Thread Chasing question

[Emiliano Achaval]

I'm watching John Berkeley number 1 dvd on thread chasing. It's finally available! It was out of production for quite a few years. A company in Texas is selling them again. On the video, John uses a "16 TPI Whitworth" hand tap to make a thread on a little hole on a box lid. He then uses a 24 TPI male chaser to create a little-threaded rod. The little-threaded rod is to hold a small flower for the top of the lid, with, of course, threads.
Question is: If a 16 Whitworth TPI tap goes with a 24 tpi chaser, what tap goes with a 16 tpi chaser? Also, I have a 20 tpi chaser, amongst others, but I want to use my 20 tpi to hold the flower. What tap do I buy for the 20 tpi? I'm going to try Lowe's, I will take my chaser, and see what matches the teeth. But, if someone knows what to buy, maybe on Amazon, that would be helpful. Bear in mind I have no idea about taps. Furthermore, you have millimeters and inches when you look at taps...
John Berkeley is by far my favorite Brittish woodturner when it comes to chasing threads. I highly recommend his dvd's. He has a series of them, To get started, you need Screwples Number 1. A company in Texas is selling them: Search for Chuck's Plus. I also bought a DVD about tthe Escoulen off-center chuck made by Vicmarc. I bought it last year, and only used it a few times, maybe I can get a better understanding of what I can do with it... Happy New Year! Aloha from Maui.

 

[Doug Rasmussen]

Are your chasers Whitworth thread profile or American standard? For close fitting threads the two thread styles don't match exactly. For threads to match both the tap and the chaser need to have the same pitch (tpi ot threads per inch). So, a 24 tpi chaser does not ever match with a 16 tpi tap.

When you tap a hole you get a tpi and a diameter of thread (major diameter). When you use thread chasers you get a tpi, but the major diameter is only determined by the user (there are diameter standards for Whitworth and American style threads if you choose to use them).

The only 20 tpi taps you'll find at Lowes will be a 1/4-20 or a 1/2-20..

Could you tap a 16 tpi Whitworth hole and put a 24 tpi threaded part into it, yes, but the threads won't match. According to the BSW (British Standard Whitworth) a 16 tpi Whitworth hole will have a minor diameter of .295". A properly sized (per the Whitworth standard) 24 tpi thread will have a major diameter of .1875", it'll drop into the hole loosely. But, that makes no sense since the threads won't contact. I suppose he could be chasing a 24 tpi thread with a major diameter of .295" for a close fit and the only function of the threads is to provide a rough surface for better glue holding..

 

[Emiliano Achaval]

Are your chasers Whitworth thread profile or American standard? For close fitting threads the two thread styles don't match exactly. For threads to match both the tap and the chaser need to have the same pitch (tpi ot threads per inch). So, a 24 tpi chaser does not ever match with a 16 tpi tap.

When you tap a hole you get a tpi and a diameter of thread (major diameter). When you use thread chasers you get a tpi, but the major diameter is only determined by the user (there are diameter standards for Whitworth and American style threads if you choose to use them).

The only 20 tpi taps you'll find at Lowes will be a 1/4-20 or a 1/2-20..

Could you tap a 16 tpi Whitworth hole and put a 24 tpi threaded part into it, yes, but the threads won't match. According to the BSW (British Standard Whitworth) a 16 tpi Whitworth hole will have a minor diameter of .295". A properly sized (per the Whitworth standard) 24 tpi thread will have a major diameter of .1875", it'll drop into the hole loosely. But, that makes no sense since the threads won't contact. I suppose he could be chasing a 24 tpi thread with a major diameter of .295" for a close fit and the only function of the threads is to provide a rough surface for better glue holding..

