Setting up a Mini Mill & Stuart 10V Machining

I'm afraid I regularly climb mill on my old X2...

Only experience and a few failures will teach you when you can and when you can't with a given machine.

Neil

It might well be the cutters. I'll try it again when the new ones arrive. Unfortunately I decided to make a start on all this with the few cutters I had from experimenting with the vertical slide on the ML7, and delivery of new ones is obviously a bit hit and miss at present.

The first post in this thread explained what you did to set up this mill, including removing leadscrews. Nowhere does it say anything about measuring and minimising backlash. A lot of the machines supplied for hobbyists on a limited budget can benefit from checking the fit of the leadscrews in their support brackets where there may be some gaps that would benefit from shims being added. Also most leadscrew nuts have some form of adjustment. It is possible to work with backlash using a dro but sometimes climb milling may be required and low backlash will help. You will not get zero backlash without tightening everything to the point where you can't turn the hand wheels with sensible effort or wearing parts too fast.

Martin C

... 'the backlash in the lead screws is terrible even after adjustment.'..

I think you've answered your own question...

George.

0.5mm in what looks like 6-8mm thick "tool steel" is probably pushing it for the SX2, try half of that (but should be OK in mild steel )all non moving axis and quill locked and use the top of the cutters flutes not the bottom end to reduce overhang as much as possible

You have only mentioned adjusting the gibs, have you adjusted the split nuts that the leadscrews run in?

Edited By JasonB on 11/05/2020 19:22:26

Martin, Jason,

I adjusted the split nuts back in September when I first got it. I suppose I could try again, but the difference between smooth and sticking was a pretty marginal tolerance (much like the gibs). To be honest there’s only so much adjusting I can take; after a while it seems like I’m back where I started. Either way, would backlash cause an issue for conventional milling? After all I’m pushing the cutter with the lead screw flanks at a fair rate, and it’s not trying to move Itself away from contact by rotation.I do lock the axes I’m not using when machining.

Should not affect traditional cuts much.

What slideway lubricant are you using?

Have a look at these 3 videos I did to go with the beginners series, although it is the SX2.7 it should give you an idea of the type of cuts these machines can take and types of feed rate. EN3 mild steel and a fairrly cheap HSS 10mm 4 flute cutter

Thanks Jason, very helpful. Could well be depth of cut. Maybe I underestimated the tool steel.

I’m using “Slidex” - I got it from a local supplier years ago. Same place gave me some “Hydex” for the ML7 drip Oilers. Both seem to work fine. It’s a shame the mill doesn’t have oil nipples like the Myford. Guess I could add some at some point.

This morning just as a quick test I put up a piece of 8mm gauge plate on my SX2P and tried a 0.5 mm deep edge cut using a 10 mm 3 flute HSS TIAIN cutter from the ARC premium range.

No issues at all the mill sounded and felt fine which is something I always go by. I went with 1250 rpm and a steady not too fast feed. I tried it at slower speeds but it was best at 1250. A picture below of the finish which I can't detect with my finger nail so good enough I think.

p. s. I forgot to say going by the hanwheels my machine has 0.2 mm backlash which never gives me any problems and with the DRO, s I am lazy and tend to ignore it. Also I sometimes climb mill for a better finish but nothing too heavy. I guess I really should try to reduce the backlash before it catches me out. 

Edited By Ron Laden on 12/05/2020 05:58:51

Edited By Ron Laden on 12/05/2020 05:59:52

Thanks Ron. Looks good. I'll do some further tests when I get my new end mills. They've not arrived yet.

Yes thanks for posting that Ron, goes to show that the Premium cutters are worth that bit extra both in the finish they give and the ability to remove a bit more metal on each pass without the mill complaining. When I did those videos I deliberately used a budget cutter as that is what a lot of new people to the hobby tend to buy.

