ACME 1/2 - 8 LH rod available ?

[morrisman]

I see ROTON sell this size in stainless and in mild steel lengths ? . Is it available anywhere in Aust. ? Are ROTON OK to deal with ? Mike

[Dave J]

It would be available from Aus, but at a hugely inflated price like everything else.
I have heard good things about Roton from the US guys, but haven't heard anything about Aussies buying from them
This is a thread from not long ago here, it seems postage was expensive. If you do go that way maybe Dean would go in with you to get his piece.
http://www.woodworkforums.com/f65/roton-us-not-replying-142633/

Dave

[morrisman]

Thanks Dave ... maybe I could try to make a length myself .... others have done it . The tricky bit is grinding the tool . Mike ..PS have you ever made a ACME thread yourself ? But , because I need around a 14" length , I think I would need a travelling steady for the Sheraton , which I havent got .

[RayG]

Hi Mike,

There were a few related threads to that, I think the best deal was from use-enco...

Try here..
Enco - Guaranteed Lowest Prices on Machinery, Tools and Shop Supplies (http://www.use-enco.com/CGI/INSRAR?PMSECT=0000000451)

Regards
Ray

[PDW]

Thanks Dave ... maybe I could try to make a length myself .... others have done it . The tricky bit is grinding the tool . Mike ..PS have you ever made a ACME thread yourself ? But , because I need around a 14" length , I think I would need a travelling steady for the Sheraton , which I havent got .

ACME is a PITA to cut and I do speak from experience. I once made a new leadscrew for a lathe back before I knew better.

I'd rather cut a square thread. Much easier and just as good for moving slideways etc. Hard to impossible to machine-cut using dies etc so that's where ACME is common.

I recently made some new screws for a P-B chuck, they were 1/2-8 LH IIRC. I cut about 250mm length without using a travelling steady without problems though using one would be better.

Making a square thread tap is a PITA, however, so nothing is perfect. I made a long one with a gentle taper and a pilot when I did it. Silver steel witt the teeth backed off using a file & Dremel grinder, heated with an oxy torch, quenched & tempered to dark straw then used carefully once. Probably still in a box I haven't unpacked yet...

PDW

[morrisman]

OK ... about it being difficult to cut . There is a very detailed thread ( no pun intended ) on that USA practical metalwork forum , about cutting a ACME thread . The guy wrote it up very well and explained it . He had a ACME thread gauge to set up the tool. Its worth trying , as the material is so cheap... how much is one metre of 12L 1/2" stock , peanuts . Might take 3 or 4 attempts to get it close , then :2tsup:

[Dave J]

Thanks Dave ... maybe I could try to make a length myself .... others have done it . The tricky bit is grinding the tool . Mike ..PS have you ever made a ACME thread yourself ? But , because I need around a 14" length , I think I would need a travelling steady for the Sheraton , which I havent got .

Hi Mike,
I have never cut an acme thread my self because I have never had a machine that needed it. If I needed one I would do my best to make it, and think I could pull it off easy enough. It's the same with square thread that I am going to need one for my taper attachment. If we don't try we will never know, but I think you could do it.
Even if you just use a short piece of mild steel mounted in the chuck to practice on, so you don't need a steady for the time being, it will give you confidence in cutting it.

The tool grinding is not hard, but I do think you will need a follow rest, even if you just make up something out of scrap steel welded up to suit. Roller bearing fingers might work better similar to the ones Pipeclay makes.

I gave this link in the second thread below, so it should help you out in seeing the process, it's the same one PDW talked about above.
Making a new Cross Slide Acme Screw - Practical Machinist - Largest Manufacturing Technology Forum on the Web (http://www.practicalmachinist.com/vb/south-bend-lathes/making-new-cross-slide-acme-screw-150571/)

http://www.woodworkforums.com/f65/cross-slide-lead-screw-wear-issue-143259/

The diamond style car jacks have 1/2 left hand square thread from memory. I have heard of a few guys using these for cross slide and compound screws.

If you go ahead and make one keep us updated, as I am sure eveyone will help out if needed.

Dave

[Dave J]

I see you have already have seen that PM thread.:doh:
I forgot to say if you need a acme gauge, Len on ebay has stainless steel ones for $15 posted. They look to be OK but I don't know as I haven't bought on as I have a old Starrett one here. Most gauges have them on the end.

Dave

[PDW]

OK ... about it being difficult to cut . There is a very detailed thread ( no pun intended ) on that USA practical metalwork forum , about cutting a ACME thread . The guy wrote it up very well and explained it . He had a ACME thread gauge to set up the tool. Its worth trying , as the material is so cheap... how much is one metre of 12L 1/2" stock , peanuts . Might take 3 or 4 attempts to get it close , then :2tsup:

If I was going to do it again, I'd cut the thread root first, same as a square thread, then clean up the flanks. That would be a lot easier and I think you'd get a cleaner thread.

