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X-Bracing

ja762

Aluminum
Joined
Dec 12, 2017
I was just looking at this ad for some SB parts, when this caught my eye...

"Also have a 6' hard bed with the much sought after and hard to find "X" bracing, and no ridge like 90% or more of the machines have." IMG_0811.JPG

Just wondering how common or uncommon the x-bracing was. Obviously x-bracing has much more torsional strength/rigidity than straight bracing, but is there any noticeable difference in actual use?
And, is it really that common for old SB's to have a ridge on the ways?
 
I was just looking at this ad for some SB parts, when this caught my eye...

"Also have a 6' hard bed with the much sought after and hard to find "X" bracing, and no ridge like 90% or more of the machines have." View attachment 221231

Just wondering how common or uncommon the x-bracing was. Obviously x-bracing has much more torsional strength/rigidity than straight bracing, but is there any noticeable difference in actual use?
And, is it really that common for old SB's to have a ridge on the ways?

The ridge is a pretty common indication of bedwear.


I do think it would make it would make stringy chips an even bigger pain in the ass.
 
I do think it would make it would make stringy chips an even bigger pain in the ass.
It's funny you mention that. Yesterday I was doing some turning and was ending up with 6'+ long chips, and I was amazed at how they just snaked right down between the x's and into the chip pan w/o ever getting caught up.
I'm sure that wouldn't always be the case. But, then again, if I were using a proper tool I wouldn't have 6' long chips, right?
Oh well, I'm still learning.
 
A bed really shouldn't see heavy torsional loads to begin with
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Cutting loads are torsional loads on the work pieced, which are grounded through the headstock to the bed, back to the cutting tool. Not insignificant on heavy cuts, think 1/4 deep cuts with 0.040 feed on 6" work piece.

From The specific cutting force
cutting force for "steel" ranges form from 1500 to 3000 N/mm^2, converting say 2000 N/mm^2 to lb/in^2 is 290000 lbs/in^2, cut area is 0.25X0.04 total force is 2900 lbs, working length is 1/4 foot total torque is 725 FtLbs. For comparison the 2018 Ford Powerstroke engine list torque as 935 Ft/Lbs.

CarlBoyd
 
Cutting loads are torsional loads on the work pieced, which are grounded through the headstock to the bed, back to the cutting tool. Not insignificant on heavy cuts, think 1/4 deep cuts with 0.040 feed on 6" work piece.

From The specific cutting force
cutting force for "steel" ranges form from 1500 to 3000 N/mm^2, converting say 2000 N/mm^2 to lb/in^2 is 290000 lbs/in^2, cut area is 0.25X0.04 total force is 2900 lbs, working length is 1/4 foot total torque is 725 FtLbs. For comparison the 2018 Ford Powerstroke engine list torque as 935 Ft/Lbs.

CarlBoyd

I agree, it seems to me that the loads on a lathe are almost entirely torsional. But, the numbers are really quite a surprise. 725 ft/lbs? :eek: That's more than twice as much torque as my old Camaro.
 
Cutting loads are torsional loads on the work pieced, which are grounded through the headstock to the bed, back to the cutting tool. Not insignificant on heavy cuts, think 1/4 deep cuts with 0.040 feed on 6" work piece.

From The specific cutting force
cutting force for "steel" ranges form from 1500 to 3000 N/mm^2, converting say 2000 N/mm^2 to lb/in^2 is 290000 lbs/in^2, cut area is 0.25X0.04 total force is 2900 lbs, working length is 1/4 foot total torque is 725 FtLbs. For comparison the 2018 Ford Powerstroke engine list torque as 935 Ft/Lbs.

CarlBoyd

You're right, just like a pump frame. I edited my post to reflect. No more statics before caffeine. :)

Might be a fun statics problem. 1hp at 50rpm = ~105 lb-ft or torque. How much would the bed twist up?
 
I agree, it seems to me that the loads on a lathe are almost entirely torsional. But, the numbers are really quite a surprise. 725 ft/lbs? :eek: That's more than twice as much torque as my old Camaro.

My 3hp gear head will lay down ~930lb-ft in lowest setting.
 
With those kinds of numbers I can definitely see the advantage of the x-bracing, then.
I had no idea one of these machines could apply that much force.
 








 
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