# Single Point Threading Between Centers



## erikmannie (Feb 24, 2021)

Hopefully this will work because I am underway. I parted off some lengths of 1” steel hex, faced and center drilled both sides & chamfered one side.

My setup is a dead center in the spindle nose, faceplate, driving pin, dog on the hex bar (doesn’t seem to be a problem), and a live center.

I am turning this down to 20 mm OD, and we’ll see what happens with the single point threading and chamfering.


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## erikmannie (Feb 24, 2021)

The bolt will be an M20-2.5. The major diameter is 20 mm.

I am turning at 620 RPM with .005”/rev feed. My passes are .889 mm with CF.

This is the sub optimum finish that I am getting.


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## macardoso (Feb 24, 2021)

Out of curiosity, why the love for turning between centers?

I get when it is necessary (e.g., a shaft with existing centers and concentric features), but for a shop made bolt, why not rip it out in one operation with a 3 jaw chuck? Face, OD turn, thread, Part off partway, chamfer in situ, finish parting off.


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## benmychree (Feb 24, 2021)

The finish really does not much matter since you are threading it and will very likely finish/deburr the tops of the threads with a file.  Good finish is why I like to use TPG inserts, those molded inserts that you use are not very sharp at the cutting edge; good for roughing, especially with a interrupted cut, but not so nice for finish work.


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## Lo-Fi (Feb 24, 2021)

Probably the cutting force making the dog/driver flex and vibrate. Agreed, I'd pop in the three jaw and support with the tailstock center.


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## erikmannie (Feb 24, 2021)

Here is how it is going. The thread relief OD is 16.1 mm for a minor diameter of 16.933 mm.


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## erikmannie (Feb 24, 2021)

macardoso said:


> Out of curiosity, why the love for turning between centers?
> 
> I get when it is necessary (e.g., a shaft with existing centers and concentric features), but for a shop made bolt, why not rip it out in one operation with a 3 jaw chuck? Face, OD turn, thread, Part off partway, chamfer in situ, finish parting off.



Well, it is not for practical reasons. I tend to not be very pragmatic. I like doing stuff the old ways: gas welding, stick welding, manual machining, and the like.


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## erikmannie (Feb 24, 2021)

benmychree said:


> The finish really does not much matter since you are threading it and will very likely finish/deburr the tops of the threads with a file.  Good finish is why I like to use TPG inserts, those molded inserts that you use are not very sharp at the cutting edge; good for roughing, especially with a interrupted cut, but not so nice for finish work.



I saw your inserts; they were flat and smooth. I wondered about those; are those for light cuts? I switch to HSS for light cuts.


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## erikmannie (Feb 24, 2021)

Lo-Fi said:


> Probably the cutting force making the dog/driver flex and vibrate. Agreed, I'd pop in the three jaw and support with the tailstock center.



I did some with the 3J (and 4J), with and without tail support. That worked very nicely indeed.


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## benmychree (Feb 24, 2021)

erikmannie said:


> I saw your inserts; they were flat and smooth. I wondered about those; are those for light cuts? I switch to HSS for light cuts.


I use the TPG inserts with double end Aloris holders and use them for nearly all the work I do, the holders have adjustable chip breakers and work well for both rough and finish work.  I have them in both positive and negative rake (negative for interrupted cuts).


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## markba633csi (Feb 24, 2021)

Just curious, why is your dog missing a leg? "Here Stumpy!"  woof woof


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## mmcmdl (Feb 24, 2021)

We had a dog in the neighborhood with 2 legs , a missing eye and half a tail . His name was " Lucky " .

But yeah , I agree . Turn it , thread and part it off in a 3 jaw .


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## Aukai (Feb 24, 2021)

Eric is testing, and learning, and when the need arises he'll have it down....


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## erikmannie (Feb 24, 2021)

The pitch diameter I am looking for is 18.376 mm. I measured the pitch diameter of the bolt that I bought from the store, and it measures 18.352 mm.

I just measured the work on the lathe, and the pitch diameter is 18.771 mm, so I won’t even bother to try to fit a nut on yet.




I elect to just do careful spring passes until I just get to the specified pitch diameter.

Can I have full confidence that the work will return to the exact same position if I take it out and put it back in?

EDIT: with the zip tie on the dog, nothing changes position while test fitting a nut.


