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View Full Version : Best way to machine ball screws?



Ross77
15-07-2010, 09:55 PM
Hi everyone,

I'm trying to set up my lathe for machining ball screws but I'm not sure of the best tooling to use. I've seen a couple of other posts that say to use carbide inserts but are there different types, shapes and qualities of carbide?

The sets of 5 indexable look to be a winner but are they overkill?

I also need a quick change tool post holder as well if anyone can recommend a good one, life's to short to spend it shimming cutting tools.:heehee:

Thanks in advance

Swarfing
15-07-2010, 11:00 PM
Ross

Try this guy on Ebay under number 290448499618. I bought one of these for my Southbend 13" and have to be honest been bloody pleased with it. You have to machine the plate to match your saddle slide. Check the details so that you get the right size on his pages.

Normsthename
15-07-2010, 11:48 PM
When I built my machine a couple of years ago I had to have the ballscrews machined.
The guy who did it is an experienced tool maker who is used to working with hard materials etc
But he had a right job machining the ballscrews because they were so hard :sad:

Andy

Swarfing
16-07-2010, 12:10 AM
In general a lot of these are only case hardened, use a grinder to take off the bulk and the the lathe to square everything up. just make sure cutters are very very sharp and expect to get them blunt. If you are using indexable tips then there are plenty around that are specific for hardened materials. Use plenty of coolant.

Ross77
16-07-2010, 02:56 PM
Try this guy on Ebay under number 290448499618. I bought one of these for my Southbend 13" and have to be honest been bloody pleased with it. You have to machine the plate to match your saddle slide. Check the details so that you get the right size on his pages.


Thanks that looks good, dose the dovetail holder tail pull in really tight? 100 seems to be about the price for them as well


When I built my machine a couple of years ago I had to have the ballscrews machined.
The guy who did it is an experienced tool maker who is used to working with hard materials etc
But he had a right job machining the ballscrews because they were so hard :sad:

Yeah I'm not expecting it to be easy, just want to have a fighting chance by using the most suitable tools.



In general a lot of these are only case hardened, use a grinder to take off the bulk and the the lathe to square everything up


That sounds perfectly feasable but isnt there a danger that the heat generated will futher harden the shaft?

Swarfing
16-07-2010, 06:54 PM
You get real good fit and it is very tight and as for the hardening i would say nothing that i noticed. When i did my last lot of screws it worked really well, chucked the screws in lathe and set it up so that the turn was opposite to the grinder. It comes off really quick and you will be surprised how accurate you can be with it. Make sure the doors and windows are open when you do, dust everywhere :-)

black5f
16-07-2010, 07:57 PM
Hi Ross. Try Chester tools,they sell add on quick change tool holders in different sizes. Dont know what size mine is, pretty sure its their piston T1, has dovetail slots, but its big and fitted to a 11 inch lathe and never had any trouble. Be prepared to bore them out / make a bush to fit you cross slide post. Most after market posts will need some tinkering to fit. You wont look back if you get one they are wonderful, life IS too short! Re machining ball screws, some are ground out of very hard stuff! Cheaper ones are case hardened and light hand grinding will remove this easily. The simple route is to cut em off and make a collar to attach to a custom turned end. If you mean to turn the actual screw ... v diff to get the linearity you need. Many people refer to a ball screw but mean an acme screw with an anti backlash nut (apologies if you mean a ball screw!) The are plenty of suppliers of acme screws, Chester sell spare lead screws for their lathes and they are relatively inexpensive (compared to say a replacement myford lead screw) and you can buy acme taps. You can cut a long acme thread but unless you have spent a lot of money on a very accurate lathe.... it wont run well and the backlash nut will bind in certain places. TC indexable are good but go off quick, horses for courses, TC isnt always the best. That all sounds rather negative, its not meant to be so sorry! Shame you dont live next door mate, we could stare at the problem for a bit over a few beers and I'm sure all would fall into place!

routercnc
16-07-2010, 10:44 PM
Hi Ross,

I had someone else machine my ballscrew ends to fit into an angular contact bearing block - that is 16mm ballscrew turned down to dia12 for bearings, then M12x1 for nut, then dia 8 for motor coupling. 3 off cost me 50, and he did a great job, turning it around in a couple of hours whilst I visited relatives.

