Hand-Chasing Threads

[OGYT]

I've been wanting to learn how to hand-chase some threads in wood for about 3 years.
I recently attended a demo by Anthony Harris, at SWAT (South West Area Turners) Symposium in Wichita Falls, TX. His demo was "Turning Spheres - Three Ways".
Because I had seen some of his spectacular spheres in the Instant Gallery (they were all halved, hollowed, and threaded, to screw together), I went early to the demo room and found him there. He was getting some blanks ready to turn, and I asked him if he was going to show us how to chase threads also. He said, "No". I told him that I'd seen his spheres in the IG, and that I had hoped that chasing threads was included in his demo. I also told him that I understood if he couldn't include it.
He glanced at his watch, and said, "We've got a little time, let's chase some threads." (It was 15 minutes before the demo.):oo:
When it was time for the demo, he had finished a little box - threaded lid and all - and had answered all our (a crowd gathered quickly) questions while doing it. He's one terrific guy, and an exceptional woodturner. (I also got to buy the little box.):D
I then went to the Craft Supplies booth and bought a set of 16tpi thread chasers.
Since I returned home, I've turned approximately 15 sets of male and female threads - the last two sets work, but not ideal. While turning the last threads, I think I finally learned the secret of chasing threads... a very light touch, and absolutely centered cutting point.
I know that the rapidity of your movement is directly dependent upon the speed of the lathe. (Sorby suggests 200-300 rpm, I think, but with my shaking hands, I couldn't do it that slow. I cut the male threads on the Oneway at about 450rpm, and I cut the female threads on the little Vicmarc's slowest speed, 682rpm)
Question: Am I right... is the real secret to hand-chasing threads just having a very light touch and cutting right dead center at spindle height? Any hand-chasers out there? Inquiring mind wants to know.:?:?

[Toolin Around]

Yup

A very light touch and a few practice passes helps. By practice passes I mean drop the handle so the bottom face is scoring the piece not the top surface where the cutting is going to take place. This will give you an idea as to how fast you'll need to be and the timing needed for a smooth entrance (can't think of a better word). As well as being real smooth and consitent.

Don't push too hard. You have to practice to know how much wood to remore per pass without ripping the top off the threads. I've found less is best.

I've found that if I slightly skew the thread chaser a bit so the cut get progressively deeper across the width of the tools works pretty good.

I have the top face of the thread chaser at the center of the piece so it's roughly flat when held.

The tool rest need to be flat and clear of defects that will hangup on the edge of the thread chaser. Even the slightest hangup will wipe out the threads. A quick sand of filing will make the tool rest smooth and the thread chaser will slide easily.

I have the sorby thread calipers that make it easy to determine the inside and outside diameters of the threads.

A gentle but yet firm "entrance" into an already started thread is needed. I've found this is where I really stuff up the thread peaks if I'm at all hesitant.

On difficult woods, usually softer and coarser grained, water as a lubricant can help. Not a lot, dip the fingers in a cup of water then run them along the piece.

I've tried going with the grain on threads and found them to be a complete failure as the threads tend to follow the grain. They're always nice and clean but not consistent spirals.

Some like to use the hook for internal threads. I've never been struck on that method. It just adds another variable that I don't think is necessary YMMV.

I'm yet to find a really consistent wood that will work all the time. WHen you find out let me know.

Basically practice is the only way to learn the charcateristics of the tools and especially the woods you plan to use.

Some food for thought

[BernieP]

G'Day Al

Always found thread chasing fascinating, but decided its beyond me, read a book called All Screwed Up by John Berkeley about the subject, was a copy in Hurstville library, so see if you can borrow a copy somewhere, also a bit about it at http://www.peter.hemsley.btinternet.co.uk/CDB/Technical/Screwcutting/screwcutting.html

Hope this is of some use and look forward to seeing your efforts.

