I finished choppng the steel bar down to size, and am threading them by hand. Here's a couple of finished bolts, with the remainder of work in progress:
I finished choppng the steel bar down to size, and am threading them by hand. Here's a couple of finished bolts, with the remainder of work in progress:
Do you mean the Die?
I used to use the end of the tailstock shaft to square up the die.
Yes of course I meant the die. My memory is failing me. I used the tailstock to start all of the threads. But that was slow, and didn't do a good job, judging by the damaged threads. I couldn't see what I was doing and it was hard to reverse the die four times per turn like I did with the rest.
It's really worth using a tailstock die holder for this, if you can find one for your lathe. IMHE, they're such an improvement that it's worth buying dies to fit them, rather than using those from your hand set that doesn't.
What's the damage? If it's tearing, you cut too much at one pass - always a problem with a thread this big. If it's wobbling or a slack pitch, then it's an uneven hold on the die and using the tailstock will help to keep them square.
That's for taps, where there's a problem in clearing swarf. If it's dies and the swarf is coming out cleanly anyway, you can thread continuously.
I bought a book yessterday, "The Munition Worker's Handbook" of 1916. It's a very cut-down machinist's handbook / Zeus tables, with an extra chapter added to the back on how to turn shell casings from raw forgings. Full of advice on machining stuff like this.
How can I cut a different amount? Surely that depends on the die. Which in my view is too thin. I'd rather have more threads in it, with a gentler taper.
I've been told to reverse the die up to 6 times per turn, for large threads. I have since discovered that the person who told me that was not a real trained engineer.
Many years ago I used a fancy 5/16" tap on a capstan lathe that cut a long thread in steel in a couple of seconds and opened automatically.
How can I cut a different amount? Surely that depends on the die. Which in my view is too thin. I'd rather have more threads in it, with a gentler taper.
I've been told to reverse the die up to 6 times per turn, for large threads. I have since discovered that the person who told me that was not a real trained engineer.
Many years ago I used a fancy 5/16" tap on a capstan lathe that cut a long thread in steel in a couple of seconds and opened automatically.
I remember those.Was it a Coventry Die Head? It used to click open when the traverse hit a stop. There were 4 individual cutting tools and they were set using a screw gauge. 40 years ago!
Are you sure you have the turned diameter correct? What lube are you using - have you tried Rocol RTD?
As with all thread cutting dies, it should have some way to alter the cutting depth of the thread. Capstan dies, well, I was 15 at the time just starting on my apprenticeship and I can't remember how they were adjusted. Hand dies were mounted in a holder that had a securing grub screw and two grub screws to alter the compression to determine what diam the thread would end up. The die should have a split in one side. See
But I want to cut a standard Whitworth thread, which is a standard size. So I don't want an adjustable die. If you are suggesting that I use an adjustable die several times on each bolt and tighten the die up, that isn't going to happen. The job is hard enough as it is. The die sets available to me are not adjustable. What I think I'd like is a very fat die with lots of threads in it that cut progressively deeper.
up
Conventionally you would take a roughing cut maybe 10 thou oversize then readjust to finished size. A die box has a little lever that can be flipped into one of two positions, oversize and on size.It also has a wide range of adjustment if you need to make none standard diameter threads. With a split die in a die holder you open it up for the first cut then close it down to standard for the finishing cut but the range of adjustment is pretty limited.
AWEM
But I want to cut a standard Whitworth thread, which is a standard size. So I don't want an adjustable die. If you are suggesting that I use an adjustable die several times on each bolt and tighten the die up, that isn't going to happen. The job is hard enough as it is. The die sets available to me are not adjustable. What I think I'd like is a very fat die with lots of threads in it that cut progressively deeper.
I believe that you are not using a proper die - but a thread cleaning tool or chasing die. Does the die have a lead-in to progressively cut the thread? Are you using it the correct way round - with the internal chamfer / lead-in going first?
How are we supposed to know that Matty wrote the first paragraph of that, and that you wrote the second?
Not using Windows Live Mail would help, there are plenty of alternatives to choose from, e.g.
That's my reading of this too - plus his comment about the die being too short and requiring clearance cuts each revolution. Using a proper split die allows the first thread cut to be made with the adjustment screws well in giving at least 10 thou over size; the second cut I make tweaking the settings till I get the fit I want and is nice a and clean. It really doesn't take any time at all even with a larger thread.
A die holder to go in the tailstock is an almost must for a lathe user. I will admit to being fortunate in inheriting my father's lathe and he made his own that can be reversed to take smaller dies and also is slotted to take a tap holder.
Rob
Yes I am using Rocol. I have tried another die and that works much better. The one I was using must have been damaged.
Here's the finished job:
corner at the head are likely to be considerably weaker than forged head types.
ypic.com/2zogrgx.jpg
Matty - those are die nuts and would have been used to tidy up the thread on your old bolts rather than cut the new threads - no wonder you were struggling. What you want is a die that looks like this - Ebay 370092890759 (found by searching for whitworth die). As said by several of us, the slot allows a degree of adjustment when in an appropriate die holder to give a rough cut and then a final cut.
If you are cutting a lot of threads using taps or dies and can mount the item in a the lathe then life would be much easier if you had a tailstock holder - if you want to see the one my father made let me know and I'll get some pictures up somewhere.
Rob.
Well, we have nothing like that in NZ. Few suppliers here stock Whitworth any more. If they did, we bought all their stock. Besides, 6 X 1/2 BSW TEE BOLTS Price: =A3253.25 Excluding VAT at 20%, pack size 25 would cost over =A3300, or NZ$600. Worth the money, except that we want square head bolts to fit in existing woodwork, and those are Tee bolts. And my time is free!
And its more fun making them too.
They look like they have square heads but the picture is a bit small. If you were bolting metal to metal I would buy the T-bolts as they are forged and heat treated so are much stronger. It shouldn't matter for bolting to wood as I would expect the bolts to pull through before breaking.
But much stronger than the 109 year-old softwood that the bolts are holding on. For hidden bolts that need maximum strength I would certainly use high tensile bolts.
Or just a few hours in an electrolyte derusting bath followed by a wire brush and a quick pass over with the die nut.
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