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The Artful Bodger
11-05-2013, 02:15 PM
Old books show the use of thread chasers, hand held tools used with a tool rest to cut, repair and finish threads in the lathe. They do not seem to be readily available now so what happened that they have apparently gone out of common use?

Doozer
11-05-2013, 02:20 PM
The engine lathe got invented.

--Doozer

The Artful Bodger
11-05-2013, 02:23 PM
Yeabut if you are using an engine lathe how does one properly finish a Whitworth thread?

Doozer
11-05-2013, 03:05 PM
Whadda ya mean? Because it has round root geometry?

-D

Jon Heron
11-05-2013, 03:35 PM
Do you mean like a thread file?
Like this?
http://www.miataturbo.net/attachments/suspension-brakes-drivetrain-49/65373-axle-thread-repair-files2-jpg?dateline=1358976805
Or a clamp type job like this?
http://toolmonger.com/wp-content/uploads/2007/09/450_05S2102_large.jpg
I have a couple of them, they are great for touching up threads in a hurry.
Cheers,
Jon

Jono
11-05-2013, 03:45 PM
You can bodge the crest radius with a file, which is quick'n'dirty but does the job. Chasers are nice, though- also really good for restoring damaged threads. They are still available, but usually of the machine type.
Die box inserts are a source of external ones, and you can sometimes use a tap if it's a "special" internal that you're cutting.
Generally, these days you do it all with a full form insert, which is the best way of all. BSP is the commonest use of Whitworth form nowadays, I used to cut a lot of pipe threads in 300 series, and they do a great job.

lakeside53
11-05-2013, 03:47 PM
Yeabut if you are using an engine lathe how does one properly finish a Whitworth thread?

Buy the right full-form insert or grind the correct 55 degree and root geometry, then the crest.

Doozer
11-05-2013, 03:52 PM
That's what I was thinking.

-D

Mike Burch
11-05-2013, 04:00 PM
John, Trade Tools sell Coventry chasers – see www.tradetools.co.nz

Zadig
11-05-2013, 04:08 PM
I still use them.

http://i1118.photobucket.com/albums/k618/Ingenous/Burrell%20Pics/DSC05528_zpsa18acbe8-1.jpg

Arthur.Marks
11-05-2013, 04:31 PM
Zadig, why? What is the advantage for you? Do you make those chasers yourself? The traditional, old machinist books explain these as a hand tool. Are you holding the tool shown above by hand or is it affixed to a toolholder out of frame? You obviously have a modern toolpost---providing the "hand rest" in the photo. It's interesting to me. I've never heard of anyone actually using this vintage process/tool.

Zadig
11-05-2013, 04:47 PM
I cut my threads using the method that does not involve altering the top slide, whereby you wind in the topslide half of the depth. The thread is then chased up by hand using the chaser shown. These are bought items, but are not so readily available these days, most being purchased used, from eBay. They give a good final finish to the thread with the correct form. By hand chasing you can also get good accuracy on the finished thread size, especially if you have already made your nut. The method is to use a rest as shown and with a file handle on the end (it has a tang) apply pressure to where you want the metal to come off. I suspect health and safety have played their part in its unpopularity, but I wouldn't be without them.

CarlByrns
11-05-2013, 05:29 PM
In the USA, Snap-On and Mac sell chaser sets for repairing lightly dinged threads. Works a treat.

Arthur.Marks
11-05-2013, 06:10 PM
I cut my threads using the method that does not involve altering the top slide, whereby you wind in the topslide half of the depth. The thread is then chased up by hand using the chaser shown.
Thank you for the reply, Zadig. I've never heard anyone with actual experience using these tools explain the process. One clarification, if you don't mind. "I cut my threads... The thread is then cased up by hand..." Is my understanding correct that you initially use a single point tool and advance straight in with the cross-slide to produce a partial thread form? Then you use the chaser on the pre-cut thread to finish to size?

