Lag screws in an MDF workbench?

[Charles Darwin]

There are two thing that I have picked up from reading this and other forums: 1) I really really need a workbench, and 2) I should start with something simple and build something nice in a few years when my skills have improved.

I have seen several simple plans that use 2 layers of MDF for a workbench surface. I am particularly leaning toward a modified version of this bench featured on FWWs Getting Started in Woodworking

http://images.taunton.com/downloads/GSIW_workbench.pdf

It seems like a decent bench but I am concerned about using lag screws to attach a heavy woodworking vise to MDF. Won't the lag screws rip out if I clamp something heavy or apply considerable pressure to the vise? Is there a better way to attach the vise or do I have nothing to worry about?

thanks,

CD

[cabinetman]

I would rather use nuts,bolts, and washers. Or, a bolt and tee nuts.
.

[Richard in Smithville]

C-man is the one to listen to. Definately run bolts right through. Make sure you use washers to spread the force.

[Tom Miller]

Lag screws vs. bolts? In two layers of MDF, I'd say neither. A lag bolt will only have 1" - 1.25" to grab, and assuming you'd countersink the bolt heads, that leaves you with ~1 layer of mdf.

But, there's an easy solution; something you'll probably have to do anyway to keep the top of the vise at or below the top of the bench. Just add a couple more layers of MDF between your vise and the bottom of the bench top. These layers only need to be a couple inches wider and deeper than the outline of the vise. Better yet, make these pieces plywood, like I did. Then, 1/2" lag bolts will hold a pretty good-sized vise.








Something else to consider: sink the back face of the vise into the apron of your bench so it's flush.

Regards,
Tom

[Charles Darwin]

Thanks for the suggestions, everyone.

Tom - I was planning on placing plywood between the vise and the MDF to make the vise level, but I wasn't sure if this would add much additional support since the plywood would be screwed into the MDF. But it looks like that is exactly what you did, and it seems to be working.

I assume that I would need to drill significant pilot holes for 1/2 inch lags, right?

Also, how satisfied are you with the Groz? I was leaning toward the Groz 7 inch, but have seen some complaints about uneven closure.

[mpauly]

My workbench is 3 layers of MDF and I have rockler's quick release 9" vise attached with either 3/8" or 1/2" lag bolts (I forget which at the moment) and the face recessed into the bench. It's been very solid for my use for over a year, but I'll admit, I don't abuse it.

You will need to drill pilot holes just under the diameter of the shank of the lag.

Michael

[pecker]

I made my bench top as a core of plywood with a layer of mdf on either side. The mdf was mainly there for it's mass. I thought the plywood would help with the lag bolts for the vise, as well as giving bench dogs something a little more solid to rest in.

This also made it easy to cut the whole thing to size...as long as the plywood core is cut squarely, you can make the mdf pieces a little oversized, then trim each to the plywood's dimensions with a flush trimming router bit.

[LarryG]

Charles,

I see that the bench design you're considering has its legs set flush with the top's edge. That's excellent in itself; but it also allows me to make this suggestion: forget the iron face vise and go with a leg vise instead.

Here are two shots of the leg vise on the temporary mock-up bench I built to use while I'm building my new, Roubo-style workbench (the mock-up also serves as a prototype, to work the bugs out of the design):





As you can see, a leg vise consists of only three elements: a movable jaw, a vise screw, and a mechanism to hold the jaw parallel to the bench leg on which it mounts and which serves as the fixed jaw. For my parallel adjuster I used a threaded rod and a large wooden jam nut, but more common is a wooden arm with holes for a movable pin. The final version of my new bench will use this latter type; the jam nut works great but I have determined that it unacceptably limits the length of the workpiece I can clamp vertically.

Leg vises are incredibly powerful and MUCH more versatile than the common iron WW vise. The screw on mine is 10" down from the top, so I can clamp a workpiece much wider than an iron vise allows; it's also possible to clamp a workpiece vertically, between the movable jaw and the bench's leg. Leg vises are also cheap: a good-quality vise screw that will give you a 12"-14" net opening (depending on the movable jaw's thickness) costs less than $40. And they're dead easy to make and install. They do have two small downsides: the need to fiddle with the parallel adjuster (which, in practice, isn't done nearly as often as one might think), and the lack of a quick-release. But both of these "flaws" are more than offset by their simplicity and versatility.

Comparatively few modern-day woodworkers are familiar with leg vises -- I certainly wasn't, until about a year ago. Once I had the movable jaw made, it took me only 40 minutes to get the first version of mine installed and fully operational. And it only took a couple hours of use, after that, to turn me into a believer.

[footprintsinconc]

i used lag bolts and did exactly what tom miller did and its been fine so far.

[Tom Miller]

Thanks for the suggestions, everyone.