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## erikmannie (Feb 24, 2021)

I was getting no chips at all on the spring passes. Theoretically, I still have to go in another radial .1975 mm.

The metric divisions on my compound are .02 mm. I don’t know if this is radius or diameter, but I would guess radius.

I will go in 2 divisions on the compound with spring passes until I get no chips.


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## Lo-Fi (Feb 24, 2021)

You'll be fine removing the part, it's a good reason to be working between centers. Pop an indicator against the compound and verify the dial, just for your own peace of mind?

Looking over the pictures again, I reckon you might be able to tweak your setup by increasing the skookumness of your driver bolted to the faceplate. Not being critical, but hopefully helpful!


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## erikmannie (Feb 24, 2021)

It took a lot of time to get the pitch diameter down to 18.356 mm, and the specification is 18.376 mm.


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## erikmannie (Feb 24, 2021)

Lo-Fi said:


> You'll be fine removing the part, it's a good reason to be working between centers. Pop an indicator against the compound and verify the dial, just for your own peace of mind?
> 
> Looking over the pictures again, I reckon you might be able to tweak your setup by increasing the skookumness of your driver bolted to the faceplate. Not being critical, but hopefully helpful!



I absolutely welcome constructive criticism. What is skookumness?

Edit: I looked it up, and I got that skookum means cool or impressive.


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## mattthemuppet2 (Feb 24, 2021)

looking good but for the love of god put a chamfer at the start of the thread at least


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## erikmannie (Feb 24, 2021)

The nut fits wonderfully. Here is the tailstock end chamfer with the nut on there so as to repair the threads as the nut comes off.

Quite the retreat angle on the 60° tool there.


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## erikmannie (Feb 24, 2021)

mattthemuppet2 said:


> looking good but for the love of god put a chamfer at the start of the thread at least



I was doing just that while you were posting it LOL.

Here is the chamfer at the base of the bolt head. I had to search through a lot of tools to find one that would do this.


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## Ken226 (Feb 24, 2021)

You gotta rub some dirt on that driving dog or something!  That makes the paint in my newish truck look dull in comparison.

Do you wax that thing?  It's downright pretty.


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## Lo-Fi (Feb 24, 2021)

Looks good! Sorry, I should use proper words. I tend to use it as a catch all for sturdy, rigid, beefy. I blame a certain YouTuber!

I reckon a bit of triangulation from the end of the driver rod to near the bolts would work wonders for stiffening the driver up and hopefully help your surface finish. Won't need much, just enough to stop any potential for flexing/ringing of the plate/rod.


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## brino (Feb 24, 2021)

Those threads look great Erik!

-brino


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## erikmannie (Feb 24, 2021)

Here is the M20-2.5 bolt threaded between centers with a nut made using a 3J.


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## erikmannie (Feb 24, 2021)

Now I am going right into an M18-2.5 bolt threaded between centers.




What I will do differently this time:

(1) Get a chamfer on both ends (i.e. base of bolt head and end of threads (at live center)) before threading,
(2) Thread confidently until I get close to a crested V,
(3) I can make the safety groove shorter. I have been using my foot brake to end travel toward the headstock. It stops immediately. After stepping on the foot brake, I put the power lever in neutral, back the cross slide out 5+ mm, and then put the chuck in reverse to get my threading blade back out to the tailstock end of the threads. The half nut is left engaged throughout the threading process,
(4) Remember to use the fishtail to check alignment of the threading blade! I had merely squared up the tool post.

The first time, I was overly afraid of overshooting the depth of thread so I was very gun shy with the compound travel. Now I see that I can cut freely as long as I am not near the crested V. Having said that, I notice that crazy deep cuts make for a terrible finish. I like a lot of spring passes and oil.


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## erikmannie (Feb 24, 2021)

Ken226 said:


> You gotta rub some dirt on that driving dog or something!  That makes the paint in my newish truck look dull in comparison.
> 
> Do you wax that thing?  It's downright pretty.



Drench your truck in oil-based CF and you’re there.


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## craniac (Feb 24, 2021)

erikmannie said:


> I absolutely welcome constructive criticism. What is skookumness?
> 
> Edit: I looked it up, and I got that skookum means cool or impressive.