So the small fly cutter holder arrived today. I put my Sandvik 8mm left hand tool holder in it, fitted with a DCMT 070208 insert for steel, and had a go at fly cutting for the first time. Must say I was really happy with the results, finally a bit of progress. Workpiece was the same mild steel I've been using for the vice clamps. I went up to 0.5 mm cut depth with no issues.





The only slight problem was vibration due to the tool holder being long. I ground it down a bit and that resolved that. The grub screws in the holder appear to be made of cheese, so having got the tool well and truly stuck, I spent a good 30 minutes drilling them out and replacing with caphead screws, which was fun.

Missed the postman due to work, so the milling cutter test will have to wait, but in the meantime, for the 10V castings, what do folks recommend for facing: milling or fly cutting? I did get some DCMT070208 inserts for iron too.

Thanks.

I usually use a multi tooth cutter to surface cast iron bit the insert won't know that it's on its own so why not give that a try, at least if there are ant hard spots you won't blunt your HSS cutters when they arrive

So I got the new end mills from ARC today. Again, face milling is fine, but there's no way side milling is right. even a 0.1mm cut in 15mm thick steel is hopeless - noise, vibration, terrible surface finish. I tried it again with a Sandvik cutter, and it's the same. I'm wondering if it's the material I'm trying to cut. Pretty sure it's mild steel - I've made 4 vice clamps now, with no real issues with fly cutting, face milling or drilling. As soon as I switch to side milling, there's just no way it's having it. All axes are locked apart from, in this case, y. Tried changind speeds and feed rates, to no avail.

Thanks.

You need to have the quill locked and the spindle bearings properly adjusted to make these type of cuts. The head should be as low as possible with minimal quill extension.

Martin C

Thanks Martin, but there is no quill extension to lock on the SX2P. As I said, the head (z-axis) was locked, as was the x-axis.

I was using an ER25/R8 collet chuck, with the cutter inserted as far as possible. The workpiece was in a vice, so head height was also minimised.

Spindle bearings? No idea. There is no discernable play in the spindle, but I think there could be an issue with them judging by the noises now coming from that area. Something tells me it's not that though. It's not rough, but I think rather some plastic part is rubbing somewhere.

I can't find any strip-down guides to the SX2P, but I'm sure it's not rocket science. Since it's only been used a few times, I've contacted ARC, so we'll see what they say.

Just out of interest clock the taper on the inside of the spindle, my SX2P has 0.01mm runout and its done a lot more work than yours. You should be seeing similar or even better, though I suspect 0.01mm is pretty darn good for a small hobby mill and probably wouldnt get any better.

Ron

Ron,

This is the maximum runout on the inside taper of the ER25 collet holder (not the spindle):



Call it 0.02mm?

Again, I tried side milling. This is the setup - everything tapped down and tightened:





Again, the result of a 0.1mm cut is akin to a very loud tuning fork. The vibration/chatter results in a swirly pattern on the workpiece (not too obvious here TBH):



This sample was marked "unhardened tool steel", and was fine for face milling, drilling, fly cutting etc.

Anything deeper than 0.1mm is unbearable - at least for anyone with a shred of mechanical sympathy.

Anything less than 0.1mm and I might as well use sandaper.

I'm wondering now if I've somehow changed the resonant frequency of the column by shimming it. To be fair, the shims are pretty narrow, and some are just in the corners. The deflection under hand load doesn't seem excessive compared with what other folks have said though. Then again I'm running out of ideas.

As I said earlier lower the tool so you are cutting towards the top of the flutes as that will help,

What diameter is that cutter?

Try some mild steel as that tool steel could be part of the problem.

What is the runout of the tool close to the collet?

I very much doubt the problem is anything to do with resonance. Chatter is all to do with the cutting process, not the resonant frequencies of the machine tool. Chatter does not imply resonance of the tool or workpiece, but unstable cutting conditions.

I'd agree with JasonB. The cutter looks blunt to me. A shallow cut with conventional milling on unknown material with a blunt cutter will almost certainly lead to rubbing and then cutting, and back to rubbing. A slow feedrate will make matters worse.

Andrew