Thread cutting help, please...

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dfwcnc

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I have an Atlas, 618 lathe that is run by a VFD (infinite speed control), and am wanting to cut threads, but I have no extra gears. The guy I bought the lathe from stripped them and put them on the package of another lathe. I was very disappointed to say the least. Needless to say, I have the manual for the Atlas Lathes, however my banjo gear bracket is not like the one in the manual, I only have two arms, the one in the manual has three. So, I'm stuck.

Your help is greatly appreciated. Thank you...
 
Check EBay. If you are in a hurry you will pay dearly but if you wait and WATCH there are deals to be had. I saw a set go for $75 a few months ago.
 
Thank you for your responses.

The gears are all over ebay, so I can buy the gears I need, or the whole set. I've never seen less than three sets for sale. I also have a cnc so I can make them in steel if I can get my hands on one to spec, then the CNC will pump them out all day. Sell the rest I guess.


Also, I have a double channel banjo, the one in the manual is a triple. So I have no desire to replace it, but figure out why mine is not in the manual and if anyone else has a double and how they cut threads. Obviously Atlas made this for the unit so there has to be some manual out there explaining how to use it.

Thanks~
 
I would like to use my banjo (that sounds weird).

A buddy tells to blow it off and cut threads manually and call it a day. Well heck, I guess I could do that, and will for my current project, but want my machine to do what it is intended to do.

I don't know what a hobb is, but will look it up. And after spending almost 800 rebuilding my 618, it's unlikely I'll be buying a new Chinese lathe, however, it would have probably been easier, that's for sure.

sssfox said:
The banjo will probably work if it fits your lathe. It only holds the gears in the proper positions. The slots allow a lot of adjustment, so the shape usually isn't critical.

Your problem is the gears. They are expensive and hard to find. I've talked to people who bought a lathe just to get the gears.

You would probably be better off learning to cut gears with a single point cutter or a hobb. I bought one from a guy in China that was reasonably priced. He also sold the cutter sets. Make sure you get the correct Diametric Pitch (16) and Pressure Angle (14.5).

You can make them from plastic, PVC or aluminum. They don't get a lot of pressure on them. You also need a milling machine and a rotary table or dividing head. If you search the internet, there is a ton of information on gear cutting.

It will be easier to buy a newer lathe that comes with gears, but if you plan on working with old iron, it would be better to learn gear cutting.

Steve Fox
Click to expand...
 
dfwcnc said:
I would like to use my banjo (that sounds weird).

A buddy tells to blow it off and cut threads manually and call it a day. Well heck, I guess I could do that, and will for my current project, but want my machine to do what it is intended to do.
Click to expand...

What does he mean by "manually"?
I also remember something about there being a stock size gear sold (Boston Gear maybe?) that fit the Atlas 618. The tooth pattern and sizes were right on but you had to ream the center and broach a keyway. There was also something about a banjo with 3 arms used for threading metric. Try the 618 Atlas/Craftsman Yahoo group that might be were I have seen it. Sorry my memory eludes me and I am more of a practical machinist than some where I would just buy a set for $150 before I spend $149 and 6 hours making a set. I would rather take that 6 hours and make something with the machine. Everyone is different.
 
Hobbs are more accurate, but you need a hobber to use them. Form cutters are probably better if purchasing a cutter. Or you can try making your own cutters ala HobyNut on Youtube. I have tried this method, and it works very well.

Did the guy leave you with power feed at least? If so, you should be able to measure the gear pitch off of the remaining gears. Measure the outer diameter, and the number of teeth. The pitch will be (number_of_teeth+2)/outer_diameter IIRC.
 
If you do cut some threads please post pics with the good and bad,I will be glad when I get mine going.All I can do is read about others----kroll
 
The straight cut hobs (approximate hobs) are the ones I was describing as done by HobbyNut. He has 4 or 5 videos on how to make the cutters, from machining the blank, to tempering, sharpening, and cutting your gears. I've tried it, and it works very well. The hob you linked was a spiral type. I've used the method you described (gash the blank, then let the hob drive it) to make a worm gear. It works reasonably well, but depending on the drag on the gear blank, the teeth don't come out quite uniform (at least mine didn't).

Here are the HobbyNut videos (well, link to the first one)

[video=youtube;nMS2un-kbg0]http://www.youtube.com/watch?v=nMS2un-kbg0&feature=share&list=UUUioUkO0IQyfii1K0mAZMHA[/video]
 
http://www.youtube.com/watch?v=qu0GToSvnxk This is another way to get a lathe to cut US or metric theads by adding a stepper motor to the end of the leadscrew. This could be easyer for you. Depends a lot on how many parts your missing. If you put a second stepper on the crosslide, you can also do tapers, and slotting jobs. Just another way to get a lathe to do threading without getting into the gear making biz. Any of the videos on you tube with the title ELS , Electronic Lead Screw should give you a better idea. ELS is also on yahoo groups as well.
 
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