Inside threading, can you recommend some tooling?

[stupoty]

I agree. Don't have a grinder that can do this right now. I have a belt grinder with a rest. I've done lathe tooling with it. Also have a horrible pedestal grinder with tin foil rests. The horrible grinder has nothing solid to bolt to for a rest. The shields are made of thin sheet metal, rather than being cast. Hard to adapt. Sure I could make it work, but I think making a little boring bar like @Larry$ is a much easier task. I can grind the tooling on my belt grinder.

I tend to rough the threading bits on the grinder and final shape with bench stones.

Stu

 

[WobblyHand]

Found some 0.1875" diameter HSS in my stash. Ground a flat and a 60* point with 15* relief angles. That was the easy part. The hard part (for me) is honing it and not destroying it in the process. It's real hard to maintain the angles with such a small flat, but I'm plugging away at it. I have some 1/2" 1144 I can use for the bar. Without making my own boring bar holder, the biggest I can go is 1/2". I'll drill a hole through the 1144 for the round rod and a set screw. Guess I will use the boring bar to hold the HSS in place while I grind it off. It won't be a heavy duty setup, but I hope to be able to internally thread 1/4"-3/8" worth of threads. At 24 TPI that would give 6 threads, which is plenty.

Lets just say it could be a lot better, but it's what I can do right now.

 

[Larry$]

Between you and me, I'd rather pay $1 per, than $10 or more

I've never bought the high end inserts so I don't know what I'm missing. I prefer using HSS though I have a few inserted tools that I use when it happens to strike my mood. I've got a D bit grinder so I can (sort of) easily sharpen lots of different tools. I also have an 8" G Bear bench grinder that is terrible. Our shop has a nice Baldor 8", huge difference. I just free hand on the bench grinder.

 

[Larry$]

Found some 0.1875" diameter HSS in my stash.

When I use round stock for the tool I grind a small flat along it's length for the set screw to always hold it at the correct angle.
You can use tool holders with a V in the bottom to hold round boring bars or mill flats on the bar for a regular tool holder.

 

[ericc]

Hi Wobbly. Here's mine. It uses a broken drill bit. You have to be careful, since the shank is soft (gouges visible). I used this to make my chuck back plate thread to attach to the spindle (1-1/2"x8). It worked just fine.

 

[Larry$]

Ericc, you proved that function doesn't require beauty. But it is beautiful in it's own way.

 

[WobblyHand]

@ericc nice tool! Looks like it will do the job.

Thanks to some great ideas graciously donated here, I'm nearly complete with the bar and tool. The bar was pretty easy, just chopped off some 1/2" 1144 and drilled a couple of holes. One was reamed to 0.1878" since the HSS miked out to 0.18755" and the other was drilled and tapped to 8-32. I ground an 8-32 SHCS to the approximate length. Might go with a set screw, we'll see if the screw gets in the way. While I had the bar in a collet block, I milled a flat in the top and bottom faces, enough so it can be grabbed and turned.

The threading tool was previously ground but there was no flat on it for the screw. I really don't have a good fixtured way to grind things. So I decided to sacrifice an 1/8" carbide end mill. Since these end mills were incredibly inexpensive, (I got 10 for $3 due to an eBay snafu,) I thought it might be worth a try. I didn't want to try a good carbide end mill. So put the 3/16 HSS in the toolmakers vise vee and indicated the flat I had ground at the tip.

Got it as level as I could, about 0.0002" over the 0.15" area I could indicate. I then used an 1/8" carbide end mill to make a flat. Was surprised it worked as well as it did. Is it good? Not really, but it is good enough, especially with a little touch up with a hone. Haven't dared to look at the end mill yet, suspect it is in poor shape now.

Have to cut off the tool bit, as it's 3.5" long! Be back in a little while with the completed assembly.

 

[WobblyHand]

Took me a while. Not to cut the HSS, but to find the little bugger when it bounced on the floor and rolled away. Flashlight chose to work for 15 seconds at a time. Eventually found it. I cut it too long, but that's ok as the plan was to grind it off in the tool holder after a bore test fit. Set up to work in the smallest bore of about 1". What I want to eventually thread is larger. The SHCS head is too high, it hits the bore for an 0.84" ID. Think I will turn an 8-32 set screw to length. It needs to be around 3/16" or so.

I had ground off the 8-32 SHCS but didn't get it flat, This is slightly turning the bit. If I do the set screw in the lathe it will be reasonably flat.

This all has been an interesting and fun diversion. Never made something like this before. I'm liking having this capability, gives me the giggles.

 

[WobblyHand]

Tool is done, but I must be tired, because I'm not cutting a good thread. Trying for 24 TPI. Used chart on side of mini-lathe and did a scratch pass, which seemed ok. When I measured the sharpie "thread" it was 24 TPI, or so I thought. Chart setting is one of the allowed settings for 24 TPI. A,B,C,D = 40, 65, 45, 60. This is a valid setting according to littlemachineshop. I'm backing the tool into the workpiece using a stop for a reference. Then advancing directly into the piece. I wait for the thread dial to hit 1 and start the feed. I'm getting multiple threads. Seems I'm missing something obvious. Am I not taking up the backlash of the leadscrew properly by starting without thread relief? I tried multiple times, and wiped out the thread entirely. Good thing this is a test piece! Almost positive I'm not shaving off the back side, but will check again.

Have to say, this is good practice, and I don't feel bad about this piece at all. Rather make my mistakes on junk, rather than expensive stock.

Edit: thought of something. Do I need to drop the tip down of the tool bit? Most other tools are rotated below center to gain additional clearance.

 

[Larry$]

The SHCS head is too high, it hits the bore

Put the set screw in from the end.