not the usual carbide question

Rod Williams · Jul 16, 2007

ok, so my 9A does not like carbide. i can deal with that. what size lathe, what horse power and what mass, is needed before carbide realy shines?

Robert Lang · Jul 16, 2007

I use carbide on my 9A all the time and it works fine. Are you using pos. rake or neg. rake tools. Pos. rake works the best. Rob

D.spencer · Jul 16, 2007

What type of issue are you having using carbide? Usually, even the smallest and lowest of horsepower lathes will benefit from using carbide since it cuts easier than HSS(IMHO). As stated, pos rake is easier cutting. are you taking heavy cuts? maybee really hard material? dull carbide? wrong feed or speed?

Rod Williams · Jul 16, 2007

in truth i tried cheap brazed on carbide tips. even tried sharpening with a dimond hone. could only take a .015" cut, with HSS could take a .040" cut. same feed and speed. have not tried carbide inserts due to expence of holder and inserts.

JHowell · Jul 16, 2007

The cheap brazed toolbits, in my experience, cut about like you would expect for the price. I bought a batch of "sale" bits from Enco, and, had I not previously had success with more expensive brazed bits, I might have reached the same conclusion as you. Think fine chef's knife versus dollar store item. Then there's the indexable carbide insert, to be used with a separage toolholder. That's another kettle of fish altogether, about which I'm not qualified to speak, but which is what most working machinists seem to mean by "carbide."

Another issue besides the quality and type of the tool is the way you're holding it. Most carbide tools seem designed to be held in quick change toolholders with the shank at 90 degrees to centerline. Lots of us still use the lantern style toolposts on SBs, which hold the tool up to centerline at an angle. Depending on the rake and relief of the carbide tool, this can be a bad thing.

Perhaps Denny will chime in with a copy of his excellent contribution to a discussion of the same subject a few weeks back on the Yahoo forum.

No need to give up on carbide entirely just yet. If you find a use for junk carbide toolbits, let me know. : )

Jack

mf205i · Jul 16, 2007

Hi Rod, the speed for carbide needs to be 3 to 4 times the recommended HSS speed. Try this, shim your Enco bit to a neutral rake, For mild steel try about 400 SFPM, no less than .010 DOC, more is better. Let it rip and be prepared to be astounded as to the performance of your old gal! Now, all that said, I still prefer HSS. With carbide, these old lathes don’t have the high RPM necessary for small diameter parts or the power and rigidity for heave cuts and with normal carbide tooling you must take a fairly heavy cut for a good finish, you can’t sneak up and take a super light skim cut to final dimension.
Have a good one, Mike

heavyKen · Jul 16, 2007

In my experience the cheap brazed carbide tools are pretty much junk. I'm sure there are some ok ones out there, but it's just not worth it.

My recomendation is to try micro-100's brazed carbide. The form factor is familiar to the HSS tools we're used to.

I concur with the comment about ~3x speed increase. I'll add that that's for uncoated carbide. It only goes up from there for coated carbide (which is another nod for the micro-100 tools since they're uncoated).

Also true about needing to take deeper cuts. The rule of thumb is you want to cut at least as deep as the toolnose radius. I don't mean to sound preachy, but the micro-100's are also nice in tha they have a fairly small radius. The average inserts have good size ones (but I know you can get ones with small radii -- just saying the large ones are more prevalant).

And right-on about the lantern tool post. You can use it, but you need to be using the tool holders designed for carbide. They hold the tool bit straight rather than at an angle. But I will agree that you are much better off with a QC post if you can swing it.

I unfortunately don't have my heavy 10 running yet to give first hand comments, but I've used carbide alot on similar lathes. In fact it's pretty much all I use now.

Ken

weld'n tom · Jul 16, 2007

Here is a photo of my first milling project its a lantine style tool holder for the elcheapo carbide tools, just kept it all streight with centerline, made a big differance cutting. I only cut .010 to .012" at a time with it.
Tom

JHowell · Jul 16, 2007

Looks nice, Tom. Might make an additional difference if you could tweak things to reduce the overhang a little more.

Jack

weld'n tom · Jul 16, 2007

Thanks Jack
It was made out of a peace of 2"x4"x3/4" CRS would have been a lot nicer to have a 5" long peace
Tom

detroitmachinery · Jul 16, 2007

I think the length of the brazed carbide tool bit is sticking out too far from the tool holder. If you shorten the length of the shaft on the carbide insert it will reduce chatter. These brazed inserts are not that good, but the 45 degree pointed head carbide works better than the type in the picture. If you lean the tip away from the direction of cut it also helps produce a better finish. I have no problem making .040" cuts using brazed carbide with pointed tips. For best results make a light .003"-.005" final cut. If you have a quick change tool post you should give the indexable carbide inserts a try. The .030" radius inserts work well for these lower power lathes.