Cheers
Bernie

[TePe]

I think you may have been better beginning with 20TPI chasers, the more the TPI the slower you have to move sidewards for any given lathe speed. As you get to less TPI you have a lot more surface area of timber to shift, and you have to increase your traverse speed. You are correct saying you use a light touch, especially when starting the thread, you can increase the pressure slightly as the thread forms but there is no need to. Just take more light cuts.

The way I was taught was to imagine I was scribing a small clockwise circle with the chaser tip. At the bottom of the circle you come into contact with the wood, you move up to center height while traversing left with the thread. Once the beginning of the thread is established you can use the chaser in a horizontal circular motion to cut the thread to completion.

As to timber types, don't forget that when chasing you are really scraping the wood, all be it in a shearing form. Which means you will only succeed with very close grained hard woods. Box/African black wood/Lignum vitae/ebony are some of my favorites. If you are using a wood which crumbles a little you can try soaking the thread area with CA adhesive, it can sometimes harden the wood enough to take a thread. My preferred method if the wood is too soft is to use a insert collar of one of the above woods to take the threads then glue it into the piece. I have made a couple of small burr urns using this method, and the removable handles on walking canes.

Just a thought if you want to purchase more chasers, a few years ago I bought a job lot of engineering chasers on ebay most of the older ones seem to be the "whitworth" thread form which are ideal for use on wood. If you get any you may have to doctor the leading edge. Some have a half tooth at the side, grind the side edge until you are left with a full tooth form, gently grind a shallow hollow on the top edge and away you go. I got 11 pairs 32 TPI - 4TPI for £9.50 UK, don't know what that is in your currency but it isn't much. All I had to do was make handles for them.

Apologies for going on, good luck with your chasing.:2tsup:

PS - Don't forget it is possible to chase while turning the lathe spindle by hand, then you can see how everything is going.

[Richard Findley]

Hi All,

I think that different people view the challenge of thread chasing differently, but to me, the "secret" is to allow the chaser to do the work for you. I discribe it as a "clever" tool: all the other tools need to be firmly told what to do but the chaser already knows what to do. The secret is to let it do it. Most people's natural tendency is to aply too much pressure or grip it too tightly or try to make it do what they want it to, but all you have to do is show it the wood, very gently at first, in those circular motions mentioned earlier, and the clever little chaser will do the rest for you!!:;

Oh yeah, and lots of practice!!!!:doh:

Cheers

Richard

[TePe]

Hi again Al, try this link for some ideas and help on chasing.

Robert Sorby (http://www.robert-sorby.co.uk/) click on the movie clips there are some wmv files on chasing, and lots of other stuff on the use of the tools that Sorby's make.

[ss_11000]

Richard Raffan i think it is has a video on thread chasing.
i'm pretty sure its raffan, tho i havent seen it for a while, i borrowed it from the library

[OGYT]

Thanks to all for the answers and tips. I've been out of pocket so much the last few days, that my 'puter time has been limited.

TA - Thanks for the tips. I've copied and pasted them into a document I can print out and take to the shed. As I have done with most of the other posts. The tip that I think is really going to pay off, is the one about that bloody hook tool. I've had more trouble trying to hold that darned thing than any other part of chasing. I don't know why I need it, so I'll use the handle for something else. Thanks, TA.

Bernie - I appreciate the link. I've copied Bill's Tutorial, and I'll read it thoroughly before I start threading again, which will be this afternoon. BTW, all screwed up is how I felt as I was pitching all those bad threads into the scrap box.

Tam - It took my dial-up forever to load those RS videos on thread chasing, but I did it, and now I can watch to my heart's content. Thanks for the link.
That's a good idea on using collars of dense wood. Someone else told me that, also, so it must be going around.
I would sure like to find a deal like yours on those engineering chasers. I don't know about Whitworth threads, but I'm gonna try to find out.

Richard - I'll try to remember that the chaser is a clever tool. Maybe it's more clever than me...

Stirlo, RR is one of my favorite people.

Thanks again, all.