10L spindle gauge - external thread on cast iron

[StrayAlien]

Hi all,

I am attempting to make a gauge that apes the spindle for the 10L. I have some cast iron of unknown quality - cut from elevator weights. I am using cast to get some practice in for making some back plates - which will be cast iron.

I really am having difficulty getting it not to tear to hell when cutting a thread in it. Tool is a new brazed-on 60deg carbide that I have diamond-honed the nose down on to get a snug fit into the spindle thread.

I am cutting dry at the lowest speed back gear only taking 2-3 thou feed increments at compound with tool post at 29 degrees.

The only way I have managed to get a good finish on this material is spinning at about 700rpm and using a carbide tip. But I can't do that while threading.

Machinery's handbook says helix angle for 2.25" at 8tpi is just a little over 1 degree, so I figure the larger-than-one-degree angles on the tool will give enough clearance not to rub. (?)

Any hints? All help appreciated.

Greg.

 

[johnoder]

Any hints? All help appreciated.

You are trying to learn but what you're learning is that trash cast iron is not much to write home about.

Get some real stuff, like DURA Bar - or the down under version

Way better cutting with properly ground HSS

Don't neglect clearance for the fact that you are in a bore - when that is tried

Here is an old thread getting threading tool ground - just so

http://www.practicalmachinist.com/v...rinding-pointy-tools-285565/?highlight=pointy

 

[CalG]

really, why do people keep choosing to use carbide and then run at carbon steel speeds? Not even HSS is needed at "lowest back gear" speeds. Of course, it's getting difficult to find good carbon steel lathe tools these days.

 

[StrayAlien]

really, why do people keep choosing to use carbide and then run at carbon steel speeds? Not even HSS is needed at "lowest back gear" speeds. Of course, it's getting difficult to find good carbon steel lathe tools these days.

I am not sure if that is advice. Should I not? The choice of tool is because it was there, and the slow speed is because the thread goes near to a shoulder and I need to give myself time to disengage the half nuts and not crash it. Which I managed to not quite do in time and broke a tooth of a gear .. which I am really crapped off at .. but that is another story! Its also put any threading on hold as I can no longer thread ....

John: agree. I am learning that using scrap material that can be bought for next-to-nothing is painful. Re dura bar. Despite the enormous amount of Iron mined in Australia is is darned hard to find cast iron flat bar here. The irony being that many people buy their bar stock in from the US ....

 

[steve-l]

My 2 cents and I expect some flak on this, but carbide should not be used on your lathe. It is too light, not stiff enough and too slow. That machine was designed long before the availability of carbide tooling. Use HSS tooling. Learn to sharpen your own tooling.

 

[jonesturf]

Good carbide inserts will actually work well on an H10 with the correct speeds and feeds. I was running 0.025 doc on 4140ht at full speed and a high feed and it looked like glass while OD turning. Carbide can definitely be used but it's easier to learn with HSS and then progress.

Sent from my SM-N920V using Tapatalk

 

[StrayAlien]

Steve (and CaIG), no flack from me. I am always happy to hear the opinion of people that know more about this than I do. As a software developer of more than 30 years, I am happy to help progress knowledge to those that follow. I am an absolute beginner here though.

I did try a number of HSS shapes and angles - as a learner I experiment to see what works and what doesn't. Presently, it is mostly in the 'doesn't' category. :-) However, I can say that after a number of HSS experiments with almost all leading to fast dulling of the edge etc I tried an insert - a cheapie at that, and the results were *immediately* waaaay superior to HSS. So I could run at three times the speed and get better results and the edge lasted longer. Pretty compelling stuff really. With a carbide insert I could actually get a finish that had a sheen - there seemed to be nothing I could do with HSS to achieve same - not saying it was not possible, just all my attempts were not successful. 5 degrees and less with diamond honed edges that I could cut the hair off the back of my hand with. No joy.

Having said that, I will still persevere with HSS because I have lots of it that cost me almost nothing - and good stuff too!

I did go and get some 1214 (no 'L') and, honestly, was *amazed* at just how easy it was to machine. Nice. I thought I'd try creating a gauge in that stuff and then "Mr Bozo" entered the room and I stuffed up and broke a gear. Great .... no threading until I fix that.

 

[gadget73]

Doesn't low grade cast usually have a lot of silica and whatnot in the mix? I would figure that if you're cutting what amounts to metal mixed with sand its not gonna do so well for cutting or the cutting tool. Not an expert by any means, just taking a guess based on the trash I've seen inside of broken apart iron weights.

 

[steve-l]

There are lots of very well written info on effective HSS tool shapes and relief angles out there, so do a lot of reading. In my experience of more than 50 yrs., the advantage of HSS over carbide is that tool loading is much less because you can use more relief than with carbide, which reduces tool friction. Tool loading is important to minimize when using a small, light lathe. Yes, carbide has greater heat resistance, but the cost is tool load. HSS also offers more DOC than carbide. The very fact you are using a small, light machine means that speed is not a priority. As a beginner, speed is not always your friend, especially when single point threading. You can achieve every bit as good a finish as with carbide. I still use HSS during at least 50% of my lathe time. Now however, I use almost exclusively cobalt HSS tooling as it withstands higher temperatures and the edges last significantly longer than non-cobalt alloys. There are two simple rules when grinding HSS. First make certain your tool nose radius is never a point. That radius should equal 1,5 times your preferred feed rate and second, make certain that the tool back rake is large enough to prevent trapping swarf between the back of the tool and the work. You may also come to realize that the finest feed often does not deliver the best finishes. This is because the smallish chips are easily trapped behind the cutting edge and dragging on the work. Remember the number one problem in cutting anything on any machine is chip clearing.