In a local native dialect Skookum means strong or powerful, like the Skooumchuck river in WA. Or for jail you say Skookum house


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## erikmannie (Feb 24, 2021)

Lo-Fi said:


> Looks good! Sorry, I should use proper words. I tend to use it as a catch all for sturdy, rigid, beefy. I blame a certain YouTuber!
> 
> I reckon a bit of triangulation from the end of the driver rod to near the bolts would work wonders for stiffening the driver up and hopefully help your surface finish. Won't need much, just enough to stop any potential for flexing/ringing of the plate/rod.



I just grabbed on to that offset dog driving pin, and it does indeed flex. Maybe a gusset would be in order.


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## macardoso (Feb 25, 2021)

Beautiful threads! Nice work. Single point threading gets a lot faster after the first 10-20 times you try it. Starts to become routine.

For chamfering the corners of a hex head, I like to use a threading tool. Each side is a 30 degree chamfer tool and you can hit both edges in the same setup (assuming of course the dog wasn't there). It ends up looking pretty darn close to factory.


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## erikmannie (Feb 25, 2021)

macardoso said:


> Beautiful threads! Nice work. Single point threading gets a lot faster after the first 10-20 times you try it. Starts to become routine.
> 
> For chamfering the corners of a hex head, I like to use a threading tool. Each side is a 30 degree chamfer tool and you can hit both edges in the same setup (assuming of course the dog wasn't there). It ends up looking pretty darn close to factory.



I did that at the beginning and end of the threads. Thanks for the tip.


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## erikmannie (Feb 25, 2021)

I had a problem. I saw that I was able to make cuts as deep as .20 mm (10 divisions on the metric scale). After taking my son to work and then returning to the project, I dialed in 10 divisions on the Imperial scale. This is 30% more of a cut, and it busted my threading blade. Look at this carnage:


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## erikmannie (Feb 25, 2021)

I will try to recover from this, but I think part of the OD is gone.

This is why I can’t have nice things.


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## brino (Feb 25, 2021)

Erik,

I think we can blame your son for this one for "taking you out of the zone".   

That's the type of tool that just gets ground flat on top to present a new edge, right?

-brino


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## erikmannie (Feb 25, 2021)

My Dad came over, saw this & said that I have scrapped the work. Just as a learning experience, I am going to try to recover.

I grabbed this 60° preground HSS bit, and I put it in the tool holder so that it fits into the threads that I have cut so far. My half nut remains engaged.

Looking at the photo up close, I can see that I need to make an adjustment.


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## erikmannie (Feb 25, 2021)

brino said:


> Erik,
> 
> I think we can blame your son for this one for "taking you out of the zone".
> 
> ...



Yes, it must be ground flat on the top, just as it came from the factory. That’s what the mill & carbide end mills are for.


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## erikmannie (Feb 25, 2021)

There we go. Hopefully the fishtail on the tailstock quill is good enough. At present, the OD of my threads are serrated.


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## erikmannie (Feb 25, 2021)

Well, at least I crashed into the dog driving pin.


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## JRaut (Feb 25, 2021)

erikmannie said:


> Yes, it must be ground flat on the top, just as it came from the factory. That’s what the mill & carbide end mills are for.


You sure about that......???

Dressing it flat using a grinder (or belt sander if you've got one) is the way to go for these.

Trying to do it on the mill sounds like a recipe for disaster.



erikmannie said:


> Well, at least I crashed into the dog driving pin.


Oops...

+1 for just holding it in your 3-jaw.


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## erikmannie (Feb 25, 2021)

Using a hammer and a bench vice, I temporarily fixed the offset dog driver pin bracket. It will be re-engineered.

I carefully made some cleanup passes, and I went in another .10 mm (in two passes). I tested the nut, and it was too tight.

I wanted to file the OD, but since the half nut remains engaged I had to move the tailstock quill all the way out (6”) and do the filing as the carriage advanced.

Here it is before I clean it up more.


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## erikmannie (Feb 25, 2021)

JRaut said:


> You sure about that......???
> 
> Dressing it flat using a grinder (or belt sander if you've got one) is the way to go for these.
> 
> ...



I don’t know how to sharpen this P-6 threading blade. Maybe someone could chime in and let me know. I have done it on the mill using a carbide end mill, and I didn’t like how it turned out.




