Thread Cutting on the Lathe, Part Three - Grinding the Tool

In this episode we apply what we learned in part two and grind a thread cutting tool.

[@RickSaunders13]

Thanks. Brings back what I learned in a machine tool course nearly 40 yrs ago. Even today I use the act of sharpening a lathe tool bit as something that needs to be seen, that three dimensional knowledge and skill that can not necessarily be learned from a book.

[@TomsTechniques]

Books only provide so much information. At some point you need to get out and get your hands dirty, or at least watch someone else get theirs dirty. Tom

[@Lordfud13]

I just started out in machine work and this is the best explanation I've seen about how to grind a tool bar none! Thanks. Tom

[@rsmetal6805]

Thank you so much Tom, for sharing your time and experience! It is greatly appreciated. You take the time to not only explain the how, but also the why... in a common sense manor. Looking forward to the rest of the series!

[@3sporttri]

Excellent videos. I'm a total green horn regarding metal working, and these videos do a great job explaining from start->finish. Thank you!

[@TomsTechniques]

Thanks. Glad you enjoyed them. Tom

[@kenzpenz]

Wow, had I not witnessed this tool grinding myself, I never would have believed it. Holding that tool steel to the grinder takes a bunch of experience. I have sent a few pieces of metal, like small bolts flying over my shoulder and causing the dog to seek shelter. You sir are indeed a pro. I'm hooked on your videos, so keep em coming. Oh yes, the four minute attention span applies to me, but I did hang in there and learned a lot. Great sense of humor, reminds me of my Army days. Thanks Ken

[@RaysGarage]

Excellent lesson Tom, thank you very much! Everytime I view your video's I realize how much I don't know about machining, keep them coming, and thanks for sharing! Ray C.

[@brcisna]

Thank you for the multi-part instructions on cutting threads on a lathe . Have had a west bend lathe in shop for many years as a hobby usage piece. Now I want to actually use it for cutting threads. Need to cut threads on a custom made bottle capper shaft for the capper bell piece i'm engineering. Very nice detailed info down to getting a good understanding of calculating the actual thread setup,along with manually grinding a native tool bit.. Thanks, Tom.

[@Okie-Tom]

Very good demonstration on grinding the tool bit. Thanks, Tom

[@ch1psandegg]

Today my mini-lathe thread cutting in steel went from pretty crummy to pretty good, thanks to ditching my carbide tool and grinding my own from high speed steel. Loving Toms Techniques :-)

[@TomsTechniques]

That's good to hear. Carbide of any kind is definitely not for beginners. Tom

[@samspade2612]

Yes, like you said there are plenty of videos covering this discipline but as you also said yours will be a bit different. I watched yours starting at 1 and I must say they're absolutely stellar!

[@TomsTechniques]

Thanks Sam!

[@dirtyharry793]

Thanks Tom, a GREAT primer!

[@arkansas1313]

Tom, very nice tool forming! Thanks for the lesson....13

[@LeifMaginnis]

Very thorough, good explanations.. great stuff. I've been using carbide inserts and never realized the economy and utility of HSS tooling, thanks!

[@TomsTechniques]

+junglemap Inserts definitely have their place, but for the hobby machinist, HHS is usually the better option. Thanks for watching. Tom

[@davidclay1362]

Its your kind of video that makes youtube useful

[@TomsTechniques]

Alright, I'm useful! Thanks David.

[@brcisna]

Tom, Mentioning. Was lucky enough to find a couple of good PDF files for my particular lathe that another owner of the same lathe I have, had posted for download. Trying to get my head around how to calculate which gears i need meshing to get the desired 5/8"-18 threads /inch (fine) on my lathe. The PDF provides an updated threading chart that corrects mistakes in the 'factory thread chart" that is embedded inside the end cover. The lathe is actually built by Atlas Press with the "Craftsman" badge on it. 12x36". Needless to say it is pretty limited but has served me well for my simple needs. Even the wording in these old printed 19xx? manuals sound like british speak to a degree. Thanks.

[@aintgonnahappen]

You make a highly skilled task seem attainable. Thank you!

[@TomsTechniques]

aintgonnahappen It absolutely is attainable. All it takes is some basic information and lots of practice. I provided the info and the rest is up to you. Thanks for watching. Tom

[@tezfair9629]

Superb information. As a new comer to engineering I have watched a lot of videos, but I can't recall any talking about the helix. Thanks for taking the time to do these videos.

