All Category - Hubbard (Welch Type) Expansion Plugs - Metric Sizes to DIN 470

Metric Sizes to DIN 470

  • Inexpensive, efficient, permanent method of closing/sealing manufactured holes in castings and other processes.
  • Hubbard (Welch Type) Expansion plugs are perfect for limited space (depth) hole closure applications.
  • Less expensive than cupped style plugs.
  • Require a counter bore for installation.
  • We have the widest range of sizes available anywhere – from 1/8” diameter up to 5-3/4” diameter.

Expansion plugs with a ground edge are available for applications requiring an exceptional degree of holding power or leak resistance.We are the original patent holder and manufacturer of the Welch Expansion Plug since 1913.

Stock Materials:

  • Steel: SAE1008/1010 low carbon steel: ASTM#A109 or A569 depending on gage.
  • Aluminum: 1100H14 to ASTM#B209.
  • Brass: ASTM#B36.
  • Stainless Steel: ASTM#A313

* These are materials we stock in various thicknesses. It does not mean we have finished inventory of all plugs in each of these materials.

** Customer specific materials different than those listed above are commonly run.


  • Steel: provided plain finish with a light oil. Expansion plugs can be provided with a wide range of coatings: mechanical zinc (processed in house), electro-zinc, black oxide.
  • Aluminum: provided plain finish. Aluminum plugs are washed in a light mineral spirit in order to remove any solvents or residue.
  • Stainless Steel: Provided plain finish. Stainless Steel plugs are washed in a light mineral spirit in order to remove any solvents or residue. Stainless plugs can be passivated.
  • Brass: provided plain finish. Brass plugs are washed in a light mineral spirit in order to remove any solvents or residue.

Entering an RFQ:

Find the desired plug diameter from the list of part numbers below. Click on this part number and then enter the requested information from the choices provided – material type, material thickness, requested finish (for steel), and desired quantity. You will also have the opportunity to send us any special notes or requirements for our review.

Item #
Nominal Diameter 'A'
Maximum Diameter Limit
Minimum Diameter Limit
Spherical Radius
Note : click on item number to submit request for quote
HPM-118 33.032.973
HPM-157 44.053.954
HPM-197 55.054.956
HMP-236 66.055.957
HPM-315 88.057.959
HPM-394 1010.059.9512
HPM-472 1212.0511.9516
HPM-551 1414.0713.9319
HPM-630 1616.0715.9322
HPM-709 1818.0717.9325
HPM-787 2020.0719.9328
HPM-866 2222.0721.9330
HPM-984 2525.0724.9334
HPM-1102 2828.0727.9340
HPM-1260 3232.1331.8745
HPM-1417 3636.1335.8750
HPM-1575 4040.1339.8756
HPM-1772 4545.1344.8763
HPM-1969 5050.1349.8770
HPM-2205 5656.1355.8780
HPM-2362 6060.1359.8785
HPM-2480 6363.1362.8790
HPM-3150 8080.1379.87112
HPM-3937 100100.1399.87140
HPM-4921 125125.13124.87180
Total: 25