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Gearbox Setting Vs. Longitudinal Feed

Bob Leistner

Plastic
Joined
Feb 3, 2010
Location
Pgh PA USA
Hi, I have gotten my 9" Type O up and running and I have a question that I haven't been able to find an answer. What position is best to set the gearbox when using the cross or long. feeds? Does it matter? Seems it should have an effect but I can't wrap my head around how exactly they interact.Seems if it were a big deal, I would have found the answer myself. Thank you for any help in advance.
 

Kevin T

Stainless
Joined
Jan 26, 2019
Hi, I have gotten my 9" Type O up and running and I have a question that I haven't been able to find an answer. What position is best to set the gearbox when using the cross or long. feeds? Does it matter? Seems it should have an effect but I can't wrap my head around how exactly they interact.Seems if it were a big deal, I would have found the answer myself. Thank you for any help in advance.

It matters! That is the "feed" rate in the "feed and speed" calculation. There should be an id plate on your gearbox that says how far the cutter will travel per revolution of the spindle. You can get big variations in the results by changing the gear position. Everything from a barber pole gouge in your work piece to a mirror finish!

Someone posted this calculator a while back and I saved it to use as a guide. Check it out.

Speeds & Feeds - LittleMachineShop.com

Now having said that... I "usually" leave my gearbox in the position where the oil tube drips onto the gear on the change lever.
 

SLK001

Stainless
Joined
Feb 8, 2015
Location
Coral Springs, FL USA
Here's what an H10 does feed wise. The longitudinal feeds are shown under the thread pitch feed and the cross feed is 3/8ths that of the longitudinal feeds. You set them depending on the material, surface finish you want and tool you have. All this interacts with how fast you want to get your operation done. Yes, it matters.

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johnoder

Diamond
Joined
Jul 16, 2004
Location
Houston, TX USA
Note the apron gearing on the H10 provides a 3 to 1 ratio between threads and long feeds.

This may be differing on the Series O

You will also find that in any number of pages of really OLD info that in the old days feeds were expressed in TURNS PER INCH
 

Bob Leistner

Plastic
Joined
Feb 3, 2010
Location
Pgh PA USA
Yes, the plate clearly says-Longitudinal Feeds 3 1/4 Times Threads Per Inch. Now I can see how wildly variable it can be. I was thinking it to be so small that it was insignificant. Thanks again for straightening me out.
 

Kevin T

Stainless
Joined
Jan 26, 2019
HA! You guys made me check my label. I never noticed the .375 times notation before for the crossfeed!
 

johnoder

Diamond
Joined
Jul 16, 2004
Location
Houston, TX USA
HA! You guys made me check my label. I never noticed the .375 times notation before for the crossfeed!


Indeed. Say your H10 was set for 10 TPI - that is .100 per turn - except the apron gearing changes that to .0333 per turn on long and .375 times .0333 on the cross slide
 








 
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