Drawtube Installation Help!

[chacho]

Good night everyone!

We need to install a drawtube on our Doosan Puma 700L. We took the original drawtube out from the chuck side; it has slots at the end face that allow it to be screwed or unscrewed to the hydraulic cylinder (Samchully SDL-30516). This original drawtube came our very easily and there were no signs of any adhesive on the thread – it is brand new and presumably factory installed.

We had an independent service tech visit and install the new drawpipe and chuck. We started machining a set of softjaws but noticed the chuck motion range to be decreasing after some clamp/unclamp cycles – the drawtube became loose from the cylinder. Fortunately, it was softjaws we were machining and not a clamped part that would have flown off.

We called the tech, and he was no help. I don’t believe he tightened it enough when installing and he admitted to not verifying if the whole thread was screwed in/engaged at any time.

Neither the Samchully hydraulic cylinder nor the chuck manual make any note of Loctite being applied at the thread and there is no locknut either. Am I missing something? How is this assembly prevented from unscrewing?

Does anyone have experience with these cylinders? Do I need to use Loctite or just make sure it is properly tightened? I would like to avoid gluing the drawtube and cylinder together if unnecessary, it could complicate disassembly in the future as this is a large machine.

Thanks for your help!

 

[chacho]

Hi everyone!

Should I just tighten or should I use Loctite for the drawtube and cylinder thread?

I'm thinking on using the blue Loctite 242 medium strength adhesive so I can break the bond without heating.

Sorry for bumping this thread but I'm getting ready to install and would like some advise.

Thanks!

 

[guythatbrews]

If you locktite something that big even with blue you will never ezver get it loose ever! Without heat.

The drawtube should be shouldered on the end in the actuator. Just really hold the end of the spanner deal in tight and rap the handle with a piece of brass or something. The chuck end should have some kind of detent to kinda hold in place. If the new chuck is a different brand the drawtube length might have changed.

If everything is the right length there is not much extra room to unscrew enough to make a difference.

 

[Fadriver]

Good night everyone!

We need to install a drawtube on our Doosan Puma 700L. We took the original drawtube out from the chuck side; it has slots at the end face that allow it to be screwed or unscrewed to the hydraulic cylinder (Samchully SDL-30516). This original drawtube came our very easily and there were no signs of any adhesive on the thread – it is brand new and presumably factory installed.

We had an independent service tech visit and install the new drawpipe and chuck. We started machining a set of softjaws but noticed the chuck motion range to be decreasing after some clamp/unclamp cycles – the drawtube became loose from the cylinder. Fortunately, it was softjaws we were machining and not a clamped part that would have flown off.

We called the tech, and he was no help. I don’t believe he tightened it enough when installing and he admitted to not verifying if the whole thread was screwed in/engaged at any time.

Neither the Samchully hydraulic cylinder nor the chuck manual make any note of Loctite being applied at the thread and there is no locknut either. Am I missing something? How is this assembly prevented from unscrewing?

Does anyone have experience with these cylinders? Do I need to use Loctite or just make sure it is properly tightened? I would like to avoid gluing the drawtube and cylinder together if unnecessary, it could complicate disassembly in the future as this is a large machine.

Thanks for your help!

Greetings from Ca.
We had same problem several years back lost a part at very end of a cycle no damage
part or injury, we removed chuck and close cylinder and tightened drawtube no locktite
bought the center nut new, that carry a ball bearing small like 3/16 that makes spin when
everything is lubed, chuck end, that prevents the drawtube to un-tighten, ours is hollow
for bar, have other cnc lathe fitted with solid chuck and at end have a ball bearing that spins
if draw tube tries to unscrew, just tight draw tube, and check chuck for the small bearing it maybe
missing,its why had to purchase oe part ours are kitagawa 12"

 

[chacho]

Greetings from Ca.
We had same problem several years back lost a part at very end of a cycle no damage
part or injury, we removed chuck and close cylinder and tightened drawtube no locktite
bought the center nut new, that carry a ball bearing small like 3/16 that makes spin when
everything is lubed, chuck end, that prevents the drawtube to un-tighten, ours is hollow
for bar, have other cnc lathe fitted with solid chuck and at end have a ball bearing that spins
if draw tube tries to unscrew, just tight draw tube, and check chuck for the small bearing it maybe
missing,its why had to purchase oe part ours are kitagawa 12"

Hi! Thanks for your reply.

Did your drawtube unscrew from the cylinder or from the chuck nut?

 

[Fadriver]

Hi! Thanks for your reply.

Did your drawtube unscrew from the cylinder or from the chuck nut?

From cylinder, its why length increases and let the part go.
it was scary for me as owner, it my operator gets hurt big f**deal,
thanks god, was like 8yrs ago.

 

[chacho]

Thanks for the replies!

It is a new 24" chuck, but we made this drawbar to proper length per the chuck and cylinder operator's manual instructions. So I'm hoping we are good on length.

Our cylinder does have a long stroke. When the cylinder is totally retracted the drawpipe does fit in between chuck and cylinder, even if totally unscrewed from the piston.

