Thread: What did you learn today?

Originally Posted by .RC.

That was the case many years ago, but not today... There are some quite tough grades of inserts out there...

Agreed. I you try doing an interrupted cut in HDPE with those vastly overpriced inserts that are supplied for the useless sets of cutting tools in wooden boxes from the import shops, you will have no success. I have been banging my inserts over interrupted cuts on the (now gone) Nuttall for several years and it has lots of wear in the cross slide. I often wonder why people have issues with this.

I would guess the holder has something to do with it too.

Dean

Originally Posted by .RC.

That was the case many years ago, but not today... There are some quite tough grades of inserts out there...

Richard,

Do you use carbide on your little 260? If so, what do you use?

I use Kennametal CCGT high positive inserts on my dainty 9. I was using one this morning to reduce some 50mm diameter 1045 to 12mm, 6mm at a time. Worked well yet if I tried an interrupted cut I'd snap the tip off. I'm with Grahame. I use my Diamond Tool Holder with HSS for turning rough to round.

Bob

025 (Large).JPG

You guys really need to get onto Cermet inserts. They are available for most of the standard toolholders if you look around. As long as you keep the DOC and feedrate reasonable interrupted cuts in any material are fine, and generally leave a BETTER finish than continuous cuts.
Then there is the myriad of other benefits -no need for coolant, surface finish like you wouldn't believe, crazy DOCs and feeds/speeds, ability cut black steel and tougher grades like butter... need i go on?

Originally Posted by andrew_mx83

You guys really need to get onto Cermet inserts. They are available for most of the standard toolholders if you look around. As long as you keep the DOC and feedrate reasonable interrupted cuts in any material are fine, and generally leave a BETTER finish than continuous cuts.
Then there is the myriad of other benefits -no need for coolant, surface finish like you wouldn't believe, crazy DOCs and feeds/speeds, ability cut black steel and tougher grades like butter... need i go on?

Andrew,

After your listing of the merits of Cermet I had a look and found these - 10pcs Kyocera Ceratip CCMT09T304HQ TN60 Cermet Inserts | eBay The correct geometry and size for my holders but I'm wondering how they would perform with only one horsepower on tap. Any clues?

Bob.

Hi Bob,

I've used Cermet's before on bigger and more powerful machines (Jessy Majors). We where supposed to use them for finishing cuts only due to the finish and mainly the cost of the bits. From my experience they where more brittle and more likely to chip when not stored correctly than carbides. When I was using them I ran them at high speeds (from memory up to 2000rpm - the highest on the lathe possible) and high feeds. You could take really fine cuts with them as well. In the end we used them for pretty much everything.
I think they would go ok on a 260 as you can get I think 1700 ish rpm on them (not sure on the speed's on the 9"). Not sure about taking big cuts though. The biggest I can take with a carbide is about 3mm of the diam before I stall the lathe. Even with the DTH and a Crobolt piece I can't really get much more than 2.4mm cut.
If you do buy a packet of ten maybe you could do a group buy? I'd be up for a couple to try out.

Ben

So far today has been rich with learning opportunities!

• If you are trying to get a LH thread to line up angularly (that is, so the lever on the head points a certain way) you need to think about fractions of a turn as CCW and not CW - Still I did get to make up a second bolt when the first one was shortened too much.
• DRO suppliers who tell you that they supply all the fasteners you need sometimes forget to mention that they may not supply the right size for the hole...
• The chipbreakers on my inserts don't work despite what the suppliers say
  
  • Corollary - when swarf birds nests around the part, even using pliers to try and pull it away will not stop it whipping around and letting the blood leak out.
  
  
• Carbide parting tools work much better if they are supported to the very end of the tip (otherwise they snap).
• Labyrinth seals only stop grease flying everywhere when nothing moves. As soon as the spindle turns all bets are off despite what tribology experts will tell you

I think I'll stop now and find a book to read before I do anymore damage. Maybe I won't be quite as brainless tomorrow

Michael

Originally Posted by Michael G

• The chipbreakers on my inserts don't work despite what the suppliers say

Michael

Generally a sign you need to increase speed, feed or both until the chip breaks, or something else does. Or get a different insert since your lathe has more than enough rigidity & HP to really drive the cutter.....

PDW

The shaft was around 19mm being taken down to 16mm diameter and around 100mm long. I got short chips at the T/S and the H/S but the centre section of the shaft changed to continuous. Dark, dark blue. A spring pass afterwards did not show any appreciable difference in diameter (a few thou?).Inserts are CCMT.

Michael

Originally Posted by Anorak Bob

Andrew,

After your listing of the merits of Cermet I had a look and found these - 10pcs Kyocera Ceratip CCMT09T304HQ TN60 Cermet Inserts | eBay The correct geometry and size for my holders but I'm wondering how they would perform with only one horsepower on tap. Any clues?

Bob.

Hi BT

I'd think they would be fine, maybe not as heavy on the DOC, I'm interested in getting some of the same, and comparing notes.

Ray

Originally Posted by RayG

Hi BT

I'd think they would be fine, maybe not as heavy on the DOC, I'm interested in getting some of the same, and comparing notes.

Ray

I had a quick look for wnmg's but only found one. I'm sure I could find more but to be honest I'm more than happy with the iscar inserts I use. Bit of course I wouldn't mind trying a cermet just to see how it goes......

