# Mounting Bearings in a Wooden Project



## MJCD (Nov 28, 2011)

Members:

Another Technical Question -

I'm making a device which entails mounting Linear Bearings in plywood. I could use a simple steel rod through the rotating pieces - essentially 3 knuckles which lie in the same plane - with the rod then becoming a bearing/pivot point. This approach does work. However, there are significant side-to-side loads on the joint, and over time the rod will egg-out the wood surrounds. This is a precision device, and I prefer to engineer-in something for life. I don't have the metalworking skills to make the device in aluminum - which is actually the better alternative.

What I'm looking to do is mount a 1/4" - 1/2" shaft inside bearings, and to then secure the bearings in the plywood. I have considered using flanged bearings - this would provide 4 mounting holes (at the flange corners); though, I'm wondering if there is a better solution.

Thanks,
MJCD


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## crank49 (Apr 7, 2010)

I f I understand what you want to do I think you could get the biggest fender washers you can find; probably will be for 3/8" bolts and be about 1 1/2 to 2" OD. This washer will have a hole in it of approximately 7/16". You could drill 2 or 3 holes in this washer to mount it on the plywood and enlarge the center hole to just fit the rod you want to mount.


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## MJCD (Nov 28, 2011)

Crank49:

Very interesting approach - and a better solution than I could have conjured. The high OD provides several orders higher contact area - metal to wood.

Thanks for the consideration …
MJCD


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## LeeBarker (Aug 6, 2010)

I like MJCD's approach. Something like that would be necessary in softwood plywood.

However, in something like Baltic Birch, I would think a slightly undersized hole with the bearing pressed in (your vise would work) would work famously.

Kindly,

Lee


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## MJCD (Nov 28, 2011)

Lee & Crank49

So … you undersize the hole by 1/64, then press-in the bearings. You'd stack the pieces, then in a single motion drill the 3 holes (3 knuckles, or rotating parts) with a forstner bit - this, to ensure the holes are a uniform setback from reference surfaces. Assuming the individual bearings are .75" each wide, you'd have 2.25" (3x .75") of load-bearing/straight-line creating surfaces.

Crank49's approach would be very cost-effective; the Bearing approach, though much preferred, would set me back $300, my guess - I'd need a high-precision shaft, plus three quality flanged bearings …

Thanks.
MJCD


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## MJCD (Nov 28, 2011)

Well, I've slept on this - didn't dream about it one bit; but found my answer somewhere in between remembering one high school basketball buddy (whom I haven't thought of in 44 years) and a boss I had 10 years ago.

I'll build the 'Crank49' version first - as this is a clearly simpler and less expensive approach, and I'll force it to fail prior to building the one I want, but don't want to afford. This also provides me with an opportunity to assess how much use the machine will get; and a plausible argument when I tell my wife I'm raiding the retirement fund for the Flanged Bearings.

Essentially, I'll drill the designed 1/2" hole, then a 1" forstner bit to provide an inset for a 1/2" ID x 1" OD Fender washer - using epoxy to secure the washers (4x spaced along the shaft line). This will provide enough metal surface to support the remainder of the shaft. If this loses tolerance, I'll bore-out the holes to allow the Flanged Bearings to do their work.

Thanks for your considerations.
MJCD


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## MJCD (Nov 28, 2011)

Just a clarification on phase-ology - "force it to fail" means use the simple approach, and if the application overwhelms it, then use the more elegant. I implemented computer systems, and users always wanted the latest-greatest-most expensive solution; while the simpler solution would address 90% of the user's needs.

Thanks, again.
MJCD


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## runswithscissors (Nov 8, 2012)

I'm concerned that the fender washers will give very little bearing surface, and will wear grooves in your shaft in short order. Another solution would be to use bronze bushings. These can be had with a flange. Possibly hold them in place with short pan head screws, lapping an edge over the bushing's flange, or with a very large washer (the hole size would be irrelevant, as long as it's big enough). Drill the washer around the circumference, maybe 3 or 4 holes, and use screws or machine screws with nylocks to hold the bushing in. The bushings are available in all standard bores (1/2, 5/8, 3/4) and are self lubricating. If you heat one up with a torch, you can see the oil ooze out. They are also very inexpensive.


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## ChuckC (May 13, 2010)

I'm not sure I fully understand your problem but is this close to what you are after. I did this in a DIY router lift. The added benefit is that you can adjust the rod with the 4 screws in each block.


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## 33706 (Mar 5, 2008)

Never discount the possibilities of Lexan, polycarbonate or plexiglass. My last requirement for a cheep fix was an escutcheon to mount a radio in a Dodge ram van. I just scabbed off a 1/4" chunk of carpet protector, (the kind you put under your office chair to prevent wearing out your carpet) drilled the holes, cut out the face for the radio, flat black spray paint, and…voila! You'd swear it was original. I've used Lexan for mounting shafts for recirculating ball bushings, it really does the job! Use a wooden block as a support, and mount your shaft to the Lexan. Stop collars with a set-screw are perfect for controlling end-play too.


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## MJCD (Nov 28, 2011)

Thanks for chiming in … I've been vague about the application; so, I'll get this clarified.

I'm making a modified version of Wandel's Pantorouter - his design is inspired! The pantograph mechanism, which supports the router and handles all thrust and racking loads, hinges on (4) 3/16" rods, and the associated metal-to-wood contact as the Bearings & Race. I often work with very dense woods (Jatoba, Teak), and one modification I want to make is to strengthen the load-bearing surfaces.

I can see clearly the concern over the fender washer cutting into the bearing/rod; also, it is subject to binding, if the washer becomes non-perpendicular to the rod. I've considered using a Flanged Bushing, but am out-of-my-depth when it comes to Bearings & Bushings - Let's see there's THK, Thomson, PBC, ... - and I've been through there websites several times …

Assuming other factors are equal - pari-passu, if I read Runswithscissors correctly, I could get a a series of flanged copper bushings (at least one at each end, with the flange either pre-drilled or self-drilled, and use this as the bearing surface, and incorporate a high-quality 316 SS rod across the load area.

If correct, this makes sense to me.
MJCD


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## MJCD (Nov 28, 2011)

Please accept my sincere thanks for the considerations - LJs is a great forum, with members like you.

I like the bronze bushing concept, I'll use this to provide strong rotational reference points for the shaft.

MJCD


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