 

[Dobermann]

If you're threading to a shoulder, you can really help yourself and reduce the chances of a clash and gouge against the shoulder (which would snap off a brazed carbide tip by the way) by cutting a small relief zone up against the shoulder down to a diameter that's the minor diameter of the thread. That way, you have a small "resting zone" which will give you time to disengage the half nuts without needing to worry about backing out the tool at the same time.

If you insist on grey cast iron, make sure you get some decent material. Good quality cast iron machines very easily. Stuff like old sash weights, barbell weights, and similar stuff is really poor quality and will likely contain some nasty inclusions which will contain mold sand and which will tear up just about any tool, especially something with a sharp point like a threading tool.

 

[StrayAlien]

gadget: agree. That is likely the case with this stuff I guess. It just eats tools.

Dobermann: I did have a relief zone. But my Mr Bozo beginners mistake was to in a moment-of-lapsed-thought, grab for the clutch wheel and not for the half nut lever. Bang. Oh well ...

Steve: thanks. Been doing what reading I can. I suspect my poor results may be to the tool dulling very quickly. Actually, not just dulled but looking like its edge has been filed off, so I reckon, as gadget says, this material is likely hard on tools. I prefer the idea of using HSS. And I have lots of it ...

Now to figure out how to restore threading capabilities .... :-/

 

[hitandmiss]

I have been threading on my 10L for over 35 years now.

I use the belt tension lever to drive during the cut. Just enough to make the spindle turn and not completely engaged.
As the relief shoulder approaches, start letting the belt slip, and finally the left hand is used as a brake on the drive pulley at the end of cut.

A little busy with coordination when you are starting out, but with a very loose belt drive, bumping a shoulder just stalls the spindle.

With a little practice, you don't need to be in back gear for threading.

Bill

 

[steve-l]

I have been threading on my 10L for over 35 years now.

I use the belt tension lever to drive during the cut. Just enough to make the spindle turn and not completely engaged.
As the relief shoulder approaches, start letting the belt slip, and finally the left hand is used as a brake on the drive pulley at the end of cut.

A little busy with coordination when you are starting out, but with a very loose belt drive, bumping a shoulder just stalls the spindle.

With a little practice, you don't need to be in back gear for threading.

Bill

Nice tip Bill.....Whenever I need to single point to a shoulder, I wuss out and use my big L&S as it has a spindle clutch and brake. I actually prefer to use my little SB 10K most of the time for single point threading.

 

[jim rozen]

From 20 feet away, this looks like: He's using carbide tooling because the elevator weights probably have
chilled spots in them. These would be 'harder than billy goat's dicks' to use the technical term.

1) no reason not to use carbide tooling in a small machine like this. Don't expect big lathe material removal
rates. If using them you need to have a diamond wheel to sharpen the tools, this is main impediment to
carbide tooling. A green wheel doesn't work that well.

2) get some better material. The durabar is a great choice.

3) machining the 8-pitch screw thread for this application means you have a HUGE amount of tool buried
in the stock at the end. This is probably part of the problem and will be there no matter what type of
tooling is used. This is the main rigidity problem. Keep all the machine gibs snugged up and be sure the
side clearance (helix angle) is correct on the back side of the tool so it does not scuff. The tool does
need to be dead center to get the correct thread angle.

4) there are ways to rough out a thread like this so you don't have the entire tool buried in the stock, and
take only a skim cut at the end. At the very least do NOT attempt to cut this thread as plunge in 90 degrees.
Be sure you understand the correct position for the compound, you are cutting an internal thread:

a) put the compound straight back away from you, so the handle as towards the rear of the lathe.
b) shift it 30 degrees (ignore the numbers on the dial, just count graduations) to the right. 29-1/2 if you are compulsive.
c) feed by turning the compound handle clockwise, looking along the screw axis from the handle end, that
is to say feed by increasing the number.

 

[JimBoyce]

Get left hand tooling, run spindle backward and thread to the right away from shoulders.

 

[StrayAlien]

Bill yep. Nice tip. That is one of the things I love about this forum. Simple truths on how to do stuff. Like JimBoyce's post. I almost laughed out loud at that! Thanks Jim. Something SOOO obvious! But you get wrapped up in other stuff. Nice one. That is how I will do it from now on. :-)

Jim(Rozen): Thanks. Your posts are also full of wisdom - I pay attention. I was using the compound as you say and not plunge cutting but I suspect the material is just a bit crap^2 and too porous. I'll get some pics up here but I suspect I may have to relegate this material to just what I bought it for initially and that is making some risers for the mill.

Sir Ted (all hail Sir Ted) has mustered up a replacement gear from his dusty catacombs of South Bend parts. I'll have to sell my other kidney but it'll get me going again. Given the amount of stuff I do that seems to involve a gear or three being crap or broken I'd best figure out how to make 'em. But that is another story ...

Greg.

 

[rokbottom]

Photos, no substitute for photos.
I am putting my money on tool relief angel.

 

[gadget73]

Just watch running it in reverse and cutting if you have a threaded chuck. if the tool digs in you'll just unscrew the chuck and that would not be good.

 

[michiganbuck]

QT:
[so I figure the larger-than-one-degree angles on the tool will give enough clearance not to rub. (?)]

I put (about) 5 or 6* clearance on my CI tool bit.. 7* for steel (about just eyeball).. bump my nose flat at the same (5 or 7*)not following the intersect of the two angles. Flat top for iron and flat top with a rake angle off the cutting edge for mild steel and aluminum perhaps 5-7*.

Put a piece of tape on my chuck to watch for pull out to a shoulder..easier to see than looking at the part.


TOOL BIT GRINDING #3 South Bend Clausing logan Lathe tubalcain - YouTube

 

[rokbottom]

Any updates?