How to get a better Finish

I've machined fully hardened silver steel (Rc > 65) using ordinary carbide inserts and CBN inserts. In both cases I ran pretty fast and the swarf was coming off dull red. I assume that the shear zone was red hot and therefore the cutting took place with softened metal. As far as I could tell the hardness of the parent metal wasn't affected.

Although I haven't turned HSS I do mill it when I'm too idle to faff about removing large amounts with the grinder. I use ordinary carbide endmills and again run at speeds and feeds that gets the swarf dull red. It doesn't do the endmill much good but the finish is pretty good.

Andrew

Hi

Poor finish can also be caused by a out of balance pulley or a drive belt that is vibrating .

A test for vibrations is to rest the tip of a DTI on the lathe and watch for the tiny wobble of the DTI needle . You can also rest your hand on the lathe and feel for the vibrations at different speeds . Or use a bowl of water and look at the waves / ripples . Mike

I have give up for now I'm not enjoying this lathe thing at all I need another hobby I think. All I'm doing is filling up the scrap bin.

Take a break and come back to it fresh.

Dave, like all craft work, you have to learn how to do it step by step. First step would be to get yourself a good book or two on using the small lathe. Someone already mentioned Harold Hall's book "Lathework A Complete Course," which is very good. So is LH Sparey's "The Amateur's Lathe".

I have found that toolbits ground the way they are for larger industrial lathes do not work so well in these smaller model engineers lathes. Both Sparey and Hall show very simply how to grind sharp HSS "knife" tools that will give you a nice finish on mild steel, as well as recommendations for speed and feed for different diameter work.

Without a starting point like one of these books, you really are groping around in the dark clutching at straws held out on net forums and the by the fellows at work.

Edited By Hopper on 07/09/2015 06:40:52

Make sure your gib strips are well adjusted (tightened up). Any slop or backlash will make it difficult to get a decent finish.

Where are you? Perhaps a local ME could offer practical help?

What works for Me is: join every Machinist forum, grab a cuppa of what suits Your fancy and dig in. The content will be varied so once in a while something will be discussed that is immediately relevant. Other times it goes in the mental "library" for later use. It all will click sooner or later. I have 10 years of experience along with life lessons, and the depth of knowledge out there is astounding. This is not "school", almost of the tests are self administered with oral answers permitted as long as We cannot hear it over here.

What other machinist forums do you visit.

Hang in there Dave.

I'm also a beginner and have the same issues but am getting better.

I was moaning to a friend about it, and he reminded me that he'd done years of 5.5 days a week as an apprentice and I shouldn't expect to to be an expert after a few hours work.

I get a lot more pleasure from good work because it's not easy.

I stripped the whole thing down cross slide the carriage every thing then re built it all everything is tight. Its rock solid now. I have projects I want to get on with. Ill have another go at the weekend.

Hello

I was really intrigued by Dave running his lathe at 3000 rpm. That boggles my mind. Mine can only reach 1260 and my milling machine just over 2000 and I've never been over 600 rpm on either, and at the higher range only with small work and/or a small tool on mild steel.

I still consider myself a relative beginner as I've only had the lathe about 10 years and the 'mill' about six, but am I being very timid? I also would rarely take a cut deeper than a fifth of a millimeter on steel. I don't however, have, for my purposes, a problem with finish using a sharp tool and, on the lathe, automatic feed - not 'mirror' but smooth and even.

By the way, Andy with the stalling Warco (another would be 2000 rpm runner!) was disappointed with his after sales service from this company. So was I with my mill. Great when I was buying it, but very disappointing when I thought I needed a new belt for the gearbox. 'Can't help - go to your belt shop (not so simple when you're in rural France) and anyway, we don't sell those machines anymore; they're obsolete'. Not what you want to hear, about what was then a three-year-old 'mill'.

Martyn

Maintaining a stock of spares for a large range of hobby machines is one of the biggest costs for the companies supplying the hobby market, and this overhead is one reason why the bigger companies have to charge a bit more.

