All Category - Hubbard (Welch Type) Expansion Plugs - Standard English Sizes

Standard English Sizes



  • 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.

Finishes:

  • 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' Fraction
Nominal Diameter 'A' Decimal
Maximum Diameter Limit
Minimum Diameter Limit
Spherical Radius
Note : click on item number to submit request for quote
HP-1010 1.010-1.0131.0071-1/8
HP-125 1/80.1250.1270.1247/64
HP-145 .1450.1450.1460.1447/64
HP-156 5/320.1560.1580.1545/32
HP-166 .1660.1660.1670.1655/32
HP-187 3/160.1870.1890.18611/64
HP-197 .1970.1970.1980.196.167
HP-219 .2190.2190.2210.21715/64
HP-239 .2390.2390.2410.23715/64
HP-247 .2470.2470.2490.24515/64
HP-250 1/40.250.2520.2487/32
HP-253 .2530.2530.2550.2517/32
HP-262 .2620.2620.2640.2591/4
HP-278 .2780.2780.280.27515/64
HP-281 9/320.2810.2820.289/32
HP-303 .3030.3030.3050.30015/64
HP-312 .3120.3120.3140.30917/64
HP-313 5/160.3130.3150.3117/64
HP-317 .3170.3170.3190.31417/64
HP-334 .3340.3340.3360.3315/16
HP-343 11/320.3430.3460.3411/4
HP-354 .3540.3540.3570.35215/32
HP-375 3/80.3750.3770.37213/32
HP-380 .3800.380.3820.3771/4
HP-406 13/320.4060.4090.4047/16
HP-420 .4200.4200.4220.41715/32
HP-433 .4330.4330.4350.43015/32
HP-437 7/160.4370.4400.43515/32
HP-444 .4440.4440.4470.44115/32
HP-451 .4510.4510.4540.4497/16
HP-469 15/320.4690.4720.4675/8
HP-500 1/20.50.5020.49717/32
HP-502 .5020.5020.5040.49917/32
HP-516 33/640.5160.5180.5139/16
HP-525 .5250.5250.5280.5239/16
HP-531 17/320.5310.5340.5289/16
HP-550 .5500.5500.5530.5481-1/8
HP-562 9/160.5620.5650.565/8
HP-593 19/320.5930.5950.5901-1/16
HP-619 .6190.6190.6220.6173/4
HP-625 5/80.6250.6280.6223/4
HP-636 .6360.6360.6390.6333/4
HP-656 21/320.6560.6590.6533/4
HP-684 .6840.6840.6870.6817/8
HP-687 11/160.6870.690.6847/8
HP-698 .6980.6980.7010.6957/8
HP-717 .7170.7170.7200.7147/8
HP-735 .7350.7350.7380.73215/16
HP-741 .7410.7410.7440.73815/16
HP-743 .7430.7430.7450.7415/16
HP-745 .7450.7450.7480.74215/16
HP-748 .7480.7480.7510.74511/16
HP-750 3/40.750.7530.74715/16
HP-755 .7550.7550.7580.75215/16
HP-768 .7680.7680.7710.76515/16
HP-780 25/320.780.7820.77731/32
HP-806 .8060.8060.8090.8031-1/32
HP-812 13/160.8120.8150.8091-1/32
HP-852 .8520.8520.8550.8491-1/8
HP-858 55/640.8580.8610.8551-1/8
HP-875 7/80.8750.8780.8721-3/32
HP-882 .8820.8820.8850.8791-3/32
HP-895 .8950.8950.8980.8921-3/32
HP-906 29/320.9060.9090.9031-1/8
HP-921 .9210.9210.9230.9171-5/32
HP-928 .9280.9280.9310.9251-5/32
HP-937 15/160.9370.940.9341-5/32
HP-949 .9490.9490.9520.9461-5/32
HP-982 .9820.9820.9850.9791-1/4
HP-988 .9880.9880.9910.9851-1/2
HP-995 .9950.9951.0000.991-3/16
HP-996 .9960.9960.9990.9931-1/8
HP-1000 111.0030.9971-1/8
HP-1008 1.0081.0081.0111.0051-3/16
HP-1014 1.0141.0141.0171.0111-1/16
HP-1031 1-1/321.0311.0341.0281-1/4
HP-1038 1.0381.0381.0411.0351-7/32
HP-1062 1-1/161.0621.0651.0591-1/4
HP-1112 1.1121.1121.1151.1091-3/16
HP-1120 1.1201.121.1231.1171-3/8
HP-1125 1-1/81.1251.1281.1221-3/8