He was John S from Nottingham - it has taken me a while to realise it, but I'm sure it is the same John S from Nottingham (HobNob man!) who posts on here, so hopefully he'll chip in soon ! I saw his advert for machining services on the Arc Euro website.

Best of luck

Ross77
17-07-2010, 12:10 AM
Thanks everyone



Hi Ross. Try Chester tools,they sell add on quick change tool holders in different sizes. Dont know what size mine is, pretty sure its their piston T1, has dovetail slots, but its big and fitted to a 11 inch lathe and never had any trouble. Be prepared to bore them out / make a bush to fit you cross slide post


Sounds like thats what i need. its for my Halifax which an atlas clone and is 10" swing. mounting shouldn't be a problem as I have a tee slot table to go on the cross slide:smile:

I do mean ball screws but only machining them for bearings etc.


I had someone else machine my ball screw ends to fit into an angular contact bearing block - that is 16mm ballscrew turned down to dia12 for bearings, then M12x1 for nut, then dia 8 for motor coupling. 3 off cost me 50, and he did a great job, turning it around in a couple of hours whilst I visited relatives

I have considered just getting some one else to do it but wheres the fun in that? its also quite expensive for me to get it done locally.


Shame you dont live next door mate, we could stare at the problem for a bit over a few beers and I'm sure all would fall into place!

yeah I seem to be in the wrong part of the country for engineering.:nope:

Ross77
18-07-2010, 11:39 PM
OK so thanks to all for the advice, Ive narrowed it down to the piston type from chester or Ebay number 290448499618.

But I have also seen this from RDG, who I have dealt wit in the past and found them very good.http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=290451108950&fromMakeTrack=true

This uses a cam system to lock and looks like the expensive Dickson ones http://www.lathes.co.uk/latheparts/page13.html

it also the looks like it would also fit on the compound slide which apparently is the easiest way to set up for screw cutting. (after hacking through the hard stuff)

Any one have a preference or experience with either type?

Ross77
18-07-2010, 11:48 PM
He was John S from Nottingham - it has taken me a while to realise it, but I'm sure it is the same John S from Nottingham (HobNob man!) who posts on here, so hopefully he'll chip in soon ! I saw his advert for machining services on the Arc Euro website.



Did you leave with a handfull of "borrowed tools"? If not then its somone else. :heehee:

I'm suprised some of the others havent chiped in as they nornally do. Must have bored them to death with the structural and dynamic vibration ramblings in the other threads :smile:

John S
19-07-2010, 12:11 AM
Sorry some Dynamic vibrations put me to sleep.

Not sure how successful it will be doing ballscrews on a small machine due to rigidity.
It also depends on how far under you need to go, a 12 mm diameter by 4 mm pitch will just clean up to 10mm but will still be on the hard part.
A 16mm x 5 will clean up to 12mm but again be hard, down to 10mm and you are into the soft core.

I rough down using old tips that have been licked on the top to give more rake, all I'm interested in is getting rid of material, surface finish doesn't matter. Once I'm close I change tips to a diamond coated, small cut to clean up and get a size then the ballance is taken off at one cut.

This is where you need a rigid machine as the tips are 49 each, no misprint and they don't do rubbing or light cuts.

Another alternative is to stub the screw, I have to do this for one customer as he uses 16mm ball screws but the bearings on the drive end are 20mm. On these I stub with a piece of 25mm turned down to 12mm and pressed into the end with some serious force plus Loctite plus a secret machining operation. The screw is then turned down to whatever diameters and threads to ensure concentricity.