When I did mine I used 1085 hot rolled bar. That was not fun even on a big, rigid Yamazaki lathe with follow rest. Worked, though, well enough to restore a clapped out lathe to some years more use as the old screw had a round thread profile & split nuts to (very loosely) match.

PDW

[4-6-4]

Greetings chaps the trick to cutting an acme thread is in grinding the tool. To get the most strength in the bit it is advisable to use a round piece of tool steel. A holder has to be made so you can rotate the bit so the clearance is the same on both sides of the bit. Anothe problem is that the bit has to be narrower that the finished thread so there is clearance so the bit will not dig in. I would have thjought that the nut would have been a bigger problem. I will look in my collection and see what I have. 4-6-4

[PDW]

I would have thjought that the nut would have been a bigger problem. I will look in my collection and see what I have. 4-6-4

For 1/2" I agree. You really need to make/buy a tap which is what I did for square threads this size. When I made replacement ACME split nuts it was 7/8" so using a tool in a boring bar worked fine. Cast iron is a lot easier to machine than steel as well.

PDW

[Dave J]

I know it doesn't help you out (unless you wanted to make a new dial), but I thought I would let everyone know RDG have cheap acme taps in both LH and RH.
The sizes are 7/16 x 10, 3/8 x10, 1/2 x 10, 5/8 x 10 and 3/4 x 5. http://www.rdgtools.co.uk/acatalog/ACME_TAPS__LEFT_HAND_.html (http://www.rdgtools.co.uk/acatalog/ACME_TAPS__LEFT_HAND_.html)

RDG Tools - Online Engineering Tools ACME TAPS "RIGHT HAND" (http://www.rdgtools.co.uk/acatalog/ACME_TAPS__RIGHT_HAND_.html)

They also have the dies in 7/16 x 10, 3/8 x10, 1/2 x 10.
RDG Tools - Online Engineering Tools Acme Split Dies (http://www.rdgtools.co.uk/acatalog/Acme_Dies.html)

I put a guy in the US onto them and even though he only wanted one, he found to buy a second one was nearly free postage. It worked out $55 US for the 5/8 pair posted, and both him and the fellow that did the job for him, where both happy with the quality and the way the taps cut.

Dave
PS
You can add things to cart on the RDG website to see the postage price.

[morrisman]

He has two informative U tube movies on the topic ... he uses acetal rod to demonstrate the process of cutting a ACME thread . MIKE

[Michael G]

4-6-4 is right - the hardest thing about cutting an ACME is grinding the tool right. After that it's not much more involved than cutting a normal thread. I find that if the thread needs replacing the chances are that the nut does too, so provided you have the right pitch you the form does not have to be 100% as you can make to suit each other.
One trick I'd like to try one day is cutting the thread a little longer and gashing the end so that it would act as a crude tap to do the final clean up of the nut, as it's usually the corners of the nut thread that cause me problems. With luck it should also give you a size for size thread nut combination.
I make machine nuts out of phosphor bronze, so something to bear in mind is really sharp tools are needed otherwise there is a lot of heat and not a lot of chips.

Michael

[Dave J]

Hi Michael,
I have read about many guys that have either cut the thread longer than needed or bought a longer thread rod to make a tap up for the nut. I also see it recommended on a lot of forums from guys with experience, so it would work fine.

Dave

[Bryan]

Several times in that video the operator reaches over the revolving chuck, and with long sleeves too. This is a very bad and dangerous example. :((

[welder]

oh i didn't really think about it on a safety standpoint.

http://www.youtube.com/watch?v=DgwsigIyz0c

[Bryan]

Andre, my angry face wasn't directed at you but at the makers of the film, and the operator. I think it's ok to show the link, since the point has been made. Just my view.

[RayG]

Thanks for posting that Andre, great video, and a flash back to the days when machinist's wore ties... :2tsup:

I think all the key steps were covered pretty well, the only bit that could have been done better was comparing reversing with the half-nuts engaged (which is what I always do anyway) versus reversing by hand and using the thread chasing dial. It might be just my lathe but cutting metric threads I can't get consistency unless I keep the half nuts engaged.

Never mind Bryan, he's just jealous of the tie... :D

Regards
Ray

[Stustoys]

Something in that video I dont recall having seen before. Marking center height on the quill of the tailstock. 3.33

Stuart

[Dave J]

Thanks for that Andre:2tsup:. I don't go on You tube to look at videos, and only see them if I am sent a link to a specific one like this.

I might be the only odd one out here :o, but I don't see any problem with that video and wear similar cloths myself in winter time. He is an experienced operator and he has probably done it his whole life wearing the same type of cloths without any accidents. It also looks like the lathe is probably only doing 20 rpm, if it was going to fast the wedge holding the lathe dog would fly out.

We are lucky over here with warm weather, but with some of the shops over their it could be snowing outside, so it is way to cold to roll up your sleeves.
I agree loose clothing around lathes is no good at all and should be taken off, but his sleeve looks to be buttoned up tight.

Ray,
My lathe is the same, you need to keep the half nuts engaged doing metric threads, but I would rather have the imperial lead screw, than be changing all those gears on the thread dial with a metric lead screw.