Graniteguy
11-05-2013, 06:56 PM
When I was a kid, my stepdad had a full set of thread chasers that looked for all the world like regular threading dies. They were Proto brand, if I remember. Check Internet Archive. They have a lot of old machine literature for free. It wouldn't surprise me if there were instructions on how to make and use thread chasers.

boslab
11-05-2013, 07:13 PM
I have an assorted box of oddball chasers, internal and external, odd threads like brass and british standard bicycle, left and right hand!, they do work quite well, very fast to use on brass, you can 'strike' a thread as the old boys used to call it quite well, by hand or in the tool post for small tpi.
They are still made even though full thread form inserts are gradually replacing them, a certain amount of 'intestinal fortitude' is required on a big workpiece
http://www.woodworkingtalk.com/attachments/f6/8013d1238117623-home-made-thread-chasers-10-16tpi-tools.jpg
Btw you can make external chasers by using one cutter from threading machine dies, they work well but require a handle for hand use or a slot holder for toolpost, i regulary cut pipe threads and metric with one in the lathe as i dont have a threading machine,....yet
Mark

Jono
11-05-2013, 07:15 PM
They're not necessary for standard US threads, or ISO metric either, unlike whitworth form, which must be radiused. I must confess I do the machinist"s no-no of not using a file handle, but I won"t tell if you don't.

Not sure how you make them- hobbed I guess.

BTW, if they looked like dies, they were die nuts, not chasers

J Tiers
11-05-2013, 07:21 PM
brass was mentioned, and that is where even the older books show them in use. On brass-worker's lathes.

of course, since brass threads are so few in tpi, there are more "modern" ones with a backside nut arrangement somewhat like one of the old miniature lathes. Apparently only a couple thread pitches were in use for brass, so it was handy enough to have the "guide" on the back.

Still true, it seems, lamp parts (traditionally brass) all seem to use the same thread.

The Artful Bodger
11-05-2013, 11:19 PM
Zadig, thats exactly what I had in mind last evening when I was cutting a 1.5mm thread in 32mm "steel of mixed parentage". The thread as cut was really rough but today I managed to find some "thread files" as shown by John Heron. They have nicely finished the thread.

The Artful Bodger
11-05-2013, 11:23 PM
John, Trade Tools sell Coventry chasers see www.tradetools.co.nz

Ouch! I got a set of three thread files from The Front Shop today, they are 'Lang' brand, imports of course but they seem to be of adequate quality!:o

Zadig
11-06-2013, 03:07 AM
Thank you for the reply, Zadig. I've never heard anyone with actual experience using these tools explain the process. One clarification, if you don't mind. "I cut my threads... The thread is then cased up by hand..." Is my understanding correct that you initially use a single point tool and advance straight in with the cross-slide to produce a partial thread form? Then you use the chaser on the pre-cut thread to finish to size?

Yes, the thread is first cut using normal screwcutting methods and then chased up with the hand chaser to produce a tidy finish. I use the method of screwcutting that does not involve rotating the topslide around to produce the correct included angle. Keeping the topslide in its normal zero position, the single point tool is advanced on the cross slide and also advanced on the topslide, but only by half. For example if you wish to take a cut of 0.010" on an initial cut of a thread, then with the cross slide zero'd the tool is wound in 0.010" and then top slide (zero'd), is wound in 0.005". This process is repeated until the full depth of thread is achieved. I usually leave about 0.005" on a thread, which allows for a clean up with a chaser.

Winding in the topslide by half means that the tool is only cutting on the front edge. You do end up working close to the chuck on occasions with the chaser whilst putting a fair bit of weight behind it and as has already been mentioned, a certian kind of fortitude is needed.

mike4
11-06-2013, 04:12 AM
Thread chasers are often listed on Ebay , I have used the ones for pipe threading to clean up damaged pipe threads ,just make a holder and they work a treat no setting up for threading just another tool change .
Michael

The Artful Bodger
11-06-2013, 04:36 AM
Thread files fixed my problem for me but I would still like to try a 'real' chaser but looking at the prices online disheartens me somewhat. I looked at maybe brazing a piece of a tap to a handle but it seems they would be left handed (when cutting external threads)!.

