# Trying to turn stainless steel taper.



## FTlatheworks (May 31, 2021)

I have been cutting a tapered hole in tool steel and putting it in my headstock and tailstock chuck. I then place a ball bearing in between the work on both ends and drive it with a lathe dog. I’m only turning 1-2 degree tapers. Lately it is chattering and tearing the metal. Can anyone help me out with this.


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## davidpbest (May 31, 2021)

What kind of tool are you using to cut the material?  And are you cutting stainless or tool steel?   I don't understand your setup as described.  How about a photo?


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## FTlatheworks (May 31, 2021)

I will when I get back to the shop in about 30 minutes.


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## FTlatheworks (May 31, 2021)

FTlatheworks said:


> I have been cutting a tapered hole in tool steel and putting it in my headstock and tailstock chuck. I then place a ball bearing in between the work on both ends and drive it with a lathe dog. I’m only turning 1-2 degree tapers. Lately it is chattering and tearing the metal. Can anyone help me out with this.


I’m cutting stainless 304 with a carbide insert. Ccmt insert in a straight shank.


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## benmychree (May 31, 2021)

How long and what diameter is the part?  perhaps a positive rake insert with small radius and sharp cutting edge may help, also switching to 303 SS would help with tearing and chatter.


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## FTlatheworks (May 31, 2021)

benmychree said:


> How long and what diameter is the part?  perhaps a positive rake insert with small radius and sharp cutting edge may help, also switching to 303 SS would help with tearing and chatter.


I cNt get 303 where I’m at unless I order a huge amount.


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## benmychree (May 31, 2021)

FTlatheworks said:


> I cNt get 303 where I’m at unless I order a huge amount.


Try McMaster Carr


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## markba633csi (May 31, 2021)

A super sharp, well supported HSS/cobalt tool should be able to cut it if you are able to grind bits yourself
Stainless is challenging because it tries to work harden if you don't take aggressive cuts
-M


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## benmychree (Jun 1, 2021)

303 stainless does not have much tendency to work harden and can be cut nearly as fast as CRS.


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## FTlatheworks (Jun 1, 2021)

benmychree said:


> 303 stainless does not have much tendency to work harden and can be cut nearly as fast as CRS.


I wasted so many tools tonight. It must have work hardened cause I was taking some monster cuts just making everything concentric and taking off material before tapering the part to the final specs.


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## FTlatheworks (Jun 1, 2021)

Just curious, should one cover their ways all the time when working, or only when sanding? Also, am I going to destroy this pm1236 by working on stainless so much?


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## Suzuki4evr (Jun 1, 2021)

I use carbide wnmg PC9030 inserts on stainless. You said you have a ccmt holder? You get ccmt with a 4mm nose radius in PC9030. It machine stainless very well for me. In fact, and some my differ from me but I use the pc9030 wnmg on almost everything for years and I can't say that there is extra wear because I use it for different material.


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## FTlatheworks (Jun 1, 2021)

That will fit the shanks I use? I’m still learning about shanks and insert designation.


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## Suzuki4evr (Jun 1, 2021)

If you have a ccmt external turning holder then look at the number on the holder and look up the insert size for that tipe of holder. The pc9030 is the insert grade for stainless steel turning. If I am wrong, then please correct me any of our seasoned members. Can you post a pic of the holder you are using? You won't damage your lathe cutting stainless, what lathe beds don't like is gritt or gritt like paste like cast iron dust mixed with oil and grinding dust, tgat will ruin your lathe bed. The chips itself is wiped away with the way wipers. As for covering way beds, I can only suggest wiping it as often as possible and if you want you can bolt a piece of plate or plexiglass onto your carriage where your steadyrest bolt on. Just long enough so when you are near the chuck that the plexiglass or plate doesn't hit the headstock behind the chuck and wide enough to cover the bed ways. That will also help keep chips of the way beds. My two cents.

Michael.


