I heard old folks used to said, if thread is rusty and you can't unscrew screws.To hit a with hammer on handle of hardriver.I dont know is this true or false.

Wd-40 or warm it up with a blow torch

drill it out, and use extractor bit.

.To hit a with hammer on handle of hardriver.

This is what an impact driver is all about! You can try pushing and twisting on the screwdriver till it's tight and then smack it with a hammer.

 

Ian

impact driver Wikipedia

 

I use a paste made with fine sharp sand or glass to make the bit grip the head of the screw.

 

If you are talking about bolts or studs with a hex or allen key head that is a different story

Thanks for answer i think i heard that this work for bolts  and screws.

Usually heating to expand the metal and an impact to break the rust bonds works. Otherwise use a good penetrating oil and let it soak. Hit it every now and again to break the rust bonds and reapply the penetrating oil to let it soak in deeper. It took a while to rust shut so take some time and go slow in order to break it loose.

I started at the beginning of last year being a millwright apprentice and I have seen many trades hit things (not just rusty stuff)  to help loosen them when they are to tight to just move with the tools at hand.   So it can work but won't always.  

Greetings Nat,

 

I have been restoring machinery for years ,  and a auto mechanic for 32....  You are correct ..  The reason for hitting or using a impact style driver is that you cause a vibration in the incline plane of the threads which compacts the rust and allows for lubrication to get into the spaces..  That is what heating does with expansion..    I have had much success using a pneumatic air hammer ,  heat, and a good solvent .  and PATIENCE..  Rule of thumb .. If you bull it ,,, it will brake.. I hope this helps

 

Forge on and make beautiful things

Jim

I do it all the time, works good. They also have impact drivers that you put the screwdriver bit in, then smack with a hammer.

If you have a drill press you can put the screwdriver bit into the drill chuck, then use the feed handle to keep the bit forced into the screw head as you turn the chuck to loosen the screw. I have done this with several tight screws on firearms to keep the screw slot from getting torn out.

Thanks for guys tips.I did this. I unscrew old valve in school that are need to be dissasembled.And it need a litle bit force.Some guys don't have  feeling and get bolt busted.The bolt was made from brass.It is really fragile material.

Actually heat dehydrates the rust making it take up less space.  It also allows the hole to expand a bit more than the item stuck in it---remember the old science experiment about the ball and the hoop and heating them both the ball will still fit through the hoop?

I dont know i thik ball wont fit in the hoop.

was part of a team working on restoring an orangery, had hundreds of steel screws in cast iron, others tried and got 1 in 10, destroying the rest, I got about 98% out with no problems.

placed an 8mm  ( 5/16 ) not on the screw head or top of the tread if the head had gone and filled it with the mig, kept a spanner ready to turn the nut whilst it was still glowing, back and forth a few times and then out

This might help.  Copied it from this site a long time ago.  

 

Why not just >give the link (grin)

Parafin wax....heat the area well with a torch,while still hot rub the wax block on the heated area.
You can watch the liquid wax get pulled into the hole.
That method hasn't failed me yet and it usually only takes one application of the wax to work.

Wait i guess parafin wax is just simple candle.

well I always heat them up red hot and Quench with water this most times I could remove with little effort if not I heat it more I have completely restored a 37 ford and several old tractors and lots of old machinery hope it helps

I never saw  using heat to unscrew nut or bolts.I guess it can be done by support of heat .

If it is a Philips screw with a damaged head,put an elastic band between the head and screwdriver and push driver well home BEFORE trying to loosen it. If a steel bolt is broken and stuck in threads then mig weld a piece of scrap across the bit sticking out. The heat will help to loosen it.Brass being softer is better to drill and use an extractor,for cast do as Iron Dwarf suggests. Whichever method you use,it's better to loosen a little at a time.

I've had crayons in my toolbox for years to solve rusted stuck screws and bolts.
Heat the head, tap gently and touch the crayon to the edge. It smokes if it's to hot but you'll see the wax wick into the threads. I tap the part til the wax solidifies some then give it a turn. Rarely do I need to repeat.

Also it's imperative that you use only the white crayons! Cause your kid doesn't use the white ones anyway and they get mad when you jack their favorite color :-)

was part of a team working on restoring an orangery, had hundreds of steel screws in cast iron, others tried and got 1 in 10, destroying the rest, I got about 98% out with no problems.

placed an 8mm  ( 5/16 ) not on the screw head or top of the tread if the head had gone and filled it with the mig, kept a spanner ready to turn the nut whilst it was still glowing, back and forth a few times and then out

Actually this works even better if you let it entirely cool before turning. 

Two reasons; 

1. The warm or hot bolt is soft (weak)

2. The warm or hot bolt is enlarged. 

Thought I'd mention that I've had occasion to learn that sometimes tightening a little before trying to loosen will work something loose.

 

I watched a buddy who restored old vehicles patiently work a bolt in and out to preserve both the bolt and the part it was threaded to.

Tightening does indeed work well on occasion.  If the hole is a through hole ( and the bolt is broken in the hole) use a standard drill.  The bolt can then have the option of going through.  If a blind hole or other area where you must have the fastener come back out, use a left hand drill.  Right hand drill will tighten the fastener in the hole.  I have used square tapered extractors but not in years.  Your Mileage may vary.  I have used flat stock, angle iron and or nuts and welded this to the inside of the hole or to the screw head.  A slight turn tightening and let it set sometimes is the ticket, sometimes not.  I use ATF or Kroil these days more than anything but Marvel Mystery oil works very well.  Some larger ones in castings just have to be blown out with a torch and than use a cape chisel to clean the hole and run a tap trough to clean up..  Indeed a soak and a 6 point socket may solve the issue and save the bolt too.