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Yes.Quote:
is that the locking bolts I can see at the back of the head casting?
Re: long drill and tap - quick n dirty fix
In your lathe with the appropriate tapping drill (6.8mm?), drill into a length of 3/8" bar , grind a small flat on the drill, insert it into the bar and dot-punch into the flat - it should hold well enough to drill into the quill
Similarly, drill a hole just small than the square end of your M8 tap and hammer the tap into it .
Now you tell me.. cheers any way. may still need to do that.Quote:
Re: long drill and tap - quick n dirty fix
In your lathe with the appropriate tapping drill (6.8mm?), drill into a length of 3/8" bar , grind a small flat on the drill, insert it into the bar and dot-punch into the flat - it should hold well enough to drill into the quill
Similarly, drill a hole just small than the square end of your M8 tap and hammer the tap into it .
Attached some pics of the progress so far. My brain must be playing tricks on me, I could have sworn it was 125mm last time I measured it. :rolleyes: M8x100mm bolts on order, so see how it goes.
Seen a few other modded drills on the net and the ones that seem to work are like mine, with the X-Y table mounted on the base(lose the flexible table) and then lower the head to suit.
There will be no going back once I cut the pinch groove in the head casing..:eek:
It'd have to be 125mm to screw into the quill ?Quote:
My brain must be playing tricks on me, I could have sworn it was 125mm last time I measured it.
You'll need to mill/file a slot into the block to clear the end of the taper (the draw-screw must pull the taper into the quill - it's not just there to stop it falling out)
That'll be it then....Quote:
It'd have to be 125mm to screw into the quill ?
Damm you people have good eye sight. Realised that after I made the key....Thought about grinding a bit of the chuck, but dont want to damage it. Theres not much of the quill at that point to support it tho, might have to remove to bevelled edge. This option isnt looking so good now.:thumbdown:Quote:
You'll need to mill/file a slot into the block to clear the end of the taper (the draw-screw must pull the taper into the quill - it's not just there to stop it falling out)
Decided to drill for both options just in case the key idea fails. May help someone else who wants to do this but dosnt have a lathe.
Started your drill extension holder tonite. should work fine. Just my poor machining skills letting me down now. Still practice makes perfect, (havent used a lathe for 15 years) :whistle:
Ok quick up date.
M5x100mm bolts arrived and modified the key to clear the chuck. Glad I didnt grind any off as I can now sill use the wedge to knock out the chuck. :smile:
Should make some good progress tomorrow as I've finally got a full day in the workshop :dance:
Ok. drilling the quill has turned into a nightmare, made the drill extender and drilled it no problems, however I couldnt get a 6.8mm bit locally, so thought a 6.5 would be ok. However the tap was extremly tight.
So I measured the narrowest part of the thread on an M8 bolt and it was 7.2mm, Re drilled the quill with a 7mm bit but the tap still jams when only a quarter of the way in :sad:
Dose this sound correct or have I just got a useless tap? (new but a Machine Mart cheapy)
An M8 tread, inside the quill for the full length of the tap (30mm or so)Quote:
What thread exactly are you wanting to make?
8mm with 1.5 pitch......Must be the tap then. Have I buggered it by drilling the 7mm hole?Quote:
So what pitch is the thread you require? 8mm 1.5=6.5mm drill.....I'm hoping you have an M8x1.0 tap for a 7mm drilled hole? Use cutting fluid it helps ;)
I have used cutting fluid as well
Very funny. I have a few hens teeth tho...Its still a very good fit when i screwed a bolt in......Is this likely to be the tap then. now problem with buying a better tap, just want to make sure I need it.Quote:
By my number crunching.. :D you have 0.25mm of thread left....Do you have a 9mm tap for round 2 :D
M8 thread with a 1.5mm pitch?
I've been tapping a whole heap of holes for my recent CNC build. For an M8 thread with the more common 1.25mm pitch, a 6.8mm hole is the norm (you sure it's a 1.5mm pitch? as this might account for why your tap is getting stuck!)
http://www.efunda.com/designstandard...ewm_coarse.cfm
Yup,
M8 is 1.25 pitch with 6.8 tapping drill.
7.0 mm will do in a push, that's the usual size for tough stainless.
Wouldn't have thought Machine Mart did specials like 1.5 pitch.
The reason it won't thread is probably because it's a crap tap, can you borrow one off someone ?
Quote:
The reason it won't thread is probably because it's a crap tap, can you borrow one off someone ?
