Threading Stainless Steel Shafts

[Curt]

First I read about the machine technicalities and metallurgic properties, I once worked in a chemistry lab of a foundry, then I sourced advice from "experts", machinists, and old timers. Finally I bought a new die set, not the Harbor Freight junk, the expensive high speed steel ones. For hand threading the major diameter is the key, along with lubrication and slow threading with small advances. It's not brass! This metal is really hard. It heats up and sticks if enough care isn't taken. I wasn't sure at the outset that I could cut decent threads in stainless steel shafting but it worked. I'm threading the ends for SS knobs and using SS gears on it. This is all going on the camera I'm building. X2, front and rear drive shafts, bearings, gears, and knobs. One never stops learning.

[Nathan Potter]

Curt, nice going, I think you have the idea. It's a slow process of threading by hand and it may help by having the diameter of the piece slightly under sized. Also use the best cutting oil. When threading, go a bit then back off letting the cutting chips fall free. Then continue, alternating cutting with backoff.

What is the diameter of the piece you are threading. Also what stainless alloy are you using? Low chrome and higher nickel content will help. Type 316 is a bitch while 25-5 is a lot easier.

Good luck.

Nate Potter, Austin TX.

[Leigh]

What alloy? There's a big difference.

- Leigh

[Tin Can]

Curt,

I'm a hack. I worked in a materials test lab for 30 years. My main mission was make it fast and just good enough, since we trashed every set-up as soon as we were done. Custom does not always means highest quality.

I admire your efforts. Tapping and cutting can be difficult at first. Everything you learn will be useful again.

I would have tack welded the knobs to the shaft with a Mig welder. Done in a jiffy. I was team leader, my meticulous understudies always preferred beauty over speed.

We await your camera, DIY lives!

[Curt]

Curt,

I'm a hack. I worked in a materials test lab for 30 years. My main mission was make it fast and just good enough, since we trashed every set-up as soon as we were done. Custom does not always means highest quality.

I admire your efforts. Tapping and cutting can be difficult at first. Everything you learn will be useful again.

I would have tack welded the knobs to the shaft with a Mig welder. Done in a jiffy. I was team leader, my meticulous understudies always preferred beauty over speed.

We await your camera, DIY lives!

Nate, Leigh, and Randy, thanks for the feedback it's all excellent. I have an Oxy Acetylene but no TIG here at my home shop. I'm not adversed to having a machine shop thread the ends but I'm confident I'll be able to do the job. I have what I think is a 303 shaft that earlier I threaded to 10 32. That piece was 3/16" and I had to reduce the diameter but the threads came out great. Nice and smooth. My standard is the Ebony line. I'm using Rosewood and Ebony, no Restricted Wood, but no titanium. I don't expect to achieve the Ebony status but getting as close as I can will be rewarding. It's going to be an 11x14 and I have already made a film holder to ANSI specs and that's very detailed. I'll show it at the end. It's in a different species, the final wood has been in the shop for years and is as stable as its going to get. I have a wood shop so I put a lot of pressure on myself to get a fine product. At 61 I've had a lot of technical background and college along with my Seabee stent and can do attitude from the Navy and Vietnam.

[Curt]

1/4" and I'm going to get several pieces and see which is the best. I'm interested in a D-Profile in 303 but I had a thought about how accurate the gear hubs set screws are located. That could be unfortunate. Machinability verses hardness is a determining point too. I'm aiming at a single material instead of say brass and stainless mixed. Many old wood cameras have done very well with brass for the shafts, racks, and pinion gears though. The problem I have decided to work out is getting the gear specifications, bore and OD, pitch, etc., to work with a shaft that requires a diameter specified for the knobs I have picked out. Without elaborating on the details it's a choice between knob style and hub size verses pinion hub bore. It's just one of the many technical exercises on this project. I'm enjoying it though and that makes a world of difference.

[Erik Larsen]

Curt, if you have any problems, you can try all thread rod instead. I hate working with stainless, it's my nemesis
Erik

[Curt]

Curt, if you have any problems, you can try all thread rod instead. I hate working with stainless, it's my nemesis
Erik

Erik, that's right, there are SS tubes with ID clearance that makes it look good. If all else I could use that for the visible portion and not have a problem with it. That falls into a "best fit" option. Thanks for mentioning that option.

[Scott Walker]

Stainless steel is a wonderfully metal to work with but it does take a bit of experimentation to get perfect results when doing any machining. Having a good understanding of the properties of the metal is paramount as well. My area of expertise is with 316LVM, 316, and 304. Probably the most universally important aspect of machining these alloys is a good lubricant, we used jokisch paste. We tried every available product and the jokisch paste gave us the best finished surface quality by a big margin and also the longest tool life. Chances are you will not be working with fully annealed metal and work hardened stainless is indeed a bit more difficult to cut threads in. If you are threading rod it is important to get the die started squarely, believe it or not you can actually thread a rod crooked and it is way easier to get the threads crooked than straight. The easiest way to ensure the threads start straight is to cut the rod square and taper it at the proper angle and taper it uniformly all the way around, if you have a lathe this is pretty simple, if not a drill press or even a hand drill will help, you can spin the rod in the drill and get the end fairly square and evenly tapered with a smooth or second cut mill file. We literally made miles of threads in stainless steel, some utilizing a lathe or jigs to ensure the thread was square and some entirely by hand and either way the results sucked if someone got sloppy squaring and tapering the rod before threading. I also sharpened all of our taps and dies to my own specs for cutting stainless, which helps greatly as well, but likely not necessary for your application.

[Curt]

Stainless steel is a wonderfully metal to work with but it does take a bit of experimentation to get perfect results when doing any machining. Having a good understanding of the properties of the metal is paramount as well. My area of expertise is with 316LVM, 316, and 304. Probably the most universally important aspect of machining these alloys is a good lubricant, we used jokisch paste. We tried every available product and the jokisch paste gave us the best finished surface quality by a big margin and also the longest tool life. Chances are you will not be working with fully annealed metal and work hardened stainless is indeed a bit more difficult to cut threads in. If you are threading rod it is important to get the die started squarely, believe it or not you can actually thread a rod crooked and it is way easier to get the threads crooked than straight. The easiest way to ensure the threads start straight is to cut the rod square and taper it at the proper angle and taper it uniformly all the way around, if you have a lathe this is pretty simple, if not a drill press or even a hand drill will help, you can spin the rod in the drill and get the end fairly square and evenly tapered with a smooth or second cut mill file. We literally made miles of threads in stainless steel, some utilizing a lathe or jigs to ensure the thread was square and some entirely by hand and either way the results sucked if someone got sloppy squaring and tapering the rod before threading. I also sharpened all of our taps and dies to my own specs for cutting stainless, which helps greatly as well, but likely not necessary for your application.

Scott, I spent some real time searching for the points you listed here. If I had read a description like this I would have been way ahead of the curve. I'm experienced with tap and die threading but Stainless Steel raises the bar. The lubricant is imperative and the type is important. I read about alignment and calculating formulas for finding the major and minor diameters. 60 & 90 degree angulation and other specs. In college I completed calculus, trig, and geometry but reading some descriptions caused me to go to sleep. So I beveled the end to start after I reduced the shaft diameter a little. For the real deal I'll use calipers and use more care. The threads were full depth though so I did something correct. When cutting I advanced the die only a 1/16" then backed it all the way off. Maybe overkill but it made the motion very smooth. The bottom line is cutting threads is a skill that takes practice and it is a valuable skill when learned correctly. Thanks for the instructions!