=============== Generally C2 and similar grades are for aluminum.
Steel generally uses C5 or C6.
However in this case there seems to be something else at work. FWIW - when you have a bad chatter condition, HSS is generally more resistant to microchipping and wear.
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Unka' George [George McDuffee] ============ Merchants have no country. The mere spot they stand on does not constitute so strong an attachment as that from which they draw their gains.
Thomas Jefferson (1743-1826), U.S. president. Letter, 17 March 1814.
John, You are doing something wrong. If you can file or hacksaw your
4140 then for sure you can machine it.
The most usual problem people have is too high a cutting speed. Were you running the lathe at the slowest speed possible? And how slow is that?
If I were having problems I'd try to get the cutting speed down around
30 - 35 FPM to start. (circumference in feet X RPM) and if that is successful then you can go from there.
Given you are having problems I'd say try something in the vicinity of
75 RPM which is pretty slow but if you are successful you have proved that you can cut it. Once you have made a successful cut you can start increasing cutting speed and feed rates to find an optimum for that material.
If you are consuming tool bits then go slower until you can make a full cut without damaging the tool. If it is 75 RPM than that is what it is. From what you have written you have troubles machining without wrecking the tooling so the first step is to make a full cut without problems. Then change something, cutting speed or feed, until the tooling fails. then go back to square one and change the other variable.
If you find that you can make the cut at, say, 75 RPM and 0.010 cut per rev. then increase the speed one step and try it again. You'll soon reach a speed that eats the tool bit so slow back down to 75 RPM and make a cut at, say 0.015/Rev. If that works kick the feed up a bit until you reach a feed rate where things seem to be straining the lathe.
By now you should have a pretty good idea what RPM and feed you can use for that material.
Now I'll tell you a secret. Nearly all job shop machinists do exactly what I've described. Of course, they've been at it for fifty years, or so, so they have a better idea of where to start but if you watch then real close you'll usually see them start the first roughing cut and after a bit they will kick the speed up a bit. Then, maybe you'll see them reach over and jog the feed rate up just a notch.
"The cutting edge of the tool bit should almost always be set to the center height of the lathe spindle.
There are several methods for checking the height of the tool bit. Perhaps the simplest way is to place a thin strip of metal, such as a steel rule or feeler gage, between the work piece and the point of the tool bit. If the height is correct, the strip of metal will be held vertical. If the top is leaning toward you, the tool bit is too low. If the top is leaning away from you, the tool bit is too high..."
You may find some of the use/running instructions helpful too (shrug).
Good tips/ideas are found most anywhere and require due diligence to locate. Of course if you spend all of your time reading you won't get anything done :)
If you had the HP the carbide would have allowed you to run a faster RPM. There is no doubt that you can take a heavy cut with HSS. Carbide inserts though can handle a higher temp.( not brazed carbide you will melt the braze) than HSS. Now if you add coolant to the HSS or the Carbide you can cut even faster if you machine has the HP and stiffness.
OK for tonights experiment I tried a HSS tool at 65 RPM the belts just sliped and came to a stop. For some reason back gear seams to cause the belts to slip more. I would have thought it would be the other way arround. Back into high gear after tightening the crap out of the belt from my previous back gear experiments, I broke the belt. So now hear I am screwd. What little I got done seamed to indicate the HSS was just as good as the carbide, which aint saying much. Fortunatly I have another belt, but it's a continious one so the whole head has to come appart to replace it. I have a fealling that I just did not do too good a jub in sharpening the HSS bit. I only have a large course wheeled general pourpose grinder for sharpening.
Are these leather belts? If so you can glue them. There used to be kits made to splice leather belts. Looked like a bunch of long staples. Below is a site that discusses leather belting and splicing them.
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It seems strange that engaging the back gears caused the belt to slip more. Should be the other way around. I may be insulting you (if so I apologize in advance), but you did pull the pin that disengages the head stock pulleys and lets the drive go through the gears?
============ save yourself a massive amount of aggravation.
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Most car parts stores will also have what they call an emergency fan belt that will work.
if this is the one
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is what they call a carbide grinder. The supplied silicone carbide [green] wheels are for carbide and will wear rapidly if used for steel. You will need to install an aluminum oxide [white] wheel for steel.
The carbide style grinder is *MUCH* better than attempting to grind the rake and relief by hand, but the base machine [even the Baldor] has limited accuracy with the table tilt and miter gage. Even more important is the repeatability so you can "slightly" change the rake/relief and when you find what works for you duplicate this. click on
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You may also wish to consider a 6 inch disk/4X36 belt sander in place of the grinder, with an improved miter gauge and tilt setting gage. With the proper belts/disks this will do a fine job on HHS lathe tools. I like the blue zarconium oxide belts for roughing and fine grit disks [again check with the auto stores paint departments/sections] will put a mirror finish on your tools.
A quick way for the legendary hand-honed edge is to use a blue bristle brush in your drill press at low speed and quickly swipe the edge across the brush.
However until you get the current turning problem solved, even the best tool grinds won't make that much difference. FWIW Emco's M2 lathe bits will work just as well as 5 or 10% cobalt at 1/2 or less the price and these are much easier to grind.
