Homebrew 1-off die

I have a few unhardened HRS studs with 1/4-20 LH threads on the end, which I didn't turn down enough- they're big enough that they won't fit in the holes I just threaded with a proper tap- the OD is not unreasonable, but the threads aren't deep enough. Otherwise the studs are fine, so I'd like to deepen the thread by maybe 3 to 5 thousanths or so. I've tried re-chucking and threading a little more, but its really hard to get everything set right and the consequences are a wrecked thread.

Since its just a couple studs that need help, I was thinking I might be able to build a cheapie die (avoiding paying McMaster's highway robbery for such things) by drilling & tapping a short length of 1" diameter stock, then slitting it to provide relief for the swarf/chip/turnings (I still don't know the difference..)- and hardening so the sharp edge of the slit will last long enough. Maybe I could run the slit in at something less than perpindicular to the tangent of the stock to give the edge a bit of rake. Maybe I could also be clever and slightly ream the end of the hole to introduce the edge more gradually.

Would this work, or is there a better approach?

Thanks,

Gregm

Reply to
Greg Menke
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When yo uchuck a thread and want to dig it deeper, first start the threading with the bit too far out and then set the cutter to the right spot, making sure that you don't move the slack on the lathe. Having the cross slide and the compound at different angles makes this easy.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works every time it is tried!

Reply to
Bob May

I've tried resetting everything, then doing a couple test passes with the tool pulled slight away from the stock, to watch the alignment. Then when things look like they happening right, apply the tool.

Due to no doubt forgetting details here and there, I've messed it up about as often as getting it right- but a messup means I have to redo the whole part, so I was looking for a not too painful way to tweak the parts in a less potentially irreversible way.

Gregm

Reply to
Greg Menke

Rechuck the stud, set the speed kinda slow use a small triangular file and deepen the threads. Since the file has a 60 degree angle it does a nice job of cleaning up 60 degree threads.

You might want to practice on some threaded rod to get the feel of this before you try your parts.

Reply to
Roger Shoaf

I've made button dies, but not by that method! I've drilled and tapped a hole in a suitable slice of oil-hardening bar, then used a rotary table on a drill press to locate and drill the holes for the cutting edges ala the factory jobbies. After hardening, a little Dremel work sharpened up the cutting edges and slit the button for adjustment. Now, you could probably avoid all that by either paying the freight from MSC for a suitable button die or learning how to pickup threads again. It isn't hard to rechuck a threaded piece and resume threading, it just takes a little practice. Here's my method:

Make sure the gear train or gearbox is set for the right thread(ruins your whole day if it isn't!). Make sure the tumbler is set correctly(ditto). Compound set at 29.5 degrees and kicked the correct direction for RH or LH, depending. Mount your part in the 4-jaw and dial it in. Use your thread gauge to make sure the threading tool is correctly set and that the profile is correct. A little stoning might not hurt to give a nicely finished thread. Now here's where it gets interesting. I engage the half-nuts at any convenient location close to the middle of the piece. I then use a combination of adjusting the cross-slide and compound to move the point of the tool to the root of the thread on the work piece. At this point, when I'm sure it's touching at the point and both sides, I zero the dials and set the threading indicator to a suitable number. I then use the cross slide to back out of the work piece, unlock the half nuts and traverse to the start of the thread. Move the cross slide back in to the zero point and you're ready to thread! Doesn't take long at all. If you're really nervous, engage the half-nuts and crank the lathe spindle by hand for a few revs to make sure everything lines up. Then take your skim cuts to reduce your thread. One thing you might want to do is tap a scrap for a gauge, then you don't have to remove the piece to check it.

Stan

Reply to
Stan Schaefer

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