[@TomsTechniques]

Thanks. It's not always necessary to consider the helix angle, but it is good to be aware of its existence.

[@snteevveetns]

Your experience shows! Great videos.

[@TomsTechniques]

Thank you.

[@lodhiautos9761]

Thank you Tom for your gift of this technical video.

[@TomsTechniques]

You are very welcome

[@lodhiautos9761]

Tom its my pleasure to have a reply from yuor good self.

[@TomsTechniques]

Thanks Rob, that's good to hear. My goal is to make this stuff easy to understand AND remember. I'm not sure how the commercial thing works, but watching it has to help! Tom

[@SuperTruck35]

You teach very good, the best video i have seen on cutting threads. i would like to learn more from you

[@TomsTechniques]

+SuperTruck35 Thanks. Keep watching, there is much more to come. Tom

[@TomsTechniques]

Thanks, I'm glad you are enjoying it. Tom

[@TomsTechniques]

Thanks, glad you enjoyed it. Tom

[@kingjamez80]

Great video, thank you Tom! I'm going to go grind a HSS threading tool right now for my Mini-Lathe.

[@TomsTechniques]

That's the spirit! There is nothing like getting your hands dirty when learning a new skill. Tom

[@TomsTechniques]

Thanks, I'm glad you like them. It was a rocky start on these three, but I think they are now as I intended and I'm ready to move on to part four and make some chips. I'm out of town this weekend but will be back at it next week. Tom

[@chrisstephens6673]

I am pleased you raised the issue of a flat on the tip of the tool to strengthen it, but the real need for it is to allow the machinist to use depth of thread charts, for they are all based on having such a flat (or radius for Whitworth threads but that is a whole new ball game)

[@jamesmorikawa453]

Great video. Thanks!

[@chrisstephens6673]

I totally agree, theory and practice don't always agree but they should be pretty close. In this case disagreement could result from the difficulties in grinding a tool to "micron" accuracy in a small shop environment. I, for instance, will often go to theoretical depth using a tool with a small flat, then widen the thread by use of the top slide (set in-line with lathe axis) till the nut fits if I have it, or use thread mic or wire-wrap if I only have an original to copy or a book to follow.

[@olivierTUBO]

Great video, thank you!

[@liyawei]

Thank you for the threading tutorial Regards

[@TomsTechniques]

Thanks Ray!

[@MrShobar]

Nice job. That tool will work well.

[@TomsTechniques]

Yes, the tool will work for internal or external threads. The difference is that you'll likely need to grind a smaller tool for internal threads so it will fit in a boring bar and inside the bore of the thread. I normally use 3/8" bits for external threads and 3/16" bits for internal. Tom

[@TomsTechniques]

Just remember that those depth of thread charts are theoretical. The only way to determine the proper size of a thread is to measure the pitch diameter. I get the impression that many new machinist tend skip that step, relying on the charts to determine the size of the thread. Thread wires or a thread micrometer are a necessary tool to have when cutting screw threads. Tom

[@jayphilipwilliams]

As far as quenching, do you just use water? And dip it whenever it gets too hot? Something that was unclear to me was the angles. The leading side was undercut. I understand that--you cut more metal away on the bottom than the top. But on the trailing edge, is it the opposite? Is the bottom sticking out farther than the top? The opposite of the leading edge? So it's really an "overcut" (if that's a word)? I just discovered your channel and am really enjoying it. Thanks!

[@TomsTechniques]

Yes, just water to keep the tool cool enough to handle. The tool can handle 1000ºF, but your fingers can't. With very coarse threads (high helix angle), the trailing edge can have a negative clearance angle, but normally it just has less clearance than the leading edge. Glad you are enjoying the videos. Tom

[@jayphilipwilliams]

Great. Thanks for the clarification.

[@Canon060009]

Thank you Mr Tom. It’s a great video how to use protractor to set the angle 150 degree to make the right 60 one on the hss bar. Previously I have to use the pen to mark the 60 degree on the hss bar, and it’s so difficult to know It’s right or wrong properly. Thank you so much.

[@TomsTechniques]

Just estimate the first angle, measure it, and correct it. There is no need to try to mark anything.

[@Canon060009]

Toms Techniques The main issue is use the protractor to measure correct angle.