Thanks All, new expensive tap it is then, dont like borrowing tools (sods law it will break) and its not like I'm never going to use it again. The quill must be tougher than I gave it credit. Did a trial run with the 7mm hole in some Al and it worked fine, a bit loose even.Quote:
A problem I've noticed with cheap tools is they aren't always the size they claim....I remember drilling the last hole in a big expensive job 18mm instead of 17.5mm caused me no end of trouble...New glasses fixed it ;)
Im going to have to take a note pad out to the workshop as it appears my memory is useless..:whistle: yeah the tap is 1.25 pitchQuote:
M8 thread with a 1.5mm pitch?
I've been tapping a whole heap of holes for my recent CNC build. For an M8 thread with the more common 1.25mm pitch, a 6.8mm hole is the norm (you sure it's a 1.5mm pitch? as this might account for why your tap is getting stuck!)
Thanks again and sorry for the duff info
With the stalemate on the quill I've been looking at the X-Y table, bit concerned with the flex in the 22mm rails and skate bearing arrangement on one side, and then making up some sort of T slot table.
For £80 I can get a cast iron compound table (not as big as I would have liked) or I can use some of my THK rails, but still need to sort a table.
Is 8080 extrusion ok for a table if the rails are bolted to it? Still want it to be as cheap as possible but realised that cutting corners still costs in the end.lol
Ok feed up with messing around and decided to take the advice of you guys (think it was the 2nd or 3rd post) and buy a compound table...:clap:
Got this one
http://www.axminster.co.uk/product-A...able-21825.htm
Free delivery is a bonus. Bit of work and it it should be ok. T slot tables of the same size where the same price, so at least I will have a decent table. If it works I will have only spent £100 as the drill was free and the other tools are useful for other projects
Extra long tap and suitable bolt also on order. Hoping it will all be here for the weekend. :biggrin:
Problem solved, new tap cut like a hot knife in butter. Wont be buying any more tools from Machine Mart...........Quote:
A problem I've noticed with cheap tools is they aren't always the size they claim....
Compound table is useable after all lot of rework. (Think it was cast, rough milled and bolted togother)
The bit I'm struggling with is eliminating backlash in the acme screw. I've Cut a slot and fitted a pinch bolt, but as the screw and thread are so rough the friction caused is not good.
My question is how critical is it to completly eliminate backlash or is the compensation in Mach able to overcome it?
I can probably improve the current state (about 2 or 3 deg. as a guess) but will take more time...
Photos soon If anyone is interested
How about using a Delrin nut instead of the brass(?) one (or a second nut made of delrin to remove backlash)Quote:
The bit I'm struggling with is eliminating backlash in the acme screw.
Cheers. The originals are cast iron, will the delrin be strong enough on their own if I replace them?Quote:
How about using a Delrin nut instead of the brass(?) one (or a second nut made of delrin to remove backlash)
Wheres the best place to get ready made ones? as the thread is imperial (1/10 inch) Or is it still cheaper to buy a tap and make them my self?
I'd guess they'd be strong enough, although wear rate might be high.
I think one of the guys on the forum has been making and selling them (I don't know whether he has the correct tap for your threads)
What diameter are the lead-screws?
Are the nuts cast in place or are they removable?
Pictures would be good.
Ok you'll have to excuse the photos and the state of my workshop. For some reason if i dont use the flash then there not in focus..:cry:
The screws are 16mm dia. (15.65 on the calipers) and have a 2.54mm lead (imperial 0.1") Cleaned and polished the screw so thats looking better but just noticed the nut has cracked where I have been tighting the pinch bolt, so definetly need a new one, ups.
The nut on the x axis is removable and the y axis is fixed.
Ive had a quick look on tinternet and found lots of different ideas but I'd like to know If any one has a tried and tested method, I've fitted bearings to the screw which was a major improvement, so just need to sort out the backlash in the nut..
Hopefully when its finished it should be a good MILL.....:whistle:
Screws are 5/8" x 10 tpi not metric,
Unfortunately 5/8" usually comes in 8 tpi.
Is it definitely an Acme screw or square thread, acme has tapered sides at 29 degrees ?
Then are they both RH, LH or one of each.
Bugger.. I thouht Acme was square, and trapazoidal had the taper?Quote:
Screws are 5/8" x 10 tpi not metric,
Unfortunately 5/8" usually comes in 8 tpi.
Is it definitely an Acme screw or square thread, acme has tapered sides at 29 degrees ?
Then are they both RH, LH or one of each.
Anyway they are square and both RH, y axis moves correct but the x is opposite to the lathe (clockwise rotation moves it towards you)
Square is square.
Acme is 29 degrees and usually imperial [ not always ]
Trapezoidal is 30 degrees and always metric
Let me have a look tomorrow to see what taps I have, definitely got 5/8" x 8 LH Acme but not sure on the rest.
.
This rather depends on the accuracy you are trying to achieve.Quote:
Originally Posted by Ross77
The software can add extra travel when you reverse direction but that means the slides have to be tight enough to resist side forces from the tool so only the nuts can move them. Once the slides are set tight you have to worry about spring in the system.
