Preventing galling: a maintenance checklist for hatch hardware
Dissimilar metals, the right gasket and a grease gun — how to keep dogs, tumble bolts and T-bolts turning.
Short answer
Galling happens when similar metals seize under load. Sinooutput pairs dissimilar metals (stainless T-bolt with brass thread block, bronze tumble bolts with steel or stainless dogs) and offers dog handles with grease zerks. Inspect gaskets, grease fittings and replace worn hardware with matched kits.
Why hardware seizes
When two surfaces of the same alloy slide under pressure, they can cold-weld and tear — galling. Salt, grit and paint make it worse. Sinooutput designs around this by pairing dissimilar metals: stainless T-bolts in brass thread blocks, bronze or stainless tumble bolts with steel or stainless dog handles, and lug bolts and nuts in different metals.
Quarterly checklist
- Grease dog handles fitted with zerks (3/4-10 UNC-2B threads).
- Check tumble bolts (3/4-10 UNC-2A) for bending and thread damage.
- Inspect gaskets for cracking, compression set or paint contamination; replace with the matching nitrile or neoprene profile.
- Confirm keeper chains on single-bolt and twist-lock hatches are intact.
- On T-bolt hatches, replace lost hardware with the UMC-430-KIT (T-bolt, nitrile and brass washers, brass nut, stainless cotter pin).
Spares worth stocking
Raised watertight, single-bolt, T-bolt, twist-lock, ullage and manhole gaskets; steel, bronze and stainless dog handles; long and short tumble bolts; flame screens.
Frequently asked questions
What threads do Sinooutput dog handles and tumble bolts use?
Dog handles use 3/4-10 UNC-2B; tumble bolts use 3/4-10 UNC-2A.
What is in the T-bolt hardware replacement kit?
The T-bolt, a flat nitrile washer, a flat brass washer, a brass nut and a stainless cotter pin.
