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View Full Version : Ok, now that I have the power..do I have the speed?? Carbide insert questions...



cuemaker
02-23-2013, 11:05 PM
If you happen to miss my lathe gloat..Please, let me do it again...

Jet 1440-3pgh with a 7.5HP motor... Max speed is 1600rpm

http://i201.photobucket.com/albums/aa129/xringx/0223131120d_zps325a585b.jpg


Now that I have the power...I am curious if I have the speed to run carbide inserts? I typically cut 4140HT that is 35hrc (I get it free)...

From my researches it looks like that max speed of 1600rpm is to slow except for large diameter stock...

I want to settle in my mind if I can use inserts effectively. Either I buy inserts, or a good grinder (I should have a good grinder anyways..)

Toolguy
02-23-2013, 11:27 PM
The idea that you have to run high rpm to use carbide is a leftover notion from when all the carbide tools were negative rake and you were having to melt the metal at the cutting edge to bulldoze through the material. Modern inserts with positive geometry and chipbreakers now cut a lot more like HSS tooling. They will shear the metal so you don't need the high rpm. The new inserts are rated for higher rpm because they are very efficient and are often run on high horsepower spindles that can move a lot of metal very quickly for running production. Still, you can run positive inserts and solid carbide endmills at HSS speeds with perfectly good results. A heavy lathe like that can make good use of inserts. I find that a mix of HSS and carbide give the best results by using the tool most fitting for the job at hand.

Tony Ennis
02-23-2013, 11:34 PM
I'm using inserts to good effect on my Atlas Noodlelathe (tm). You'll be fine.

cuemaker
02-23-2013, 11:45 PM
Ok.. Recommendation on insert shape (type)? I am smart enough to read the charts from there I think. Also..I have a CXA tool holder on the way...look for 3/4 insert holders?

PixMan
02-23-2013, 11:54 PM
Yup, look for a DCLNR124 or MCLNR4 for CNMG43x size inserts, the most commonly found ones. If you know you're going to do a lot of steels and want the best overall performance and value consider going to the 6-edge WNMG43x inserts and a DWLNR124 or MWLNR124 holder.

That speed and HP is good for negative rake insert tooling, and you'll be pleasantly surprised at just how fast you can peel off metal now.

BTW, the difference between MxLNR and DxLNR holders is the clamping system for the inserts. The newer DxLNR style uses a top clamp with an integral pin that reaches into the hole in the insert and a single screw pulls it back into the pocket. The older MxLNR style uses and eccentric center pin/screw and separate top clamp. Those often fill the eccentric screw's hex socket with chips, and you always have to have two wrenches handy. Those oder ones are more vcommon and available from cheaper sources, the new style ones are mostly available from quality tool manufacturers.

Toolguy
02-24-2013, 12:06 AM
Yes - 3/4 holders will work fine with CXA. There are lots of good brand names for cheap on eBay. Also, check Shars tools. They have good holders cheap too.
I just bought a set of boring bars from them that I like. They are the SCLCR series with 80 degree diamond shape insert. Trigon inserts work good too. With the diamond and trigon you can turn and face without having to adjust the angle. This is mainly for finishing cuts as the insert is at a slight obtuse angle to the workpiece. If you try to rough like that the insert will want to dig in and go deeper. There are other holders that present the insert to the work at a different angle for roughing. With the right insert you can probably turn off 1/8 per side (1/4 on diam.) per pass on that lathe in mild steel.

flylo
02-24-2013, 12:34 AM
I've been in that building & YOU STILL SUCK!:p

If you happen to miss my lathe gloat..Please, let me do it again...

Jet 1440-3pgh with a 7.5HP motor... Max speed is 1600rpm

http://i201.photobucket.com/albums/aa129/xringx/0223131120d_zps325a585b.jpg


Now that I have the power...I am curious if I have the speed to run carbide inserts? I typically cut 4140HT that is 35hrc (I get it free)...

From my researches it looks like that max speed of 1600rpm is to slow except for large diameter stock...

I want to settle in my mind if I can use inserts effectively. Either I buy inserts, or a good grinder (I should have a good grinder anyways..)

PixMan
02-24-2013, 12:48 AM
A 7.5HP lathe with good tooling can easily peel off a .150" depth of cut at .012" per rev feed in even tougher 4140. My lathe is rated at 5HP, got perhaps 4 in reality and I can take .100" depth of cut in 316SS with a negative rake inert at 1200rpm and .0118" per rev. Steel is usually easier.

I wouldn't buy a Shars holder because I'd want to know I could get parts for my holders tomorrow if I needed them. Good tooling doesn't cost, it pays.

BTW, I'm surprised to see that machine without a foot brake for the spindle. Did it have one at the time it left the factory?

Jaakko Fagerlund
02-24-2013, 04:33 AM
A 7.5HP lathe with good tooling can easily peel off a .150" depth of cut at .012" per rev feed in even tougher 4140. My lathe is rated at 5HP, got perhaps 4 in reality and I can take .100" depth of cut in 316SS with a negative rake inert at 1200rpm and .0118" per rev. Steel is usually easier.
Just for comparison, a chinese lathe with 8 kW motor on it and DNMG inserts (nose radius 0.8 mm) I can peel of 10-12 mm from the diameter (5-6 mm DOC) with 0.3 mm feed per revolution and coolant running, same prehardened stuff.

