Tornado Screw 3/8-16 x 1-1/4″ 19171

3/8-16 is the coarse-thread size used on this machine where a fastener has to carry real load — structural brackets, mounts, and the points that take the weight of a full tank. Part number 19171 is the genuine OEM screw at 1-1/4 inch long.

Compatible Models for the Screw 3/8-16 x 1-1/4″

This part fits the following Tornado machines:

• Tornado 98164 MWH-800 8-Gallon Self-Contained Carpet Extractor
• Tornado 98166 20″ Marathon 800 Carpet Extractor (8 Gallon, 115V)
• Tornado 98167 20″ Marathon 800 Carpet Extractor (8 Gallon, 230V)
• Tornado 98168 12 Gallon Self Contained Carpet Extractor
• Tornado 98168 20″ Marathon 1200 Carpet Extractor (12 Gallon, 115V) — all series
• Tornado 98169 20″ Marathon 1200 Carpet Extractor (12 Gallon, 230V)

Length is the specification, not a detail. This machine uses 3/8-16 screws at more than one length, and they are not interchangeable in either direction. Too long and the screw bottoms out in a blind boss, so it feels tight while clamping nothing — the joint is loose the moment it is loaded, and nobody suspects the fastener because it was done up firmly. Too short and there is not enough thread engagement to carry the load at all.

The rule of thumb worth applying: a screw should engage at least its own diameter of thread. If a replacement has fewer threads in the hole than the one it replaced, it is the wrong length whatever the head looks like.

Inspect a used one before refitting. A 3/8-16 that has been carrying structural load shows thread wear as a dulled, slightly rounded crest on the first few turns, and a screw that has been over-torqued has a visibly stretched section just under the head. Either means it has yielded and will not give the same clamping force again.

Corrosion matters here more than on the small fasteners, because this size is usually holding something that matters. A screw that is pitted has lost section, and section is strength. Detergent reaches most of this chassis, so inspect rather than assume.

Fit with clean threads, the correct washer arrangement, and to a firm torque rather than the hardest you can manage. Where a lock washer is specified, fit a new one — a reused lock washer has spent its spring and the joint will work loose again.

Browse every assembly for this machine on the Tornado 98168 Marathon 1200 parts hub, and see the manufacturer’s range at tornadovac.com.

Frequently Asked Questions

What Tornado machines does the screw 19171 fit?

It is used on the Tornado 98164 MWH-800 8-gallon self-contained extractor, the 98166 and 98167 20″ Marathon 800, the 98168 12 Gallon Self Contained extractor and the 98168 20″ Marathon 1200 in all series. Call 763-535-0770 with your model number if you are not sure.

Does the length really matter if the thread is the same?

Yes, in both directions. Too long and the screw bottoms out in a blind boss, so it feels tight while clamping nothing and the joint goes loose under load. Too short and there is not enough thread engagement to carry the load. A screw should engage at least its own diameter of thread.

Can I reuse a 3/8-16 screw from this machine?

Inspect it first. Thread wear shows as a dulled, slightly rounded crest on the first few turns, and over-torquing leaves a visibly stretched section just under the head. Either means it has yielded and will not give the same clamping force again. Pitting from detergent means lost section, and section is strength.

How do I order the Screw 3/8-16 x 1-1/4″ (part# 19171) or get help?

You can add the Screw 3/8-16 x 1-1/4″ (part# 19171) 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.