What are you machining?

[Lewis_RX8]

Wrote out a nice message here but refreshed and deleted it bugger

Bit of playings on the training lathe not my own , trying to achieve a nice finish with the inserts and tool we had. First tried the manufacture recommended speeds and feeds however these where the quite fast and hard which did get a nice mirror shine off the cut however was a lot of grooves and deep lines chatter and stuff as not sure if these lathes 2hp and not very rigid can really handle that may have been some slop somewhere did try tightening gibs but not a huge help.

Then a mate recommended the complete opposite low feed and low speed thought hmm that seems like it'll work even less but worked quite well IMO , insert spec sheet shown and it was set at

80 then 180 RPM same finish
0.001 inch per rev / 0.03 mm per rev feed
Coolant flood

Only thing is with those speeds / feeds its a boring job lol sitting there waiting for it to travel across only good for final finishing dimension cuts but also works well for that as can tickle off a few thou easily and still produce a good finish rather than being stuck with needing to take a bigger DOC for proper carbide speeds / feeds

Camera makes the finish look worse I think picks up all the lines but really impressed with finish really smooth doesn't catch fingernail and can see reflections in it

 

[fizzy]

Wrote out a nice message here but refreshed and deleted it bugger

Bit of playings on the training lathe not my own , trying to achieve a nice finish with the inserts and tool we had. First tried the manufacture recommended speeds and feeds however these where the quite fast and hard which did get a nice mirror shine off the cut however was a lot of grooves and deep lines chatter and stuff as not sure if these lathes 2hp and not very rigid can really handle that may have been some slop somewhere did try tightening gibs but not a huge help.

Then a mate recommended the complete opposite low feed and low speed thought hmm that seems like it'll work even less but worked quite well IMO , insert spec sheet shown and it was set at

80 then 180 RPM same finish
0.001 inch per rev / 0.03 mm per rev feed
Coolant flood

Only thing is with those speeds / feeds its a boring job lol sitting there waiting for it to travel across only good for final finishing dimension cuts but also works well for that as can tickle off a few thou easily and still produce a good finish rather than being stuck with needing to take a bigger DOC for proper carbide speeds / feeds

View attachment 319394View attachment 319393View attachment 319395

Camera makes the finish look worse I think picks up all the lines but really impressed with finish really smooth doesn't catch fingernail and can see reflections in it


View attachment 319397View attachment 319396

Time to get those tools I linked to.
Yesterday though I was just turning down a bar to act as a spacer. In a bit of a rush pushed the old Triumph a lot harder. Seriously deep cut could actually hear the lathe working. The swarf flying off was golden brown and smoking - best finish I have ever had with a cnmg or whatever they are called

For normal use though I prefer those sharp aluminium cutting tips.

 

[Lewis_RX8]

Time to get those tools I linked to.
Yesterday though I was just turning down a bar to act as a spacer. In a bit of a rush pushed the old Triumph a lot harder. Seriously deep cut could actually hear the lathe working. The swarf flying off was golden brown and smoking - best finish I have ever had with a cnmg or whatever they are called

For normal use though I prefer those sharp aluminium cutting tips.

Yup those tips really need pushed on a ridgid powerful lathe to get a good finish I think , not sure how the YouTubers make it look so easy lol

Yes ground / polished inserts for aluminium is the next try

 

[fizzy]

Well the Triumph is certainly capable of those cuts

 

[minimutly]

Time to get those tools I linked to.
Yesterday though I was just turning down a bar to act as a spacer. In a bit of a rush pushed the old Triumph a lot harder. Seriously deep cut could actually hear the lathe working. The swarf flying off was golden brown and smoking - best finish I have ever had with a cnmg or whatever they are called

For normal use though I prefer those sharp aluminium cutting tips.

If you don't have to jump out of the way now and again you're not trying @fizzy

 

[Lewis_RX8]

If you don't have to jump out of the way now and again you're not trying @fizzy

oooh aaah ouch eeee as the blue hot chips fall down your collar

 

[fizzy]

If you don't have to jump out of the way now and again you're not trying @fizzy

You are right there only baby cuts in the past.

 

[fizzy]

oooh aaah ouch eeee as the blue hot chips fall down your collar

Or worse

 

[Lewis_RX8]

Or worse

I paid for all 7.5HP of the triumph got to attempt to use them

 

[fizzy]

I paid for all 7.5HP of the triumph got to attempt to use them

Indeed so.
And lets not forget how big a leap carbide tooling is. That tiny delicate little tooltip can remove large amounts of tough metal and absorb vast amounts of power.

 

[Lewis_RX8]

Wait until you try the ceramic tips Fizzy.

What is special about these?

 

[Munkul]

What is special about these?

Nothing good about them unless you're trying to cut hardened stuff I believe...

 

[Lewis_RX8]

Nothing good about them unless you're trying to cut hardened stuff I believe...

I have seen is them on cutting edge engineering where he uses them for cutting the hard chrome off rams like you say but that's as far as my knowledge goes.

