Thread Chasing, density and other considerations

[Emiliano Achaval]

I have been told that I work too much with Koa... Perhaps they are right, but, if you had the chance of always working with gold, wouldn't you? LOL
I guess thats why I'm not an expert about other woods. As you know, I just started Hand Thread chasing.
My instinct was right with the first wood I had a hunch was going to work: Lychee. Perfect little ribbons come out when you chase threads...
Then, yesterday, I tried Ohia. Ohia is a very hard wood, very heavy. My question is: can a wood be hard and heavy but not dense enough for chasing threads? I assume hard woods are dense, but I just learned today and yesterday, hard and heavy doesn't equal dense, or dense enough. You also hear about "Tight grain" Is that another name for dense?
Today I tried with Koa'ia. A cousin of the Koa. Much better than Ohia, but not as good as Lychee...
On the other discussion, someone mentioned I should try Milo. Milo is considered a hard wood, but compared to Koa, or Koa'ia, is soft. I can leave Milo glassy, makes me look really good! I'm guessing its dense, but not too hard or heavy...
I f you never tried Thread chasing, do not try it. It is highly addicting, your life will be on hold for a while, making the wife upset. Aloha from Maui

 

[Bill Boehme]

Heavy and dense are two sides of the same coin ... and I suppose that hard could be the third side. However, none of those are a guarantee that the wood won't crumble. I think that with any wood you have to be careful about how the tool follows the thread. and the least bit of inattention to that can mean ripped up threads.

 

[Emiliano Achaval]

Heavy and dense are two sides of the same coin ... and I suppose that hard could be the third side. However, none of those are a guarantee that the wood won't crumble. I think that with any wood you have to be careful about how the tool follows the thread. and the least bit of inattention to that can mean ripped up threads.

So... a wood can be heavy, but not dense? And can a wood be dense, yet soft like maybe Milo?

 

[Doug Rasmussen]

Emiliano, you currently have two threads here on this forum regarding chasing of wood threads. You make reference to videos and conversations from another forum. It may not have occurred to you, but not all of us access that forum.

Can you show us some examples of your threaded pieces, both successes and failures, plus maybe your tools and techniques?

I'm very familiar with tools used to hand chase metal threads back in times before screw cutting lathes. Several years ago in my business we came up with a method to salvage by hand chasing obsolete precision internal threaded parts when our customer slightly enlarged the thread diameter. In that case we used a tap of the correct pitch as the cutting tool set such that it had a negative rake. I have some ideas how by using cutters from production threading equipment wood threads might be done easily, but would like to see how you do wood threads too.

 

[Bill Boehme]

So... a wood can be heavy, but not dense? And can a wood be dense, yet soft like maybe Milo?

No, I should have said that heavy and dense are inseparable. But, I don't know that you can say for certain that means that the wood is also hard. Lead is heavy and dense, but it's not hard. Tungsten is heavy and dense. It is also extremely hard.

Emiliano, you currently have two threads here on this forum regarding chasing of wood threads. You make reference to videos and conversations from another forum. It may not have occurred to you, but not all of us access that forum.......

The other forum, World of Woodturners (www.thewows.com), used to be by invitation only, but recently changed to allow anyone to join or to view as a guest although I think that guests still need to register.

 

[hockenbery]

The better woods for threading usually have hard to see growth rings and some interlocking grain. Holly and dogwood usually thread quite well. Ash and red oak not so well.

Poor Threading is sort of like screws not holding in endgrain. Screw threads and threading cut the wood fibers the fibers to leave ridges. In striaigt grained wood the ridges made by screws or threading tend to fall off. Screws pull out and threads get a chipped look.

Many tropical rainforest woods thread well because they grow 24/7 365 and often have no distinguishable ring pattern.

 

[Gerald Lawrence]

I have only threaded wood with a tap or a die and I have had better luck as Al said with interlocking grain such as white oak. Heavy and dense does not matter if the grain will not support the thread and interlocking grain will do the support

 

[robo hippy]

Most of my threading is with a threading cutter, the Bonnie Klein one specifically. It is cheating because the cutter works in just about any wood. Probably as much or more important than density is the grain itself. Closed tight grain works better than open grain/long fiber. Probably worst example would be some thing like palm. Better for hand chasing, are lignum, box wood, holly, hard maple, some bubinga. You can cheat a little with waxing or lubricating the threads as you cut, and I just read about some one using a NRS (negative rake scraper) thread chaser. Maybe hickory would be bad, to open grain, and it likes to tear and splinter just from looking at it.

robo hippy

 

[Emiliano Achaval]

I will post a picture of my latest box. Today I tried Milo. Consider hard wood, threads ok but they don't hold, even with a finger nail they break. I refuse to use CA. So far lychee is the champion.
A friend gave me some Surinam Cherry. Will try it tomorrow. I will take a picture of my tools tomorrow. Going to do a YouTube live also... Got my chasing tool rest today and a point tool. I have to finish 14 Koa bowls for an order, but this threading has me obsessed haha.

