Buying a mini mill

[Robert1998]

Hi again.

I´m setting up the mill and I have realized that is nor totally square. There is a difference of 0,15mm (6 thou) between the red and the blue area (Along the Y axis)



It's a 960£ hobby machine, so I Idon´t know if this is acceptable or not. And do you have any aidea about fix that?

Thank you.

best regards

 

[Lewis_RX8]

Hi again.

I´m setting up the mill and I have realized that is nor totally square. There is a difference of 0,15mm (6 thou) between the red and the blue area.



It's a 960£ hobby machine, so I Idon´t know if this is acceptable or not. And do you have any aidea about fix that?

Thank you.

best regards

Does the top swivel change the angle of the cutter , I have had my mini mill at this angle

Then used a indicator in a circle pattern till there was no difference in each side to know it was perpendicular (Which I believe is the right term )

 

[Robert1998]

Thanks for your answer.

No no, the problem is in the Y axis. My mill is like yours, but with this you can only adjust changes in the X axis. Or this is what I think, I´m new in this things and I dont have to much idea.

 

[striker]

Can you not shim the column at its base to compensate.


Oh, maybe not. It looks like it pivots there.

 

[RobCox]

6 thou out isn't great. You probably can't send it back now as you've taken it apart, but if you did the replacement might be worse.
When I had a mini mill I ended up shimming the column (it wasn't a pivoting type like @Lewis_RX8 shows). You'll have to get creative to make it perform as you want it.

 

[addjunkie]

Strip it down clean it all up,and check again. Shim if required.

 

[Sean64]

Shimming seems to be very common with these size of mills ...

 

[james butler]

Shimming seems to be very common with these size of mills ...

the alternative is to bolt the axis to the table instead and use the miller backwards to machine the casting flat, should be pretty close then
ive had to shim mine too but its pretty bob on now

 

[james butler]

Mill fixed column

I have had my Super X1L mill for many years and it has served me well in that time. I have done a number of improvements to it over the years adding stops, belt drive and power feed. It has only a...

mikesworkshop.weebly.com

 

[nick952]

The area that you measured does not do the guiding and so the 0.16mm here is irrelevant, check again on the face below the dovetail angle and go from there.

 

[Pete.]

Thos mills are notorious for out of square columns. It'll need shimming but you'll need a reference of some kind to set it up. If it was mine I'd remove the column and scrape the base to make it stand up straight.

 

[Robert1998]

Thanks for your answers. I think I could fix a little.

One questión. I have started facing a aluminium cylinder along. The mill has 750watts. I´m using a 4 teeth carbide inserts face mill 50 mm 2 inches aprox



I have calculated RPM = 3,82 x SFM/diameter = 3,82x400/2 = 776 rpm

Chip load per tooth = diameter/200 = 2/200 = 0,01

Feed rate = RPM x number of teeht x chip load = 776 x 4 x 0,01 = 31 inch/min

And using the formula for the HP needed HP = Feed x WOC x DOC x machining factor 0,8 = 31x2xDOCx0,3 DOC = 0,04 inch

But even if I use a deep of cut of 0,03, the mil vibrates so much. Are my calculations wrong?

Thank for all your help

 

[addjunkie]

Little machine, big cutter, flimsy stand. Is the vibration similar when cutting in all directions?

 

[Sean64]

Thanks for your answers. I think I could fix a little.

One questión. I have started facing a aluminium cylinder along. The mill has 750watts. I´m using a 4 teeth carbide inserts face mill 50 mm 2 inches aprox



I have calculated RPM = 3,82 x SFM/diameter = 3,82x400/2 = 776 rpm

Chip load per tooth = diameter/200 = 2/200 = 0,01

Feed rate = RPM x number of teeht x chip load = 776 x 4 x 0,01 = 31 inch/min

And using the formula for the HP needed HP = Feed x WOC x DOC x machining factor 0,8 = 31x2xDOCx0,3 DOC = 0,04 inch

But even if I use a deep of cut of 0,03, the mil vibrates so much. Are my calculations wrong?

Thank for all your help

Probably relatively poor quality spindle bearings . 50 mm face will test the ability of the mill to it's max .

 

[optima21]

I have a hobbymat mill, its different but a similar size

I wouldnt even think about trying a 50mm face mill on it. I have occasionally used a 1" or 1.25" shell end mill on it

but normally I'd just use a flycutter for facing work, its slower but has less loading on the machine the one on the left fits in a 13mm collet and the one on the right fits a 1 morse taper socket

this cutter was ground from a broken 1/8" carbide drill

and this one was an old carbide face mill cutter insert (industrial quality) this was silver soldered to a steel bar and Ive been using that for the last 20+ years

and in use

and when using end mills, I dont normally use ones more than 8mm diameter as the vibrations start under load and the quality of finish goes down quickly. just because the smaller machines can use larger cutters doesnt mean you should, as they dont have much sympathy for the machines. also when you're milling you need to lock the other two slides in position that you're not using, especially the Z axis if you're not doing that as that will increase he vibration .

