Threadcutting in wood.

[Davyboy]

Hi all,

I'm a very new member but thought you might like to hear about an interesting new tool that will be on the market soon.

About 18 years ago, I devised a piece of kit for cutting threads on turned wood, boxes & the like, after seeing a photo of the old Carbatec Threadmaster in a woodworking magazine. It was made up of old lathe parts & with the right cutter, would cut internal & external threads from 1" up to 4" or even 5" diameter.
Recently, I bought another tool from someone in the North of England & happened to tell them about it. After several emails they are going to make a small version which fits into the tool stem holder. It's a good little device, which obviates the need to use hand thread chasers. I believe you may see it on eBay in the not too distant future. Charley, I hope you won't treat this as an advertisement, it's intended to make people aware of this device as at the present time I don't believe there is anything like it in the UK.

 

[robo hippy]

Sounds like the Bonnie Klein jig. A cutter on the headstock, and an x y jig on the ways of the lathe to spin and advance the wood into the cutter. Good toy. Only problem I had with it was that I had to get a mini lathe to put it on. Wouldn't fit on my 25 inch Robust lathe.

robo hippy

 

[loz]

Whats wrong with thread chasers ?

 

[cornucopia]

there's nothing wrong with them Loz its just that some people struggle to master the traditinal hand thread chasing technique so prefer to use a jig- also jigs will allow you to cut slightly softer woods than hand chasers can do.
its a bit like hollowing jigs v's hand hollowing- theres no right or wrong just what you prefer

 

[PeterBassett]

Charley, I hope you won't treat this as an advertisement, it's intended to make people aware of this device as at the present time I don't believe there is anything like it in the UK.

:lol: :lol: I'm not bothered about you talking about it at all, but, do you know what an advert is?

 

[Weasel Howlett]

Charley, I hope you won't treat this as an advertisement, it's intended to make people aware of this device as at the present time I don't believe there is anything like it in the UK.

:lol: :lol: I'm not bothered about you talking about it at all, but, do you know what an advert is?

:lol: :lol: :roll:

 

[shedhead]

Thanks Davyboy, I have been looking for something like this myself. I was put off because there was nowhere in UK to supply. Can you please keep me/us posted of any more info.

Dermot.

 

[jlawrence]

From what I remember of my metal working days (seems like another life), cutting threads was quite a challenge.
I'd imagine it's no less of a challenge cutting one in wood so a jig (or added contraption) would certainly be of use - especially to others like me who haven't touched a lathe in many many a year.

 

[Davyboy]

Yes, it is similar to the Bonnie Klein & the Baxter, but this one mounts in the tool stem holder. The Bonnie Klein & the Baxter jigs are expensive & unavailable in the UK.
I have my version at home which which I made up from an old metalworking lathe cross slide with a threaded barrel attached, & fits directly on to the lathe bed via hardwood packers, but I think the tool stem version is brilliant for smaller work. Who knows, a larger version may follow!!
I will keep everyone that's interested informed as to when it's likely to be available.
There is nothing wrong with hand thread chasers at all, IF you can use one, as a lot of people cannot. The jig makes life easy for perhaps the less skilled amongst us, including me!! Anyway, it's nice to have a few options eh?

Davyboy.

 

[robo hippy]

I was fortunate to have a 3 day workshop with Stewart and Allen Batty. I did a little hand chasing of threads for boxes with Allen. The biggest problem with it is that you are really limited with which woods you can use. Box wood, lignum, mountain mahogany, ebony, cocobolo, and a few of the other hard straight grained dense woods. With the thread cutter, you can cut them in just about any wood, no matter how soft. No matter what you do, they are labor intensive and it is difficult to get your money back out of them. They are a good thing to have for show sales: "how did you cut those threads? It was just another excuse to buy more toys for the shop." I would be interested in seeing how you take on this project.

robo hippy

 

[Davyboy]

I have used the 'prototype' just as a trial & it's a fabulous little tool, & as you say it will cut threads in any kind of wood, since the cutter is a standard HSS milling cutter. I think the makers intend to market this tool at a reasonable price, unlike the Bonnie Klein & the Baxter jigs which are expensive.