Jono
11-06-2013, 05:24 AM
New ones are most likely HSS machine chasers. Look out for old carbon steel, tang handled ones. You'll never get them hot enough to ruin them, and they take a superb edge. Carbon steel wasn't the cheap option back then, quality will be A1

loose nut
11-06-2013, 07:47 AM
What's wrong with using thread dies, that is what they are for.

Arthur.Marks
11-06-2013, 12:08 PM
Thanks again, Zadig. I understand now. Yes, I am familiar with the X/Z tool advancement method you explain. It is championed by Martin Cleeve in his excellent book Screwcutting in the Lathe. My question was always if these tools were used for the full process of cutting the thread or only to finish to proper form and fit. Looks like the latter.

Timleech
11-06-2013, 12:49 PM
Thanks again, Zadig. I understand now. Yes, I am familiar with the X/Z tool advancement method you explain. It is championed by Martin Cleeve in his excellent book Screwcutting in the Lathe. My question was always if these tools were used for the full process of cutting the thread or only to finish to proper form and fit. Looks like the latter.

I was taught, first at school and later at apprentice training school (I did an 8 week version of what the apprentices did in two years, to give insight into engineering processes) to cut threads winding the tool straight in. I think hand chasers were probably thought too dangerous for school, we probably finished threads with a die, but we were taught to use hand chasers in the apprentice training school, along with dire warnings about the hazards to yourself and others if you weren't sufficiently careful, stories about them ending up in the roof or impaled in the next lad's head!

I do have a fair number, but confess that I tend to cheat and use them clamped in the toolpost.

Tim

The Artful Bodger
11-06-2013, 01:06 PM
What's wrong with using thread dies, that is what they are for.

32mm x 1.5 $28 plus freight ($50 if I had to order from the US) and I only want to make a couple of these threads, this is the "Home Shop Machinist" forum.

loose nut
11-06-2013, 01:11 PM
Do you ever think about moving to a country were they don't pull your pants down and bend you over a table ever time you want to buy tools.:o;)

Jono
11-06-2013, 01:20 PM
32mm x 1.5 $28 plus freight ($50 if I had to order from the US) and I only want to make a couple of these threads, this is the "Home Shop Machinist" forum.

Why must you chase it? Metric threads don't need them. Besides, a laydown toolholder and insert should cost about the same, and you'd still have the holder (insert too if you got a general 60 one).

The Artful Bodger
11-06-2013, 01:32 PM
Why must you chase it? Metric threads don't need them.
In this case because the cut thread was very rough and I wanted to improve the finish and get a nice fit.

The Artful Bodger
11-06-2013, 01:32 PM
Do you ever think about moving to a country were they don't pull your pants down and bend you over a table ever time you want to buy tools.:o;)

Thank you for your kind words.

Jono
11-06-2013, 02:04 PM
In this case because the cut thread was very rough and I wanted to improve the finish and get a nice fit.

Yes sorry I'd forgotten that. Did you use an insert tool? I strongly recommend them. Metric and UN just need deburring, with great finish, even with just radial infeed.

Boucher
11-06-2013, 02:08 PM
I keep 3 1/2 sticks of Cratex 120 - 320 grit on the shelf above the lathe. To polish threads, just throw a paper towel over the ways and press the abrasive into the threads. It cuts into the rubber and follows the thread.

The Artful Bodger
11-06-2013, 03:02 PM
Yes sorry I'd forgotten that. Did you use an insert tool? I strongly recommend them. Metric and UN just need deburring, with great finish, even with just radial infeed.

It was a brazed carbide(?) tip but I usually use HSS.

loose nut
11-07-2013, 01:22 PM
Thank you for your kind words.

Just trying to help.

Daveb
11-07-2013, 01:31 PM
Do you ever think about moving to a country were they don't pull your pants down and bend you over a table ever time you want to buy tools.:o;)
Nah! It would take all the fun out of buying tools.