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1943 16", broken gear, tumbler area

Greg White

Titanium
Joined
Jan 22, 2007
Location
Pinckney Mi.
This machine is a single tumbler, the gear in question is the smallest one thats closest to the left end, it is in the row of gears that get bigger as they go to the right, I use that position a lot(a whole lot) for a job I do.
I want to pull the gear box assembly and get it on the bench.
How do I remove feed screw from this gear box?

Should I pull the big gear on left end outside the box,
along with the arm that goes towards the back and up into the other gears before or after i remove tumbler box?

Where can I buy the broken gear(s)?

Thanks guys, it also broke my heart when the gears broke.
Gw
 
Hello Greg,

It's been a while since I took my 16" SB lathe apart, but I ended up removing the bearing block at the tail stock end, temporarily supporting the feed/lead screw. I got the banjo gearing out of the way, then removed the gearbox with the feed/lead screw attached. There is a tapered pin that affixes the feed/lead screw, and is much easier to get at, as you can put it on a bench, upside down.

I hope this helps.

Brian
 
Here is the assembly diagram and parts list for your single tumbler GB:

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If I read your post correctly, you need part number PT615K16FH1 "Cone Gear 16T". Ted may have them, but in 1995 they were listed as "THESE PARTS ARE NO LONGER AVAILABLE". Don't despair, tho, just search Amazon for BOSTON GEAR.

You will need:
1) Number of teeth
2) Diametral Pitch
3) Pressure angle (in this case, it is 14½º)
4) Bore size
5) Key slot width
6) Face width
7) Material (Cast Iron)

Gather all the above info and we can proceed from there.
 
Thank you folks so much,yesterday when she come un done
just made me dizzy, didnt get much sleep last nite,but still got a better out look this morning. Thanks men, i will per sue
what you have given me.

the big gear on left,outside of gear box,with the arm(casting) the extends up and towards the back, thats the "banjo"? should that come off before i remove tumbler box?
Gw
 
Yes, take off the banjo, then pull out the lead screw.

There is a hole on the left side of the gearbox that lines up with the lead screw. Stick a socket extension through the hole, put on the correct socket, and use an impact to remove one, and then the other jam nut holding a gear on the lead screw. The gear is keyed, but should slide off. At that point, you can remove the right side lead screw bearing on the far right end of the bed, and slide the lead screw to the right.

If you leave the carriage in the middle of the bed, the lead screw can just hang there. You may want to tie it up though.

Now you can remove the screws in the v-way that hold the gear box to the lathe and drop the gearbox off. It is heavy.

If you don't have a parts breakdown, go to manufacturer's index, South Bend section of vintagemachinery.org and get one. Taking the gearbox apart is not without hazards.

When you get ready for the new gear, get in touch with me. I may have one for you.
 
so I got it on the bench,thing is heavy with that lead screw attached. SLLK001, you are correct about part number.
thank you for helping sir and other sirs!!!
never made gears nor did any in depth work with them,
what is diametral pitch?can i even measure it? i will head back to barn for other data.
I looked at amazon,boston gear, got overwelmed ,

16 teeth
1" bore
5/8 wide
3/16 keyway
Greg
 
nt1953, I missed your post,your directions woulda saved me considerable effort, i did get her on the bench,thanks for the gear offer, does it match the datas I posted above? that would be awsome.
Gw
 
what is diametral pitch?can i even measure it?

It relates to TOOTH SIZE. Only so many "big" teeth can fit on a diameter that many small teeth would fit on

Its commonly "abbreviated" to "DP"

Here is a way to FIND OUT what gear has what DP

Measure OD with mic

Count teeth, add two to that count

Divide the dia into the count plus two

Say your 16 tooth was 1.500 OD

18 divided by 1.5 = 12 DP - but sounds too small to accommodate a 1" bore with a key way

Maybe 10 DP and 1.800" OD ?
 
The gear i need broke in two,cant measure od, i think anyway, its early havent been to shop yet.
This gear is the smallest in the set, and feeds at the fastest feed it will go,it split at the keyway area, in retrospect, i am very very surprised it worked as hard as it did, i will lighten up on er when it goes back together.
I really do appreciate you fellas taking the time to think and talk aboot MY problem,thank you all.
Greg
 
the gear on the selector arm that mates with that gear will be the same diametral pitch...tooth count and outside diameter of it will tell you what pitch you need.
 
The gear i need broke in two,cant measure od,...
Just stick the halves together and throw some calipers across them. Doesn't have to be real close but with 16 teeth, I'd be concerned that was non-standard. With 14 1/2* pressure angle you get a fair amount of undercut with low numbers of teeth. It's pretty common to avoid that by "spreading" the teeth on the pinion. Your od measurement will give you a clue to whether that has been done.
 
I'll guess since it broke in half that it is 1.500" OD and 12 DP. I'll further guess that it failed at keyway

More than one way to skin that O.D. cat

If you are comfortable that the bore really is ONE INCH, then a radial measurement with something as ordinary as a machinist's hook rule will tell you that side of bore to top of tooth is 1/4" for a 1.500 OD, and near 13/32 (.400") for a 1.800 OD
 
I got my mics into measure the shaft it fits on,
1.000+- a 1/2 thou,headed to barn to do ur measure
John.....,from rad.of bore to od of gear is as you said, .400,by putting the tree pcs this gear broke into( not a easy task),2 big pcs,and 1 tooth from above keyway, it is 1.8 in dia., how the heck you know all this is beyond me guys, one lifetime isnt enough, would be great to work along side/for/with you all.
Greg
 
10 DP should do ya, then. Not spread centers, luckily. 90% chance it's 14 1/2* pressure angle.

Should be able to get one from Boston or Browning or one of the other places ... as I remember, in the smaller gears you can get steel ones instead of cast iron. Seems like a good idea in this case.
 








 
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