Doug, thank you for helping me with this. What I'm trying to do is, I have a pair of English 20 TPI Whitworth chasers. I need the corresponding tap. You told me they sell 1/4-20 or a 1/2-20.. at Lowes, so, I'm guessing they should work with my 20 tpi chasers? You are years ahead of me when it comes to this.... All I know is how to grab a chaser and make threads, LOL Was my posting clear enough? You understand what I'm trying to do, right?
"So, a 24 tpi chaser does not ever match with a 16 tpi tap." I rewinded the video a few times, so I could write down what he said. The little hole with threads are just perfect, now I'm really confused. If you say they will never match?? Hmmm I usually watch the videos over and over, I will have to pay more attention next time. And, I have both, English Whitworth and American Standards. I have found some really old chasers in good condition for excellent prices out of Ebay England. Thanks again for the help!!!

 

[john lucas]

Quite interesting. I was not aware of whitworth threads. Will have to look that up. Basically for what I use here in the US the TPI must match. So if you have a 16 tpi tap.it would need a 16 tpi chaser. Of course metric taps are different and I dont know if they make chasers to match unless that's what the Whitworth chasers are. I will try to do some research later.
Hey i got the box of wood yesterday. Thanks a bunch. Cant wait to play with it.

 

[Doug Rasmussen]

For Emiliano the solution is decide on either a 1/4-20 or 1/2-20 tap from Lowes. Use the 20 tpi Whitworth chasers to make as close as possible matching part. Keeping in mind the American taps from Lowes have a slightly different thread form than his chasers, but the tpi still match.

Chase the male threads until they screw into the tapped hole. That's about it.

In industry if you were making critical parts you would never mix an American thread form with a Whitworth form, acceptable for the application here though.

 

[John Torchick]

That's a new one on me. I always heard of a tap for cutting thread in metal and a die to cut or chase threads on metal. I'll ask my son if he has ever heard of this.

 

[john lucas]

Just for interest I went to the shop and looked at my metric and american taps. a #9x1.25 metric has almost the same thread pitch as 1/4 x20. Not the same diameter. The pitch is off very slightly over 10 threads. I was reading about the Whitworth threads and they are 55 degree standard where american are 60 degree. Doubt that would make any difference in wood.

 

[Emiliano Achaval]

Just for interest I went to the shop and looked at my metric and american taps. a #9x1.25 metric has almost the same thread pitch as 1/4 x20. Not the same diameter. The pitch is off very slightly over 10 threads. I was reading about the Whitworth threads and they are 55 degree standard where american are 60 degree. Doubt that would make any difference in wood.

Thank you John. Some of the whitworth tap are very expensive. At Lowe’s are cheaper.

 

[Emiliano Achaval]

For Emiliano the solution is decide on either a 1/4-20 or 1/2-20 tap from Lowes. Use the 20 tpi Whitworth chasers to make as close as possible matching part. Keeping in mind the American taps from Lowes have a slightly different thread form than his chasers, but the tpi still match.

Chase the male threads until they screw into the tapped hole. That's about it.

In industry if you were making critical parts you would never mix an American thread form with a Whitworth form, acceptable for the application here though.

Thank you again Doug! Happy new year!

 

[Bill Boehme]

For something that small in diameter I would think that the typical woodturning thread chasers might have a pitch that is too shallow to cut threads successfully. It might work better to cut a die apart and use one set of teeth welded to a handle. Other than the novelty of something different, it's a lot of work compared to just making friction fit parts.

 

[Emiliano Achaval]

For something that small in diameter I would think that the typical woodturning thread chasers might have a pitch that is too shallow to cut threads successfully. It might work better to cut a die apart and use one set of teeth welded to a handle. Other than the novelty of something different, it's a lot of work compared to just making friction fit parts.

John Berkeley shows his taps in a wooden handle. Anybody can make an insert an apply CA. Adding an African Blackwood flower with threads to a threaded insert to the lid of a box with hand chased threads, well, that's classy. I have to at least try to make one... Bill Jones chess pieces had an average of 8 threaded parts...

 

[john lucas]

I made several chasers with different techniques. One was to simply braze part of a tap onto a piece of metal. One was brazed horizontally and one vertically so I had an inside and outside chaser of that thread. Actually I may have silver soldered them on, I don't remember for sure.

