Rebuilding Single Tumbler Gearbox - Suggested Materials?

xplodee · Jan 12, 2019

Hey All-

I have a 1942 SB 10L that I rebuilt to excessive standards. I didn't rebuild the gearbox though, as well as a few other items. A while ago I located a better gearbox to re-work and install in place of my existing gearbox. It features the needle bearing version of the single tumbler which is a big improvement.

Anyway, I want to more or less create from scratch all of the shafting and any gears that are worn out. My questions are:

What is a good material for the two gear shafts and what is a good bearing material for these to run within? Originally one side runs in brass and one side runs within the cast iron itself, but these are worn out so I will rebush them. I'd like to select the best material possible. Unhardened 4140 and 932 bronze? 4140 and hardened tool steel?
What's a good material for the gears? It's easy to cut them from 1018 but I assume I should be using something better. 4140?
The splined tumbler shaft is particularly prone to wear. Any suggestions on how best to machine this? Should I bush the tumbler with brass to be a bit softer on the splined shaft?

I know that none of this is necessary, I've been running my machine for years with a worn out gearbox and it's fine. But I'd just like to do this as a machining learning process. Thanks for any advice and guidance!

iwananew10K · Jan 13, 2019

i don't think its brass...terrible bearing material...likely 932 bronze or something similar, so you're on the right track.

nothing wrong with 4140 for the pinion shafts but probably overkill, 1144 would be fine and work a little easier.

Gears maybe 1045? The 1018 would suffice but maybe just go all 1144?

Perhaps Mr. Oder will reply.

Good on ya for going all in.

EDIT- 2 materials, 1045 shafts and gears and 932 bearings sounds pretty darn good to me.

kitno455 · Jan 13, 2019

I'd use 4140 HT (prehard) for the gears. For the shafts, I'd use whatever I could get that was TGP in the correct size, but have a preference for 4140HT or 4142HT. For that splined shaft in particular, 1144SP or 1045 would be too soft, IMHO.

allan

iwananew10K · Jan 13, 2019

Agree that you certainly can't go wrong with the 4140.

Don Kinzer · Jan 13, 2019

xplodee said:
The splined tumbler shaft is particularly prone to wear. Any suggestions on how best to machine this?

I'm in the planning stage for making a 7/16" 6-spline shaft about 5 inches long (for a telescoping crossfeed screw for a taper attachment). I searched online for a supplier of such shafting and didn't find anything that small.

My plan is to cut the splines on the vertical mill using a dividing head and tailstock setup, first milling out a square bottomed groove and then finishing the spline tooth form using a single-point tool in a fly cutter. My main concern, other than grinding the cutting tool, is dealing with deflection. I suspect that I'll need to rig up some way to support the opposite side of the shaft.

iwananew10K · Jan 13, 2019

It isn't a spline.
It an involute gear that also serves as a shaft...if I am thinking of the right part in the gearbox.

kitno455 · Jan 13, 2019

iwananew10K said:
It isn't a spline.
It an involute gear that also serves as a shaft...if I am thinking of the right part in the gearbox.

Chad- you were fooled, Don is talking about something completely unrelated

allan

iwananew10K · Jan 13, 2019

actually, i thought Don was fooled by the opening post calling the gearbox shaft a spline.
in my effort to clarify,i muddied the water.

kitno455 · Jan 13, 2019

Well, I guess we can call it giant pinion wire

allan

Don Kinzer · Jan 13, 2019

kitno455 said:
Don is talking about something completely unrelated

If the OP is actually talking about a splined shaft, then my comments are on topic. The fact that my splined shaft is in a different part of a different brand of lathe is completely irrelevant. On the other hand, if the part in question is *not* actually a splined shaft then my comments don't apply.

iwananew10K · Jan 13, 2019

we used to call it involute shafting.

sorry for the off topic racer, i know you know what it is.

BTW- there is a guide to rebuilding the single tumbler box on the yahoo SB group...I'd link it but yahoo is screwy on iPad.

xplodee · Jan 14, 2019

Sorry guys, yes I'm referring to the shafting cut with an involute cutter, a long gear?

Thanks for all of the input! Looks like I'll be using 932 for the bearings and 4140 or something else for the shafting. I may reuse the existing two gear shafts and bush the ends with a hardened and ground material.

iwananew10K · Jan 14, 2019

you know you want to replace it all...

xplodee · Mar 2, 2019

While we’re on the topic- does anyone know the diametrical pitch and pressure angle of the single lever gearbox gears? I believe it is 14DP and 14 1/2 degrees pressure angle

SLK001 · Mar 2, 2019

I believe all 10L's have 16DP gears with a PA of 14½º. You can check this by measuring the outside diameter of any gear and dividing that by the number of teeth + 2. The result of this is the Diametral Pitch.

I at least know that the twin tumbler QCGB has 16DP gears (as well as all the other gears).

kitno455 · Mar 3, 2019

I think the gears inside the 10L single tumbler are 14 DP, but you should measure to be sure.

allan

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Rebuilding Single Tumbler Gearbox - Suggested Materials?

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