[@stuarth43]

may I offer a suggestion, hold the tool in the vice then with the FLAT of the disc on a 4 or 5 inch angle grinder rough the tool out, this is fast accurate, your vid was very helpful to me, btway you will not burn your fingers this a ways Remember 55 degrees for unc whitworth

[@KeyWestBluesX]

i definitely admit that blew my doors off--it made me feel like i never knew anything about grinding a thread tool

[@TomsTechniques]

Theory alone is pretty darned boring, but when applied in a demonstration it's almost tolerable. :) Thanks for watching! Tom

[@shehzadali3886]

What a amazing toms

[@TomsTechniques]

Fixtures are necessary for sharpening end mills, but for tool bits and even drills, grinding them free hand is much faster and can be just as good. I once had a contest with another machinist who claimed he could sharpen a drill better and faster using a drill sharpening machine than I could by hand. I guess I won because mine drilled just as good a hole except I sharpened it faster. :) Check out my drill grinding video to see how it's done. Tom

[@bajrangishidhartmech.7743]

Superb

[@riphaven]

And that's why you wear a full face and eye wear together.

[@adamjones4052]

Nope. That's why you get the apprentice to grind the tools ;)

[@harpalwalia]

Nice 👍

[@erniehenshaw4065]

You just said it Thanks.

[@paulgreenlee190]

I learned a lot watching your series on cutting threads and making a nut to match. The Helix angle degree and width was an eye opener. What about cutting ACME threads, I looked in the Machinist Hand Book and the illustrations show an angle such as the Helix angle. I don't know much about square threads but shouldn't all threads have a pitch and helix angle? I'm a hobbyist, retired, and learning. Thanks Tom.

[@TomsTechniques]

The pitch for any given thread is one over the number of threads per inch, regardless of the thread type. The helix angle is determined by the pitch. A higher pitch (fewer threads per inch) equates to a larger helix angle. Acme threads are fun to cut if your lathe has good rigidity. Square threads are pretty much obsolete because an Acme is much easier to cut and nearly as strong.

[@IH1940HAY]

Would it be possible to use the same tool to cut both the external and external threads, that seems like it would make for a perfect fitt. Other grinding two "form" tools need to be a perfect match.

[@Raven1oh1]

Very well described instructions!! I noticed at the * minute mark when you moved to the fine wheel, the top of the cutting tool had been ground. What angle & why. Thank you in advance.

[@TomsTechniques]

+Larry .Rangen Thanks Larry. I always touch up the top of the tool bit just to clean it up. Don't know that it improves the cutter in any way, but it does make me feel better. :) Tom

[@JosephDAndrea0121]

Could you put layout dye on the tool than using the thread gauge and a scriber scribe two 60 degree lines to use as a guide?

[@TomsTechniques]

Joseph, You could, but it would probably burn off with the heat from the grinder. After you grind a few bits, you'll find that it's pretty easy to just grind and check until you get it right. Tom

[@robertsawyer1464]

How do you get close to a shoulder grinding tool to the center of HSS blank?

[@TomsTechniques]

I guess the answer would be, you don't. But if you offset it to the left, how would you get close to a shoulder on the right?

[@aldimmett]

Tom, I'm confused about the helix angle. You showed, 3 ways, that the Helix angle was 2.5 degrees, but said that when cutting steel it should be about 5 degrees. 2.5 added to the lead side and 2.5 removed from the trailing side. Am I misunderstanding you?

[@TomsTechniques]

You are confusing the helix angle with the clearance angle. The leading side of the tool will need to angle 2.5º for the helix of the thread, plus another 5º for clearance under the cutting edge, for 7.5º total. The trailing side needs to angle 2.5º the other way to follow the helix angle. Let's call it -2.5º. Add 5º to that for clearance and you end up with a 2.5º angle on the trailing side. Remember, the trailing side will be angled less because of the helix angle of the thread. All of these angles are measured from vertical if that helps to clarify what's going on. Tom

[@aldimmett]

Thank you so much for answering my question. I'm a real newbie and appreciate your response.

[@RollingEasy]

Tom.... I'm beginning to wonder whether or not the compound should be set at 90 deg minus the Helix angle?? Common practice says to move the single point at 60 or 60.5 but I'm now questioning that. I've done a lot of threading as per standard but gut feeling is saying to examine that compound angle and maybe who knows? I understand the argument about the tool cutting on the leading edge but if the tool is set correctly to the axis, ANY compound angle.... ANY angle, is going to to cut a thread. Only Depth will be reached after probably too much metal is removed sideways to get there. However, what's happening with each turn on the compound is that the Lead Screw to Spindle Ratio is now messed around minutely. This does not happen on the so called 90 deg plunge threading. The lead (and Ratio), remains exactly the same with every pass.... Even if there are 100 of them. The other thing is that if you view a thread from above with the 60 deg tool in position, it looks for all money that it should move forward directly on the Helix line..... ?