Ross77
20-07-2010, 02:43 AM
Thanks John.

So do you think I'm wasting my time then? Im not looking to mass produce them just modify or machine the odd one as I need them, Is the diamond tooling essential or just the best value for you given the amount of work you do?


I rough down using old tips that have been licked on the top to give more rake, all I'm interested in is getting rid of material, surface finish doesn't matter. Once I'm close I change tips to a diamond coated, small cut to clean up and get a size then the ballance is taken off at one cut.

Is that TC tooling or normal HSS?, not sure i would have the skill to get the correct finnish diameter in one pass anyway....

I have a traveling steady so will this help or is it dangeous to use with such hard metals, tool shatter etc....?

Maybe I wil have to try 2e0poz suggestion with the grinder, sounds messy tho and will have to try and protect the ways.

As another solution Is it ok to turn a 16mm screw down to say 10mm or to the softer core so its easier to thread and then make a sleeve to bring it back up to the size of the bearing?

John S
20-07-2010, 09:47 AM
You need tipped tooling, HSS just won't touch these. You can use normal TC tooling I just use the diamond coated because of the work I do, I machine quite a few screws for other companies, ARC advertise my services others say they do them their selves.

Never tried a travelling steady, never found one that I can get into the right position. I do centre the ends and support on live centres. Sleeving up to a bearing size is OK but use an over size sleeve and turn to get concentric.

Ross77
20-07-2010, 07:14 PM
Thanks John

Care to elaborate on the "licked on the top to give more rake" , not sure I follow. I presume you use the triangular inserts but do you use the side or the radius point?

z3t4
20-07-2010, 11:42 PM
Hi Ross

Did you see the Dick Stephen X3 conversion articles (http://www.arceurotrade.co.uk/projects/X3-CNC/X3_Article_Part_2.pdf) on Arc's site?
He turned extensions out of mild steel (with all the clever stuff on for the bearings etc) then machined a narrow shaft on these extensions, to insert and loctite into reamed holes in the ballscrews. Avoids the need for angle grinder / special tooling.

Seems that this is an alternative to


machining the screw itself (using proper tooling and skill like John's got)
machining the screw itself (using < grinder to de-skin screw)
buying pre-machined
paying somebody to do it.

As a complete newb I'd probably get pre-machined, but Dick Stephen's method does at least seem accessible.

John

John S
21-07-2010, 12:35 AM
Dick has actually had a couple come loose but I feel that it's more they way he did it.

Ok I'll share my secret machining technique here, anyone of a gentle disposition needs to shut their eyes at this point.

You drill and ream the hole in the end of the screw and put a slight countersink on so the new slug fit flush, now get an oversized slug of material and turn down for a nice slip fit into the hole, turn a tad over, allow to cool then polish with emery cloth, again don't get it too hot.

Then put a light to medium STRAIGHT knurl onto the last half of the spigot, that's the bit up to the shoulder, smear with the shaft fit Loctite and with the end of the ballscrew held between alloy or brass plates in the vise, push the slug in and whack seven shades of sht out of it until it's flush.

Fit into the lathe and take a light facing cut , centre drill and support.
Then do all the machining needed and believe me that puppy isn't going to shift until hell freezes over and with Global Warming that's not likely.


you want 30 to 40mm inside the screw

Ross77
21-07-2010, 01:22 AM
Did you see the Dick Stephen X3 conversion articles (http://www.arceurotrade.co.uk/projects/X3-CNC/X3_Article_Part_2.pdf) on Arc's site?



Thanks John no I didn't, certainly is an option if my little old lathe isn't up to the challenge.



Ok I'll share my secret machining technique here


Ta most appreciated, :beer: so your addition is the Knurling! nice.

I like the way you and Bogs always make everything sound so simple, :smile:



smear with the shaft fit Loctite and with the end of the ballscrew held between alloy or brass plates in the vise, push the slug in and whack seven shades of sht out of it until it's flush.



thats my favorite bit, got plenty of big hammers



Dick has actually had a couple come loose but I feel that it's more they way he did it.