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## FTlatheworks (Jun 3, 2021)

Suzuki4evr said:


> If you have a ccmt external turning holder then look at the number on the holder and look up the insert size for that tipe of holder. The pc9030 is the insert grade for stainless steel turning. If I am wrong, then please correct me any of our seasoned members. Can you post a pic of the holder you are using? You won't damage your lathe cutting stainless, what lathe beds don't like is gritt or gritt like paste like cast iron dust mixed with oil and grinding dust, tgat will ruin your lathe bed. The chips itself is wiped away with the way wipers. As for covering way beds, I can only suggest wiping it as often as possible and if you want you can bolt a piece of plate or plexiglass onto your carriage where your steadyrest bolt on. Just long enough so when you are near the chuck that the plexiglass or plate doesn't hit the headstock behind the chuck and wide enough to cover the bed ways. That will also help keep chips of the way beds. My two cents.
> 
> Michael.


Thank you, I have been using paper for the time being. I will look into those inserts. They will fit my shank.


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## FTlatheworks (Jun 3, 2021)

davidpbest said:


> What kind of tool are you using to cut the material?  And are you cutting stainless or tool steel?   I don't understand your setup as described.  How about a photo?


Sorry, I don’t know how I missed this, but here is the photos.


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## Liljoebrshooter (Jun 3, 2021)

Get rid of that CCMT insert and try a CCGT.  

Joe


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## Suzuki4evr (Jun 3, 2021)

Liljoebrshooter said:


> Get rid of that CCMT insert and try a CCGT.
> 
> Joe


Why?


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## Suzuki4evr (Jun 3, 2021)

These are the ones I am speaking about


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## FTlatheworks (Jun 3, 2021)

I was gonna say the ccgt would damn near crumble if I tried to use it with this setup. You like these for 304, or are you just a fan in general.


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## FTlatheworks (Jun 3, 2021)

Liljoebrshooter said:


> Get rid of that CCMT insert and try a CCGT.
> 
> Joe


Was this a mistake? I have used ccgt (they are for aluminum and brass) just to clean up surface finish. They chip instantly on this 304.


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## Suzuki4evr (Jun 3, 2021)

FTlatheworks said:


> I was gonna say the ccgt would damn near crumble if I tried to use it with this setup. You like these for 304, or are you just a fan in general.


Like them in general, but they machine S/S great for me.


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## FTlatheworks (Jun 3, 2021)

Suzuki4evr said:


> Like them in general, but they machine S/S great for me.


Would you consider them expensive? I found a set for 60 bucks.


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## Suzuki4evr (Jun 3, 2021)

That doest sound toooo bad but, I buy mine on fleabay, but I can't remember now what those cost. Is that a venders price or where did you source that one? Is it korloy or another brand?If you can afford it and it is genuine, I think you can go for it. Just remember that some ebay stuff is not bad quality and others......well. As the rule goes,  buyer be ware. That being said, if the quality suck, contact the seller.


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## FTlatheworks (Jun 3, 2021)

Suzuki4evr said:


> That doest sound toooo bad but, I buy mine on fleabay, but I can't remember now what those cost. Is that a venders price or where did you source that one? Is it korloy or another brand?If you can afford it and it is genuine, I think you can go for it. Just remember that some ebay stuff is not bad quality and others......well. As the rule goes,  buyer be ware. That being said, if the quality suck, contact the seller.


It’s Korloy on Amazon. Do you know anything about turning tapers?


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## Suzuki4evr (Jun 3, 2021)

If you can afford it, take it, they will last you quit a long time. I turn them by setting the compound. Check out Jo Pi's youtube video about setting tge compound. Good info.


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## FTlatheworks (Jun 3, 2021)

Suzuki4evr said:


> If you can afford it, take it, they will last you quit a long time. I turn them by setting the compound. Check out Jo Pi's youtube video about setting tge compound. Good info.


You can’t do more than a couple inches setting the compound, I don’t think? I will have to watch that.


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## Suzuki4evr (Jun 3, 2021)

No you can't but you can still use his method to set your angle. Let us know what you decided on the inserts and if it worked for you.


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## macardoso (Jun 3, 2021)

I've had luck with CCGX (designed for aluminum) inserts in stainless. They are super sharp and leave a stunning finish. Same concept as using HSS. Sharp cutting edge, low cutting HP and pressure.

Edit: I see this has been recommended above. I buy them from ebay or AliExpress at ~$10 per box of 10. Long shipping time usually but cheap. Korloy brand (or knockoff of it)


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## MrWhoopee (Jun 3, 2021)

I didn't see the difference between CCMT and CCGT explained. The M stands for molded insert, the G stands for ground. The ground insert will have a sharper cutting edge than the molded one. This has nothing to do with the suitability for machining a particular material, that is determined by the grade of carbide.


