Inexpensive kit: bearings on threaded shaft, or drilled nuts on smooth shaft?

woodguy2 · May 31, 2019

Let me start by stating that I'm not a machinist, but a woodworker.

I'm working on a kit for a woodworking power feeder that I'd like to market in some quantity. The power feeder is not meant for a shaper, but rather for router table and lighter table saw use, and for resawing on the band saw. This video shows the feeder resawing 5" thick cherry:
YouTube

It consists of a gear reduction box with 12 mm thick baltic birch plywood laser cut gears driving 3" polyurethane rollers at about 5-40 rpm. I want the kit to be buildable by your average woodworker with a drill press and ordinary drill bits, and it needs to be cheap.

I'm having trouble deciding between threaded and unthreaded shafts for the shafts that drive the rollers. I've built one prototype that uses shafts from fully threaded studs (.5") that measure about .492. I JB Welded a loop of .002 brass shim stock to create a bearing surface. The resulting surface is a slightly irregular .498 or so, and seems like an adequate fit for the inexpensive R8ZZ .5"ID bearings. The threaded shafts make it easy to secure the rollers with nuts and jam nuts. For the gear with this set up I use a thick Nylock nut with blue loctite, and press the plywood gear onto the nut. This set up would require no machine work for the kit builder.

The alternative is using 1045 ground and polished steel shaft which fits the bearings , but lacking threads, creates a problem for retaining the wheels and gears. I can within my budget have the shafts end drilled and tapped by a machine shop for a 5/16-24 bolt that will retain the wheel against a pinned nut on the other side. But the user will have to drill out a nut and pin it for that, and then do the same for a nut that will be a hub for the gear. It seems like drilling out 1/2-13 nuts to .5" ID accurately is a little dicey.

Any advice for these issues is most welcome.
Thanks!

Tony Quiring · May 31, 2019

Most hobby stores have brass tubing that can be cut and slipped onto your shaft.

Or bushings can be selected.

Sent from my SAMSUNG-SM-G930A using Tapatalk

DDoug · May 31, 2019

woodguy2 said:
Let me start by stating that I'm not a machinist, but a woodworker.

I'm working on a kit for a woodworking power feeder that I'd like to market in some quantity. The power feeder is not meant for a shaper, but rather for router table and lighter table saw use, and for resawing on the band saw. This video shows the feeder resawing 5" thick cherry:
YouTube

It consists of a gear reduction box with 12 mm thick baltic birch plywood laser cut gears driving 3" polyurethane rollers at about 5-40 rpm. I want the kit to be buildable by your average woodworker with a drill press and ordinary drill bits, and it needs to be cheap.

I'm having trouble deciding between threaded and unthreaded shafts for the shafts that drive the rollers. I've built one prototype that uses shafts from fully threaded studs (.5") that measure about .492. I JB Welded a loop of .002 brass shim stock to create a bearing surface. The resulting surface is a slightly irregular .498 or so, and seems like an adequate fit for the inexpensive R8ZZ .5"ID bearings. The threaded shafts make it easy to secure the rollers with nuts and jam nuts. For the gear with this set up I use a thick Nylock nut with blue loctite, and press the plywood gear onto the nut. This set up would require no machine work for the kit builder.

The alternative is using 1045 ground and polished steel shaft which fits the bearings , but lacking threads, creates a problem for retaining the wheels and gears. I can within my budget have the shafts end drilled and tapped by a machine shop for a 5/16-24 bolt that will retain the wheel against a pinned nut on the other side. But the user will have to drill out a nut and pin it for that, and then do the same for a nut that will be a hub for the gear. It seems like drilling out 1/2-13 nuts to .5" ID accurately is a little dicey.

Any advice for these issues is most welcome.
Thanks!

Your video doesn't show the feeder.

Wood gears ? are they sacrificial in case of a crash ?

Price point ?
Price point of Chinese competition that doesn't need assembled ?
Liability when user get's limb caught ?

BoxcarPete · May 31, 2019

Might you consider something along these lines?

McMaster-Carr

Threads, ground shaft-like area, and a socket head. What more could you ask for?

woodguy2 · May 31, 2019

digger doug said:
Your video doesn't show the feeder.

It doesn't show well, but it's there....

Wood gears ? are they sacrificial in case of a crash ?

Well, that's one advantage. Main one is cost, and with their big teeth they should last.I know they induce skepticism. Anyone have experience to back that?

Price point ?

About $125 for full kit, $85 for those with laser or cnc capabilities who can cut their own gears and bearing plates.

Price point of Chinese competition that doesn't need assembled ?

about $400, but mine is more versatile, lighter, easier to set up.

Liability when user get's limb caught ?

Definitely a concern! I talked with my insurance company about it and they said my current blanket liability for my woodworking business would cover me. Maybe I need to get that in writing?Anyone have a horror story to scare me with?

Shoulder screws don't get me what I need. I also would like to stick with .5" shaft for compatability with off-the-shelf-wheels and other componants that work with them.

Comatose · May 31, 2019

I use half inch body shoulder screws by the bucketload. You drill and through bore for one side, put a small pocket at the shoulder diameter on the other side, then drill the rest of the way though at the clearance diameter for the threads. Put a lock nut on the far side and torque it tight.

