Larin 5" vise repair

[khnitz]

My trusty (20+ year old) Larin 5" vise stopped holding position on its swivel base recently. In the end, the trouble was that one of the holes for the locking bolts in the clamping bar had stripped. After looking over what was wrong, I decided to repair it, rather than replace it. I also didn't want to drill new holes in my bench top to fit a different vise.

Here are a couple of images of the original clamping bar. It's 3/16 thick steel, so only a few threads from the locking bolts actually had purchase for tightening the base down. Also, the original clamping bar didn't make use of the full diameter in the base, so less surface area was available for the clamping force.





I was going to check a local welding/fabricating shop to see if they had a scrap piece of steel from which to fashion a new clamping bar, but first I thought I'd check what I had around my shop. I have no idea where or when I picked it up, but I had a 2' piece of 1/2" thick steel bar stock that would do the trick. It took a while, but I had the best luck cutting through it with a hacksaw.


The new 1/2" thick, 5" long and 2" wide piece of bar stock will provide better surface area to clamp the swivel base in place, and being thicker than the original clamping bar, it will allow for more of the threads of the locking bolts to engage.


The location of the holes were set - 3.75" apart, center-to-center.


The holes were drilled for the M10-1.5 locking bolts. An R size drill bit was used.


And then the threads were cut with an M10-1.5 tap.


Here is the new clamping bar in place.


And my trusty "Old Faithful" vise is installed back on the bench, ready for further use!

 

[steaks&anvils]

Nice. Always a great feeling to fix a favorite tool!

Good user vise there. I suspect my user vise swivel will last forever. I can't actually remember the last time I used the swivel base?

 

[seber]

Not important now but the formula for friction resistance is " coefficient of friction of mating materials times force". In other words, the area of contact is immaterial. Any engineering book will say the same.

 

[liliysdad]

Good job...but man, that's a lot of work!!

Sometimes I take for granted having tools like a bandsaw, mill, lathe, etc...

 

[khnitz]

Not important now but the formula for friction resistance is " coefficient of friction of mating materials times force". In other words, the area of contact is immaterial. Any engineering book will say the same.

Thanks for the clarification I read up on it some more after your post to refresh my memory (it has been many years since my mechanical engineering class).

So, then, the force at play is the force normal to the clamping surfaces. Looking at the original clamping bar, it had also bent and pulled inwards. With that, then the 3/16" thick bar was no longer applying 100% of the clamping force normal to the surfaces in contact.

With the 1/2" thick bar, the possibility of that bend repeating should be near nil and I'll be able to maintain the full force of the locking bolts normal to the clamping surfaces.

All that said...when I tighten the locking bolts, my vise doesn't spin anymore