You don't need the speed so much with a carbide, though the excell at higher speeds. Good indication is to take cold rolled and peel it off with 'too low' speed and the surface looks like a little torn albeit still smooth feel. Crank up the RPM up to what you got and take another peel and the surface shines :)

cuemaker
02-24-2013, 07:45 AM
BTW, I'm surprised to see that machine without a foot brake for the spindle. Did it have one at the time it left the factory?

It did..in my original thread I said that I want to fix that

Peter N
02-24-2013, 08:36 AM
I used to use Carbide insert tooling almost exclusively on my old Myford ML7, and that had a top speed of 640rpm, no problems at all and beautiful cuts & finishes.
My Colchester Bantam only has a top speed of 1600 and I use Carbide exclusively on that too, apart from one HSS parting blade, and tbh I donlt often run it over 1000rpm.
You'll be fine.

lakeside53
02-24-2013, 12:13 PM
Speed? It's not "speed", it's SFM. Your machine is rigid enough, but you won't turn much below 3/4 inch diameter if you want surface quality and chip breaking.

SFM depends on the diameter turned. I aim for 350-800sfm (insert and material dependant) . Most of my toolling is negative rake, BUT most of the finishing grades are positive rake (and/or approaching positive) in the negative holders. Some I can take a miniumum cut of 3-4 thou (finishing grades), some it's 15-20 thou. I can throw chips way way deeper than that at decent feed rates (14x40, 4kw motor)!. I mainly use WNMG, with DNMG close behind.

1 inch at 1250 rpm is 327sfm. I figure that's the minimum sfm for most of my carbide. On the other hand... 6 inches at 250 rpm is 392sfm.

Jaakko Fagerlund
02-24-2013, 02:16 PM
Speed? It's not "speed", it's SFM.
Yes, surface speed to be exact.

michigan doug
02-25-2013, 12:21 AM
And you get free steel????

You really, really suck.

How did you get that little sweetheart arrangment?

troy

legendboy
02-25-2013, 01:43 AM
that is a large chunk of lathe

cuemaker
02-25-2013, 01:50 PM
I manage a location for Dan-Loc Bolt and Gasket. We manufacture studs and threaded rod, typically ASTM A193 B7/L7...which is really 4143HT, and we also manufacture ASTM B8 and B8M which is 304 and 316

I also have B16 rod and a few other goodies..

So I grab the cut offs from bar to short to work with.. You should see my bin for recycling bin with cut offs.. Upto 4" diameter is not a problem

750KO
02-25-2013, 08:47 PM
cuemaker I own this same lathe. I bought it new and have the manuals. If I can be any help PM me.
Randy

cuemaker
02-25-2013, 10:05 PM
cuemaker I own this same lathe. I bought it new and have the manuals. If I can be any help PM me.
Randy

This is very much appreciated. I found manuals and parts list online..but I need to recreate the back splash..PM on the way...

Doozer
02-25-2013, 10:21 PM
Cuemaker-
Again, nice score, I am so jealous.
I would not worry about 1600 rpm top end.
How fast did you run your small Sheldon/Monarch?
I will say, first get used to the rigidity of your new machine.
Take more per cut, play with increased feed rates.
Consider this, If you are turning a lot of 1/2" stock and below,
you might want a smaller (faster) lathe.
Unless you are running production with it to make money,
I seriously doubt that 1600 is a limitation.

--Doozer

cuemaker
02-25-2013, 10:45 PM
Cuemaker-
Again, nice score, I am so jealous.
I would not worry about 1600 rpm top end.
How fast did you run your small Sheldon/Monarch?
I will say, first get used to the rigidity of your new machine.
Take more per cut, play with increased feed rates.
Consider this, If you are turning a lot of 1/2" stock and below,
you might want a smaller (faster) lathe.
Unless you are running production with it to make money,
I seriously doubt that 1600 is a limitation.

--Doozer

Doozer,

I ran my Sheldon to fast for its plain bearings...Its rigidity is very poor..in cutting 4140HT, I would go through several inserts pretty fast. I had some better luck with cermeted carbide and HSS, but the little lathe was just not up to it. On mild steel and aluminum it did ok. Usually a poor finish though. Also, I have fixed it up quite a bit and I am tired of messing with it. If I had the room, I would tuck it away and slowly repair it, make it a project. With with just half a garage, its easy to let it go and use the money for tooling on the big one.

I have not turned any 4140HT under half inch, in fact most of its was above 1". Most times I would start with something like 2" threaded rod and would remove the threads to make something.

And very little what I do is for money.. so its all play time for me.

I am so excited to get this lathe going.. After checking around, I am going with WNMG inserts. Partly because of recommendations, partly because in the 4 way tool post was a Kennametal DWLNR124 insert holder... seemed like fate was calling.

Right now I am working on where to place it...