Rod Williams · Jul 16, 2007

maby some day i will spring for a quick change tool post and get some holders and inserts. i do have the south bend four position tool post but only one half moon base for the tool . i will look into the micro 100's. where do you get yours.
back to the original question. how much horse power and mass to make carbide realy work. ya never know some day may have a bigger lathe.
thanks for all the replys.

detroitmachinery · Jul 17, 2007

I have a 3/4 HP motor on my lathe, and it works fine, except for drilling large holes 3/4" or larger. You can't hog metal, but .030"-.040" depth of cut is not a problem. I usually run my lathe on the middle pulley, and I have a variable speed motor. What do you mean by "mass"? Are you referring to work piece diameter? I can cut work pieces from 1/4"-3" diameter with equal ease, and equal surface finish and quality. The smaller the diameter work piece the faster you need to set the rpm's to keep the same sfm. You should also take lighter cuts on work pieces under 1/2" diameter. Use your own judgment as to what is producing the best surface finish. You should listen to the sound to help you determine when the lathe is working too hard. All materials have there own sweet spot for optimum surface finish. It is a trial and error process for each material. You need to do some experiments with rpm's, feed rate, and depth of cut. Start out with a medium rpm, and .0037" per rev feed rate for a fine finish. That was the setting I was using for the 6061 aluminum bar in the picture. If you doing a rough cut use faster feed rate to save time. These are the settings that produced the best surface finish on 1.5" diameter 6061 aluminum.
http://www.flickr.com/photo_zoom.gne?id=539032016&size=o

Rod Williams · Jul 17, 2007

by mass i mean weight of the machine. i have been using t-15 1/4" cutters. they hold up very well and can hone to a keen edge. have played with different feeds and speeds alot. with mild steel can take .040" cut ( .080" off the stock ) and with alumminum have taken up to .100" at a time. my question was more towards what to look for when getting a larger lathe.

heavyKen · Jul 17, 2007

The horsepower required is determined by the material and the volume of material removed per unit time. I can look up the formula for you if you want. But that said, I wouldn't really worry about it.

I've never seen any formulaic information on mass (really you care about rigidity) of the machine. Intuitively I can see you want to apply a force to various parts (spindle, toolpost) and see how much they move -- not unlike the procedure for checking play in the spindle bearings.

Ken

Wally M · Jul 17, 2007

weldin:

Very handsome tool holder.

Generally I've been having good luck with Borite's turning holders and TPGT inserts (1/4 I.C.)

Good finish, work well aggressively, and appear to hold up.

See MSC.

Wally.

weld'n tom · Jul 17, 2007

Thanks Wally
It was fun to make and I learned a little about milling in the process.
I will have to check out MSC web, havnt been there yet.
I have been looking at some cheaper bits with carbide inserts, here is one set I found on ebay
http://cgi.ebay.com/3-4-INDEXABLE-CARBIDE-LATHE-TURNING-TOOL-BORING-SET_W0QQitemZ7541530138QQihZ017QQcategoryZ633QQcmdZViewItem
Im wondering if they would be any good or if its one of deals you get what you pay for. I allso have the KDK 200 QC for my south bend 16".
I was told by one of the local machinrey dealers that sells this same type of bit that you need to be turning over 1500 rpm for the insert type to cut right.
Rod
South bend recomends the 2 hp on my 16" to run it at full potential but a lot were sold with 1 hp, mine has the 1 hp running on a static phase converter so it only running about 2/3 hp and it will take a lot heavyer cut than my logan 10" with a 1-1/2 hp, must just be the size of tooling and being more solid that makes a differance not so much the hp
Tom

weld'n tom · Jul 19, 2007

I went to MSC web site and I had a price shock for 3/4" tooling anyway this morning I went to Johnston industrial supply and talked to them about the carbide inserts for these old lathes. They came up with the WNMG 431-M3 TP200 it has about the same rake as the TPGT. Its rated to cut .020" to .200" at .006" to .020" feed rate.
I couldnt resist had to try one. They are a little tricky dialing them in but I think I have it close .014" feed rate and .020" cut on 1" mild steel, I would like to get a little better finish, this insert is the medium one and they have a finish one that cuts .008" to .120". heres a couple pictures of my progress.

Tom

pepo · Jul 19, 2007

IMHO the best thing about inserts is chip control. The right type of chip groove or chipbreaker for the material and what you have to do. Never buy flat top trianglular positive grind carbide inserts. These are the ones where there are 3 tips on one insert. An exception would be for fine finishing, like the last .020. For general digging around in mystery metal these suck,too weak,and no chip control. Weldntom..good all around choice on the toolholder,those are tough. Change the seat if you notice the insert isnt "sitting flat". I usually break them before they get a chance to wear out.
If you are making 100 shafts on a CNC turning center,you need a certain level of tooling. Inserts and such.
If you are making one,at home,you need less. High speed gets a bad rap because there is a lot of really low grade stuff out there. A lot of it wont live in steel. Get cobalt or better M42. Youll notice it at the grinder when you shape it. Its easy to get it as sharp as carbide,but it cant take as much heat before it gets dull. Hence the lower speeds.

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