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## tcarrington (Jun 3, 2021)

FWIW, I see a relatively high length to diameter ratio on the shaft your are turning. That will increase the tendency to chatter. It will also limit the depth of cut you can achieve. The real trick here is getting the RPM up to near "entitlement" for stainless. From there your feed and depth of cut will probably favor a higher feed and small depth of cut. I would favor a carbide solution to allow a higher RPM. I will caution that it is entirely possible on a workpiece that looks as long and thin as yours to pull it up and over the tool. 
But, be brave and send it. it is very easy to not remove enough material at a time and work harden it to near impossible state to machine.


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## macardoso (Jun 4, 2021)

MrWhoopee said:


> I didn't see the difference between CCMT and CCGT explained. The M stands for molded insert, the G stands for ground. The ground insert will have a sharper cutting edge than the molded one. This has nothing to do with the suitability for machining a particular material, that is determined by the grade of carbide.



While you are technically correct, I’d like to explain my reasoning.

The carbide grade refers to the particular mix of different carbides and binders and determines the hardness vs. toughness as well as temperature resistance. Grades are designed from the manufacturer for particular materials depending on their machining requirements (high heat, abrasiveness, hardness, etc.). I believe that coatings also get mixed into the grade for the same reasons as above. 

But the grade is only part of the story. The edge prep, chipbreaker, insert geometry, and insert clamping all play a big role in cutting performance. Manufacturers typically pair up grades, edge preps, and chipbreakers for specific materials or even specific machining operations of one material. Unfortunately these are always done for large production CNC equipment, or are offered as generic geometries.

Here is my opinion based on my experience. The inserts made for specific materials seem to often cut best with more rigidity, surface footage, and horsepower than my lathe (12x36, 1.5HP, 1000 lb) can provide. Positive rake medium inserts barely break a chip correctly in many cases before my lathe chatters, and most inserts create massive cutting forces that make hitting tolerances difficult. I think this is why many people turn away from inserts and go to HSS.

Inserts are great in production CNC machines as there is a ton of rigidity to back them up, but on our smaller hobby machines the bluntness of the edge (great for tool life) limits the effectiveness of the insert tool.

This is where the xxGT or xxGX inserts come in. The ground and polished edge is super sharp and cuts with extremely low horsepower and cutting forces. They are comparable to sharp HSS tooling. Their tool life in nonferrous is excellent, but I’ve also found good use for them in medium alloy steel, stainless, and even cast iron. The inserts are extremely free cutting and produce a good surface finish even in tricky materials like 1018. They also allow a very fine minimum depth of cut (only a few tenths) without rubbing. This allows you to turn precision tolerances on parts.

I’ll admit the tool life in ferrous materials is not great, but at $0.50 per edge, they are very affordable and I reach for them every time I have a critical dimension or need a good finish. When roughing is required, I always choose a tougher insert, ideally one designed for my material if I can.


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## FTlatheworks (Jun 4, 2021)

macardoso said:


> While you are technically correct, I’d like to explain my reasoning.
> 
> The carbide grade refers to the particular mix of different carbides and binders and determines the hardness vs. toughness as well as temperature resistance. Grades are designed from the manufacturer for particular materials depending on their machining requirements (high heat, abrasiveness, hardness, etc.). I believe that coatings also get mixed into the grade for the same reasons as above.
> 
> ...


I use them for thou doc for finishing, but it still leaves lines, no matter what shank I use. How do you achieve excellent finishes with them? What shank?

I’m afraid with my lack of experience I don’t know what can be achieved with tooling on the lathe, or sandpaper and file.


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## mikey (Jun 4, 2021)

I just wanted to chime in to clarify something. The aforementioned CCMT and CCGT inserts are both available as molded inserts. What seems to be confusing folks is that CCGT inserts _also_ come with an AK chipbreaker; inserts with an AK chipbreaker are typically ground with sharp edges, are uncoated, have a very positive rake and are best suited for aluminum and non-ferrous materials. The molded CCGT inserts do work well with stainless but these inserts are typically available with a different chipbreaker morphology. So, when you see someone referring to "ground sharp edges with high positive rake" on a CCGT insert they are referring to an insert with an *AK chipbreaker*. The grade of the insert is something else entirely.