Is that because of the technique or the fact thats not been knurled?

Sorry to ask so many questions but I was just about to order some TC tooling but it looks like I need decent drills and reamers instead.....

Thanks again for the help

cncezee
02-10-2010, 01:18 PM
You are allmissing the thread,, ball screws are case hardend,which means the centre is soft.

simplydrillout the centre and insert a steel pin of your desired size, lock it in with anarobic glue.

Works ever time for me,and i have never had one come loose yet

irving2008
02-10-2010, 02:31 PM
You are allmissing the thread,, ball screws are case hardend,which means the centre is soft.

simplydrillout the centre and insert a steel pin of your desired size, lock it in with anarobic glue.

Works ever time for me,and i have never had one come loose yet

ummmm but thats exactly what JohnS was doing...


You drill and ream the hole in the end of the screw

His approach was more about how he does it so the extension stays put...

Colin Barron
02-10-2010, 03:46 PM
Would it help to stick the pin in the freezer and the end of the screw in boiling oil.

John S
02-10-2010, 03:49 PM
You have been watching too many medieval siege films.

.

Colin Barron
02-10-2010, 11:56 PM
This is a method to fit main bearings into an aluminium crankcase, instead of being a tight fit with the risk of damage using this method the bearing would just drop. It is also used on high speed drills and collets.

John S
03-10-2010, 12:04 AM
Sorry I missed the smiley. :lol: :lol:
You are not American are you ? :whistling: :whistling:

gavztheouch
14-06-2012, 07:06 PM
I think I have read about every thread, tutorial and watched every youtube video on ball screw end machining there is. Now im about to start machining some screws for my laser cutter.

I was about to start by grinding of the hard casing with a bench grinder, but I reckon my 15mm diameter rolled screws will still be hard at the required 12mm dia for the bearings.

I only have a Myford MLR so carbide tips are out, so I reckon the steel rod glued into the ball screw sound like the best idea.

Has anyone got any suggestions as to the best type/number of loctite to use.

JAZZCNC
14-06-2012, 09:41 PM
I was about to start by grinding of the hard casing with a bench grinder, but I reckon my 15mm diameter rolled screws will still be hard at the required 12mm dia for the bearings.

Not necceserialy If chinese origin then think you'll find there only 3-4mm of hardening.?
I've machined a few, I use indexed tipped tooling and buy tips from cutwell tools designed for cutting hard materials. They easily deal with hardening, my lathe is a bit more robust than the myford but it's only a boxford AUD so not exactly heavy duty.!!

Maybe some body's got a bit of an offcut that you could practice on.? . . . Don't think I have but will have a dig about if you want to try.?

EDIT: Opp's sorry didn't read properly didn't see the 12mm dia,yes it will probably still be hard but the hard tips will still handle the hardening on chinese screws.!!

John S
14-06-2012, 10:06 PM
Problem is here that the OD at 15mm will start to become the softer core at 12mm but the roots of the thread will still be hard so it's very hard to get an even finish at the 12 mm diameter.
For 15 down to 12 I'd grind them on a cylindrical grinder, only way to get a true surface.

can you redesign and go down to 10mm ?

gavztheouch
14-06-2012, 10:07 PM
Thanks,

I think they are Chinese, they are branded Gten. Definitely not top quality whatever they are?

What sort of carbide holder and tips would you recommend? I am looking to try a carbide holder for my Myford so a nice general shaped holder would be ideal, but I am new to lathes and don't know what that would be?

Thanks for the ball screw offer, but I ordered some extra length on each ball screw to try it out. :calm:

The only problem would be I have a HSS threading tool and the 12 dia might still be too hard to thread with that.

gavztheouch
14-06-2012, 10:13 PM
Can you redesign and go down to 10mm ?

