angular contact bearings preloaded against each other, which is not unlike the arrangements used in many modern "hobby" milling machines.

Compared to a more modern drill press, that definitely qualifies as being over-built (as in the design and materials of construction significantly exceed the minimum required to do an acceptable job).

My experience using Fobco drills is also that the fit and finish of the quill and the bore it slides in is also unusually high by modern standards, as is the inclusion of a quill lock of the highly rigid split casting type.

As such it is actually uniquely suitable to be re-engineered as a lightweight milling machine, in a way that very few drill presses actually are.

My big drill press is an early '90s Sealey with an MT3 spindle, and is far more capable as a drill than a Fobco star is, as well as seeming like a far more substantial machine…

But in reality it's internals have been heavily value-engineered to give maximum drilling for minimum money, so it would rapidly shake itself to bits if used for milling.

OP needs to be aware that not all drills are made equal, and if he wants to go down that route he needs to examine parts diagrams or sectional drawings to understand if the construction of the spindle is suited to conversion to milling.

Edited By Jelly on 11/02/2023 20:13:03

If you can make a good strong accurate drill then you can do 80% of a lot of milling jobs, it's a lot cheaper on the tooling too, and faster, the drill swarf can really pile up compared to a light milling cutter because you can do up to 12mm and work it hard

Then swap tooling and finish with light accurate cuts with the 5-6mm milling tool

I suppose that's a good way to test an unknown drilling machine, stick a sharp 12mm drill into the chuck and see how it does with drilling through a 20mm mild steel block. If it's a doddle then you only need to add an X-Y table to give yourself a light milling machine

One on the bay at the moment that would get me excited if I was in the market

Edited By Ady1 on 11/02/2023 23:49:00

I should add one caveat, you MUST use a collet to hold a milling cutter, a drill chuck simply won't hack it, the side forces mean your cutter will eventually wander into or out of the chuck jaws and mess the job up

Vic. That looks like a very nice Fobco Sar drilling machine. I imagine that one has the 2MT tapered quill.

Very sort after now. There was one on sale on Home Workshop for £80 "a bargain" but I dont think it had the 2mt quill. Was almost tempted but with 2 mills I do not need a drillpress.

regards