Alternatively use two nuts. If you lock them together then wear becomes your problem. Spring them together with sufficient force to resist the tool pressure and you need monster size motors to turn 'em.
If it was easy to eliminate backlash with cheap screws nobody would sell expensive screws :beer:
40 years ago men were sent to the moon. Most of the machines that built the rocket that got them there had backlash to some extent.Quote:
My question is how critical is it to completly eliminate backlash...
The critical bit is reducing the backlash/play/give/flex/strain/vibration/call-it-what-you-like it the whole machine down to workable level and working the machine to reduce the effect of the errors.
The important thing it to lock them together with the smallest possible clearance. This can mean that, with a poorly formed lead-screw thread, the nut will be slack in places while tight in others (lapping the thread with a nut and abrasive e.g. metal polish can reduce the tight spots).Quote:
If you lock them together then wear becomes your problem. Spring them together with sufficient force to resist the tool pressure and you need monster size motors to turn 'em.
Thanks for all the advice, Taken it all on board. From looking on here and the CNC zone I always planed to use servo motors, linear rails and ballscrews for the main machine, and now I know why.....
Still all good practice, dont know If I can justify ballscrews for this one. No point in having an ultra precise table if the head flexs all over the place. May be I should just get it working and then if its just the backlash thats an issue, I can sort it then.
Made the tap tonight and tried it on some plastic I had kicking around. Worked fine but I think the plastic is to springy and the tap wont cut the last bit for clearance, very tight over a 40mm length. Ive tryed tapping fuild and a drill but the end result is a very hot and shiney leadscrew, Still at least I know the best way to polish them now :clap:. I'll have to order some delrin,or try narrower sections.
Changing the subject, what is the best way to hone the dove tails on the slides? I've got them really smooth, with no play, except for the the first 30mm or so where i can feel an bump, Cant get the oil stone in and dont want to over do it by using a grinder.....If I carry on lapping it will both parts wear and then cause problems over the whole length?
Thanks again
If it is cast iron you scrape it, use engineers blue to find the high spots. I would be very careful about introducing any kind of abrasive unless you are blessed with a Rowlingesque magic wand, "Accio grit" :beer:Quote:
Originally Posted by Ross77
Cheers. whats the best tool to scrap it with? looked in to this when setting up the lathe but looked like a "Black ArtQuote:
Originally Posted by Robin Hewitt
What is Accio grit? Im sure Ive read that it ok to use abrasive compounds as long as it is properly cleaned with parrifin afterwards...
The famous Mexican bandit :heehee:Quote:
Originally Posted by Kip
You could try just lapping the parts together dry (i.e. degrease it and rub). Cast iron is fairly abrasive stuff so a few dozen cycles should polish the machining marks.
BTW Use proper 'way oil' e.g. Mobil vactra. (Keep that old can of Duckhams for the car use only ;) )
No need to get personal.:heehee: Office workers can very usefull....making tea, sweeping the floor etc.Quote:
If you want to scrape the ways then a scraper is the best way forward....made from an old file or similar.
Requires manual dexterity and mastery of hand tools....not for the office workers :naughty:
Unfortunatley its not just machining marks, there is a proper lump that needs removing. Still I'll give it try.Quote:
You could try just lapping the parts together dry (i.e. degrease it and rub). Cast iron is fairly abrasive stuff so a few dozen cycles should polish the machining marks.
BTW Use proper 'way oil' e.g. Mobil vactra. (Keep that old can of Duckhams for the car use only ;) )
Is that a typo? or did you mean scrap itQuote:
The best tool to scrap it with is a grinder......
Bugger, thought I had you then. Dont know how that happened! I'm normanally reeelle gurrd @ speiling ;o)Quote:
Your typo? my implication :naughty:
No I havent, better find it and have a look, make sure Im not doing the same......:whistle:Quote:
Ever see the fanboy posts on cnczone where they all went mental and set about knocking the stuffing's out of their dovetails with grit lmao
All this oil is playing havoc with my manicured nails...lolQuote:
You got me on the making tea strike.....Can't call em completely useless eh :D
[quote]
I can only imagine the ruin it's doing to those dainty fingers... :whistle:
[/QUOTE
The middle one is very dainty, do you want to see it......:yahoo:
Just ordered some delrin as a last attempt to salvage the leadscrews. Think I've got a worn 10mm lead, ballscrew kicking around that came with a motor I bought. Probably would be easier to rebuild that with new balls than mess around with delrin and leadscrews......
More questions if I may.........
Made the 2 delrin nuts no probs, mounted one each side of the connector block (what was the original nut that I trashed).