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## macardoso (Jun 4, 2021)

mikey said:


> I just wanted to chime in to clarify something. The aforementioned CCMT and CCGT inserts are both available as molded inserts. What seems to be confusing folks is that CCGT inserts _also_ come with an AK chipbreaker; inserts with an AK chipbreaker are typically ground with sharp edges, are uncoated, have a very positive rake and are best suited for aluminum and non-ferrous materials. The molded CCGT inserts do work well with stainless but these inserts are typically available with a different chipbreaker morphology. So, when you see someone referring to "ground sharp edges with high positive rake" on a CCGT insert they are referring to an insert with an *AK chipbreaker*. The grade of the insert is something else entirely.


Thanks Mikey - you are correct.


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## macardoso (Jun 4, 2021)

FTlatheworks said:


> I use them for thou doc for finishing, but it still leaves lines, no matter what shank I use. How do you achieve excellent finishes with them? What shank?
> 
> I’m afraid with my lack of experience I don’t know what can be achieved with tooling on the lathe, or sandpaper and file.


I use them with a SCLCR 1/2" shank. It should not matter much. Any insert will leave lines in tough to finish materials. Higher speed and a very steady feed rate (power feed) seem to do the most. If the feed is unsteady, the insert will cut deeper when the tool is feeding slowly, and deflect more when feeding quickly.


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## FTlatheworks (Jun 5, 2021)

macardoso said:


> I use them with a SCLCR 1/2" shank. It should not matter much. Any insert will leave lines in tough to finish materials. Higher speed and a very steady feed rate (power feed) seem to do the most. If the feed is unsteady, the insert will cut deeper when the tool is feeding slowly, and deflect more when feeding quickly.


I’m still learning, so I apologize, but I mean angle provided by the type of shank. Does this make sense? Feel free to tell me what’s wrong about my terminology. It’s either run my lathe, work, and school, or read about lathes, work, and school.


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## macardoso (Jun 5, 2021)

FTlatheworks said:


> I’m still learning, so I apologize, but I mean angle provided by the type of shank. Does this make sense? Feel free to tell me what’s wrong about my terminology. It’s either run my lathe, work, and school, or read about lathes, work, and school.


Well the inclination of the insert (Rake) into the cut is defined by the insert rake and holder. The CCMT/CCGT inserts are positive rake so the top of the insert is flat (parallel) to the floor and the cutting edge is provided by the rake ground into the insert. Negative rake inserts require holders that tip the insert into the work since the insert has no rake built into it. 

The second angle is the angle of the holder relative to the work. With insert tooling, I personally keep the toolpost square to the work (and thus the tool holder square to the work) as all the clearances are built into the holder geometry in this configuration. Special cases may force you to rotate the tool post.

Finally the last angle is the included angle of the insert. CCMT/CCGX is an 80 degree diamond. VCMT/VCGT is a 35 degree diamond (different holder). The smaller the included angle, the lower the cutting forces, the lower the likelihood of chatter, and the weaker the insert.

Others have other opinions about all this, but this is what works for me!


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## FTlatheworks (Jul 11, 2021)

Hopefully this post hasn’t been dead too long. Can anyone help out with the turning long tapers. I keep getting horrible chatter and finishes. I also keep bending the part trying to part it off. It is a 1.5 degree taper 5-7 inches long.


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## FTlatheworks (Jul 11, 2021)

tcarrington said:


> FWIW, I see a relatively high length to diameter ratio on the shaft your are turning. That will increase the tendency to chatter. It will also limit the depth of cut you can achieve. The real trick here is getting the RPM up to near "entitlement" for stainless. From there your feed and depth of cut will probably favor a higher feed and small depth of cut. I would favor a carbide solution to allow a higher RPM. I will caution that it is entirely possible on a workpiece that looks as long and thin as yours to pull it up and over the tool.
> But, be brave and send it. it is very easy to not remove enough material at a time and work harden it to near impossible state to machine.


Is there a better way to turn tapers than how I am doing it? I feel like my stock being on two ball bearings is the problem.