 

[john lucas]

Woods can be dense or what I would call heavy but still be soft. I don't know what the wood was I turned for a Hand mirror the other night but it was quite heavy. It cut like butter and sanded even easier. It would be a very lousy wood for hand chasing because it chipped easily with scraping but cut very cleanly with bevel rubbing tools. Cocobolo is similar to this strange wood in that it is quite heavy, cuts and sands easily but for what ever reason is quite easy to chase threads.
A couple of tricks that might help. Play with the feed rate of the cutter. To fast or what I call pushing the cutter tears up the threads and dragging the cutter or letting the wood pull the cutter is just about as bad. There is a sweet spot in the middle of push and pull where it just feels right. I'm still learning that touch but it makes a difference. Also if you will cut a recess at the bottom of the male thread where the chaser has chance to come out of the cut you will get a little cleaner last thread and you won't have a problem with the female thread binding up on that last thread.

 

[Doug Rasmussen]

Definitions... thread chasing: making threads with a multi tooth, non rotating cutter, limited to finer thread pitches. Thread milling: making threads with a high speed, rotating tool, both ultra fine and very coarse thread pitches.

The issue is not that you can't do acceptably strong threads in softer woods, the issue is how you cut the threads. For strength you need a coarse pitch. Coarse pitch by chasing, probably not, but you can do them by thread milling as robo hippy mentions in his posting by using the Bonnie Klein threading jig. (BTW, we made Bonnie's threading jigs for years in my shop).

As I see it, a container of say over two inches benefits from a very coarse thread. Something on the order of a bottle thread where it only takes a turn or two to completely tighten/remove the lid. Checking a plastic food container from our refrigerator, 3.5" diameter container takes one and a half turns with a thread pitch or roughly 5.5 threads per inch. Nice feel to it, the lid can be removed in a single gripping. But a pitch like that is way too coarse to chase in most any woods, easily thread milled though.

Do any threading jigs on the market handle very coarse thread pitches? By its design the Klein jig can't do very coarse threads.

 

[john lucas]

The Baxter threader can go down to 8tpi with the right adaptor. I have hand chasers down to 11 tpi. I think with a lathe that goes slow enough you could probably chase 8 tpi threads. I will look at my antique chasers and see if I have anything courser. On some of them I only have either the inside our outside chaser and not both.

 

[Emiliano Achaval]

I considered spending the money and buying a mechanical, or whatever it is called, thread mill? But, I'm old fashioned, I prefer to do it the old way. Practice is paying off!!! Today I got my tool rest and point tool.... The arm rest is great!! Point tool..... Had some nasty catches, felt like a beginner... Not sure yet how to use it.... Today I went back to Lychee. But I experimented with Surinam Cherry, works great!!!

 

[john lucas]

To use the 3 point tool you plunge it in and then drag it back out scraping the surface to shape what you want. It was designed to do beads so you plunge it in to the depth you want and the pull it out shaping one side of the bead up toward the top. For clearance for the male thread chasing tool I mostly use a sharp pointed spindle gouge. The 3 point tool should work well if you push it in and move the tip to shape the area at the bottom of the thread.

 

[Pete Blair]

Emiliano, Stewart Beaty demos it's use in his video, he warns about catches and how to best overcome the possibility. Course, most of us can't turn as well as he. I like to use a thin parting tool to make the relief at the end of the male threads. I made my first thread chaser from a large tap I got for .50 cents at a garage sale. I ground off two of the four cutters and use it for both inside and outside threads . . .

 

[Doug Rasmussen]

I'd like to hear opinions of screw on box lids. My question is, given a choice do you prefer a lid that goes completely on with two or less turns or one that takes maybe 5 or more turns?

It's interesting to check the lids on various household consumer items, foods and cosmetics containers for instance. The cap on a tube of toothpaste requires more turns than I would have guessed, but those turns are more of a rolling action of the cap between your fingers with no wrist action. A jar of pickles needs less than two turns, more than a wrist can do with a single grip, divide the rotation between both wrists, turn jar and lid at the same time and it happens.

 

[john lucas]

I prefer few threads but it's just hard to do in wood. Sometimes it feels like forever to get a lid of my boxes and yet there are actually very few threads. It's just that 16tpi takes a few turns. For hand chased threads the courser threads make it hard to get out of the cut before hitting the shoulder on male threads. 16 isn't bad. 11tpi and you gotta have quick hands if you want that type of thread. What I did on some boxes was to thread about 2" on a good wood. Then cut off what I needed for a box and put a tenon on it. Glued this into the box. This gives me course threads that only have about 3 threads so they don't stick up far. It would be impossible for me with my skills to do that as one part.
It's kind of like asking whether you want a snug fit or loose fit on a box. I have found when selling boxes that small boxes can have a friction fit. Larger boxes need to be loose enough to remove the lid with one hand.