[@TomsTechniques]

Plunging straight on puts excessive load on the cutter. It would be fine on light metals, but tool steels would break off the point of the tool. I rough cut the thread with the compound ar 60°, then plunge straight on for a light finish cut.

[@RollingEasy]

@@TomsTechniques I'll agree with you on the plunge for the finishing cut. Until I can prove it to myself otherwise, I'll stick to now believing that while compound cutting is good to get 95% of the thread, its the final plunge which happens to deliver the thread geometry as it should be at the end of the job. My CADD is not good enough for me to model a thread being cut but its something I'd love to see and done with some very powerful software. I just have a hunch it would shed a new light on threading set ups. Just a hunch.

[@domenicaloisio5136]

It looks like you put a relief angle on top of the tool.

[@TomsTechniques]

No, the top is flat. I may have touched the top surface to clean it up, but it's still flat.

[@erniehenshaw4065]

What grit is that wheel Tom.

[@TomsTechniques]

I normally use 100 grit for smaller tools/bits and 80 for larger ones.

[@dochollowood5763]

I don't think this guy has any idea how much skill he has with that very well balanced grinder - and it appears he has the stem dna asbestos fingerskin upgrade from the local doctor lab... ;-)

[@mickeybetty]

I'm interested in square threading some i' hardwood dowel.

[@TomsTechniques]

It'll take a very sharp tool with lots of clearance, but it can be done.

[@mickeybetty]

I assumed Square threads were required for wood - it looks like a false assumption! Building a simple wall loom with wooden screw tensioners. I'll check out some in-between thread options - much thanks for your input.

[@TomsTechniques]

Acme threads will work as well and are a LOT easier to cut. Tom

[@mickeybetty]

I hear you loud and clear - can't wait to get started! thanks again and best wishes...

[@takuya7523]

If the tool rest was for resting hands then it would suppose to be bigger, wouldn't it?

[@TomsTechniques]

But what if you happen to have really small hands? Then what? Use the rest however you like. I'm just demonstrating the way I use it that doesn't require the rest to be readjusted for each of the various angles on a tool.

[@billybonewhacker]

Wait till you get your caught finger in that wheel ,. You'll change that tool rest theory

[@TomsTechniques]

Fifty years of practice says that as long as the rest and guards are properly adjusted, tool bits and fingers will not get "caught" on the wheel. Friction burns cans still occur, but doing that once or twice will teach you not to do it again.

[@SuperShannon4444]

This is old school new school is better they make carbide inserts with these you can obtain greater accuracy the tool is only as good as can be measured and not likely to be used for cutting class threads that require tolerances in the millionths this is also known as blacksmithing

[@MrShobar]

You aren't cutting "in the millionths" with the equipment shown. Or even measuring to this degree with the equipment he has. I've hand-ground HSS for regular and acme single-point threading and have had no problems, provided you pay attention to detail. I often use inserts, but the life is limited.

[@SuperShannon4444]

MrShobar no offense ment to his method I learned this 25 years ago and have hand ground countless numbers of HSS tools for all applications just saying that there is a new school of tools and that this is blacksmithing I've done it

[@TomsTechniques]

Shannon Dustin These videos are intended for hobby machinists who are operating with a limited budget and limited machinery. Carbide tooling is very useful in a high production commercial application, but is neither productive nor cost effective on light hobby type machinery. High speed steel is much less costly, much more forgiving and easier to work with than carbide. And BTW, I can hand grind a HSS threading tool that will cut a thread every bit as accurate as a purchased carbide insert. Tom

[@SuperShannon4444]

If your cutting mat. that is free machining but not going to hold up against stainless

[@TomsTechniques]

Shannon Dustin Sorry Shannon but that is simply not true.Stainless steel was introduced at the turn of the century and cemented carbide didn't become available until the late 20's. That means that ordinary carbon steel tooling was used to machine it in the interim. Carbide tooling definitely lasts longer than HSS, but it isn't the only tooling that will machine stainless steel. Tom

[@muhammadshezan3949]

Hello