Destructive Method for Opening the Thumbwheel Padlock

An entry appeared in our guestbook: "One can open the 4 wheel resetable locks by prying out the bottom plate." We decided to give it a try. We used our home handyman and mechanic experience and worked the bottom plate out in less than 15 minutes using ordinary hand tools. The plate (on our lock, see picture on right above) is shaped like an oblong cap for a container, with a rounded edge between its "flat" surface and its wrap around side. Three dimples fit into notches in an interior assembly. The edge is slightly flared, and fits tightly inside the lock body.

After the plate was removed, the dials still turned freely. Holding the lock horizontally so the numbers are vertical and read right side up, each dial has a cam next to it, to its right. See the pictures below. The cams have a flat side and a small notch. The dials need to be turned so the flat sides of the cams are at the top (notches to the bottom.) Then, the dials show the correct combination. Push the shackle in. A four tonged "fork,"one tong to the right of each thumbwheel, drops down. (Only the square ends of the tongs are visible in the pictures. Click on each picture for an enlarged view. Use the browser's back button to return.) The left picture shows the correct combination and the tongs have dropped down. The lock opens when the shackle is released. The right picture shows a wrong first digit. The left tong is pushed up. Since the other three tongs are part of the same fork, they are pushed up, also.

If you decide to give removing the plate a try, to avoid injury, please observe standard safety practices, including wearing safety glasses and workman's gloves! You disassemble the lock at your own risk. Since it would be expensive to buy several locks and refine our techniques, we have disassembled only one lock. However, on our lock, it appears that the plate could be removed most easily using a small prying tool. Select a prying tool that fits horizontally into the rounded part of the combination change tool hole (using the hole for measuring only.). Then, insert the prying tool between the lock body and bottom plate, at the end closest to the hole for the combination change tool, (i. e. inside the green circle in the above picture on the left.) The plate has a slot on that side, and there is a gully below (see pictures below,) which allows the prying tool to go under the plate. Pry the plate up and out.

Naturally, we were appalled that the lock has this vulnerability, especially when the locks come from a company that uses the motto that its locks are "Tough Under Fire" (which appears on the packages for these, as well as other, Master padlocks.) We don't know if all the Master Lock thumbwheel padlocks are constructed this way, but ours was. We see no difference on the outside that would indicate that the plate on other similar locks could not be removed in the same manner. We then faced a dilemma: if we put this information on our web pages, thieves can use it to commit burglaries. On the other hand, honest people can use this information to replace the vulnerable padlocks with more secure padlocks, or to choose more secure locks in the first place. We decided that it was more important to let the honest people know. As a result of what we found, we recommend that this padlock only be used for light security applications. We find that this padlock is often used for fence gates, but have seen it used for some applications that deserve a higher security lock.

For applications where the lock is suitable, please click here for our recommendations on choosing a combination.

For those who have misplaced the combination change tool, please click here for instructions on how to change the combination.

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*Home Depot prices: $14.93 for model 175, Target price $2.99 for model 1500 (single dial padlock.) Best retail prices that we found: $11.85 everyday price for model 175, $2.50 on sale at Target for model 1500.