 

[Bill Boehme]

I made several chasers with different techniques. One was to simply braze part of a tap onto a piece of metal. One was brazed horizontally and one vertically so I had an inside and outside chaser of that thread. Actually I may have silver soldered them on, I don't remember for sure.

I'm having trouble visualizing what you mean by horizontally and vertically. Do you have a picture?

 

[Mike Amphlett]

Bill
I think this is what John means.

Mike

 

[Bill Boehme]

Thanks, Mike.

 

[john lucas]

Yes. Couldn't think of a better description at the time. I should have said inside and outside chaser but then people who dont know anything about thread chasing still wouldn't know. Kind of like when computer geeks say portrait and landscape for horizontal and vertical. As a photographer I shoot portraits and landscapes other vertical.and horizontal so that confuses the hell.out of me.

 

[Don Wattenhofer]

I first started messing around with threading wood back in 1991 using a router to drive a 60 degree double angle milling cutter. It was not until about 2010 that we had a demonstrator show how to hand chase and I think I could have learned the technique but I don't think I should have to use special woods other then what I am making the project with. The comments about mixing thread standards I do not think is a good idea since wood changes dimensions with the seasons and you don't need another variable such that the sizing tolerances between the male & female thread would be greater.
The problems of chasing small diameter female threads could possibly be solved using wood threading taps of the traditional form. The tap is a full thread with the end turned down to fit the tap drill size hole then that end is bored for chip clearance and a hole is drilled on center of the last complete thread with the remains of the thread ground off. This method was used for making hand screw clamps and it will not work on end grain. I have a 1" tap and die set made in West Germany and a homemade 5/8" set where both of the taps are made that way. I copied the taps in 1/2" and 3/8" using drill rod for the material. Now that I told you about the best tap to use in wood no one seams to make one!
Please excuse me for invading your thread.

 

[Bill Boehme]

I first started messing around with threading wood back in 1991 using a router to drive a 60 degree double angle milling cutter. It was not until about 2010 that we had a demonstrator show how to hand chase and I think I could have learned the technique but I don't think I should have to use special woods other then what I am making the project with. The comments about mixing thread standards I do not think is a good idea since wood changes dimensions with the seasons and you don't need another variable such that the sizing tolerances between the male & female thread would be greater.
The problems of chasing small diameter female threads could possibly be solved using wood threading taps of the traditional form. The tap is a full thread with the end turned down to fit the tap drill size hole then that end is bored for chip clearance and a hole is drilled on center of the last complete thread with the remains of the thread ground off. This method was used for making hand screw clamps and it will not work on end grain. I have a 1" tap and die set made in West Germany and a homemade 5/8" set where both of the taps are made that way. I copied the taps in 1/2" and 3/8" using drill rod for the material. Now that I told you about the best tap to use in wood no one seams to make one!
Please excuse me for invading your thread.

Not quite true that nobody cares about hand chasing threads. I have a set of 16 TPI hand thread chasers, but so far I have only done a little practicing, no actual projects ... however, I do have good intentions of actually using them one of these days.

 

[Don Wattenhofer]

Not quite true that nobody cares about hand chasing threads. I have a set of 16 TPI hand thread chasers, but so far I have only done a little practicing, no actual projects ... however, I do have good intentions of actually using them one of these days.

I didn't say that nobody cares about hand chasing I just said that I don't care for it, maybe because I am set up to do threading it in a way that works for me.

 

[john lucas]

It's hard to find good wood in the continental US for hand chasing which is why many don't do it. I sometimes use epoxy to fill in a groove and then have hand chased in that, although I prefer to use my Baxter threader. Some epoxy just chips when hand chasing. Adding some filler to West System epoxy makes it more suitable but I've only done a few experiments with it. One good reason to learn hand chasing is if you want to thread the end of a spindle. Hard to do that on a machine you get too much chatter on anything longer than 5" and then it has to be a large diameter.