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## benmychree (Jul 11, 2021)

Turning between centers is always less rigid than chucking, and possibly the balls make it even less rigid.


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## benmychree (Jul 11, 2021)

I sometimes back up a chattering cut with a lead hammer, trying different angularity and location behind the part or at an angle behind and above the part, looking for a sweet spot that will cancel the vibration/chatter.  It may be that turning such a part length and small diameter is not possible or practical, especially between centers.


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## FTlatheworks (Jul 11, 2021)

benmychree said:


> I sometimes back up a chattering cut with a lead hammer, trying different angularity and location behind the part or at an angle behind and above the part, looking for a sweet spot that will cancel the vibration/chatter.  It may be that turning such a part length and small diameter is not possible or practical, especially between centers.


Is there another way to do it, or are you telling me it’s not possible?


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## benmychree (Jul 11, 2021)

If it were possible to construct a follow rest that could retract at the same rate as the taper, it might be able to be done, but that would not be an easy task.  Long skinny tapers, like taper pins are produced on Swiss type automatic screw machines, where the stock is fed out of the collet while it is rotating and the tool is retracting radially while remaining stationary axially.


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## FTlatheworks (Jul 11, 2021)

benmychree said:


> If it were possible to construct a follow rest that could retract at the same rate as the taper, it might be able to be done, but that would not be an easy task.  Long skinny tapers, like taper pins are produced on Swiss type automatic screw machines, where the stock is fed out of the collet while it is rotating and the tool is retracting radially while remaining stationary axially.


Let me start by saying I have done it before. With cheap materials and very little prior experience. I’m just trying to make it easier. Should my tool be turned to the same angle as my tailstock taper attachment is tapering the stock?


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## benmychree (Jul 11, 2021)

With the very small angle that you are using, I doubt that it would make much difference, the main thing is that it should be sharp with little or no nose radius and minimal side or front clearance that would tend to make the tool dig in, the tool should be about 90 degrees to the finishes cut angle.


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## FTlatheworks (Jul 11, 2021)

benmychree said:


> With the very small angle that you are using, I doubt that it would make much difference, the main thing is that it should be sharp with little or no nose radius and minimal side or front clearance that would tend to make the tool dig in, the tool should be about 90 degrees to the finishes cut angle.


Alright, Thank you!


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## Richcan22 (Jul 11, 2021)

I’ve been cutting 316 and 304. Been challenging but I would have to check what insert I bought. When I bought my tool holder the rep sent me the tool insert. But I’m going to rebuild my tail stock spindle with stainless MT3 I have broken more cut off inserts than my regular turning tool. Plus you need to go slower speed. And make sure machine is rigid tighten up any slack in machine. I tried tapping and had to order special tap all my other taps won’t work. Bought one tap that was supposed to work but didn’t had to do the research and found one that cut like butter.


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## FTlatheworks (Jul 11, 2021)

Richcan22 said:


> I’ve been cutting 316 and 304. Been challenging but I would have to check what insert I bought. When I bought my tool holder the rep sent me the tool insert. But I’m going to rebuild my tail stock spindle with stainless MT3 I have broken more cut off inserts than my regular turning tool. Plus you need to go slower speed. And make sure machine is rigid tighten up any slack in machine. I tried tapping and had to order special tap all my other taps won’t work. Bought one tap that was supposed to work but didn’t had to do the research and found one that cut like butter.


I can turn, thread, tap,  and bite just fine. It just will not run smooth cutting a taper. It has to be something about the way in using my tailstock taper attachment, or something in my process. I have successfully turned taper 304 and 303 spindles recently. Lately, all of them have been running like crap.


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## FTlatheworks (Jul 11, 2021)

Richcan22 said:


> I’ve been cutting 316 and 304. Been challenging but I would have to check what insert I bought. When I bought my tool holder the rep sent me the tool insert. But I’m going to rebuild my tail stock spindle with stainless MT3 I have broken more cut off inserts than my regular turning tool. Plus you need to go slower speed. And make sure machine is rigid tighten up any slack in machine. I tried tapping and had to order special tap all my other taps won’t work. Bought one tap that was supposed to work but didn’t had to do the research and found one that cut like butter.


Good looking parts you made. Good job!


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