Ew

I think you would get away with 1hp, but it would be on the lower limit. What you need is the spindle speed. I leave my lathe in top gear @ 1400rpm for cermet cutting, almost regardless of diameter (ie 10-150mm), and use the vfd to give me upto 2000rpm for the really small stuff.
Of course being in top gear (1:1) gives no torque multiplier so you can load the motor up pretty quickly with heavy cuts. For heavy roughing i just pick a convenient DOC and feed it in as fast as i can without slowing the spindle.

Cermet uses the heat to cut properly, the harder you work it, the better it cuts. If you are having problems like poor surface or breaking inserts, crank up the speeds/feeds/doc. They will take light finishing cuts but there is no need, as a 2mm DOC will leave as good (or better) finish.
I usually start with a light cut to get some heat in the tool and work, then lay into it on the next cut. Remember the hotter you get it, the harder you work it, the better they cut.
Steel swarf should come off blue, but be careful, its bloody hot.
Technically cermet isnt for cutting aluminium, but i find it works great. Same rules apply, keep it hot and feed it fast.

I would suggest buying more than 1 insert to start with, they chip very easily and you may break a few getting the hang of using them. On the flip side, once you learn what NOT to do, they rarely break and the cutting edge does not appreciably wear or blunten. I went through my first 10 inserts very quickly, but now i leave them in for months and months at a time, til i F up and break one.
Yes storage is important, the inserts are very brittle so you cant go bumping them into stuff or they chip. Touching off the work needs to be done very gently, and dont knock the tool with your work when mounting or dismounting it from the chuck etc

Originally Posted by andrew_mx83

I think you would get away with 1hp, but it would be on the lower limit. What you need is the spindle speed. I leave my lathe in top gear @ 1400rpm for cermet cutting, almost regardless of diameter (ie 10-150mm), and use the vfd to give me upto 2000rpm for the really small stuff.
Of course being in top gear (1:1) gives no torque multiplier so you can load the motor up pretty quickly with heavy cuts. For heavy roughing i just pick a convenient DOC and feed it in as fast as i can without slowing the spindle.

Cermet uses the heat to cut properly, the harder you work it, the better it cuts. If you are having problems like poor surface or breaking inserts, crank up the speeds/feeds/doc. They will take light finishing cuts but there is no need, as a 2mm DOC will leave as good (or better) finish.
I usually start with a light cut to get some heat in the tool and work, then lay into it on the next cut. Remember the hotter you get it, the harder you work it, the better they cut.
Steel swarf should come off blue, but be careful, its bloody hot.
Technically cermet isnt for cutting aluminium, but i find it works great. Same rules apply, keep it hot and feed it fast.

I would suggest buying more than 1 insert to start with, they chip very easily and you may break a few getting the hang of using them. On the flip side, once you learn what NOT to do, they rarely break and the cutting edge does not appreciably wear or blunten. I went through my first 10 inserts very quickly, but now i leave them in for months and months at a time, til i F up and break one.
Yes storage is important, the inserts are very brittle so you cant go bumping them into stuff or they chip. Touching off the work needs to be done very gently, and dont knock the tool with your work when mounting or dismounting it from the chuck etc

Thanks for the reply Andrew,

I can whip the little Hercus up to 2450rpm but the spindle bearings get real warm. The cermets sound as fragile as the Kennametal High Positive inserts I use. They have a point on them like Aladdin's slipper!

Bob.

Originally Posted by Anorak Bob

Thanks for the reply Andrew,

I can whip the little Hercus up to 2450rpm but the spindle bearings get real warm. The cermets sound as fragile as the Kennametal High Positive inserts I use. They have a point on them like Aladdin's slipper!

Bob.

Hey Bob,

Thats interesting.

What sort of bearings have you got ?

My impression so far (admittedly am newbie), from what Ive read in books and posts, has been that I shouldnt think about trying to spin my 9" Hercus faster than 1400 rpm and because of the limited speed and power the various inserts are out of my league. My current max is 720.

Some inserts and holders came with the lathe but I haven't tried them yet, for that reason.

Bill

Originally Posted by steamingbill

Hey Bob,

Thats interesting.

What sort of bearings have you got ?

My impression so far (admittedly am newbie), from what Ive read in books and posts, has been that I shouldnt think about trying to spin my 9" Hercus faster than 1400 rpm and because of the limited speed and power the various inserts are out of my league. My current max is 720.

Some inserts and holders came with the lathe but I haven't tried them yet, for that reason.

Bill

Hello Bill,

My '69 9" has a roller bearing spindle. The lathe came with the high speed drive setup. The speeds available with a single speed motor are 2600 - 1850 - 1355 - 975 - 485 - 345 - 250 - 180. * The down side to the speed is that threading requires a bit more attentiveness.

Here's a link to a thread about the pulleys before I changed the motor pulley - https://www.woodworkforums.com/f65/ne...1/#post1267566

And here's one after - https://www.woodworkforums.com/f65/ho...0/#post1270203

I do have a plain bearing 1958 9". It is slug like in comparison but wonderfully quiet ( not that the AR's noisy but you can hear the bearings.)

Bob.

* page 8 , 1970 edition of Peter Hercus' Text Book Of Turning.