Leadscrew vs h/t studding

[Chipper]

Just about to buy some h't studding to make a car spring compressor (centre-coil type), when someone on another forum posted this link to leadscrew material.

Medium Carbon Steel C35 (080 A35)
Tensile Strength (Rm): <Ø16 (ØD): 520-700N/mm2 >Ø16 (ØD): 600-950N/mm2

Seems to be the same sort of tensile strength as 8.8, and has big meaty threads, so it seems better... or have I missed something... ?

 

[piman]

Hello Chipper,

Pros:- stronger threads, but like for like diameter would be slightly weaker than studding, in theory, as the root diameter is smaller.
Cons:- more effort as the thread is coarser, just need a longer spanner? More expensive?

Alec

 

[stormin]

For the job you have in mind I would stick with threaded rod. Leadscrew is too coarse a thread and will tend to unwind itself under tension unless you've got a method of locking the nuts.

 

[graffian]

My spring compressor thread is very like ACME, never checked what it was but could easily be 8tpi. Works perfectly.

 

[Pete.]

For the job you have in mind I would stick with threaded rod. Leadscrew is too coarse a thread and will tend to unwind itself under tension unless you've got a method of locking the nuts.

Leadscrew won't un-wind. If it did, you wouldn't be able to use it in a lathe or mill as the tool would back away from the work.

 

[Nimbus]

Looks just like the screw in my vice. That's pretty good at compressing stuff and doesn't unwind under tension.

 

[Pete.]

If I was making something like a spring compressor I would use Macalloy or Diwydag bar. The Diwydag (pronounced divvy-dag) you will find on most building sites as it's used for securing concrete shuttering.

My dad was almost killed by a failed spring compressor when leaning over a fully compressed Jaguar spring. It wasn't the bar or the nut that failed but the arm that grips the spring coil, so make sure you make these strong enough.

 

[Chipper]

Thanks guys. Will price up studding vs leadscrew+matching nuts.
Planning to make the jaws meaty and strong, and use chain or strap while removing/installing, and extra nuts to lock each end.
Definitely going on the cautious side, coils make me slightly nervous...

 

[the snooper]

you can buy a set of 3 for £29.36 see here

 

[gavuk]

Not sure if there is any advantage with a centre pull???? ,i have a pair like these..............spring compressors.....only used on my mk1 golf and pug 306 dti but worked really well,i liked the fact the ones i bought could be driven by hex or 1/2" sq drive ,used air ratchet last time to release......jacked up car compressing the spring to install them....saved a lot of winding ....i looked at the style Snoop linked but thought the safety claw might make the spring bind worse..?........

 

[Drains]

Leadscrew won't un-wind. If it did, you wouldn't be able to use it in a lathe or mill as the tool would back away from the work.

Can you describe how this could happen Pete? Think before you answer...

To the OP - fine thread is stronger than coarse thread - more surface area - so threaded rod would be stronger. Also the coarser pitch of leadscrew would make tensioning up more work. (which is more-or-less what Alec said ) However all that might not matter, and the advantage of Acme thread is it's quick...

 

[Chipper]

Can't use external comps, hence making a centre-coil one. Same as Mercs - no room / access for external ones.
Thread strength, makes sense. Winding is no problem, these springs are short / chopped and there's always the windy gun.

 

[Shox Dr]

Can you describe how this could happen Pete? Think before you answer...

To the OP - fine thread is stronger than coarse thread - more surface area - so threaded rod would be stronger. Also the coarser pitch of leadscrew would make tensioning up more work. (which is more-or-less what Alec said ) However all that might not matter, and the advantage of Acme thread is it's quick...

I not sure you are correct there. There is good reason why G-clamps, Vices, Acrow Props, Lathes and milling machines use coarse Castellated type threads.

Acme type threads are far stronger then V type threads, overall they are better at spreading load, working in dirty conditions and have a lower wear rate. Im also sure they are better at opposing loads, and hence better resistance to creep than V type threads



(It's a longtime since I did my training so that lot maybe a load of, but Im sure it has some truth)

 

[Pete.]

Yes leadscrews with their greater pitch would require more effort but not so much that you couldn't compress a suspension spring.

Drains, I don't understand what you mean. I say that a leadscrew won't back off under load especially when it's kept loaded by the spring.