Yes I can, bearings are bought already but hopefully it will not be a problem to swap if I pay the postage.

John S would it not be a good idea to try your steel plug trick?

How does everyone indicate there ball screws in the chuck? I know of a method by 5bears.com

And here is a great tutorial using a Derlin rod machined to slip onto the ball screw to give you a surface to indicate off. Is there any other way of doing this? http://www.5bears.com/cnc16.htm

Jonathan
14-06-2012, 10:16 PM
Thanks,

I think they are Chinese, they are branded Gten. Definitely not top quality whatever they are?

I recently machined some Gten 15mm ballscrews ... they were a nightmare compared to the standard Chinese (RM1610, RM1204 etc) ones I've done. The metal was still very hard at 12mm, so no chance of getting anything like a good enough tolerance/finish to fit a bearing unless you have a cylindrical grinder as John S suggested. Instead I just annealed the ends of the screws using the wet rag technique to limit how much is annealed, then it was easy. I didn't want to go down the putting bar into the ends of the screws since these ballcsrews were going to be put in tension - not sure if they'd hold up to that?

This is what it turned out like:

6134

Jonathan
14-06-2012, 10:17 PM
Yes I can, bearings are bought already but hopefully it will not be a problem to swap if I pay the postage.

John S would it not be a good idea to try your steel plug trick?

If you can go for 10mm I'd definitely do that... it will be much easier.

gavztheouch
14-06-2012, 10:34 PM
Those look pretty good. My screws won't be in tension and I have duel screws driving a lightweight 1.3M laser cutting gantry (Tube not mounted on gantry). So all things considered I should get away with the steel plug concept and if I mess it up I can rebore and start again?

Gary
14-06-2012, 11:16 PM
The 1520 will most definitely be hard at the 12mm.
you are best to anneal the ends or use a cylindrical grinder.
The engineer i use to machine our ballscrews does need to anneal the ends from time to time.

JAZZCNC
15-06-2012, 12:27 AM
What sort of carbide holder and tips would you recommend? I am looking to try a carbide holder for my Myford so a nice general shaped holder would be ideal, but I am new to lathes and don't know what that would be?

Will need the smaller holders which often have CCMT tips. The holder I use is SCLC with CCGT or CCMT tips and this the company I use. http://www.cutweltools.co.uk/home/lathe-tools/turning-tool-holders
They arn't the cheapist but they are quality, Can't remember the number of the tips I just told them what I wanted to do and they sent me the tips. They've worked a treat on hardened screws I've done thou I dont get more than 2 screws per tip (1 screw per tip turn) and it's slow away stuff. ( I use them on softer materials like ALu or delrin when the edge goes off on hardened stuff).

BUT . . . If your new to turning then I strongly urge you to practice on some scrap before you try machining ballscrews for real.!! . . . You don't often get a second chance.!!

Same goes with threading, if you haven't done much threading then get plenty of practice before attempting on ballscrews because like John S mentions the hardening hisn't always consistant so can easily have soft and hard spots which can make threading a real bitch, esp on a small machine that flexs.!! Again I use indexed tipped threading tool, to be honest I can't be arsed with HSS and grinding for standard stuff like threads or run the mill turning and only grind for special or awkward jobs.!! . . . Yes it's more expensive but not too much when you consider the time saving and repeatabilty of tipped tooling.!
Annealing works but again got to be done carefully and correct other wise can spread up the screw further than desired.!!

Practice and practice a bit more is my advice then go for it if you feel confident.!!

gavztheouch
17-06-2012, 06:10 PM
Thanks for the tips Jazz I made a start on some practice pieces.:playful:

For these I started with a piece of m12 threaded rod to represent my ball screw and bored a 6mm hole to recieve the steel rod I partially turned down to fit inside. The rest of the rod was left at 16mm. The weld held well when turning which is much more abusive than driving a lightly loaded screw, however im worried about the heat the welder injects into the screw. Maybe the loctite is still the best option?

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