 

[robo hippy]

The expensive part is the x/y jig. A nifty threaded thing for advancing the pieces into the cutter, and moving it side ways to deepen the threads. It does have to line up perfectly in order to work, which takes some precision machine work. It is common in the machine work industry. If yours mounts into the banjo, this could be difficult. But, again, that is the trick.

robo hippy

 

[Davyboy]

I still have the home made one that I put together about 18 years ago. A friend made up the threaded body for me at work, then I attached it to an old metalworking lathe cross slide. I have to make up hardwood packing pieces to fit my lathe, but it works beautifully. It is very heavy so absorbs a lot of the vibration, but will cut up to 5" of thread from 1" diameter up to the swing of the lathe. I now have 2 spindles, one at 8 tpi the other 16 tpi. Wouldn't part with it for gold!!!! Part of the fun is making up your own tools I think.

 

[KelseyS]

Hi Folks, I have acquired Carba tec thread cutting jig and had to modify it to fit my Jet 1642 Lathe. I have had some moderate success in threading but I lack much info to make a satisfactory, to me, decent thread. I have very limited info. I had to replace the four flute cutter with a Baxter 8 flute cutter. I have been using soft wood such as Sugar Maple, White Birch and lately White Ash. The threads leave much to be desired. One problem being the RPM I am cutting at. I know you must use low RPM when hand cutting. My assumption is that the RPM should be fast when using a jig to get a smooth cut as is using a bowl gouge etc.. How Fast? Am I making a mistake with that assumption? This Jig has been out of production for a considerable time but still does a decent Job if properly used. Can anyone point me to information on the proper setup and use of this tool? Thanks Kelsey S

 

[Spindle]

Hi

I'm not conversant with the system but if the cutter is a small diameter one which rotates as the wood is moved towards it, then the cutter should revolve quite quickly, (2000 rpm at least). It should be regarded in the same way as a router cutter. I'd also try working with beech or sycamore initially as these are easily threaded.

Regards Mick

 

[KelseyS]

Thanks Mick, i have been turning the cutter around 3k. I will try slower speeds. I have several species of wood avail such as, pecan, persimmon, fig, olive, sepele, several varieties of fruit wood. I will look for sycamore and beech.
Kelsey S

 

[tekno.mage]

Hi Kelsey - when you say that the resultant threads leave much to be desired, what do you actually mean? Are they broken away and crumbly? This can be caused by over cutting the thread (dependant on the shape of your cutter) as cutting too deep will make for sharp crests on the thread tops which are fragile and will break away in open grained woods like ash leaving a very poor looking (although probably functional) thread.

I built my own thread cutting system by mounting a suitable length of threaded rod (with a chuck to hold the work mounted on one end) on a second-hand cross-slide which I mount on the lathe bed. I use a 60 degree double angle milling cutter mounted in the headstock of the lathe and cut at around 2500rpm. I have no problems with cutting threads in softer woods like sycamore or birch, or open grained woods like ash provided I am accurate in my measurements and only cut each thread once, and not to full depth. This produces a clean cut on all woods and each thread top is slightly flat rather than a sharp point making for better durability.

However, if I get my measurements even slightly wrong (ie making for an undesirably tight screw fit) I've found it can be very tricky to go back and recut an existing thread deeper and this can definitely cause the thread crests to crumble and break away - especially on softer woods.

After some experiments, I found that the actual cutter is the least important part (provided it is sharp) - I've even tested one ground from an old bolt by a member of my turning club and found that this worked fairly well, despite being more of a scraper than a cutter!

 

[KelseyS]

Thank you Kym. I think you have answered some of my questions. I may in fact be cutting too deep. Another of my problems is getting the tenon, spigot and the mortise, recess size accurate. I am using a new double taper cutter from Baxter. I have a ring dial that i set to zero when i get the cutter to the point of cutting, it has 50 marks around the ring, i have no idea what the marks indicate, mm or thousandths of an inch.
KelseyS

 

[Spindle]

Hi

Each increment on the dial represents one fiftieth of the effect of a full turn - I assume the handle is attached to a thread, so let's say the thread is 8 TPI, (threads per inch), that's 125 thou per turn - 125 divide by 50 is 2.5 so each division in this case would equate to 2.5 thou or 0.0025".

Regards Mick

 

[KelseyS]

Thank you Mick. Math and I do not have a friendly relationship. I was going to figure it out the hard way. Attach a vertical piece of paper to head stock and a pencil in the jig, set the dial to zero and make a one turn arc on the paper and measure the length and divide by 50. Probably not the most accurate way but would give me a close.
KelseyS