Print Page - Drill diameter needed for 5-40 in sst.

Title: Drill diameter needed for 5-40 in sst.
Post by: gstours on February 16, 2018, 09:52:16 PM

I've got to tap a hole in a pc of 302/304? Stainless steel approximately 3/16 " thickness. What drill size would you recommend? I have always had a hard time with this. Just wondering?🤔
Any tips would be helpful. 🙈. Thanks.

Title: Re: Drill diameter needed for 5-40 in sst.
Post by: STRIPER LOU on February 16, 2018, 10:03:20 PM

Hey Gary, for general use a #38 (.101) is recommended but for SS I use the next size #37 (.104). I just did a bunch of holes a little while ago.

This works well for me. Sharp tap and plenty of lube.

..................Lou

Title: Re: Drill diameter needed for 5-40 in sst.
Post by: Three se7ens on February 16, 2018, 11:49:16 PM

0.104" #37 is what Id recommend as well. That gives you 65% thread engagement, which is plenty in harder materials.

Be sure to use a good, sharp drill and cutting oil. If you work harden it when drilling, you will have a harder time tapping it.

Title: Re: Drill diameter needed for 5-40 in sst.
Post by: Tiddlerbasher on February 17, 2018, 02:00:30 AM

Try and use a hss co tap - ie a cobalt one -they are worth the extra $ ;)

Title: Re: Drill diameter needed for 5-40 in sst.
Post by: Tiddlerbasher on February 17, 2018, 02:03:05 AM

Also for stainless I am using pretty much only cobalt hss drills as well - thay last a lot longer - well worth the investment :)

Title: Re: Drill diameter needed for 5-40 in sst.
Post by: gstours on February 17, 2018, 09:28:02 PM

Thanks, the advice is well received. You folks are great 👍🌊🌊🌊. I will get a going. Find the number drill box.🍀

Reel Repair by Alan Tani

General Maintenance Tips => General Questions and Trouble Shooting => Topic started by: gstours on February 16, 2018, 09:52:16 PM