 

[Don Wattenhofer]

It's hard to find good wood in the continental US for hand chasing which is why many don't do it. I sometimes use epoxy to fill in a groove and then have hand chased in that, although I prefer to use my Baxter threader. Some epoxy just chips when hand chasing. Adding some filler to West System epoxy makes it more suitable but I've only done a few experiments with it. One good reason to learn hand chasing is if you want to thread the end of a spindle. Hard to do that on a machine you get too much chatter on anything longer than 5" and then it has to be a large diameter.

You could try American Hornbeam which is an extremely hard white wood, but you would need to harvest it yourself. The first time I heard about it was from an old wood worker who used it for hand screws. The trees are small and sometimes twisted so he would split them to follow the grain and after they were dry turn them to size and cut the threads with his home made die box. I have also machine cut threads in AH.
I have never tried to use epoxy for threads mainly because I wouldn't know how to keep it in place till it sets. The softer woods can be coated with CA to produce an excellent thread but you may have to do a partial cut then recoat for the final cut. The photo shows a machine cut thread in walnut and birch end grain that I used CA to improve the quality.

 

[john lucas]

To use epoxy I simply cut grooves to act as a dam. Then cut away one wall.of the groove which leaves the epoxy exposed. I often dye it black so it kind of looks like ebony when cut.

 

[Emiliano Achaval]

John, I forgot who, but we had a demo at our club, he filled a groove with a putty, like epoxy,. Then he chased threads. Putty comes in different colors, so you can match the wood...

 

[Don Wattenhofer]

Two part epoxy putty comes in stick form available at any hardware store labeled for many different purposes but it is my guess that all types would work with wood. I have used it to fill large voids before topping off with crushed stone such as turquoise.

 

[Don Wattenhofer]

In regards to the lift used to load the lathe into the pickup I purchased a bed mounted lift at Harbor Freight that I have been happy with. The one problem I had was I mounted the the lift behind the wheel well to keep it out of the main 4' x 8' cargo area where the bed didn't have any reinforcing under it. The problem was solved with a specially fabricated bracket to clamp it to the side of the box. Will try to remember to take a picture to send.

 

[Doug Rasmussen]

Fiddling around in the shop today with a thread repair file, it occurred to me it might be used to hand chase threads.

The only round piece of wood I had was an hardware store 1" dowel. Probably about the worst type of wood to chase threads in, soft with the look of Philippine mahogany. I used a little sanding sealer attempting to prevent tear outs, but since the shop heat wasn't on it didn't set up quick enough to be totally effective.

This was done in an enclosed machine making it difficult to hold the file with both hands and move to take advantage of the sharp teeth on the file. It's a 9 tpi thread.



Link to a thread repair file on Amazon:

https://www.amazon.com/General-Tool...1546735231&sr=8-5&keywords=thread+repair+file

 

[Bill Boehme]

Fiddling around in the shop today with a thread repair file, it occurred to me it might be used to hand chase threads.

The only round piece of wood I had was an hardware store 1" dowel. Probably about the worst type of wood to chase threads in, soft with the look of Philippine mahogany. I used a little sanding sealer attempting to prevent tear outs, but since the shop heat wasn't on it didn't set up quick enough to be totally effective.

This was done in an enclosed machine making it difficult to hold the file with both hands and move to take advantage of the sharp teeth on the file. It's a 9 tpi thread.

View attachment 27634

Link to a thread repair file on Amazon:

https://www.amazon.com/General-Tool...1546735231&sr=8-5&keywords=thread+repair+file

Learned about a tool that I don't have. Now, I know that I need one. And the price is right.

 

[RichColvin]

Fiddling around in the shop today with a thread repair file, it occurred to me it might be used to hand chase threads.

The only round piece of wood I had was an hardware store 1" dowel. Probably about the worst type of wood to chase threads in, soft with the look of Philippine mahogany. I used a little sanding sealer attempting to prevent tear outs, but since the shop heat wasn't on it didn't set up quick enough to be totally effective.