Are they too expensive for what you're trying to do? A bearing running on threads is too cheesy even for the Grizzly and Harbor Freight class of machines.

jrmach · Jun 1, 2019

"even for the Grizzly and Harbor Freight class of machines"

quit swearing,,,lol

Joe Gwinn · Jun 1, 2019

woodguy2 said:
The alternative is using 1045 ground and polished steel shaft which fits the bearings , but lacking threads, creates a problem for retaining the wheels and gears. I can within my budget have the shafts end drilled and tapped by a machine shop for a 5/16-24 bolt that will retain the wheel against a pinned nut on the other side. But the user will have to drill out a nut and pin it for that, and then do the same for a nut that will be a hub for the gear. It seems like drilling out 1/2-13 nuts to .5" ID accurately is a little dicey.

I don't visualize your system in any detail, but here are some thoughts:

As others have said, don't use a threaded shaft as a bearing surface.

It sounds like the rollers are fixed to the rotating shaft by axial clamping using an end nut, the torque being transferred by friction between shaft and roller, likely mostly at the ends of the roller. This arrangement will likely prove troublesome in practice. Some kind anti-rotation key or cross-drilled hole containing a pin is needed.

woodguy2 · Jun 2, 2019

Thanks for this feedback.

I think I'll have to look into having the 1/2" ground shaft threaded. I wish I could make shoulder screws work, though those are at up to .004 undersized, so the ground shaft (-.001 )is a better fit anyway(so would my threaded shafts with JB Welded shims!).One shaft also has wheels on both sides.

The wheels are longboard skateboard wheels. I can, with my CNC router, affordably enlarge the nylon hub that is meant to accept a bearing to a hex shape to accept a nut that I can pin to shaft.I was planning to simply clamp between nuts, but I want to address the concerns expressed here, both to prevent possible problems,and assuage the skepticism that a low-priced product will invoke.

Can anyone suggest good practice for those with just a drill press to drill out 1/2"-13 nuts to a nice concentric fit on shaft for pinning? These would serve as shoulders and bushings for the wheels, and also as hubs for the wooden gears to be press fit onto. Will this require a final pass with a reamer? Is this something the right machine shop, in quantity, can do inexpensively for me?

fciron · Jun 2, 2019

Ground shaft and shaft collars won't work?

Joe Gwinn · Jun 2, 2019

woodguy2 said:
Can anyone suggest good practice for those with just a drill press to drill out 1/2"-13 nuts to a nice concentric fit on shaft for pinning? These would serve as shoulders and bushings for the wheels, and also as hubs for the wooden gears to be press fit onto. Will this require a final pass with a reamer? Is this something the right machine shop, in quantity, can do inexpensively for me?

Make a hardwood fixture that goes in a drill-press vice to hold nut and shaft in position, with a flat side of the nut face up, and close to horizontal. You will need sacrificial wood below to avoid damaging the vice. Start with a spotting drill, then switch to a rough drill, then drill out at final size. Use cutting oil - the black oil from the plumbing department of hardware stores works well. Use name brand cobalt drill bits. Buy them in packs from McMaster-Carr. You'll find that this setup goes through mild steel like butter, if the drill bit is spinning at a reasonable speed for the bit - far slower than for wood. You may need to peck, to clear chips.

If you use a scroll pin, the as-drilled hole will be good enough.

iwananew10K · Jun 2, 2019

TGP shaft and Loctite 680

Joe Gwinn · Jun 3, 2019

iwananew10K said:
TGP shaft and Loctite 680

Hmm. Use loctite to fix hex nut to threaded part of shaft? The hex nut fits into a hex recess in the skateboard wheel.

woodguy2 · Jun 4, 2019

Joe Gwinn said:
Hmm. Use loctite to fix hex nut to threaded part of shaft? The hex nut fits into a hex recess in the skateboard wheel.

Would a blue loctited hex nut (fitting into a machined recess in the nylon hub of the wheel) with a jam nut satisfy the concern about the wheels rotation? This wopuld be on the inboard side, and outboard a serated flanged hex nut would clamp the wheel in place. The nut engaged in the hex recess would need to be removable if one were to be able to open the gear box and replace a gear.

Inside the gearbox, the plywood gears will be pressed fit onto hex nuts bored for slip fit onto shaft. Could these hex nuts be adequately fixed with red loctite, rather than pinned?

Is this site an appropriate place to get quotes on the required machine work to make these shafts? How about to bore out off-the-shelf hex nuts to .5ID? In quantities of say, 100 units to start(200 shafts, 500 nuts).

iwananew10K · Jun 4, 2019

edit- now I get it...Loctite doesn't so much go by color anymore...but yes you could certainly use it to secure things to a shaft...not so good if you need to disassemble tho.

Joe Gwinn · Jun 4, 2019

woodguy2 said:
Would a blue loctited hex nut (fitting into a machined recess in the nylon hub of the wheel) with a jam nut satisfy the concern about the wheels rotation? This would be on the inboard side, and outboard a serrated flanged hex nut would clamp the wheel in place. The nut engaged in the hex recess would need to be removable if one were to be able to open the gear box and replace a gear.

Depends on the torque levels and the maximum temperature. That said, stud-locking locktite is pretty strong.

Inside the gearbox, the plywood gears will be pressed fit onto hex nuts bored for slip fit onto shaft. Could these hex nuts be adequately fixed with red loctite, rather than pinned?

Ditto. I think a drawing or two is in order.

There are a number of different kinds of locktite. Go to the Hertel website and get the relevant catalog and app notes. There is an optimum clearance between parts being fixed to one another.

Is this site an appropriate place to get quotes on the required machine work to make these shafts? How about to bore out off-the-shelf hex nuts to 0.5 ID? In quantities of say, 100 units to start(200 shafts, 500 nuts).

No it really isn't, but it is appropriate to ask here where the request should be published.

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Inexpensive kit: bearings on threaded shaft, or drilled nuts on smooth shaft?

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