 

[minimutly]

You could shorten that flycutter by half, would help rigidity.

 

[mrsbruce]

Thanks for your answers. I think I could fix a little.

One questión. I have started facing a aluminium cylinder along. The mill has 750watts. I´m using a 4 teeth carbide inserts face mill 50 mm 2 inches aprox



I have calculated RPM = 3,82 x SFM/diameter = 3,82x400/2 = 776 rpm

Chip load per tooth = diameter/200 = 2/200 = 0,01

Feed rate = RPM x number of teeht x chip load = 776 x 4 x 0,01 = 31 inch/min

And using the formula for the HP needed HP = Feed x WOC x DOC x machining factor 0,8 = 31x2xDOCx0,3 DOC = 0,04 inch

But even if I use a deep of cut of 0,03, the mil vibrates so much. Are my calculations wrong?

Thank for all your help

Don’t know if this is any help, but I have a Warco WM14 milling machine, and use a cheap Chinese cutter like that one quite successfully.

Yes, I do get a bit vibration, but the table it sits on is screwed onto the thin ply walls of my wibbly wobbly tin hut, to keep it stable My answer to vibration and noise, was to place an extremely dense vibration stop mat (20mm thick) under the mill, which killed a lot of the resonance. What is left is of an acceptable degree, and I can easily take over 1mm cuts at a time on aluminium without scaring myself, or the machine too much.

I find it best to creep up on (especially) mild steel with the cutter, taking small passes until I get the feel of how it’s cutting. It can be done though, it just takes a bit longer, and maybe use a dense mat to kill the build up of resonance. Oh, and lock all the axis’s up that you are not using, makes a world of difference.

 

[Robert1998]

Thanks a lot for all your help. I have been reading a lot in the internet Fos example I found a lot of calculations for endmills but not for facing), but your help for a beginner like me is unvaluable.

Yes, addjunkie in both directions

Yes, Fortis, I now is a cheap hobby machine, so, it´s normal no?

Yes, not done it yet only 30 pounds, but I don´t want to expend to much money at the beginning, I prefer to buy better tools when I have more knowledge about them

optima21, I bought this size because the specs said that, I have no idea. One solution could be to make lees deep cuts? Or is better to buy a 1 inch face mill?

I didn´t think about that, mrsbruce What material I could use?


And I have take videos to show you how the sound is

I was using the inserts that comes with the face mill (I think very low quality)

https://youtu.be/XFI6KvEcgc0

I have changed the inserts for other for roughing and the vibration improved (In the sound is hard to notice)

https://youtu.be/SKXJnwQLTxw

So I tried with more DOC

https://youtu.be/o429EcZs_Zw

What do you think, is too much vibration?

 

[mrsbruce]

I can’t remember where I bought the pad, but it was probibly amazon or ebay.

It was an offcut of the pad I bought to go under my leather stamping granite slab, and it was the densest anti vibration rubber pad I could find. There was certainly some weight to it.

 

[optima21]

optima21, I bought this size because the specs said that, I have no idea. One solution could be to make lees deep cuts? Or is better to buy a 1 inch face mill?

I dont think you can get 1" face mills with 4 or more insert cutters, and the 6 toothed cutters I use are HSS so if they go blunt you'll need to be able to sharpen them. you can get get them like this

Dormer Shell End Mills 1-1/4” x 1/2” HSS Metal Cutters (TD21,D3) | eBay

<p>Dormer Shell End Mills 1-1/4” x 1/2” HSS Metal Cutters (TD21,D3)</p>

www.ebay.co.uk

but you'll need an adaptor to hold them

a flycutter is an easier option, as it is a single point cutting tool it is easy enough to sharpen (if you have the correct abrasive) or if you use a cutter with an insert you can replace that. flycutters are cheaply available to try (not sure what taper you use though)

2 MORSE TAPER FLYCUTTER WITH TOOLBIT FOR LATHE MILL | eBay UK

2 MT FLYCUTTER. SUPERB VALUE FLYCUTTER FOR YOUR LATHE OR MILLING MACHINE. TAPPED 3/8 BSW FOR A DRAW BAR- OUR FLYCUTTERS INCLUDE THE SQUARE HSS TOOLSTEEL!

www.ebay.co.uk

depth of cut is relative to the sharpness of the cutter, and cutters need to be sharp, and they need to cut, if the cutters are blunt and the depth of cut is too low, the cutter will rub against the surface which can make the situation worse. What you'll find is that you need to try different things until you find something that works for you and then you'll use that setup next time. Its a learning experience and just use reference tables as a guide. over time you'll get a feel for the machine and what works for you. with flycutting I'll normally use 1600rpm (as I use carbide) and between 0.15 and 0.40mm depth of cut (depending on material and finish) I have no idea of the feed rate but it'll be somewhere between 0.5 and 1.0mm per second. if you look at the larger flycutter tip I posted earlier today the 45 degree angle at the cutting edge reduces the stress on the cuttting edge and gives a better finish than having a vertical cutting edge.