Rotary motion to reversible linear motion

[olf20]

I'm not totally happy with the way motion is transferred from the steel pressure plate to the final drive shaft via the rubber o-ring, so am making up a couple of compression spring holders to hold compression springs against the final driveshaft bearings to hold a more constant pressure between the rubber o-ring and the steel pressure plate.----Brian

All the snow blowers that use this type of drive use a lever and operator to apply
the pressure to the two. But they do work great for a long time, not to mention you
get reverse as a bonus.
olf20 / Bob

 

[Brian Rupnow]

What did I do today?--Well, not that much really. Since I am now going to put roller bearings on the shaft that meshes with the rack to drive the carriage back and forth, I had to make a new gear which gets locked to the new hardened shaft. (The old gear and shaft were machined from one piece of mild steel.) I like this gear better--the outside diameter of the first gear was not perfectly concentric to the bore, so it had a hard spot in it when the rack travelled full length. I haven't decided yet whether to make the new shaft from a piece of 1045 steel and leave it unhardened (but harder than mild steel) or to make the new shaft from 01 steel and harden the areas where the bearings ride on. Problem is, there's a keyway milled down one side of the shaft, and I don't know if the shaft will remain straight after hardening or if it will "banana" on me because of the keyway.

 

[Brian Rupnow]

Today I picked up my B68 roller bearings from Koyo, bored out my brass pillow block bearings, and pressed the Koyo bearings into place. So far, so good. Now I have a question, and all of my machinists who I used to ask questions of are now retired, so I will ask on here. I know that the roller bearings will gall a mild steel shaft. (There is no inner race). I have three types of shafting available to me, mild steel shaft, 4140 shaft, and 01 shaft. There is a 1/8" wide x 1/16" deep keyway cut down one side of the shaft. I could make the shaft from 01 steel, then flame harden and quench the areas that the bearings ride on. Only thing is, with that keyway down one side of the shaft I am afraid that the shaft will go "banana shaped" when I do that. I don't want to use mild steel shaft because, as I said, the bearing rollers will gall it. I have a piece of 4140 shaft that seems to cut just fine using a carbide tool in my lathe. I could use the 4140 shaft, in it's unhardened state, as I purchased it, but I don't know if the bearings will gall the 4140 shaft in it's unhardened state. I'm open for suggestions and hope to here from someone who has experience. ---Brian

 

[Sparky_SC]

If it is 4140PH (prehardened) I would go with that. The prehard version is very common so I would not be surprised if that is what you have. It machines well even though it is around Rc 35-40. 4140 annealed would also work for this application.

I wouldn't try hardening the o1, I think that would cause issues. The surface finish on the shaft is just as important as the hardness, perhaps even more.

In your application I doubt you will ever have enough load or run time to ever cause any problems. I would just polish up the bearing area on the shaft to a mirror finish. If it was for something like a car transmission my reply would be quite different.