Tornado Nylon Insert Lock Nut 5/16 in. Stainless X8248SS

The Tornado Nylon Insert Lock Nut 5/16 in. X8248SS is the genuine OEM stainless nylon-insert locknut used on the solution tank assembly of the PS Series professional spotters. Tornado’s dealer catalog lists it as “NUT 5/16 LOCK WITH NYLON INSERT SS”. The assembly uses two, and on this machine they are the nuts that retain the transport wheels. It also fits the Tornado PS8226 Spotter 98226, the 230-volt build of the deluxe PS Series spotter.

Compatible Models for the Nylon Insert Lock Nut

• Tornado PS Spotter 98220 — PS Series professional spotter, 115V
• Tornado PS8221 Spotter 98221 — the 230-volt deluxe spotter, Series G
• Tornado PS8225 Spotter 98225 — the deluxe PS Series spotter, Series C and Series D & E
• Tornado PS8226 Spotter 98226 — the 230-volt build of the deluxe PS Series spotter, Series D & E

The 230-volt PS8221 Spotter 98221 uses the same stainless lock nut on its main assembly, in the Series G book.

The deluxe PS8225 Spotter 98225 uses the same stainless lock nut, two of them, in both the Series C and the Series D & E book.

This is a widely shared fastener: Tornado’s factory cross-reference lists it on ninety-four machines, which is more than the cross-reference will display at one time, so an enumerated list for it would be incomplete and misleading. It fits a wide range of Tornado machines. Call us at 763-535-0770 with your model and serial number and we will confirm it against the current catalog before you order.

How a nylon-insert nut locks

A nylon-insert locknut — the type generically called a Nyloc nut — carries a collar of nylon moulded into the top of the nut, with a bore slightly smaller than the fastener’s thread. As the nut is run on, the thread cuts its own path through that nylon. The nylon grips the thread flanks along their whole length and presses the thread faces together, so the nut cannot rotate loose on its own.

That matters because this is a prevailing-torque nut: it resists rotation whether or not the joint is clamped tight. A plain nut relies on the clamping load to stay put, so the moment the joint relaxes it is free to turn. Here the wheel has to stay able to rotate, which means the nut is deliberately not torqued down hard against the hub — so the nylon is the only thing keeping it in place. That is precisely why the designer specified this nut and not a plain one.

The practical consequence: a plain 5/16-18 nut from the drawer will thread on and feel fine, and then back itself off over a few weeks of vibration until the wheel comes off the machine.

Stainless is specified because the nut sits at floor level in the wettest part of the machine. A rusted locknut seizes on its thread and has to be cut off, taking the screw with it.

When to replace it

Treat a nylon-insert nut as single-use. The thread cuts a path through the nylon the first time it is run on, and that path stays: each subsequent use grips less. Industry practice is one fitting, and a nut that spins on freely by hand all the way down has no locking function left at all.

That is the simplest field test, and it is worth knowing: if you can run the nut down the full thread with your fingers, replace it. A serviceable one needs a tool for the last part of its travel.

Replace one on sight if the nylon collar is missing, cracked, melted, hardened or discoloured; if the nut is corroded, if the thread is galled, or if the hex has been rounded off. Replace both at once, since they are the same age and sit in the same conditions.

Fitting notes

Fit a new nut whenever the wheel assembly is disturbed, together with the screw and the spacer if those are worn — they are one assembly and they wear together.

Run the nut down until the wheel stack is held with no side play, then stop and check by hand that the wheel spins freely. The clamping load should be carried by the plastic spacer, not by the wheel. Over-tightening here either binds the wheel or crushes the spacer’s ends, and neither is obvious until the machine is wheeled.

Make sure enough thread protrudes past the nylon collar — the collar sits at the top of the nut, so a thread that stops short of it is not being locked at all even though the nut feels tight. If the fastener will not reach, the screw is the wrong length, not the nut. Avoid running the nut on and off repeatedly while setting the wheel clearance; each pass costs locking torque.

Twin City Vacuum has been selling and servicing Tornado equipment since 1956.

You can browse every assembly for this machine on our Tornado PS Spotter 98220 parts page, and the manufacturer’s specifications are published at tornadovac.com.

Frequently Asked Questions

How does the Nylon Insert Lock Nut X8248SS stay tight?

A nylon collar moulded into the top of the nut has a bore slightly smaller than the thread. Running the nut on cuts a path through it, and the nylon then grips the thread flanks along their length. That gives prevailing torque — the nut resists rotation whether or not the joint is clamped tight.

Can I use a plain 5/16 nut instead of the Nylon Insert Lock Nut?

No. The wheel has to stay free to rotate, so this nut is deliberately not torqued hard against the hub — the nylon is the only thing holding it. A plain nut relies on clamping load to stay put, so it will back itself off under vibration and eventually release the wheel.

Can the Nylon Insert Lock Nut be reused?

Treat it as single-use. The thread cuts its path through the nylon on first fitting and each later use grips less. The field test is simple: if you can run the nut down the full thread with your fingers, its locking function is gone and it should be replaced.

How do I order the Nylon Insert Lock Nut (part# X8248SS) or get help?

You can add the Nylon Insert Lock Nut (part# X8248SS) directly to your cart on this page, or call us at 763-535-0770. Our staff at 5415 West Broadway, Crystal, MN 55428 has been servicing Tornado equipment since 1956 and can help confirm the right part for your machine.

Questions? Call us at 763-535-0770 or visit us at 5415 West Broadway, Crystal, MN 55428.