 

[Munkul]

I got a new 12mm boring bar last week, takes CCMTs. I was looking out for a S/H carbide bar on ebay but thought I'd take a punt.
Sold as a "reduced vibration" boring bar on ebay, paid £20. Of course it's a cheap import, but it looks nice, and it's made of some pretty hard material unlike the other 12mm bars I have which are cheap mild steel.
It performs better, too, better than the unbranded 12-16 bar which is now redundant...
Below is the picture from left to right - S12-16 boring bar, S12 "reduced vibration" and the C08 carbide bar. All at max stickout before they started squealing in mild steel.

 

[arther dailey]

Making a die holder at the moment for a training piece

The lecturer liked my two nuts together trick for how to sharpen drill bits that works on big or small ones just as good
View attachment 315573

Still getting better at the sharpening as I go but Intresting doing it on 24mm drills not the 10mm or so I'm used to doing

View attachment 315572

View attachment 315574

can you explain the two nuts trick ,no pun intended

 

[Kram]

Ceramics spray red hot chips

The hot chips problem, I have found two solutions!

External turning in reverse with a left handed holder or RH bar. The chips go away from you. 7mm off diameter was no problem, that is a big cut for this lathe!

These single edge chip breaker inserts, I like them as they break chips 100x better than normal. Instead of high velocity small C's, or high velocity curls, or stringers, you get thick, slow C's, or tight curlers (a bit lile a parting swarf wheel). Did not get burned, did not need the cardboard guards!

Problem is availability. I only know one shop with a few left, on clearance. I would have posted this before, but first I wanted to buy plenty for myself

I think KNUX style inserts are similar? Have not used them but only turning inserts I know, that are normally single edge.

 

[Lewis_RX8]

can you explain the two nuts trick ,no pun intended

Sure , quite simply just put two nuts or bolts and any hex together to get your rough angle for grinding a drill bit in

So when I am grinding and think the grind on the bit is quite hold up to two nuts and can hold up to a light to see if the grind if flat and the same on both sides at the 120° angle that you want for standard drilling

Just keeps you right as you sharpen probably not done in million pound CNC machine shops lol but works for the home shop learning to sharpen drills and if you don't enough you won't need the nuts anymore

 

[Hood]

Ceramics spray red hot chips
....

So does carbide if you are doing hard steel.

 

[arther dailey]

Sure , quite simply just put two nuts or bolts and any hex together to get your rough angle for grinding a drill bit in

So when I am grinding and think the grind on the bit is quite hold up to two nuts and can hold up to a light to see if the grind if flat and the same on both sides at the 120° angle that you want for standard drilling

Just keeps you right as you sharpen probably not done in million pound CNC machine shops lol but works for the home shop learning to sharpen drills and if you don't enough you won't need the nuts anymore
View attachment 320646

thats perfect , thanks

 

[m_c]

Ceramics spray red hot chips

The hot chips problem, I have found two solutions!

View attachment 320620

External turning in reverse with a left handed holder or RH bar. The chips go away from you. 7mm off diameter was no problem, that is a big cut for this lathe!

These single edge chip breaker inserts, I like them as they break chips 100x better than normal. Instead of high velocity small C's, or high velocity curls, or stringers, you get thick, slow C's, or tight curlers (a bit lile a parting swarf wheel). Did not get burned, did not need the cardboard guards!

Problem is availability. I only know one shop with a few left, on clearance. I would have posted this before, but first I wanted to buy plenty for myself

I think KNUX style inserts are similar? Have not used them but only turning inserts I know, that are normally single edge.

That's just a pretty extreme chip breaker, which is likely aimed for tougher materials where chip breaking is a problem.
For a chip breaker to work effectively, you need to run the cutters hard.

When you run the actual figures needed, you can end up requiring some quite scary feeds.
Looking at your photo, that looks like you started with about a 25mm bar.
Taking the numbers for the first general purpose DCMT 11 insert on APT, gives this chart -

Now lets take the lower end of the cutting speed, of 200m/min.
25mm bar has a circumference of 78.5mm, or 0.0785m.
Now to hit 200m/min surface speed, you need 200/0.0785, which gives us a touch over 2500RPM.

Then for the required feed rate, take that 2500 and multiply it by 0.12mm, which gives a nice round 300mm/min.

So to put that in to context, in order to reach the bottom end of the recommended machining area for the APT insert I picked, assuming a 25mm diameter bar, and a 25mm length of cut, you need to run the lathe at 2500RPM, and feed the length of cut in a maximum of 5 seconds.
It's not something that is practical on your typical manual lathe for a variety of reasons.


However, carbide can be made to work well, but you'll most likely be out with the recommended speeds/feeds.
Things like using polished inserts designed for aluminium can produce excellent finishes on steel, but you're far more likely to chip the insert, as the cutting edge won't be as durable.


And having just found the insert you're using, it's got the aggressive chip breaker as it's designed for being used at less than ideal speeds, which is what small parts require.
Out of curiosity, is there a feeds/speeds label on the insert box?
(I'll also add, that the shop will likely be re-stocking those inserts, as the stock message is the same for all of their products, it's just how they've set their website up to prevent backorders)