Project Southbend Gears

[Brent H]

A while ago I helped a member remove a Lathe from a basement. Well, seems like he has a couple more but they are these Southbend machines that seem to break the drive gears off fairly routinely. I figured, let’s make one out of steel and then maybe the gears would remain intact and something else can break instead -

I happened to have the cutter selection for the gears (16 DP x 14.5 PA) so that is a good thing. Gears/shaft will be made from a 2” round of mild steel and a 4” round of mild.

I started roughing out the parts today:

getting the gear spacing set

It’s nice when you get close to the dimensions required (1.6250”)

Facing the large gear down to correct thickness plus some adjustment allowance.

Plan is to press the large gear blank onto the shaft after roughing things out. The shaft of the system is 1.3125” diameter so I reduced the one end where the large gear fits to 1.3000” and left that 0.0125” lip to press the large gear up to. After the large gear is fitted I can 4 jaw church things up and get everything running try with the gears and the shaft bore.

More to come tomorrow I hope, for turning I was running the 2” shaft at 1000 RPM and feed was 0.004”. Stringy cuts but was taking 0.050” depth of cut and nice blue string with very little tool heat build up. For the 4” gear blank I was facing that at 300 RPM with a 0.002” feed across and a 0.050” depth of cut

 

[YotaBota]

I'm guessing the original is cast.
This is very interesting.

 

[Brent H]

@YotaBota - yes, original is cast iron and a one piece cast, then machined. Given the big gear and little gear are integral it would be most prudent to have a very good casting. Given that either gear seems to suffer from loosing teeth, the casting may have some flaws. As you can see in the next picture the little gear has not been brushing his teeth and lots many teeth:

There was a repair attempt to make a new shaft out of two different gears so I am thinking the failure is not limited to just the smaller gears.

today I faced off the big gear plate and bored it out for about a 0.002” press fit onto the new shaft. I then put the shaft into the 4 jaw, dialled it in and finished the small step and started boring it out. The idea is to press in a sintered bushing into the steel shaft on both ends for the gears to ride nicely on - this will also create an oil reservoir between the bushings that should help with lubrication.
Here is the rough sketch of the project:

spindle is 1.300” and the bore is 1.298”

Drill at this point is 45/64”. Next step is to drill just over 3/4 and then machine a 7/8” bore about 1” deep to accept a 3/4 x 7/8 sintered bushing.

For drilling the lathe was going 96 RPM. For boring the large gear blank I was turning 500 RPM , 0.040” depth of cut and a 0.004” feed rate. - I used the large boring bar for a more accurate and chatter free cut.

 

[Brent H]

Project update:

Performed the “Boring” task of making bushing reliefs to 0.875 diameter and 1.250” deep to accept 3/4 x 7/8 bronze bushings.

The two parts that must become one! They were pressed together and some Loctite 609 used to help add to the press fit : https://www.henkel-adhesives.com/ca/en/product/retaining-compounds/loctite_609.html
Once together I checked measurements, back in the 4 jaw, dialled back in and then cut things to proper sizes:

ready for gear teeth!

 

[Brent H]

Update: thar be some gear teeth cut!

large gear is 62 teeth and smaller one is 24. Both are 16 DP x 14.5° PA. Here is the cutter check on the large gear:

So we got the whole thing set up on the mill and away we went.

about an hour later:

And we check against the original:

Sexy!

The bushing arrived this afternoon so hopefully cut the smaller gear tomorrow, press in the bushings - drill an oil hole and Viola!

 

[combustable herbage]

Nice work @Brent H Looks like they cut nice and clean. One of the videos I watched the guy did was going back and forth doing gears but the way you did it seems more efficient the one I watched it took him hours and think he didn't do the full cut either so that's why it seemed so painful to watch.