If customers want them to stock a full range of all the extra consumables, like belts, when they can't compete with specialist suppliers who shift vastly more of them on price, then the cost of the machines would have to increase further.

Don't be afraid to take decent cuts with a small lathe - I go up to 2mm on my mini-lathe in steel.

Neil

Yep, 'fraid so! My lathe will run to 2500rpm, although I rarely use top speed due to noise (geared head). Normal turning speeds on low carbon steel up to 2" diameter are 800-1200rpm. For roughing I might use a deep of cut of 0.1" and turn the feedrate up to 8-10thou/rev. Of course I have an industrial size lathe, but 0.2mm DOC seems very small for most lathes?

My manual mill will go to 3750rpm, but I rarely run above 2500rpm, as the varispeed head is a bit shake, rattle and roll. However, I rarely go below 500rpm (bottom of high range). I only switch to low range for boring heads, large (>20mm) HSS drills and when using the coaxial indicator.

The CNC mill will run to 5000rpm, and is pretty quiet at full speed, so it regularly gets run at full speed. For instance the other night I was machining some small oil pockets in steel with a 3 flute 3mm carbide cutter. I ran the mill at 5000rpm; no point in pussy footing around!

Andrew

Home Machinist

Home Shop Machinist

Practical Machinist

Home Model Engine Machinist

MadModder

Model Engine Maker

MetalWork Forum

Home Workshop

Hobby Machinist

Metal Working Fun

Machinist Web.

On second thought, You might want to move the pot closer as You might want a 2nd or 3rd cup.

I had another go this week end. I spent some time with one of the machinists at work on the Hardinge tool makers lathe watching him machine a piece of 1 inch round steel. He demonstrated how different speeds and feeds make a difference.

I had better luck this time I used a HSS tool he ground for me. My lathe digital read out is not working so I don't know exact speed but it was a lot slower than last time I tried. I got a reasonably good finish. I switched to carbide and upped the speed a tad. I think I'm getting some were now. The work pieces are looking a lot better.

I bought some stainless 303 and some bright steel EN1A rounds to play with over the week end from M Machine.

A total disaster no matter what speed and feed carbide HSS it makes no difference the finish is terrible. I give up I'm going to get the guys at work to machine the project for me. Enough is enough its just a waste of my time.

I'd be bribing one of your workplace machinists with a bottle of hooch to come round and find the problem or you own a shed ornament.....

29/08/2015 How do I get a better Finish

19/09/2015 I give up

It takes YEARS to get any good at the intricacies of metalwork

That's why it's called "skilled labour"

I bought some stainless 303 and some bright steel EN1A rounds to play with over the week end from M Machine.

Get odds and sods from scrapyards, a tenner will buy you a hundredweight to turn into swarf

Then practice practice practice

practice practice practice practice practice practice

It's a tough road unless you are a natural

I think I'm getting some were now. The work pieces are looking a lot better.

The first couple of years are the hardest, the victories are small.

You do have a head start if you can visit a decent machine shop whenever you like

Perhaps the best thing you can do is join your local ME society

Edited By Ady1 on 20/09/2015 11:53:22

The biggest improvement on the finish of a job for me was once I started using the tailstock to support the work

A decent live centre in the tailstock was a huge help, it can never make a job worse, only better. (For best results use a dead centre)

Now I use it all the time

Edited By Ady1 on 20/09/2015 12:04:15

I'm beginning to think its more to do with the way the lathe is set up than the actual tools etc. I noticed that the tool post was moving slightly when looking down on it. I had a good tug on the cross slide and saddle etc. Thee is a lot of play/slogger. I took the carriage off and reset everything then put it back together it took a few attempts to get it some were near. I adjusted the cross slide and started again. Using a honed HSS cutter things are looking better. The cross slide still needs some attention and I'm struggling to get rid of back lash. But we will see what happens.

We don't have these problems with the Hardinge lathe at work it just works. LOL. These Chinese lathes take some fettling.