"Toothache"

Gary

SE Kansas
I have a problem with Plastic Gears, especially INSIDE the Headstock. I was attempting to make a 300 Blackout OAL blank addition to my Hornady OAL guage set. I had drilled the case with a 9/32" drill bit and was attempting the internal threading of the brass case with a 5/16 x36 Tap when I hear the gear spit teeth. LMS is getting my order for replacement gears this evening. Not sure I want to replace the bearings, but since I'll be there, I probably should. What's your opinion?
 

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Ian

Notorious member
I have zero play in the ball bearings on mine, and I've abused them a good bit with interrupted cuts and hard thrust loads. Your call. Seems the reduction gear is a high-failure item, I expect mine to go any day now but am not convinced that Grizzly isn't having theirs produced currently with the zink gear since it hasn't broken already.
 

Gary

SE Kansas
So, you replaced the bearings in your lathe without the gear upgrade. I'd do that to if that gear wasn't already gone. Guess the total deal then, bearings, and gears. At least if a gear gives it up in the future it will more than likely be a gear outside the headstock. Better get the parts ordered then; thanks Ian.
 

Ian

Notorious member
No, I haven't replaced any of it. I don't even know if the gear is plastic or not. The upgrade to the bearings is to replace the sealed, deep-cup ball bearings with tapered roller bearings per a kit LMS sells. I see no need to trade extra thrust capacity for constant need to adjust end play and preload, so I likely will never upgrade to tapered roller even if the ball bearings require replacing at some point.
 

Brad

Benevolent Overlord and site owner
Staff member
Ouch. That is worse than a toothache in your mouth.

That lathe needs an oral surgeon, and soon.
 
F

freebullet

Guest
My opinion is that you broke it.:eek: You did a fine job at that. At least you don't halfarse things.;)
 

Gary

SE Kansas
I'm not certain how to take your comment, but I'll scratch it off as being sarcastic. Anyhow, went to LMS to order parts and they are all back ordered. And in reflection, I'll leave the present bearings alone and just replace the gears.
 
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Gary

SE Kansas
UPDATE!! Called LMS and Roger says that the gear set won't be in stock for at least a month, maybe longer. I DON'T want to put plastic gears back in the head stock, but I might not have a choice. Anyone have any ideas as to where I could get the gear set I need(metal)?
 

Ian

Notorious member
Your lathe should have come with a manual, if it didn't, download the PDF manual from Grizzly's website. Find the part callout in the drawing, get the number, call Grizzly, and order a couple of them. Take two aspirin and call me in the morning.
 

Gary

SE Kansas
You didn't see the sentence whereby I stated I DON'T want to put plastic back in the head stock. I know, I know; get the plastic while I'm waiting for the metal gears. Probably going to go that route, it's very easy to get the head stock off the lathe and my neighbor has a 5 ton press so I don't think it'll be much of a chore to replace them. One other thing I thought about, is getting a hold of Seig and see if they have the parts.
Thanks for the words Ian.
 

Gary

SE Kansas
Well, bit the bullet so to speak and ordered Plastic Grizzly gears while I wait for the metal gears to be in stock. I did get a message from a Ebayer that had the "right" gears but the teeth were not the same as the stock Grizzly gears ( more teeth on each gear). Fella said they would work and the speeds on the lathe wouldn't change very much, so there's that to consider. They actually looked better in terms of finished product than the Asian gears, and less expensive. They were manufactured for a company in London. Gears should have shipped today, but they didn't. I ordered last night. Holiday misfortune I suppose. Keep you posted.
 
F

freebullet

Guest
'm note certain how to take your comment,
It was meant as a light rib poke & a compliment.:D

Hopefully, you'll get it working soon & even have spares.

In another thread it was mentioned that most lathes even fairly big ones have a plastic or phenolic gear as a break point to protect other components.
 

Gary

SE Kansas
Understood. I'm a yuuuge fan of Sarcasm, use it all the time. BTW, I got notice Grizzly shipped the gears, be back in business next week.
 

KeithB

Resident Half Fast Machinist
Rotary power is basically torque x RPM, so devices that rotate at slow RPM require/produce greater torque, meaning the force transmitted through a gear tooth is greater. If the teeth on all your gears are the same size, then the slowest rotating gear will be the one to shed a tooth. Slow RPM gears need to be wider or larger than the fast RPM gears in the gear train.

Kind of like electricity, same amount of power can be transmitted at low voltage/high current or high voltage/low current, gear trains are mechanical transformers.

Light cuts at higher RPMs might load the teeth less.
 

Brad

Benevolent Overlord and site owner
Staff member
That is something I did not know. Thanks Keith. Itmis interesting to eland things like that and then see it in action and better understand why some parts are made the way they are.
 

Gary

SE Kansas
Great info Keith!! I'm a newbie concerning a Metal Lathe and I need all the little pearls I can get. I'm behind in my reading but at least I was thinking on the right track after the fact. Now, as concerns internal threading, would a faster rpm when feeding the tap have prevented the teeth from being "pulled"? Also, was the tap I was using (5/16 x 36) a contributing factor?
 

Pistolero

Well-Known Member
Good job, Keith. Sometimes I forget that stuff that engineers take for granted isn't widely known for those
who haven't worked through the math in classes, and I fail to point out things like this unless a clear
question is asked. Didn't occur to me to mention this, good that it did for you. But then again,
you are a teacher, used to explaining, and better yet, knowing when and what to explain without the
explicit question being asked.

Reminds me of when I was a grad student, working on my thesis. We had a summer exchange student
from Russia, considered QUITE exotic in the early 70s Cold War era. He was an electrical engineer, was
interested in our hybrid electric bus and car prototypes. His English was good but not great (but infinitely
better than my Rooskie, at that time) but we were easily able to communicate with equations on the chalk board. He
pronounced torque, as "torrr-kee", a bit humorous. But I had to explain the same thing to him when were discussing the
electric drive motor and the gearing system we had used in the hybrid car. Had to adjust the "torkee"
with different gear ratios, even though the power was the same. Once he saw the equations, he got
it. Math, the universal language.

Bill