What is this tool and what does it do?

could be a clamp for clamping wood

I believe you are right. My husband is a mechanic and he agrees with you.

it is definitely a valve spring compressor,and an old one at that.

i thought it was a C clamp to.....look at the design and you understand why it was called a C Clamp

look at the bottom "jaws",they are round and have an opening in the center so the valve spring keepers can be removed.I've used same tool many times rebuilding engines and completing the valve grinding and lapping in process.

Thanks so much!

not a c clamp. thought so too, but no. sorry.

took the words right out of my mouth! lol

I thought that at first glance too Glenda but that's not what it is!

I VOTE FOF A C CLAMP TOO.. bUT IT IS A BIT UNUSUAL.

That's right I could not remember "C Clamp" my husband was/is a Carpenter and Joiner and had one of these. Glenys in Australia

Valve spring compressed for a automotive type head. The red part fits on the spring.

thanks so much - could you maybe tell what it is used for? I came across in my dads stuff and he is not here to tell me

Never mind - thanks again!

Here goes! Its a tool auto mechanics use to compress springs on the valves of car motor's head to remove the valves for service or replacement. ***** https://www.howacarworks.com/basics/the-engine-how-the-valves-open-and-close

Thanks - I got ahead of myself and excited for all the responses I didn't let your answer register - duh-- THANK YOU - this site is awesom!

It's a clamp I have one.

Thank you. Guess there isn't any old time engine builders out there. It works better than the new ones out there. Have to admit, some of the answers made my day!!!!!!!

Ouch, that would hurt

It's either an ear piercer or circumciser, LOL

Thank you!

Thank you!

Thank you!

http://www.jegs.com/p/Proform/Proform-Valve-Spring-Compressors/752354/10002/-1, and this is about the shortest, to-the-point video I found....https://youtu.be/x9hOnbs9xwc  ; Engine work...replacing or servicing cylinder valves, springs, or keepers....

Thank you