Yes, I’m definitely starting to appreciate the conveniences afforded by using a chuck.


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## macardoso (Feb 25, 2021)

Funny how making a small mistake snowballs into lots of mistakes. I watch myself do it all the time. Mess up one little thing and make a hasty correction that ruins so much more.

Glad that everything that got broken was a replaceable item. Keep up the work!


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## erikmannie (Feb 25, 2021)

The nut from the store fits very nicely. I am going to clean it up the new bolt the best that I can.

Credit to Joe Pie for showing how to bring a threading tool back in after you’ve lost your place (or, in my case, switched to a different tool bit).


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## bill70j (Feb 25, 2021)

Lo-Fi said:


> Looks good! Sorry, I should use proper words. I tend to use it as a catch all for sturdy, rigid, beefy. I blame a certain YouTuber!


that certain YouTuber first introduced me to skookum and a whole host of other adjectives, verbs, nouns .....


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## erikmannie (Feb 25, 2021)

This M18-2.5 bolt kicked my butt. I am going to try to make another one just like it without making any mistakes.


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## stupoty (Feb 25, 2021)

Have you tried a rubber band instead of the zip tie for stopping the dog bouncing ?

Stu


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## erikmannie (Feb 25, 2021)

stupoty said:


> Have you tried a rubber band instead of the zip tie for stopping the dog bouncing ?
> 
> Stu



That is a really good idea. I will do that.


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## erikmannie (Feb 25, 2021)

I made this one with zero issues, except the close up photo shows a finish that is not perfect. The chamfer on the bolt head is also asymmetric.


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## mikey (Feb 25, 2021)

erikmannie said:


> I don’t know how to sharpen this P-6 threading blade. Maybe someone could chime in and let me know. I have done it on the mill using a carbide end mill, and I didn’t like how it turned out.
> 
> View attachment 357090
> 
> ...



To sharpen a P6, you* grind the entire top flat*. You have a lot to grind away but if you just make the top flat it will reproduce the original geometry. Best done on a belt sander.


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## erikmannie (Feb 25, 2021)

With the flash on, it is a bit of a horror show.


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## erikmannie (Feb 25, 2021)

mikey said:


> To sharpen a P6, you* grind the entire top flat*. You have a lot to grind away but if you just make the top flat it will reproduce the original geometry. Best done on a belt sander.



Perfect timing with your answer. But what if I don’t have a belt sander?

I can’t use a milling machine with a carbide end mill? I did that before, but I ground it at an improper angle.


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## erikmannie (Feb 25, 2021)

I tried it with a flap disc.


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## mikey (Feb 25, 2021)

Cutting HSS with an end mill will not go well. You need an abrasive that can grind flat. A belt sander's flat platen is ideal. Someday you might consider owning one.


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## erikmannie (Feb 25, 2021)

mikey said:


> Cutting HSS with an end mill will not go well. You need an abrasive that can grind flat. A belt sander's flat platen is ideal. Someday you might consider owning one.



I wonder if something like this would be good enough. I also wonder if I could use this for fine tuning (and touching up) HSS lathe tool bits.


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## Janderso (Feb 25, 2021)

erikmannie said:


> Here is the M20-2.5 bolt threaded between centers with a nut made using a 3J.
> 
> View attachment 357014
> 
> ...


You nailed it man.


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## Janderso (Feb 25, 2021)

A scotchbrite wheel cleans up parts really nice for deburring or bluing etc.


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## mikey (Feb 25, 2021)

erikmannie said:


> I wonder if something like this would be good enough. I also wonder if I could use this for fine tuning (and touching up) HSS lathe tool bits.
> 
> View attachment 357136



Personally, I would not waste money on something like that. I know finances are tight right now so wait for a better grinder. I'll link you to something later. Have to run right now.


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## DavidR8 (Feb 25, 2021)

@erikmannie I have this one and it works well.


			https://www.grainger.com/product/DAYTON-Belt-Disc-Sander-6Y945


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## erikmannie (Feb 25, 2021)

DavidR8 said:


> @erikmannie I have this one and it works well.
> 
> 
> https://www.grainger.com/product/DAYTON-Belt-Disc-Sander-6Y945



That one looks nice. I just want to make sure to buy something for use with metal.


