Screw machines

Screw machines in the proper application are still probably one of the best types of "automatic lathe" on the market.

They dont work so well in short run job shops..but for say..a company that does repeated large quantities of the same parts over and over again..they are the utter t*ts.

Ill give you and example. Lug nuts.

They are cut from bar stock on screw machines in many cases, which includes forming any tapers, drilling and tapping and so on. Need a million lug nuts? Screw machine. Need 1000? CNC lathe

There are 2 main differences in screw machines. One type uses metal cams cut from 3/8-1/2" steel plates. The notches, rises and whatnot are put in by special cam cutting machines like a small upside down mill and just like a kids wind up music box..the various notches, rises, slopes and whatnot are used to control the actions of the various tools. These cams are saved and numbered and when the repeat job comes in again...they are installed with the proper tooling and dialed in and off you go. Cam machines often have the cams stored in a large filing cabinet drawer with the tooling for that job along with a print etc etc.

The other type uses precut cams installed in the machine which are arrainged by turning them on a shaft to different positions..much like an "adjustable cam"..which in effect they are. Works much the same way as cut cams. Set up each time can be a pain in the ass as you cant simply pull one out of the drawer and install it with the proper tooling. They dont however need a cam cutter or be sent out for cutting by a company that does cut cams.

Now there are CNC screw machines since the early 1990s Star, Citizen, Tornos, etc etc all started figuring ways to operate them via a computer with no cam. Most are just as fast as a mechanical machine and setup is far easier. Maintainence is higher of course as they are not purely mechanical, but they are able to do shorter runs of parts with much shorter setup times and often use the same tools from job to job.

A Bechler screw machine..mechanical..can be set up for a fairly complex job in 4-10 hrs. Tornos can be set up in 3-5 hrs. A Citizen screw machine, CNC, can be set up in 30minutes to an hour.. All of which require often special tooling..Screw Machine Tools..often left handed drills and so forth. Traub is another fine mechanical screw machine, along with Strohm, BSA, Acme-Gridley (usually very large work capable..up to 10" diameter) etc etc etc

Modern CNC Screw machines are blazingly fast. And expensive

I think Somma is the last American screw machine tooling company surviving

Take a look at the tooling, tool holders and other fun stuff. Most folks here will not have seen em before..and its interesting. Keep in mind..that America was built on US made screw machines like Brown and Sharpe and Gisholt and many many many others. along with the Swiss Traub, Bechler, Davenport, etc etc.

I should mention that many of them..had multiple spindles. So when you set up a machine..it took one cam..but up to 5 sets of tooling..each spindle would run the same cam program..and cut multiple parts at the same time. OR....it would perform seperate operations as the part was rotated around s circle..still in its spindle ...each position performing a seperate operation or group of operations.

Really really high effeciency..for a mechanical machine

As you will notice in some of the videos below..they are performing multiple operations AT THE SAME TIME on a single part, or one after another etc etc. Screw machines can compete with CNC lathes in many many operations. But..not all. But if you have one specific job that is long term..it can kick CNC ass for 1/100 the initial investment. Ive bought and sold perfectly good screw machines for $250-500

Try to turn out the same parts with a CNC machine sold for less than $70,000..and the screw machine will likely kick the ass of the CNC even then.

All gone now or changed over to CNC machines..but their machines still turn out billions of parts every day in little crowded stinky NOISEY shops all over America Many have been converted to mechanical /CNC.

I know a half dozen guys who have mechanical screw machines tucked away in the back of their shops that they will run one part a year. They may get an order for 10,000 lugnuts..and can turn em out in a couple days, then they put em back to sleep for another 11 months. The machines having long long ago been paid for..and are cheap to run and need little maintainence while they rest.

Most screw machines make parts from either bar stock..or rolls of "wire"...up to about 5/16" in material diameter. After that..it was bar stock in rotory feeders, or one bar at a time. Ive got a few Tornos shops that use both Omniturns for the secondary ops and the screw machines for primary ops. They turn complicated parts as small as .015 in diameter...15/1000s of an inch. Watch movement screws for example. Little bitty bastards that can take a half day to crank through a 10' bar of .018 material....bar being the only way to describe a small tiny wire..shrug

Some interesting videos on YouTube will show you how they work..and why many screwmachine guys are deaf.

They will do this, hour after hour after hour, day in and day out

(making specialty bolts from hex stock)

This particular machine will turn out a fully machined part..not just half of one....

There are a few other types of screw machines...many of which hold the material rigidly..and the tools turn..not the material. Those tend to be feed from coils of wire..as the wire spools cant be spun.

A side note..if you are going into a screw machine shop..wear your old shoes. Most of them have been running oil, both as coolant and machine lubrications..and the kitty litter (if any) used to sop up the spills and splashes will be everywhere. As you may have noticed in the above videos. They are not generally...clean shops.

Gunner, who has a serious love of screw machines..but wouldnt own one on a bet...his last 4 going to scrap because he couldnt find a buyer for very good quality, excellent condition, machines

As a side note...you may enjoy these as well...polygonal turning

Now...lets do that with a single point tool...

This is one of the better videos Ive seen

Now..polygonal turning has been around for much longer than CNC..

I maintain (2) Japanese Nikkos polygonal lathes that were built in

1967, All machancal and they will do just about anything the above CNC machines can do..except cut curves. Tapers..no problem

Gunner

Interviewed at one of these type shops about two years ago. Still remember the strong smell of cutting oil and haze in the air. Bit surprised at the size of most of the machines, much larger than I had envisioned. They had one single CNC and I think it ran oil as well for consistency with the ~20 screw machines.

You'll have a shot at 70 out of 80 machines. While still in use, this technology very much in decline. Any shop going down has beat them to shit.

Karl

Screw machines, the cam operated ones, can still make someone lots of money. But they need to be in good shape, have a good setup person, and have a very large quantity of the same part to make. Like 10,000. Eric

My thinking exactly.

i

Thanks, great post and great videos. Enjoyed them a lot.

i

Ignoramus30725 fired this volley in news:9MKdnaWQJYea6cDPnZ2dnUVZ snipped-for-privacy@giganews.com:

Yep, Gunner, that was an education! Good stuff!

Lloyd

My pleasure. Its fun to teach about something one takes a bit of joy in.