Tom - I was planning on placing plywood between the vise and the MDF to make the vise level, but I wasn't sure if this would add much additional support since the plywood would be screwed into the MDF. But it looks like that is exactly what you did, and it seems to be working.

I assume that I would need to drill significant pilot holes for 1/2 inch lags, right?

Also, how satisfied are you with the Groz? I was leaning toward the Groz 7 inch, but have seen some complaints about uneven closure.

You should both glue and screw the ply onto the mdf. And then the lag bolts should screw through both the ply, and into the mdf. Don't undersize the pilot holes too much; make them so the threads get maximum bite, but without having to deform to let the bolt through.

Regarding the Groz vise -- I'd be wary unless you get a chance to look at it. I got to look at this one at Woodcraft and was very pleasantly surprised with fit/finish, including jaw fit and toe in. But, that was a few years ago, and things may be different now. My original review can be found here.

Regards,
Tom

[SARGE..g-47]

I would listen to Tom or go with Larry's idea of a leg vise. I looked at the plan you posted and it did call for mounting the vise directly to the MDF laminate top. Whoever submitted that plan should be spanked and add a spankng to the publishers as lag screws or bolts need to be re-enforced as Tom did or they will tear out of waffered MDF.

If you are strcikly a model airplane maker or bird-house builder.. etc. etc. you might get away with it.. but I have done probably 3 task with a vise this mornign alone that would have resulted in the stock and vise lying on the floor with a ripped out MDF table-top. If you do it.. be sure you insure your top with GEICO . you'll need it to make a claim.

Good luck...

[cabinetman]

I still have to say I like the bolts, nuts, and washer idea. An alternative to that if you didn't want any recess in the top, is to use Tom's idea of adding glued and scewed plywood plates. I would use the same type of vise as in Tom's picture, as you can face the jaws with replaceable wood. You could recess a "tee" nut between the first and second layer of MDF, or into the uppermost layer of plywood. Getting the vise as close to the top would be the strongest mounting position.

I would try to talk you completely out of a leg vise. IMO, a bad idea. BTDT. Depending on how tall you are, you'll have to bend over to use it, and mounted on a leg will have it's day as soon as you walk into it. It's in the way. It leaves a very defined black and blue mark. DAMHIKT. It will also exert forces on the leg which, over time may create a problem.
.

[Sam Conder]

I have always used tee nuts when fastening to MDF and never had a problem.

As far as the vise type, I think Larry's suggestion to consider a leg vise is worth looking into. Though I never got around to building my "dream bench", I did do quite a bit of research. I visited Kelly Mehler at Berea College and looked at some benches there and the benches with leg vises really seemed to work well. Also, I bought the following book:

http://www.amazon.com/gp/product/1561582700?ie=UTF8&tag=samcondsryobbt30&linkCode=as2&camp=1789&creative=390957&creativeASIN=1561582700

Scott Landis really talked up the virtues of the leg vise in the book and liked the strength and durability it provided.

Make sure you fill us in on how you solve this one, we'd all love to know!

[SARGE..g-47]

I have always used tee nuts when fastening to MDF and never had a problem.

As far as the vise type, I think Larry's suggestion to consider a leg vise is worth looking into. Though I never got around to building my "dream bench", I did do quite a bit of research. I visited Kelly Mehler at Berea College and looked at some benches there and the benches with leg vises really seemed to work well. Also, I bought the following book:

http://www.amazon.com/gp/product/1561582700?ie=UTF8&tag=samcondsryobbt30&linkCode=as2&camp=1789&creative=390957&creativeASIN=1561582700

Scott Landis really talked up the virtues of the leg vise in the book and liked the strength and durability it provided.

Make sure you fill us in on how you solve this one, we'd all love to know!

Sam.. the leg vise has been around for centuries and they are used by many well knows WW, especially those that specialize in hand tools as Adam Cherbrinsky (I don't know how to spell Adam's last name but he write articles for PW and FWW on hand tool builds) and a host of others.

IMO.. it won't be in the way any more than a side mounted face vise. Both stick out.. both have handles.. I have a twin screw on the end of my work-bench and a face vise on both sides of the opposite end. I intend to take one face vise off and replace it with a leg vise. I just stay up to my neck with building something and haven't found time yet but... I will

So.. I wouldn't hesitate to go leg as it has stood the test of both strength and the test of time. Good luck with your bench. Drop by some week-end and I'll help you build one. And I'm talking about the bench.. not just a leg vise. But.. the last 5 for me have used Doug fir bases with 3" thick southern yellow pine tops..

With 4" thick legs through morticed... they ain't gonna rack. Frankly the base is more critical to a work-bench than the top IMO.

Regards from the south... of you anyway...

[Black wallnut]

Sarge, is that walnut on the bottom the top for the table parts on the bench? If not just ship it on up here and I'll find a good use for it!