 

[Brent H]

@combustable herbage : the depth of cut for a gear tooth is 2.250/DP so in my case it was 2.250/16= 0.141”

I set the mill up for 200 RPM and proceeded to hand feed the first tooth to see what kind of cut was going to happen and if my machine would not like it - turns out it was A-OK at a reasonable slow feed so I set that up and off it went. I was doing about a tooth a minute - hopefully not over the speed limit and the profile looks nice.

it will also help with mill size, dividing head etc. So the parts are solid.

I am also not big on farting around too much as I need to move onto the next gig and get things going on about 10 other milling/lathe projects - LOL.

One cool tool I have for my lathe is an ash scraper from Princess Auto - I cut off the log hook and it works great :

It hangs on the chip tray. $6 or something

 

[YYCHM]

An Ash Scraper with a Log Hook

 

[Brent H]

@YYCHM - it had a hook thing I think? Something for the “camper”. Anyway, I can’t find it on PA so maybe it is named something odd - I just remember cutting off a hook thing on the back of the scoop

 

[Brent H]

Southbend gears almost complete

bushings pressed in and all gears cut!! Fit to a shaft to check run out and I have about 0.0005”. So that is not bad with the original at About 0.003”.

I have the oil hole to drill - is it threaded and screw plugged like the one sample I have or is it typically a hole with a chamfer or is it like a Gits oiler plug thing????

Any preference @Canadium ?

 

[Johnwa]

@Brent H you make that look so simple! I’ve only cut a few gears and each time it stressed me out.
I’ve always thought of the teeth on the small gear as very expensive shear pins. Of the 4 gears in the back gear assembly they have highest stress on them.
I think a lot of them get broke when they are engaged to lock up the spindle when attempting to remove a stuck chuck.

 

[RobinHood]

Very nice. Should be much stronger than the original.

 

[Brent H]

@Johnwa : thank you for the nice words! I have the simple gear making a bit more dialled in now. The massive 12” rotary and 8” chuck absorb a lot of vibration and support things extremely well. Also, I have a lot of confidence (so far LOL) in the way my lathe is running right now. Seems very accurate over a long length and I can hit the numbers consistently. I was worried about having to flip the part end for end, dial it in the 4 jaw and then bore it out, but I will take 1/2 thou run out

For the rotary table calculation I just use this on line program thing:

http://www.bilar.co.uk/cgi-bin/division-calculator.pl
Works pretty slick and no guessing - just have to remember your turns and to move the indicator to the next step every time.

next projects include a bracket for the slotting attachment, a graduated dial for the tailstock, and the list goes on….

 

[YotaBota]

Well done Obi Wan.
Ref the GITS oiler - if the shaft stops with the gits facing downward, will the oil leak out or do the gits seal reasonably well? I know my 618 used a screw for the oil hole and with a rubber washer it didn't leak at all. Not as convenient as the gits but it worked.

 

[Brent H]

The Gits might dribble at the most - maybe a slow weep if left upside down. The screw is easy enough and I can machine a flat landing for it. Slight counter sink to make it sexy and that would be fine. Could update it to an Allen screw to really blow the minds of Southbenders - LOL

 

[DavidR8]

Awesome work Brent!

 

[Canadium]

Southbend gears almost complete ...

I have the oil hole to drill - is it threaded and screw plugged like the one sample I have or is it typically a hole with a chamfer or is it like a Gits oiler plug thing????

Any preference @Canadium ?

The original that I have is just like your sample, threaded and screw plugged. I would be inclined to just duplicate that myself although I am no engineer ie wouldn't know if there is an advantage to doing it differently.

Your work looks awesome so far!

 

[Brent H]

Done!

Found the manual and drawing with the screw so just robbed Peter to pay Paul. Drilled and tapped a 1/4-20 and put a wee landing for the screw. Evidently a copper washer would be the coup de grâce but I lack those. Will have to pass that baton on to @canadium…..

 

[combustable herbage]

Great Job Brent excellent outcome I hope you had a blast building it.

 

[Brent H]

@combustable herbage : building stuff is super great!! Better when it all works to perfection.

after this was done I threw a flywheel on the mill and skimmed a clutch face for my son’s good buddy - so cool