We verified our chuck drawnut has the 'holding' positions every half turn, presumably to prevent it from unscrewing -at the chuck end- but permitting adjustment. The thread on the drawnut and drawtube is not fully engaged but rather is adjusted within the holding points to fine tune the chuck clamp/unclamp range.

I think these holding position only actually 'work' when the chuck is in an unbound position (not clamped or unclamped) and thus should not be spinning. Anyway, I'm thinking we are safe on the chuck side.

I've read a couple Kitagawa manuals for similar sized cylinders and those do require a thread adhesive on the cylinder/drawpipe thread, but they do not state what strength. Samchully manuals do not mention adhesive but don't mention a tightening torque either. Drawtube designs for both brands of cylinder are virtually the same.

From the previous replies it seems Loctite is unnecessary, but loosing grip while turning seems scary dangerous. Just want to make sure we're being safe. For the time being I will install without any adhesive and keep on eye on it.

Please let me know of any additional thoughts on this matter.

Thanks again!

 

[Fadriver]

Thanks for the replies!

It is a new 24" chuck, but we made this drawbar to proper length per the chuck and cylinder operator's manual instructions. So I'm hoping we are good on length.

Our cylinder does have a long stroke. When the cylinder is totally retracted the drawpipe does fit in between chuck and cylinder, even if totally unscrewed from the piston.

We verified our chuck drawnut has the 'holding' positions every half turn, presumably to prevent it from unscrewing -at the chuck end- but permitting adjustment. The thread on the drawnut and drawtube is not fully engaged but rather is adjusted within the holding points to fine tune the chuck clamp/unclamp range.

I think these holding position only actually 'work' when the chuck is in an unbound position (not clamped or unclamped) and thus should not be spinning. Anyway, I'm thinking we are safe on the chuck side.

I've read a couple Kitagawa manuals for similar sized cylinders and those do require a thread adhesive on the cylinder/drawpipe thread, but they do not state what strength. Samchully manuals do not mention adhesive but don't mention a tightening torque either. Drawtube designs for both brands of cylinder are virtually the same.

From the previous replies it seems Loctite is unnecessary, but loosing grip while turning seems scary dangerous. Just want to make sure we're being safe. For the time being I will install without any adhesive and keep on eye on it.

Please let me know of any additional thoughts on this matter.

Thanks again!

when you said we made the draw tube, so its not the original, thread length and fitment
must be check, without chuck tighten draw tube and measure, length of chuck stroke you need
good engagement both sides,i don't recall any like teflon tape, like the one used on pipe thd.
I think this one is straight metric thd. so tape has no use, good tight and lube chuck end nut
and i would clamp something on the jaws and give some m3 and m4s and check the cuck jaw nut with
caliper very much you get constant reading is the area you detect if increase or decreases stroke
24" in. is heavy, is a vertical lathe probably.

 

[Fadriver]

when you said we made the draw tube, so its not the original, thread length and fitment
must be check, without chuck tighten draw tube and measure, length of chuck stroke you need
good engagement both sides,i don't recall any like teflon tape, like the one used on pipe thd.
I think this one is straight metric thd. so tape has no use, good tight and lube chuck end nut
and i would clamp something on the jaws and give some m3 and m4s and check the cuck jaw nut with
caliper very much you get constant reading is the area you detect if increase or decreases stroke
24" in. is heavy, is a vertical lathe probably.

what was the OE chuck specified by machine builder?
are you tryng to install something bigger?

 

[chacho]

Hi, this is a Doosan Puma 700L horizontal lathe.

The OE spec. is for a 24" Samchully HCH-24 chuck, which we bought new surplus from eBay. Unfortunately the chuck came with a smaller drawnut, we decided on making a new drawtube instead of modifying the nut, it seemed quicker and easier at the time.

Regards!

 

[chacho]

Update. My conclusion on this matter.

We have been doing some light machining since installing the drawpipe without any adhesive and everything is good.

Looks like Loctite is not needed for this cylinder/drawtube at least with our machining conditions.

I guess some thread adhesive couldn't harm anything and would provide extra safety and peace of mind. Downside is having to apply heat when disassembling, in a large machine it could be a headache to take out drawtube and cylinder together.

Thanks everyone for your help!

 

[escapethewrmhole]

Update. My conclusion on this matter.

We have been doing some light machining since installing the drawpipe without any adhesive and everything is good.

Looks like Loctite is not needed for this cylinder/drawtube at least with our machining conditions.

I guess some thread adhesive couldn't harm anything and would provide extra safety and peace of mind. Downside is having to apply heat when disassembling, in a large machine it could be a headache to take out drawtube and cylinder together.

Thanks everyone for your help!

You should never, ever need loctite on a draw tube. If anything you want to ensure you coat it in anti-seize. If you loctite it on or leave it without anti-seize you're going to have a really fun bill when it comes time to do chuck maintenance, or the actuator seals fail.

 

[guythatbrews]

If the drawtube is correct length it can't completely unscrew. If it unscrews it is too short. Never, ever use threadlock. The damn things are hard enough to unscrew without.

Correct length is the key.