This was done in an enclosed machine making it difficult to hold the file with both hands and move to take advantage of the sharp teeth on the file. It's a 9 tpi thread.

View attachment 27634

Link to a thread repair file on Amazon:

https://www.amazon.com/General-Tool...1546735231&sr=8-5&keywords=thread+repair+file

Doug,

That file is meant to clean up existing threads. Did you have a hard time instantiating new ones ? By the way, the threads you made for the picture look really good !

Kind regards,
Rich

 

[john lucas]

I have one. Never used it on anything yet. Will have to try it if I ever remember when I'm in the shop.

 

[RichColvin]

I inherited some from my father, & only learned what those files were by watching the old shop teacher, TubalCain, on YouTube. Here’s his one where he shows how to use them to repair threads :

View: https://youtu.be/8ZP9m1z7o9k​

Kind regards,
Rich

 

[Doug Rasmussen]

Doug,

That file is meant to clean up existing threads. Did you have a hard time instantiating new ones ? By the way, the threads you made for the picture look really good !

Kind regards,
Rich

Rich, It wasn't hard to start the threads. I've never chased threads before so I have no comparison to conventional chasing. Maybe there should have been a chamfer on the end of the dowel to make the start a bit easier. Or maybe a short tenon cut to the diameter of the finished thread depth to help starting. This was strictly free hand, no tool rest to help steady the file. I only tried at 500 rpm guessing that might be good. A handle for the file would help too.

As I said conditions were not ideal using this CNC machine, the machine's enclosure made it difficult to maintain a steady two-hand grip on the file.

I'll try again some day on a more open machine with a tool rest.

 

[Emiliano Achaval]

Fiddling around in the shop today with a thread repair file, it occurred to me it might be used to hand chase threads.

The only round piece of wood I had was an hardware store 1" dowel. Probably about the worst type of wood to chase threads in, soft with the look of Philippine mahogany. I used a little sanding sealer attempting to prevent tear outs, but since the shop heat wasn't on it didn't set up quick enough to be totally effective.

This was done in an enclosed machine making it difficult to hold the file with both hands and move to take advantage of the sharp teeth on the file. It's a 9 tpi thread.

View attachment 27634

Link to a thread repair file on Amazon:

https://www.amazon.com/General-Tool...1546735231&sr=8-5&keywords=thread+repair+file

Hard to tell without seeing the whole thread, but it appears to me the that these are not threads, you didn’t chase after them...

 

[Doug Rasmussen]

Hard to tell without seeing the whole thread, but it appears to me the that these are not threads, you didn’t chase after them...

Nope, they're threads. Look closely at the right end, on the first turn of the thread you can see the helix angle of the thread.

With a 9 tpi on a 1" diameter the angle is small as you would expect.

Theoretical thread angle would be arctan pitch/circumference of blank. Or arctan .1111/3.1416 or .0353. Per my calculations that comes to 2.02 degrees. Hold a straight edge up to your computer screen at the tight end of my piece, looks pretty close to 2 degrees to me.

Please anybody, feel free to check my reasoning here

 

[Bill Boehme]

I think that Emiliano's comment was tongue in cheek ... meaning that you didn't have to chase them down ... you did it while standing still. OK, so maybe Emiliano needs to keep his day job just in case stand up doesn't work out to be his calling.

 

[Emiliano Achaval]

I think that Emiliano's comment was tongue in cheek ... meaning that you didn't have to chase them down ... you did it while standing still. OK, so maybe Emiliano needs to keep his day job just in case stand up doesn't work out to be his calling.

Darn! I'm Impressed with Doug's calculations. Of course, I will take your word that they are threads, LOL. Bill, I'm working on my jokes for Raleigh, you have given me some ideas, thanks!
Doug, I have seen several beginners just leave the chaser in place, with the obvious results...