hopefully not the deepest
314 forum posts
I've finally got some cutting done on my new lathe. I decided to make some 10mm filing buttons for the baseplate of the simple oscillating engine I'm attempting to make. I thought they would be a good beginner exercise and didn't need to be too accurate.
The first facing cut left a tiny pip, so obviously I hadn't set the tool height as well as I thought I had. A little extra packing solved this. Then I tried a turning cut. Started with very light cuts (5 thou/0.125mm). Seemed to go reasonably although I had no idea what speed the lathe was running at. I set the speed control at about 9 o'clock hoping this was about 500 rpm but no way of checking at present. I know experienced users can tell from the sound or feel of the cut but I'm not there yet. Anyway, after a few cuts and confidence increased I upped the cut to 10 thou/0.25mm. The finish wasn't brilliant but it's not bad for my first attempt. I then drilled them to 4mm and, not being brave enough to try the parting tool yet, hacksawed them off. I then reversed them in the chuck and faced the other side.
I have a couple of questions for anyone.
I bought a set of carbide tipped tools that are typically sold as accessories for mini lathes. I didn't feel confident grinding my own from HSS blanks but having read more now I think I might get some and have a go. Identification of the individual tools was fairly straightforward for most of the tools (boring bars, parting tool etc.) but I ended up with two that looked very similar. They have DIN numbers on the side but I couldn't find a reference as to what the difference was between them. The numbers are 4977 and 4978. I chose to use 4978 but would like to know if this was correct.
Also, are these tools supplied ready to use or do they need final honing like a chisel would?
Thanks for any replies.
Edited By Gary Marland on 03/06/2012 10:33:50
314 forum posts
Why does this forum software seem to strip out all my carriage returns?
4129 forum posts
Get hss and Carbide tools, a hss grinding wheel and a green grit carbide one
Only experimenting will teach you to use what and when, the speeds to use etc
It's a suck-it-and-see sport
I found that stiffness was more important than power once I got going and to this end a running centre for the tailstock was hugely useful for cuts that were even a small distance from the chuck
|Steve Garnett||03/06/2012 11:14:55|
|837 forum posts|
Whilst in general it's true that tail-supported work is less likely to flex, and you'll get more accurate cuts, the extent to which this is true with anything within an inch or so of a chuck is debatable. I'd say that stiffness with small projections depends more upon the overall state of the chuck jaws, and very importantly how much of your stock that they are gripping. And, of course, the diameter of what you are turning.
So if I want to take ten thou off an half an inch of steel sticking out an inch from the chuck, I wouldn't support it if it was gripped by most of the jaw depth. But under identical gripping circumstances, if I wanted to take a couple of thou off a 1/8" diameter projection, then I would if I could.
So yes it's a suck-it-and-see sport, but only up to a point. I'd say that it's as much to do with applying a bit of common sense to the materials you are using, as anything. And yes, inevitably you learn that the painful way...
19516 forum posts
GAry your tools don't need anything doing to them before use.
I'd try HSS first before thinking of brazed carbide, you will find it easier to frind as you learn the shapes.
Probably best to put a photo of the tools onto here then we can have a stab at what you have got.
5691 forum posts
Some of these tool sets are a bit like supermarkets trying to sell you more sliced ham or whatever than you really wanted. Since you only really need half a dozen different shapes they have to invent a few unnecessary ones to bulk up the 'bargain 12 tools for the price of 6'.
314 forum posts
Thanks for the replies folks.
Ady: I'm beginning to see what you mean about it being a 'suck-it-and-see sport'. By nature I'm the exact opposite. I tend to read a lot before doing anything and like to know I'm doing the right thing before doing it. Leads to slow progress though.
Jason: I hoped that was the case as I would be more likely to make a mess of them at the moment. They are Axminster part no. 600825. The photo on their site doesn't help much. I'm not sure a photo will help as they look almost identical which is why I quoted the DIN number. I think the difference might be tip radius as one looks slightly sharper. As Ady says I'll just have to try it and see how it cuts.
Bazyle: You may be right. I read somewhere recently that most model engineers use the same lathe tool (a left hand knife tool) for 80% of all cutting.