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## DavidR8 (Feb 25, 2021)

erikmannie said:


> That one looks nice. I just want to make sure to buy something for use with metal.


I use it for both wood and metal, 99% metal, 1% wood.


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## JRaut (Feb 25, 2021)

You must have a bench grinder, right?

Just use that, no worries. Costs free dollars and it'll work great.


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## mmcmdl (Feb 25, 2021)

erikmannie said:


> I had a problem. I saw that I was able to make cuts as deep as .20 mm (10 divisions on the metric scale). After taking my son to work and then returning to the project, I dialed in 10 divisions on the Imperial scale. This is 30% more of a cut, and it busted my threading blade. Look at this carnage:


Way cool ! You couldn't make that on a cnc if you tried !   

The way you are threading doesn't leave you much space for errors . I understand you're learning , but that could have been disasterous !


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## mikey (Feb 25, 2021)

JRaut said:


> You must have a bench grinder, right?
> 
> Just use that, no worries. Costs free dollars and it'll work great.



The Aloris P6 HSS insert has to be ground dead flat on top. You cannot do that with a wheel.

Erik, I was going to link to the belt sander that David recommended. If you use ceramic belt with it, it will definitely grind HSS just fine.


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## JRaut (Feb 25, 2021)

mikey said:


> The Aloris P6 HSS insert has to be ground dead flat on top. You cannot do that with a wheel.


I respectfully disagree.

Even the Aloris website says "to sharpen, simply grind the top surface."

All you need to do is grind it flat.

Sure, a bench grinder will leave an **ever-so-slightly** convex surface, but just finish it flat with a stone if it bugs you.

Yes, a belt sander would be nice. Most new tools are nice. But you don't need one to sharpen your HSS insert.


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## erikmannie (Feb 26, 2021)

I am going to have to move forward without a belt sander now because I financially ran myself into the ground with the PM-1660TL (and tooling) purchase. Also, my shop is full. Even if somebody gave me a bench grinder, I would have no place to put it indoors.

I have done fine with my bench grinder and diamond honing files for the HSS tool bits, even though the bench grinder lives outdoors.

So how do I grind the top of a P-6 flat with no belt sander? What if I get it close with a flap disc & then get it perfectly flat on the milling machine? A carbide end mill cuts the HSS P-6 just fine.


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## mikey (Feb 26, 2021)

If you can cut it with an end mill, have at it.


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## Janderso (Feb 26, 2021)

DavidR8 said:


> @erikmannie I have this one and it works well.
> 
> 
> https://www.grainger.com/product/DAYTON-Belt-Disc-Sander-6Y945


David,
I went with the Kalamazoo.
I probably should have gone on the cheap but I do like it.
These belt sanders are very handy for all sorts of things.








						2FSMS 2 x 48 INCH BELT SANDER WITH FULL BOXED GUARD
					

2FSMS 2 x 48 inch belt sander with full boxed guard is multiposition sander belt sander that's designed to sand various materials.




					kalamazooind.com


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## Janderso (Feb 26, 2021)

erikmannie said:


> Here is how it is going. The thread relief OD is 16.1 mm for a minor diameter of 16.933 mm.
> 
> View attachment 356974


I don't know why I haven't used my Aloris threading tool-like yours??
I used it once, worked great and forgot about it.
Thinking about what Mikey said, "the edge needs to be perfectly flat". I can see using a HD tool room grinder or the U2. Then hone to a mirror finish for best results.
Looking really good man!!


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## mmcmdl (Feb 26, 2021)

The edge doesn't need to be flat . Think of it as a HSS tool bit . Grind it to so it works for the job .


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## DavidR8 (Feb 26, 2021)

Janderso said:


> David,
> I went with the Kalamazoo.
> I probably should have gone on the cheap but I do like it.
> These belt sanders are very handy for all sorts of things.
> ...


Those puppies are over $1000 in Canada...


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## Masterjuggler (Feb 26, 2021)

erikmannie said:


> I wonder if something like this would be good enough. I also wonder if I could use this for fine tuning (and touching up) HSS lathe tool bits.


I have that one, it's handy to store on a shelf in VERY limited space, but it's essentially a disposable tool. If you have some space for one, consider getting a 2x48 or 2x72 belt grinder. They're extremely useful for. Short of that, the 1x30 from horrible freight is better than nothing.


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