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Weekend Bench #9: Some comments on the twin screw

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Blog entry by dsb1829 posted 1926 days ago 1365 reads 1 time favorited 7 comments Add to Favorites Watch
« Part 8: Front twin screw vise Part 9 of Weekend Bench series Part 10: Finishing Touches on the twin screw »

In my last installment I ran through my basic install criteria for the twin screw and how I chose to build the bench mount and vise chock. I left off waiting for some brad point drill bits and some longer bolts to mount the vise with.

Brad point bits arrived yesterday.

They are huge! Near 8in of fluted cutting capacity. Can’t wait to try these things out. First I have to clean off the cosmoline or whatever they shipped them covered in.

I had already jumped the gun and mounted the vise the day before. I got some good ideas from Kem’s blog ( http://lumberjocks.com/jocks/kem/blog/5211 ) and from the LeeValley twin screw instructions on their site ( http://www.leevalley.com/wood/page.aspx?c=2&p=45114&cat=1,41659 ). I had not considered using wear blocks, but I think I will install some shortly to minimize sag. I also really like the steel pins used to keep the wood from contacting the twin screws. That will avoid damaging edges and remove the posibility of thread lube transfering to the piece.

I gotta say, this vise is a beast.

No problem what so ever holding this 9ft board with 6ft+ unsupported. I did discover one flaw to my bench though. With this long of a lever arm you can actually flex the benchtop! Not expecting that one. It actually uses the screw locations to flex the benchtop over the leg. Pretty wild. I may hve to take a video of it before I reinforce against it. Not that I would ever work this way but I still think I am going to pull the bench top and add stringers from leg to leg to prevent this sort of flexure.

Another design issue.

Not sure it really photographs well but here it is none the less. The screws actually pull the mounting block. Serious leverage on those puppies. I used 4 1/2in x 7in bolts to mount the vise block to the bench. When cranked down the screws pull the block untill all slack in the bolt hole is used up. I am going to try using 3M supper 77 to tack the block. If that doesn’t work, then I will be forced to actually use a permanent glue. I can’t have this block moving around on me.

The last issue I encountered was on the chock itself.

The vise screw collars that the chock is mounted to have a fair amount of play. How much? I dunno, I didn’t get out the calipers. I knew that this one was coming, but figured I would put it up here for the crew. Basic fix is to taper the chock so that when clamped it is flush at the top and the bottom gap closes as additional pressure is applied. The Veritas instructions mention this as well and give an number that agrees with how much play their vise has.

Okay, on a brighter note Zoe is getting to be a big girl.

Before long she won’t be leaving puddles in the shop :)

Time log: 33hr

-- Doug, woodworking in Alabama



7 comments so far

View BarryW's profile

BarryW

1015 posts in 2408 days


#1 posted 1926 days ago

just reading this and seeing this bench makes me want to build my own soon…since I just finished a wood storage system…I now can bring in enough wood to do just that…great bench…

-- /\/\/\ BarryW /\/\/\ Stay so busy you don't have time to die.

View Tomcat1066's profile

Tomcat1066

942 posts in 2298 days


#2 posted 1926 days ago

Had I not lost the gazebo/shop in the storm a few days ago, I’d probably be picking up the wood for my bench today. Alas, it wasn’t meant to be just now. Still, your bench has come along well! It certainly seems functional right now.

Any plans to put an vise on the end?

-- "Give me your poor tools, your tired steel, your huddled masses of rust." Yep, I ripped off the Statue of Liberty. That's how I roll!

View dsb1829's profile

dsb1829

367 posts in 2129 days


#3 posted 1926 days ago

end vise was added in pt.6
http://lumberjocks.com/jocks/dsb1829/blog/6876
Just a cheap QR for dirty work and for dog hole use.

-- Doug, woodworking in Alabama

View HokieMojo's profile

HokieMojo

2094 posts in 2230 days


#4 posted 1926 days ago

Just one bit of advice. Never include photos of a dog with your projects. They steal all your thunder, no matter how well you did. Thanks for this information. I hadn’t really considered that the vises could be strong enough to pull apart the bench. Something I’ll ned to consider.
Thanks!

View dsb1829's profile

dsb1829

367 posts in 2129 days


#5 posted 1926 days ago

Hey Hokie, yep screws apply a lot of force especially with 12” lever arms. There are some compromises that need to be made to have a knock-down bench. Not willing to compromise on the work holding though.

-- Doug, woodworking in Alabama

View Beginningwoodworker's profile

Beginningwoodworker

13335 posts in 2175 days


#6 posted 1926 days ago

Looks good, Doug!

-- CJIII Future cabinetmaker

View Tomcat1066's profile

Tomcat1066

942 posts in 2298 days


#7 posted 1925 days ago

Sorry about that Doug. I must have forgotten about that one. Oops ;)

-- "Give me your poor tools, your tired steel, your huddled masses of rust." Yep, I ripped off the Statue of Liberty. That's how I roll!

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