Is MDF strong enough for this Fancy Push Stick?

[Frederick Skelly]

There are times I need to cut a 1" wide part on my contractor saw. Using my favorite well-tuned push stick, the dust collector hood/vent on my Shark Guard obstructs my reach more than I'd like. I've read about "push sticks" like this one that ride on top of my Biesemeyer fence, so I set out to make one.

I decided to use some scrap 1/2" MDF (and save my new sheet of 1/2" baltic birch ply for something later). The pics below show what I did - it's just simple butt joints glued together with Elmer's Max wood glue. I copied a plane tote for a handle and mortised it in 1/4" deep. (Glued that in with epoxy because I cut the mortise a tad wider than Elmer's could fill.) I was pleasantly surprised at how easy it was to cut that mortise with a chisel and router plane. The MDF shavings looked like they were cut from a brown paper bag.

And there's my question: Is MDF strong enough to make a good strong joint using just wood glue? Or should I have used epoxy for the joints too? What do you guys think?

As always, thank you!
Fred

Pictures:

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[Brian Henderson]

It depends on what kind of stresses you're going to give it. If you're just pushing material past a blade, you're probably fine. If you're going to jump on it, not so much. You can always put a couple of screws through the joints even though they're not ideal in MDF, it won't hurt anything either. Use a coarse thread screw and support the sides of the workpiece by clamping it together with a handscrew clamp and you'll do just fine.

[Jeff Bartley]

Fred, I use glue and 18 gauge nails on a lot of the shop jigs I make out of MDF. Never had a problem.
Nice push stick!

[Frederick Skelly]

Thanks guys! I appreciate the feedback.
Fred

[Lee Schierer]

Just be careful using that type of push stick when cutting wider pieces against the fence. I would also make the leading edge square instead of curved so it doesn't tend to lift your stock.

[Jerry Miner]

mdf glues fine with wood glue-- the shavings look like parts of paper bags because paper bags and mdf are made from the same stuff!

[Frederick Skelly]

Just be careful using that type of push stick when cutting wider pieces against the fence. I would also make the leading edge square instead of curved so it doesn't tend to lift your stock.

Thanks Lee. I had a similar thought - if I use this on anything wider than a couple inches, it's an invitation for the stock to twist and kick back.

I'm not following you about the rounded nose? That whole "skate" is about 12" long and about 8" of it rides on top of the board. (Edit: you can see what I mean by looking at the bottom picture. Hope it makes sense.) What are you seeing?

Fred

[Frederick Skelly]

mdf glues fine with wood glue-- the shavings look like parts of paper bags because paper bags and mdf are made from the same stuff!

Thanks Jerry!

[Lee Schierer]

Thanks Lee. I had a similar thought - if I use this on anything wider than a couple inches, it's an invitation for the stock to twist and kick back.

I'm not following you about the rounded nose? That whole "skate" is about 12" long and about 8" of it rides on top of the board. (Edit: you can see what I mean by looking at the bottom picture. Hope it makes sense.) What are you seeing?

Fred

Ahhh, I didn't see the notch on the one side. Is the step going to cause binding on the fence if your board thickness varies?

[Frederick Skelly]

Ahhh, I didn't see the notch on the one side. Is the step going to cause binding on the fence if your board thickness varies?

No, I don't think so. In unpowered test passes, it seems to work well with anything greater than 1/4" thick (the height of the notch).

Thanks for double- checking me Lee!

Fred

[Prashun Patel]

If it were me I would not do it. This is only instinct on my part, but I suspect a risk that the handle will snap. Totes on planes are designed with the grain going forward so they do not snap.

I realize this is a different beast, but a fail would happen mid cut and would be dangerous. If I had to do this I would use plywood for the handle.

If you are married to the handle as is, then perhaps you drive a bolt or lag screw through the top of the tote into the deck.

As for the joint, wood glue is fine. But I would screw.

[Frederick Skelly]

If it were me I would not do it. This is only instinct on my part, but I suspect a risk that the handle will snap. Totes on planes are designed with the grain going forward so they do not snap.

I realize this is a different beast, but a fail would happen mid cut and would be dangerous. If I had to do this I would use plywood for the handle.

Prashun, I'll bet you're a darn good engineer - that's a good catch. I missed it.

I just checked the grain direction against that of several hand planes that still have original totes. My push stick handle matches their grain direction. But each of the plane totes also attaches to the sole by at least one screw - which in effect reinforces the handle, too. And I'm missing that bit in my design. I agree, plywood would definitely be better.

Thanks for the double check and your ideas for a fix. I'll mod it now.

Fred

[Pat Barry]

Hopefully you don't have to push so hard while using this tool to be concerned with breaking the handle. My thought would be to throw in a screw or two for insurance, and to wax the inside portions for a nice slippery fit.

[Frederick Skelly]

Thanks Pat!

[Josh Lucus]

I would add a few screws, I wouldn’t trust glue alone. MDF glues up well but has little inherent strength. A sudden mishap (stuff happens) could cause the mdf and the glued joints to delaminate.

JMO

[Frederick Skelly]

Just so it goes into the archives to help the next guy.....

I added coarse screws to the butt joints. Thanks for the tip to clamp the MDF that I was drilling/screwing in order to support it. That would never have occurred to me and I think it helped.

I cut off the solid wood handle and made sure the "stub" was flush. Over the top of that, I glued down another (partial) layer of 1/2" MDF and mortised a plywood handle into that.

I decided it was easier to use the push stick with the handle facing straight forward, rather than canted toward the fence (see original pics above). Since the push stick encloses the Biesemeyer on 3 sides, I decided it didn't need to be angled after all.

Pic of the "version 2" below, straddling the fence with a narrow piece of wood being pushed. You can just see the leading edge of the Shark Guard.

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Thanks again folks!
Fred

[Peter Christensen]

I would have the blade side of the jig screws horizontal, preferably above the max hight the blade could be raised to prevent any chance of cutting into a screw. SawStop owners think of these things. ;) I would also make the blade side vertical piece taller so that when the bottom gets chewed up you can make a new notch and drop the side down and refasten. Looks like "h" when viewed from the end when new and like "n" when reworked.

[Rich Engelhardt]

I hate to put any type of metal anywhere it could come in contact with a spinning bit or blade.
When I have a jig like that to make, instead of putting screws in it, I glue it first and screw it to hold it together while the glue dries.
Once the glue dries, I remove the screws, then drill the appropriate sized hole (1/2" for 3/4" stock - -1/4" for 1/2" stock) & glue a dowel in there.

[Frederick Skelly]

Peter, Rich - thank you guys. All helpful ideas to me!
Fred

[Frank Pratt]

Biscuits (I know, dirty word) would be a great application for this. No metal to work about & very strong. I wouldn't use screws at all because MDF has no strength against splitting & putting a screw into the edge is just going to weaken it.