Avoid getting the bit so hot when grinding that it turns color. Don't press so hard and allow a little more time for the bit to cool off. If it hisses when you dunk it in water, its too hot and it may microcrack and have rapid failure.
Also invest in a carbide stick wheel dresser and keep the white wheels clean, flat and sharp.
Good luck and let us know how you make out.
Unka' George [George McDuffee] ============ Merchants have no country. The mere spot they stand on does not constitute so strong an attachment as that from which they draw their gains.
Thomas Jefferson (1743-1826), U.S. president. Letter, 17 March 1814.
I am highly insulted, of couarse I pulled the little pin that disengages the headstock pullys. Interesting you should ask, because that is the only thing I did. Well having not used back gear on this lathe for about
15 years I'm not really insulted just feeling a little stupid. I pulled the little pin but I did not pull the back gear engaging knob up front. I thought the little pin was it.
What is ammazing is that it really wasnt doing too bad, essentially running on grease friction. In fact enough to fool me into thinking the belt were just slipping again as they always do. I would cut for about
30 seconds or so until the thing just slowd down to a stop. I think this machine is going to kick ass in back gear.
The leather belts are still available from a place called Logan Actuator Co,
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They are available in both spliced leather or continouse nylon. for about $40.00 each. In fact this company makse every part for this lathe.
Well, you are getting there. Although the traditional screw-up with back gears is not pulling the pin and when you switch on there is a big squeal and sometimes smoke comes off the belt and everyone in the shop looks over to see who screwed up.....
Usually don;'t need to do it more then once before you remember PULL THE PIN!
Like you might not believe. I had a customer years ago claim he could not take a decent cut on his 11" Logan, and at the time, we had an old Model 957 (11" cabinet model with flat belt drive) in the shop.
I went out and without any fiddling, set up some 6" dia cast iron bar stock in the chuck. Put the lathe in back gear (yeah, I remembered both the pin and the rack) and took a cut 0.100" deep (0.2" on dia) at 0.010" per rev with no problem. No stalling, no slipping, just lots of chips.
My Dad told me that back in the day, when they would exhibit at shows, they would set up a 10" Logan taking a cut 1.000" deep (yeah, 2" on dia) on steel to show off. Admittedly, they had fudged the feeds to be REAL slow, and used a specially ground tool bit, but they did it. Impressive.
Actually, the belts we have are not leather. The open belt with Clipper(r) lacing are a composition material, and have the clips already installed, the continuous belts are nylon. Both are much stronger than leather, slip less, and stretch much less.
And, for the record, yes, I am family. My Grandfather started the company, and yes, the parts we have available are all NEW parts, not old stock or used (although once in awhile, we do have used parts available).
I kind of thought that was true about removing the key from the chuck before turning on the lathe. I only use the lathe for an occasional project once every few years. But when I do, I seam to always get the baptism of key in the face.
It's a pleasure to hear you and to hear your stories. I feel like I have the top factory rep on line. I got the green nylon belt that I will spend today installing it. You know, you may be the guy I ordered the belts from about a month ago. I have faith that I will get this situation under control and do your lathes proper justice.
There is a retired machinist across the street from me. I dont like to bother him because he uses oxygen half the time. But as someone pointed out, maybe I can lure him over with the aroma of old fashion cutting oil.
My lathe is an 11" Model 922 with a turret attachment. Once I get a handel on this maybe I will start to play with the turret.
Absolutely right, if you have the meter in the red... thats your limit, carbide or HSS. The only thing you can do is fool around with the rake angles of the tool to get it to cut more efficiently meaning less HP for the same chip removal or the same HP for more chip removal.
You are right and messing around with tool angles is just so much easier with HSS then carbide.
Don't get me wrong. Many things have a use in this life -- just that some other things may work just as well.
I see all these mentions of carbide tooling, variable speed drives, DRO's, etc., on a rec.crafts group. seems like overkill to me. Certainly I can see a guy spending time and money to install a DRO. Sort of like an engraved shotgun. Don't kill birds any deader but sure does look nice.
Maybe it is just old age creeping up on me. When I did my apprenticeship the Apprentice Master was an old guy -- must have been in his 60's :-) who had started his 6 year apprenticeship when he was
14 and he taught us a lot of stuff that seemed to be redundant at the time. How to pour and scrape babbitt bearings for example -- got me a nice raise 20 years later when I scrapped in the bearings on a surface grinder that no one else in the shop had a clue how to fix.
But getting back to HHS it just seems so much easier then using carbide. You can grind anything you want - chips too long and stringy, just grind a chip breaker; cutting aluminum add a bit of rake and clearance, etc. With carbide you are always looking for a different grade of insert and "damn, where did I put those tools with the brazed inserts with the chip breaker".
Now, before someone gets to raving about CNC where they are thinking in revolutions, I'm talking about the workshop down in the cellar, or out in the garage where you go to get away from the old woman and smoke your pipe.
Well said bruce. Although I really want a DRO because my eyes are just not what they were 30 years ago. I used to only buy venerar calipers, cheap did the job, but I cant read them anymore. Plus digital stuff is now also cheap.
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