I just have the compound slide a bit tighter than the cross slide and find I can still get an even feed with it. Some might find it too tight though.

The tips are TCGT 110204 ALU AK10 from apt carbide. They are micro polished rather than coated, Think you will find that they are listed for aluminium and finishing stainless. They do several similar tips but bear in mind the bearings on the lathe do seem to be perfectly adjusted. That can make a big difference all on it's own. The cross slide was tending to move around during a cut initially and the roughing tool I used only has a very tiny tip rad.

I've used these previously which will also give a good finish but find that the coating wears off and hope that the micro polishing extends the life.

I prefer V nosed tools when they can be used as they will cut both ways, work up to a shoulder and face but the only holders I have found for them is as above in the 10mm 3/8" cheap sets. The ones i have use hex grub screws which are a complete pain compared with torx. APT look like they have some but they turned out to be for 16mm tips.

John

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While I'm on the subject the idiots that sell indexable tools like these (and others) on ebay don't generally state the tip size or type.

There are 3 sizes. 9, 11 and 16mm. The tool shank size is generally smaller on these particular sets. There is a style of holder that fully exposes the insert at an angle suitable for turning either way and facing, even shoulders lightly. They generally have some number and 92 degrees. The sets sometimes have something similar in them.

They can also be used in boring bars but the RDG ones for instance don't have the tip at an angle where it can face internal shoulders which is pretty stupid really.

The sets of 5 are the best bet in some ways. They often have 2 straight V's as per the photo so one can be used with the tips that come with them that have no depth of cut limit and the other can be used with these rake tipped types.

Don't buy unless they use torx screws as the hex key ones will soon round off the key or any that is used. Actually I have had one of the sockets round after fitting 3 tips so unless I can drill it out it's now useless.

Some people prefer the romboid come square ones but I much prefer a shape that can easily be used into a corner.

John

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Edited By Ajohnw on 22/03/2016 23:36:49

APT offer them in various numbers including 2. However when I ordered one of their holders for the 11mm size they sent one for 16mm so I'm not convinced that their listings are correct. Tip prices are very similar to ebay at the moment.

I've yet to find micropolished parting off blade inserts. I'd like to because one of the main areas where these inserts excel is aluminium. HSS needs a very high polish to match them for lack of sticking etc. They do seem to consume more power than really sharp hss and unlike hss they can't be ground to reduce that ever further via change of angles.

This lathe had another interesting fault that I initially thought was slightly loose bearings causing a little bit of vibration. It turned out to be lack of cleanliness under the compound slide mountings. There doesn't seem to be much scope for this sort of thing or miss adjustment on mini lathes as all of the bits are so thin and light. The tool post was also too far out on the cross slide. it makes more sense to set the compound slide in a position that leaves most of the cross slide guides engaged over the the usual range of sizes and not have it positioned for huge diameters. I set it so that when it was fully in the toolpost could be swung over a reasonable range of angles while still reaching centre.

John

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The tool needs to be angled suitably for maximum performance Lynne. In other words when bar turning in the normal direction the tool should be angled towards the chuck. This is to reduce the effective depth of cut. I don't usually rotate it by 30 degrees so that the cutting edge is square to the work as it would be if a bar turning tool was being used.

I'd say I generally angle it around 1/2 of that and also use it just pointing forwards.

To face a shoulder it needs to be rotated more than 30 degrees towards the shoulder and also when facing the end of the work. The tip rad if I remember correctly is 0.7mm so when a shoulder is faced it can be plunged into the work to remove the radius that would be left avoiding having to fit a grooving tool of some sort most of the time.

The basic shape is a very old idea that was often ground on HSS toolbits but with a more acute V. Usually called a general purpose bit – the one to use for a mix of things. These will even cut both ways even though rake is negative going in one direction. It isn't on the indexed inserts.

The only penalty really is facing – it can be difficult to get the tool edge anywhere near square to the cut when facing the end of work so only a little can be faced off per pass unless the tool is reversed in the holder. They also don't seem to like facing from the centre out. A common trick on larger lathes to get nice shiny ends. Due to the cutting edge angle to work the depth of cut is increased rather a lot so the extra force takes out play in the machine.

Maybe I am biased. I was trained as a toolmaker and while that was going on 99.9% of my turning making all sorts of things was done with this style of tool even though it takes a lot more grinding than the usual bar turning tool.

Looking for another set has proved interesting. There were loads on ebay when I bought the current ones. Not so many now but I did find a decent looking set eventually – Rotagrip and they don't list them on ebay. The set looks expensive but also includes a boring bar that uses the same tip plus 2 torx wrenches. As a company they have been supplying round here in the Midlands for a long long time including when there were a number of very large industrial companies about so it doesn't surprise me that they are fitted with torx even though that sort of user probably wouldn't buy them. As the tip heights are the same on all of the holders they can be swapped easily once the toolpost is set.

John

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It's mostly down to be able to set the gibs correctly Chris – on all slides that are adjustable but as I mentioned loose headstock bearings will also mess things up but usually if that is reasonable deeper cuts help and fine ones cause poor finish. What deeper means will vary according to the lathe. Faster feed can help too but there isn't much scope for adjustment on mini lathes etc.

Materials vary too and in this case as it's bright drawn mild steel the often hard stringy outside has been removed. Black bar often turns better.

I set the slides via the handle but really it's best to remove the lead screws, oil things up and adjust while pushing about by hand. There should be some definite resistance to movement. Not hard resistance but needing a bit of effort to move the slide. Play in the leadscrew shouldn't really matter then. Some lathes can be adjusted more loosely than others but generally they are always set too loose.

I would suspect that any shape of carbide tip with the same sort of rake design on them would give the same finish. This style is also cropping up on milling cutters now. In this case I like the idea of micropolishing rather than coating as coated inserts do produce a poorer finish when the coating wears off. I'm hoping that they will last longer.

Oh and as mentioned I am accustomed to using V nosed tools.

John

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Edited By Ajohnw on 24/03/2016 15:33:27