At441 Hss Microstop Countersink

Add to Wishlist
Part# 12-01591
MFR Model# 02-441


AT441 HS Micro Stop Countersink, similar to the AT442SLS unit, except with 1/4-28 female threaded nose to accommodate AT455 cutter.

California Prop 65 Warning Symbol

WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov.


James G Verified Purchase


January 12, 2022

The tools are working as advertised.

Sergio D
August 21, 2020

The first one of these I received immediately seized up at the point at which the lock ring meets the drill side of the cage barrel. I was unable to loosen it, to the point where I fractured the cage with the force of a bar passed through the cage openings. Aircraft Spruce promptly replaced the unit without additional charge, which was great customer service. I applied anti-seize compound to the threads on this second unit. That seems to have solved the problem so far. The unit does a nice job of cutting multiple countersinks to the same depth, but the manufacturer really ought, in my opinion, provide an instruction sheet on how to use and adjust it.

James C
January 13, 2023

The first one of these I purchased somehow managed to get cross threaded the first time I used it. After a few uses it became so distorted a pneumatic impact wrench couldn’t loosen the collet. I have now purchased a second only because there aren’t many affordable options that ship in timely fashion available. TBD how long it will last.

Lucas A Verified Purchase


February 15, 2022


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: what type of base does this have? Is it nylon or have needle bearings?

This has a plastic base and bronze bearings.

Q: What size is the O.D. of the cage itself?

Approx 7/8 to 1 per the vendor.

Q: 1- How is the countersink mounted, thread or set screw? 2 - If thread what size threads? 3 - Is a 120 Deg countersink or a 100 Deg countersink supplied? 4 - Can I get a 120 Deg countersink instead of a 100 Deg countersink with the unit if so supplied? Thank you, Barry

The counter sink threads in using 1/4-20 threads. The only 120 deg countersinks we offer come in a 5 piece set under part number 12-02884. The countersink cutters much be purchased separate from this countersink stop.

View in Catalog

View Image View in Catalog