HP-1132 1.1321.1321.1341.1291-3/8
HP-1136 1.1361.1361.1391.1331-3/8
HP-1157 1-5/321.1571.161.1541-1/2
HP-1165 1.1651.1651.1681.1621-1/2
HP-1174 1.1741.1741.1761.1711-1/2
HP-1183 1.1831.1831.1861.181-1/2
HP-1187 1-3/161.1871.191.1841-1/2
HP-1198 1.1981.1981.2011.1951-1/2
HP-1204 1.2041.2041.2061.21-1/2
HP-1212 1.2121.2121.2151.2091-3/4
HP-1226 1.2261.2261.2281.2241-5/8
HP-1244 1.2441.2441.2471.2411-5/8
HP-1246 1.2461.2461.2491.2431-5/8
HP-1250 1-1/41.251.2531.2471-5/8
HP-1260 1.2601.261.2651.2551-5/8
HP-1267 1.2671.2671.2721.2621-5/8
HP-1312 1-5/161.3121.3171.3071-3/4
HP-1320 1.3201.321.3251.3151-3/4
HP-1367 1.3671.3671.3721.3621-13/16
HP-1375 1-3/81.3751.381.371-13/16
HP-1384 1.3841.3841.3891.3791-13/16
HP-1437 1-7/161.4371.4421.4322
HP-1447 1.4471.4471.4521.4422
HP-1487 1.4871.4871.4921.4822-1/8
HP-1500 1-1/21.51.5051.4952-1/8
HP-1506 1.5061.5061.5111.4952-1/16
HP-1512 1.5121.5121.5171.5072-1/8
HP-1562 1-9/161.5621.5681.5582-1/4
HP-1585 1.5851.5851.591.582-1/2
HP-1625 1-5/81.6251.631.622-3/8
HP-1635 1.6351.6351.641.632-3/8
HP-1645 1.6451.6451.651.642-3/8
HP-1688 1-11/161.6881.6931.6832-1/2
HP-1700 1.7001.71.7051.6951-1/2
HP-1736 1.7361.7361.7411.7312-3/4
HP-1742 1.7421.7421.7471.7372-3/4
HP-1750 1-3/41.751.7551.7452-11/16
HP-1760 1.7601.761.7651.7552-11/16
HP-1770 1.7701.771.7751.7652-3/4
HP-1812 1-13/161.8121.8171.8072-3/4
HP-1832 1.8321.8321.8371.8272-13/16
HP-1875 1-7/81.8751.881.872-7/8
HP-1891 1-57/641.8911.8961.8862-7/8
HP-1924 1-59/641.9241.9211.9193-3/16
HP-1937 1-15/161.9371.9421.9393-3/32
HP-1947 1.9471.9471.9521.9423-3/32
HP-1960 1.9601.961.9651.9553-3/32
HP-2000 222.0051.9953-3/16
HP-2010 2.0102.012.0152.0053-3/16
HP-2020 2.0202.022.0252.0153-3/16
HP-2040 2.0402.0402.0452.0353-3/16
HP-2062 2-1/162.0622.0672.0573-3/16
HP-2095 2.0952.0952.12.093-1/4
HP-2125 2-1/82.1252.132.123-1/4
HP-2137 2.1372.1372.1422.1323-1/4
HP-2208 2.2082.2082.2132.2033-1/2
HP-2215 2.2152.2152.222.214-1/2
HP-2250 2-1/42.252.2552.2453-9/16
HP-2268 2.2682.2682.2732.2633-9/16
HP-2375 2-3/82.3752.382.273-7/8
HP-2387 2.3872.3872.3922.3823-7/8
HP-2395 2.3952.3952.42.393-7/8
HP-2472 2.4722.4722.4772.4674-5/32
HP-2500 2-1/22.52.5052.4954-5/32
HP-2512 2.5122.5122.5172.5074-5/32
HP-2562 2-9/162.5622.5672.5574-5/32
HP-2625 2-5/82.6252.632.624-1/4
HP-2637 2.6372.6372.6422.6324-1/4
HP-2687 2-11/162.6872.6922.6824-1/4
HP-2750 2-3/42.752.7552.7454-1/2
HP-2825 2.8252.8252.832.824-1/2
HP-2875 2-7/82.8752.882.874-3/4
HP-3000 333.0052.9955
HP-3062 3-1/163.0623.0673.0575-1/8
HP-3187 3-3/163.1873.1923.1825-1/2
HP-3250 3-1/43.253.2553.2455-1/2
HP-3421 3-27/643.4213.4263.4165-3/4
HP-3500 3-1/23.53.5053.4956
HP-3562 3-9/163.5623.5673.5576
HP-3625 3-5/83.6253.633.626-3/4
HP-3750 3-3/43.753.7553.7456-5/8
HP-4000 444.0053.9957-1/4
HP-4250 4-1/44.254.2554.2457-1/2
HP-4500 4-1/24.54.5054.4957-3/4
HP-4677 4.6774.6774.6824.6729-3/8
HP-4719 4.7194.7194.7244.7149-7/16
HP-5250 5-1/45.255.2555.24510
HP-5750 5-3/45.755.765.7410
Total: 169