The problem I have is that although the backlash is almost gone the resultant friction caused is making the screw difficult to turn. Theres still a bit of alignment to do which will hopfully reduce it a bit and Ive also got the gibbs set to tight. However I noticed that the last bit of backlash/play is actually the delrin flexing. Is this correct or have I made a mistake some where?
Once the alignment and gibbs are set correctly there should be no play under no load conditions.... But I cant help think that under load this problem will re-appeer and cause problems.
Has anyone else experienced problems between static/no load measurements and actual machining measurements? or am I worring about nothing :rolleyes:
I've looked around on the net and some people seem to swear by leadscrews and delrin and some only use ballsrews...
From what I can see the only way to reduce flex in the nut is to use a metal one with delrin as the antibacklash, but surley this will only "smooth" out the play as ultimately the delrin will have to compress for the metal nut to make contact with the screw during change of direction to increase the strength......
Hope this makes sense. pretty much finished the x axis motor mounts so changing to ballscrews will be a major redesign.
I cant make up my mind If an accurrate small small mill (ie ball screws) will still be usefull after its built the bigger machine....
Just like the nut, there should be a tiny amount of play in the gibs (you can always tweak it once it's up an running, so leave them a little slack). If they're too tight it'll cause you as many problems as too loose.Quote:
and Ive also got the gibbs set to tight.
Does the table slide freely now? There'll be an initial stiction (about 40lbs worth on my drill/mill) but, once moving it should move easily.
Thanks Bill, that was the advice I was after. Ive found that if I use both hands then the tables moves easily once the inertia is bult up, but this is too tight for the screw. I have readjusted it so that if i try to push it with a finger it wont budge, bit more force and it flys to the other end. with it set like this there is a small amount of side ways movement but I can only see it when there is oil on the ways.Quote:
Just like the nut, there should be a tiny amount of play in the gibs (you can always tweak it once it's up an running, so leave them a little slack). If they're too tight it'll cause you as many problems as too loose.
Does the table slide freely now? There'll be an initial stiction (about 40lbs worth on my drill/mill) but, once moving it should move easily.
Maybe I will stick with the leads and see how it performs with the motors. As much as I want to get it finnished I also want to get it right. Its been fun learning on this tho...I seem to only be able to learn when I've tried it and F**ked it up for myself:heehee:
Best way of learning.....!Quote:
Originally Posted by Ross77
If I made a list of all the things that I have fucked up I would need a lot of paper, 2 catogories, minor and major f**k ups. I am pleased to say that as you get older you don't add as many things to the list.
My best major f**k up was ripping the cross slide clean off my newish CNC lathe because I did not set the chuck pressure high enough, the part came out of the jaws when I was screw cutting and got jammed between the chuck jaws and the toolholder at about 1000rpm. I was standing right next to it when it happened and I can tell you it went with a bit of a bang, had to add a new pair of pants to the repair bill!
Repair cost - £8,000 - thank god for insurance!
Quote:
Originally Posted by HiltonSteve
That's something to look forward to then :heehee:
Nice to know Im not the only one then :biggrin:
readjusted the antibacklash nut alignment and its much better now, so it seems perseverance is key. Spent ages the other nite trying to work out why it was binding, next day I spotted the problem in 5 mins.
Thanks again for all the advice. Its ok reading from a book or off the net, but being able to ask specific questions when you get stuck is brilliant. Definetly wouldnt have got this far on my own.......:beer:
Had to put this on hold for a while and then when I got started again last week I crushed my finger whilst honing the ways.........:eek:
So decided to move on to the electrical side and sort out the stepper controller, after hours of trying to bypass the optos and feed the chips direct the L6203's (H bridge) decided to put on an impressive firework display.... @ 40V these things sure go bang.:whistling:
So all in all things arnt going to well.
Any body make curcuit boards for L297 + 2x L6203's with diode protection so I can transfer the remaining parts over to a less complicated board?
After a lot of serching on the web I think I've found out why I couldnt get it to work, There is an enable pin on the L297 that has to logic high! Am I right in thinking that will stop the chip from working?
Ive got another board to try, but not to keen to fry that one as well
You dont rate these as drivers then? Your not throwing away the good ones are you. :whistling:Quote:
I have 2 dead boards and 2 good ones....all to go in the bin and good riddance to the worst £700 I ever spent.
Just want to get this thing running. Nearly finnished the x-y axis:yahoo:
Just the spindle, motor and z axisto do....
Never put them in the bin pass them on..........Ross check for signal on the output of the Opto's if none is found when you fire the circuit up it maybe because they require some voltage. I've built a few opto isolated circuits for interfaces to my radios, every time they do not work is because they need power to one of the pins??? check the spec of the ic you are using with the manufacturers specs