Thread: Poor finish with my finishing tool.

Good luck lather. I will re-grind my tool today and see if I can get a better finish. I might run out of time though as my son finishes school at 1:30 today

Saturday leaving for a 5 day camping trip. Lathe won't fit in the car

Simon

Have a Bo-peep here. I wrote a lot of info about this very same thing not all that long ago.
https://www.woodworkforums.com/search...archid=7430941

Read all the posts and replies that I wrote and you will find all the info that you need. Rather than me re-posting the info, it will be faster if you simply look around these earlier postings. There is heaps of info. Search under the name of "Kody".

Kody

Lather and Simon,

I will put up pics tonight on this thread of a tool my uncle came round and fixed for me yesterday. I had attempted it using all the info I could get from the web and he took one look at it and said it wouldnt cut steel. He ground on WAAAAAY more back and side rake than I had been using, and now it cuts like a dream.

Lather your definately not the only one struggling with HSS...I think its one part of this sport which you really need to be shown in person. If you cant get something to work i'll send you this tool so you can try to copy it. he reccomended using half inch square HSS for tools. It takes longer to grind up, but its stronger, can hang out of the toolpost further and is easier to grind as you can see more and measure angles easier.

Re the shear tool - i had a quick play with it but had no luck. The edge would burn out pretty well instantly. Will try it again another time with less cutting depth (achievable now I have a DRO) and flood coolant.

To try and eliminate a lot of the brain strain,read the books as they are a theoretical guide,and then bring your own judgements into play.If you were to try and emulate what the books are telling you,you will be chaseing your ar s.

Originally Posted by Kody

Have a Bo-peep here. I wrote a lot of info about this very same thing not all that long ago.
https://www.woodworkforums.com/search...archid=7430941

Kody

Kody, on my browser your search link returns

Sorry - no matches. Please try some different terms.

OK,

Here are a few pics of the cutting tool I referred to above, and some photos of it in action.

The first few are of the tool from several angles. The once called "right side" which strangely enough is a photo of the right side of the tool shows how much side and back rake is on the tool. If your clever with maths you could probably figure out the side rake angle knowing the dimensions of the tool (1/2 inc square) and estimating how much has been ground away at the back (looks like nearly half to me)

The others are of the tool in action. I havent done any honing on this tool...its straight off the grinder. The photo called "redbar" is a close up of the finish I got when I first used the tool on some mild steel I have (that is painted red). This was a feed of .056 per revolution and a cut of .1mm. The black spots and smears are grease from my fingers, the finish on the right of the bar is more indicative of what it was all like til i put my grubby mits on it.

The other shots are of me cutting a piece of black bar that I have had for years which is hands down the worst material I have ever had to cut, so the finish isnt as good as I got with the redbar, still...with a bit of honing and playing around I can probably get it to improve.

The one called 'roughing' is a 1mm DOC for 2mm off the diameter. The tool slices this off, and I am sure it could easily take a cut two or three times this deep.
The one called 'finish' was when I used a feed of .056 and a cut of about .10mm
The one called 'fine feed' shows the finish after a feed of .087 and a cut of .25mm, this is the best finish I got however there are still a couple of lines here and there...i'll keep working on it.

Whilst I have sung the praises of Carbide in other threads, I should point out that im a huge fan of HSS. In addition to its cost and versatility it has some massive benefits over carbide that really make it worthwhile. Namely, the swarf comes off cool so you dont need to worry about burns when you are wearing safety thongs. Also, the slicing action doesnt deflect stock as much as using carbide does, so its great on slender pieces. Thirdly you can take much smaller cuts with it whilst maintaining a good finish... which really helps when creeping up on a diameter.

I do away with the back rake, this way as the tool gets sharpened the height doesn't change. I also cut those cylinder squares dry, like most all of my turning.

Dave

Can you stick up a photo of such a tool Dave?

historically I havent used coolant much, except for boring, and if I do its out of a spray bottle. Now my new lathe has a pump and nozzle i'll probably start using it a bit more.

Is that coolant at the right mix,it looks a bit weak?

Your 1/2" tool geometry looks OK to me , but you need more of a radius on the tip . 2mm radius is ideal . When setting up for cutting , rotate the top slide around until the radius of the tip on the tool is just kissing the workpiece . In other words, dont have the tool shank at 90 degrees to the work , but move it around so the tip radius is on the work piece . . Use a slow feed and experiment with spindle speeds . make sure the tool is at centre height MIKE

I am going down the shed soon so I will grab a photo. I never really looked at it, but the coolant does look a bit watery to me as well, now that Pipeclay mentions it.

Dave

Originally Posted by morrisman

Your 1/2" tool geometry looks OK to me , but you need more of a radius on the tip . 2mm radius is ideal . When setting up for cutting , rotate the top slide around until the radius of the tip on the tool is just kissing the workpiece . In other words, dont have the tool shank at 90 degrees to the work , but move it around so the tip radius is on the work piece . . Use a slow feed and experiment with spindle speeds . make sure the tool is at centre height MIKE

Can you explain what you mean,from my understanding a radious is the same were ever it touches the OD.

this crap drawing may help you MIKE

I think he means side clearance (that's what I call it - could be wrong). See pic. Reducing this angle can certainly improve finish.