879 forum posts
Would recomend looking at this thread
I tend to use the same tool for most basic work on the lathe but the bulk of my work is done on my Chester 626 mill
19516 forum posts
Having looked at the tools I willalter what I said. I had assumed you got replacable tipped carbide tools but you have got what are refered to a brazed tip. Though these should be sharp enough to use out of the box they will need sharpening as they wear. To do this you will need a "green grit" wheel on your bench crinder as a standard wheel will not toch them.
And yes its hard to see the exact end details from the pic.
|3334 forum posts|
If you look at this site you will find all the Din shapes and their numbers clearly marked.
|Ian S C||04/06/2012 12:08:02|
7468 forum posts
You should also invest in a diamond file or two just to give a final touch up as well as the green grit wheel. My method of use is unscientific, about .5 to 1 mm depth of cut, and a fairly fast feed rate, most others will quote figures for that. The speed I use is around double what I use with HSS (the tool I normally use). Ian S C
|Gordon W||05/06/2012 09:35:22|
|2011 forum posts|
I have a set of brazed carbide tools like yours, I found most needed touching up from new. I now only use them for rough jobs, cleaning old rusty stock, skin on cast iron etc.. Buy some HSS and practice grinding your own, it will all come together eventually.
314 forum posts
Bob: I have looked at that thread. Just goes to show there's a lot more to it than meets the eye.
Jason: A green grit wheel is on the shopping list but I think I'll have a go at grinding some HSS tools first before I make a mess of the ones I've bought.
KWIL: There are lots of sites with diagrams of the angles but they often contradict each other and they never seem to give anything more than a very vague description. I'll get on with some turning instead.
Ian: Another item for the shopping list.
Gordon: Thanks for the input.
543 forum posts
Something else you might wish to look at are "Diamond" cutting tools.
Easy to sharpen (only one facet) and produce very good results, there are also many homebrew variations of the tool.
If you want a starter project you could do a lot worse than make one of them Tangential toolholder.
|467 forum posts|
I agree with Paul about Diamond tools.I have used one for some time and had excellent results.I use tipped tools for most work,but use the diamond tool for finishing cuts ,it is a very versatile tool.If your purse stretches to it I would have one,I have never regretted mine.
|304 forum posts|
I must also add my vote for the Diamond toolholder.
When I recently started out and being too intimidated to try grinding my own HSS tools I thought that I could avoid the issue completely by only using indexable carbide tools on my little Unimat. These worked ok for some things, but on other materials, especially some steels the finish was horrible. I tried with and without lubricant, faster, slower, shallow cut, deeper cut, but nothing I tried would give an adequate finish.
So having read good things about the Diamond toolholder and despite the price, I decided to order the appropriately sized tool from the manufacturer in Australia. On arrival, after a quick perusal of the instructions I fitted the supplied toolbit into the little grinding jig, turned on the the newly purchased 6" bench grinder for the first time and less than 2 minutes later had what appeared to be a perfectly ground bit. A few strokes with a diamond hone, before attacking the same piece of steel that had given me so much trouble with the carbide tool. The result was a resounding success as smooth as the proverbial babies bum.
My only relatively minor complaint with the tool is the need to rotate the tool post to 12 degrees. And as the lathe is also the drill and mill, toolpost removal and refitting is a constant occurrence. Although apparently this isn't necessary for the larger diamond toolholders which are of a different design.
Edited By clivel on 05/06/2012 21:34:46
314 forum posts
Paul, Francis and Clive: Interesting alternative approach. Seems to cut at a hell of a rate. Something for the future maybe.
Edited By Gary Marland on 05/06/2012 22:04:20
|Ian S C||06/06/2012 04:27:21|
7468 forum posts
I was looking at one of the Diamond tool sites, and saw refrence to Crobalt tools, sort of a half way between HSS and Tungsten Carbide, looks very useful, proberble a better tool material for our lathes than TC, if you can get it, I'm going to ask my tool supplier if he knows of it. Won't be today, theres 4 to 6 inches of snow on the ground, it was supposed to stop at noon , but it's still falling lightly. Ian S C
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