Stuart,
I checked the thread before posting this and see you picked up on the tailstock mark as well. A great idea as long as you have no movement in your tailstock quill, but not a problem on something like that lathe as it's a quality one.

Dave

[Michael G]

Slight side track...
I suspect that I've thrown it out, but there was an article in MEW (I think) on thread indicator dials some time ago, where the writer went into the maths of it all. It came down to the fact that 5" was the smallest integer dimension between metric and inch measurement and so any lead screw indicator for thread cutting metric threads on an imperial lead screw lathe would have to have 127 teeth on it to indicate properly (as the indicator is really showing the points where the spindle and the lead screw are in the same angular relationship). For most jobs it's easier to keep the 1/2 nuts engaged.
I much prefer metric for calculations over fractional dimensions but tpi seems a lot easier than pitch for threading. If only when the metric system was first developed they had gone for 25mm=1", this stuff would be so much simpler.

Michael

[Dave J]

Hi Michael,
That sounds like and interesting article, anyone have a copy?

Dave

[Stustoys]

Hi Michael,
That sounds interesting. My first thoughts are that on average you'd have to wait the amount of time that it takes to cut 7.5" of thread for pick up. So unless the job was longer than that, as you say it would be better reversing(though I do wonder on my sort of lathe just what the motor thinks of that idea)

Stuart

[Metmachmad]

If I was going to do it again, I'd cut the thread root first, same as a square thread, then clean up the flanks. That would be a lot easier and I think you'd get a cleaner thread.

PDW
I tend to agree with PDW on this point. It might be a bit more messing about, cutting the root then the two flanks separately, but unless you have an A grade machine in first class condition it will be difficult to cut an acme thread with a toolbit in the Acme form. The reason being is that as you advance the tool on each successive cut the toolbit has to cut at the front and two sides simultaneously,- not an easy task.

[Dave J]

Hi Stuart,
Correct me if I am wrong, but if my calculation is right, having a 127 tooth gear on the thread dial with 8 TPI lead screw, would mean only being able to drop in ever 15,875 inches on the lead screw.

Or waiting to for the lead screw to turn 127 times, and at a threading speed of say 60 rpm cutting a 8 TPI thread would take around 2 minutes each time. That would give you plenty of time to reset the cross slide and dial in another cut on the compound, LOL
Still an interesting idea that I hadn't heard of before.:2tsup:

Dave

[Stustoys]

Hi Dave

, would mean only being able to drop in ever 15,875 inches on the lead screw.

Yes.. But, now and again you'll be lucky and not have to wait at all, other times you'll have to wait the a full turn. So the maxinum wait would be about two minutes. If you were cutting a 1mm pitch thread it would be closer to 7 minutes.

Stuart

[Michael G]

Looks like the MEW article was April 2009 (see below for previous discussion) -
http://www.woodworkforums.com/f65/imperial-worm-wheel-metric-leadscrew-97780/

Michael

[Dave J]

I was here then, but don't remember it. :?

Stuart, reading that it looks like we have it all wrong, because setting it up off the lead screw it wont do part turns of the lead screw, where his set up was directly off the spindle with change gears for different pitches, just like you have to do with a metric lead screw.

Mike sorry for the OT, have you worked out which way your going to go. I am thinking of making a bit just for fun to see what it's like to cut.

Dave

[morrisman]

Hello Dave

Been thinking about it . I will try and go ahead with it , but I need a follow rest for the Sheraton 9 , they are not cheap ( repro from tools4 cheap ) and its one of those things you use once in five years. Been reading up on them on that USA forum. They say roller bearings are the best tips rather than the plain brass tips , which wear quickly . I have a ACME thread gauge on the way ... in the post. Somebody did post about the roller bearing tips who was that ? MIKE

[Dave J]

Hi Mike,
Do you have a welder to make one up? If not you could bolt one together out of steel.
I picked up a spare fixed and traveling steady for my Chinese lathe and am going to make them both into roller steadies when I get around to it. A couple of skate type bearings will do the job.

Pipeclay had the roller fingers in the for sale section and I think they are also on that Hercus spares website from Sydney to see a picture of them. They would be easy enough to make up.

Dave

[pipeclay]

Here are some Steady Rest Jaws Fingers for South Bend 9 10 Roller type Hobby Lathe Machinist | eBay (http://www.ebay.com/itm/Steady-Rest-Jaws-Fingers-South-Bend-9-10-Roller-type-Hobby-Lathe-Machinist-/110785392063?pt=LH_DefaultDomain_0&hash=item19cb52edbf)

[morrisman]

Ok thanks for the replies . I have been informed that ENCO in the USA sell the stuff. But it isn't cheap . With postage, a 6 feet length will be around $80 I think. Making up a follow rest ..yes, I spotted steamwhisper's idea of a plate with a bush in it - might be the quick answer . I did get a follow rest with my other lathe , but its too large , the centre height is too high , but I may be able to rig up something using it for a one off job . Mike