Questions on turning

[jroma1]

I have had my H.F. 9 x 20 lathe for about two months now and in the past three days I finally got to do some practice turning. I am not really satisfied with the outcome because it seems to me I should be getting better results. Maybe I'm expecting too much,perhaps someone can comment or make suggestions.

There are four photos attached,they will show a piece of CRS steel (1018) 3/4" in diameter that was turned down in four passes. The 1st two passes were with the spindle turning at 400 RPM at a depth of .010". The third at 400RPM with a cutting depth of .005". The fourth and last was cut at 1000 RPM,depth was .002".

Included in the photos is the tool bit that cut all four passes. As far as I know this is a Hi Speed bit,I'm not to sure it's ground right for the job. The top rake for example is in question,also you might be able to detect the fact that I tried to hone down the nose with an oil stone. Another problem is that I can not seem to put the cutter on center,I'm using the tool post that came with the lathe. I am using 1/4" cutters and I have to use another 1/4" cutter as a shim to bring it closer to center. Looking at the end view you can see the little dimple

Any feedback greatly appreciated,Thanks

John

[Mike Stevenson]

jroma1,

That tool bit you are using is definitely the problem. You would be much better off with Carbide tipped bit that is professionally ground (see pic.) Ideally you should use a Carbide Insert tool that lets you easily change the cutting edge without regrinding. This way you are sure the cutting geometry is correct. This is especially useful when profiling angles and radii.

[cam1]

Hi: For what you are doing, the nose radius on the tool is pretty big, try sharpening the tool similar to the photo that Mike submitted. A small hand honed nose radius is all that's required (just to get rid of the sharp edge). You can certainly increase the depth of cut, as you are really just rubbing the cutter with a .002 finish cut.The roughing cuts do not need to look pretty. Try leaving 0.010 for the finish cut, and run it at 600-800 rpm
@ .005 inches/rev with some cutting fluid. You will achieve a better surface finish. It's a very useful skill to be able to sharpen tools, and the Machinery handbook has a pretty good chapter on cutter geometry.

regards

[acondit]

John,

The tool is important but I didn't begin to get good finishes from my 9x20 until I got the spindle bearings adjusted properly. I know you were trying to get the spindle pulley off, did you work on the bearing preload while you had it apart?

Alan

[captainlee]

John, Hi Cap. here
To add to the others I tend to change the angle of the cutting tool on the finish cut so the blade is more parelle to the part this gives more tool more side surface and really does a nice job. also sometimes I just get lazy and use the old file to help out rought finishes that were once rought and are now smooooth with a little emery cloth/wd40 to boot.
I just a newbe but thats what I do LOL Cap.

[Claven2]

That's awful too geometry. Eitehr buy commercially ground bits or consider reading the tool grinding FAQ at mini-lathe.com

[handlewanker]

Hi, here's a method I use to get MIRROR Chrome plated type finishes on bright mild steel, not really the best material to do turning with.

Now this is going to get SOME people up in arms and ranting at great length.

I'll say this once and once only, carbide has no usefull place in the small lathe and indexable tips or throw away tips are a complete waste of money.

Here is a method that if you try once you'll do it again.

1- Prepare a tool, using HSS, like a grooving tool or short parting off tool, with a width about 3mm (1/8").
2- Carefully make sure that the face of the tool is exactly on centre and parrallel to the work.
3- Set the lathe speed at 50, yes fifty RPM, or at the lowest speed you've got.
4- Start lathe and touch tool to the job to just scratch the surface and at that setting wind carriage away from the job, increase depth of cut to .1mm (about .005"), start feed at about .25mm (.010") per rev and using coolant let the cut proceed along the job.
5- The cuttings will come off in a thin curly strip like alluminium foil and very shiny.

This is a method I use when I want to have a finish that you can see your face in and with NO tool marks present at all.

I would reserve this method for FINISHING the work, having left about .1 mm (.005") for a finishing cut, having made sure that the previousn roughing cut wasn't too rough or it won't clean up.

On the subject of carbide, this is a material mainly used for production turning when tool wear is a problem for repetive turning, and requires a technique not available to the beginner or inexperienced to utilise fully.

In the hands of an experienced turner, carbide can be made to "sing" under any conditions, but it requires skill, like a surgeon with a scalpel.

You cannot ignore the requirement to sharpen lathe tools just because they appear to have confusing parameters and varied uses, and the learning curve is exponential when you get the hang of it.

I would also recommend strongly using a quick change type of tool post and once you've used one you won't go back, EVER.

If anyone would like a design for a QCTP that can be made quite easilily with not too much high tech methods, I'll post a few photos and maybe a drawing.

The one I made has eight tool holders and allows the user to remove and replace the tools without losing position and exactly on centre etc, good for a bit of repetitive turning on a centre lathe.

Here's a photo of the QCTP on a lathe I built many years ago and which I still use for a variety of jobs.
Ian.

[Jaime128]

I want to see how and what materials you used to make your own quick release tool post.

Also, what other piece of anything can I use to check that the chuck and tailstock are aligned. I only have the tail stock dead center? Still trying to get creative here...maybe I can use a nail or something...I saw pictures of the razor between them, but can't find them now...aahhh...it's not the same reading about something and having the actual machine to do it...now I have the machine, but can't find the info...hehe
Thanks...

[handlewanker]

Hi, the materials for the tool post are mild steel which I then had case hardened.

I also made the tool holders from mild steel and have not case hardened them yet, just haven't got around to it.

If you want to check the alignment of the tailstock to the chuck you will need either a test bar or a dial indicator.

A test bar is a piece of steel bar about 1" diam for a 10" swing lathe, or 3/4" for a 7" swing etc, with a good finish that has centres in each end true to the outside diam of the bar.

Just place the bar between centres and check the side of the bar by running a dial indicator along it.

Any misallignment will show up as the dial indicator moves along the bar.

Adjust the tailstock base to body setting to correct it.

How much mechanical knowledge do you have? If very little you need someone to give hands on tuition as it's hard if not impossible to learn from just a few hints.
Ian.

[Jaime128]

I'm good with the mechanical stuff. I bought both a digital and analog dial. I got the analog dial on special from littlemachineshop so I use that base for both and it worked out fine. I read someone saying that one of the analog advantages was that they didn't need a battery, so I got that as a backup which is fine. I still needed a base for the digital dial which I like using most of the time so this worked out great. I checked and HF sells the same exact base holder. I was hoping they had something with less knobs on it. I thought the HF digital indicator was going to be crap, but it's pretty decent. I like it because it also has both imperial and metric measurements just like the caliper I got from them too. I just have to find something true to turn now, so thanks, you did give me another idea on doing this. I am getting a workout with the dial. Everything I have put on the mill or lathe needed that dial. I still need to get a nice vice, but the clamps and dial will have to do for now. Things are adding up too quickly for me.

[handlewanker]

Hi, how's your knowledge of turning and milling? Do you do this as a job or just as a hobby?
Ian.