 

[hockenbery]

What John said.
Threads are usefulwhere you don't want the lid to come off when you move the box or put it in a container. Needle cases for example.

The problem with 16 tip is they take a lot of turners . One or two revolutions is the most you should have.

 

[Bill Boehme]

While ergonomics is very important, I believe we have the luxury of thinking outside of the threaded box (sorry I couldn't help myself) and not be constrained by the design of more utilitarian things such as a pickle jar in the fridge. We recycle glass and plastic containers, but hopefully a threaded wooden container has value independent of its contents. There are more relevant considerations such as the durability of the threads from breaking in actual use and situations that might lead to threads jamming.

If the box has fewer threads, they can be more easily sheared off from over tightening the lid than one with many turns where the shearing load is distributed across more threads. On the other hand, more turns increases the probability of inaccuracies in hand chasing resulting in mismatched threads that could cause tight fitting or binding if the lid is over tightened. The final choice then by necessity is a compromise between these two opposing considerations. The answer might initially be based more on one's skill, but eventually the answer is probably what looks and feels right to you, the maker. The appreciation of a well made threaded wooden container can include the tactile feel of opening it.

 

[Mike Johnson]

I was considering the Sorby thread chasers but after reviewing the threading jigs
and the ability to thread softer woods successfully I think I will go with a threading
jig which should provide a greater range of woods to be used for this application.

 

[Bill Boehme]

I was considering the Sorby thread chasers but after reviewing the threading jigs
and the ability to thread softer woods successfully I think I will go with a threading
jig which should provide a greater range of woods to be used for this application.

I watched John Lucas demonstrate the Baxter threading jig at SWAT a couple years ago and was very tempted to buy it. However, I don't think that I could rationalize the price versus how much I would use it. But, price aside, it is a top notch tool.

 

[john lucas]

Mike My decision to by a threading jig was simply because it gives you the option of so many great woods that are simply too soft to chase. I love learning to hand chase. It was a challenge that was well worth the time but I do 99% of my threading with my Baxter threader. what I did was to make lots and lots of boxes and sell them until I paid for the machine. The Baxter is probably the most expensive on the market but it's like buying a Porche instead of a Ford Fiesta. they both get you there but the Baxter threader is a pleasure to use. I originally had it built to fit my mine lathe. When I sold that lathe I was going to have to pay to have it modified to fit my bigger lathe. Since I travel and do demos the threader couldn't go with me so I built a lathe bed out of angle iron and used a router as my headstock to hold the cutter. I had to build a 1/2" to 3/8" adaptor to hold the cutter. Now I have a traveling threader. It's also very handy since I set it up on my workbench and it's very quick to go from making the box to threading the box since everything is already set up.
I also have one of the threaders from Chefwarekits.com It goes into the lathe banjo. It works pretty well but just isn't in the same class as the Baxter from bestwoodtools.com

 

[Mike Johnson]

I see that there are several different threading jigs available on the market, I have watched
demo's on several of the tools available. Does anyone have any pros or cons between the
threading jig tools that are out there? I can justify the cost of a threading jig for some items
I will be making this year.

 

[Doug Rasmussen]

Watching as many threading jig videos as I could find, one thing about all of them, they're not cutting the internal threads the best way. It's best to start the cut inside the lid rotating the jig's spindle so the cut progresses to the outside. This gives what's known as a "climb" cut which is smoother without so much potential for tearout. You should have a groove or a relief at the bottom of the threads to do it this way, same as recommended for internal thread chasing.

A climb cut is like using a hand held router and feeding in the wrong direction. That can be a little dangerous because the router wants to grab and pull into the work so you have a loss of control. But, in thread cutting you're removing so little material per pass you're able to keep the cutting action under control.

For external threads, those are climb cut when starting on the end and working onto the workpiece.

Climb cutting is basic to CNC routing which is why they can cut against the grain with so little tearout.

Several of the demonstrators coated the area with CA glue before cutting the internal threads. I didn't pay enough attention to note if they also coated the external thread areas with CA. Since the external threads are climb cut anyway there wouldn't be such an issue with tearout though.

 

[john lucas]

Typically if the wood is brittle or soft I use CA on both internal and external threads. Sometimes I will use wax if it just needs a little help. Mark StLeger uses Dawn dishwashing liquid and claims it makes the cutting easier. I didn't have much success with the Dawn but then Mark has done a lot more threads that I have.
Doug I've been trying to work out in my mind how to cut down the thread while hand chasing. Typically in machine cut threads you are cutting downhill on the backside of the thread. When hand chasing is seems like you are scraping both the backside of the thread as well as into the frontside of the next thread at the same time. The downhill cut of scraping the backside of the thread would seem to be cleaner and produce less chip out. I don't know how you can reduce the chipout on the frontside of the next thread since your just sort of pushing into the wood. Any thoughts on that.