my new lathe ... Precision Matthews 12x36 ...

[Clark]

This is one of those cost nothing to make projects.

The micrometer is a Forster Ultra seater die, that I have lots of lying around already.

The threads on one end are 7/8-14 and 40 TPI on the other end with the micrometer marking. I had to put the micrometer end where it will get bumped.

Here is a review of one:
http://www.6mmbr.com/catalog/item/1433308/945450.htm

 

[KC2IXE]

Why is the micrometer stop backwards? On all others that I have seen the micrometer dial is closer to the chuck while the hardened pin of the micrometer faces/touches the carriage.

Probably because he's using a seater die - the end that would be towards the headstock is spring loaded, and gives - the other end is solid - do he is actually stopping against the 'thimble' side. Interesting idea

 

[Clark]

I have never seen a carriage stop or used one.
I have seen old used ones on Ebay for sale.

I realize now what Wquiles and Precisionworks must be talking about.
With micrometer on the rights side, when I increase the numbers on the stop, the cutting depth gets smaller with a boring bar.

I would want the stop numbers to go up when the cutting depth goes up.

I could flip the die around and screw it in from the other side.
I could solder a bullet in a case, and shove it in the die.

 

[Clark]

I think I posted this around 11-13-2010, but candlepower lost it.

----------------------

I was doing the 100 hours gear oil change, trying to put some time on each gear first, and...
I had a key come loose in my threading gear box on my PM1236 Lathe.

I was afraid to take it apart because of what precisionworks said about getting them back together.

So I drilled and taped the shaft and counter sunk the key, got all the chips out with a vac and with a magnet tipped probe.
I clamped the key to the shaft with a 4-40 screw and Lok-tite.

Now it gets all 5 gears smoothly.

 

[recDNA]

sorry to interrupt - off topic - deleted

 

[darkzero]

I hope you guys don't mind an unrelated question? Well it is related to machining metal but not for a flashlight.

I am thinking of a project for a machinist I know but I don't want to ask him if it is so absurd I'll look like a fool.

Threre is an old fashioned Video Camera mount called an ENG mount that I would like an adapter to connect to a Nikon F Mount.

This means I would need an adapter to convert ENG (bayonet / 48mm flange distance) to F-Mount (Nikon bayonet / 46.5mm flange distance)

Would this be too difficult to machine? Feel free to pm me if you are in the mood to educate someone totally ignorant of your craft.

Thanks

You should try posting your own thread about this since it's way off topic from this thread. You will get much more exposure & I'm sure someone would be happy to help. Plus it would get buried in this very popular thread anyway (unless you're hinting Will to do it). 🙂

 

[John Hill]

My generic Chinese 12x36 lathe appears to be a close relative to the Matthews Precision 12x36, though there are small differences it does appear to be the same basic design although mine is a metric version. I have had it more than two years and it spent about 5 years sitting in a showroom before that.

The spindle bearings are noisy! I can hear a click or light thunk as I slowly turn the spindle!

I want to take the spindle out the check what need replaced!

I took the left hand bearing cover off, and the lid off. I cannot see how to pull the bearing on the left hand end? Any suggestions please?

I took the ring off the right hand end but it does not come off over the D1-4 mount, should it? I have taken the chuck off of course!🙂

With the lid off it looks like the gear to drive the lower gear box will slide off once I get that bearing removed and there is a black collar with two set screws that appears to hold the rest of the gears in position, I loosened the collar but it did not move.

So I am really at square one, any suggestions on how I should proceed to get the spindle out so that the bearings can be examined and if necessary replaced.

 

[precisionworks]

The spindle bearings are noisy! I can hear a click or light thunk as I slowly turn the spindle!

John,

There are two ways to approach this, & the easiest is to wear ear protectors while running the machine so you cannot hear the noise. I'm really not trying to be funny. Consider it a minor annoyance, something that probably does not affect the work that you do, and keep making chips.

If you absolutely, positively, without a doubt cannot live with the noise, pulling the spindle is a risky op at best. I've worked on at least a dozen Asian lathes and only one of those needed spindle bearing replacement - the others needed only flushing of the old oil & adjustment of the preload. Eleven out of twelve, roughly 92%, did not need dis-assembly. Only if your bearings have been run bone try, or if the factory left casting sand or grit in the bearing housings, does the spindle need to be pulled.

IF you still want to pull the spindle, make sure you have a few hundred dollars to spend on this project. Front & rear bearings are not expensive, about $200 for the pair (based on a similar Jet lathe I did), but there's a high probability that something else will get broken while you're figuring out the removal process. Plan on another $200 or more to replace the parts that are damaged in dis assembly & re assembly.

The total bill to my customer was around $500 in parts & well over $1000 in labor (over 15 hours). It wasn't a terribly difficult job, but neither was it a cake walk.

 

[John Hill]

Thanks for the response Barry.
Thanks for the response Barry, I did notice when I took the lid off that although the oil is midway up the sight window the biggest gear is barely, if at all, dipping into the oil and consequently the bearings were on the dry side, not really dry but certainly not flooded. I put a bit more oil in. I have also got the information on the procedures for setting the preload which I will be able to do once I get a couple of 'C' spanners made.

John

 

[John Hill]

Taking heed of your advice Barry I decided to flush the bearings as much as possible while in situ and I made tools to do the preload adjustment.

I used the procedure in the Grizzly manual which is, induce clearance by wacking on the end of the spindle after loosening lock nuts then tighten while using a DTI until no further movement then a further 4mm turn of tightening.

Naturally enough it was not as simple as described and I was really glad I had taken the time to make tools for the job, a pin wrench to fit the spindle nose holes for the camlock and two 'C' spanners for the nuts. It was easy enough to see the movement initially but at the point when movement ceased to be indicated I found I could still cause .01mm deflection just by pushing my hand against the end of the spindle, then I found I could cause the same deflection just by pushing on the headstock itself. The spindle turns quite freely and is somewhat quieter than I recall. Time to give it a run and watch for temperature rise.

 

[precisionworks]

Some temp rise indicates correct preload, while little or no rise indicates not enough preload. It seems like I set both the mill & the lathe for around 20-30°F rise above ambient.

 

[John Hill]

I assume low preload is not harmful and that I can tweak the nuts if necessary to increase preload until I do get a temp rise? I shudder to think of the sickening 'click' that might come from the casting if I over tweak it.

 

[Davo J]

Hi John,
The Grizzly lathe manuals show how to set the preload.

Dave

 

[John Hill]

Thats what I was referring to Dave. They say to loosen the preload by knocking the end of the spindle, after loosening the nuts, then tightening until no further movement. Even though I made suitable tools for the job it is very difficult to see when the movement stops. Bearing in mind the apparent vulnerability of a thin cast iron box with a 2 inch bolt through it I have erred on the loose side and propose more tweaks until I can detect a temperature rise.

Here are the tools I made:-

wrenches by aardvark_akubra, on Flickr

 

[precisionworks]

Nice job on the hook spanners and pin spanner 🙂

The headstock casting, on most lathes, is pretty robust. When setting the preload, you are eliminating the end play between the tapered bearings by compressing the bearings just slightly. Usually, as the end play is taken out, a small amount of drag can be detected when turning the spindle by hand - easier to feel on a lathe than on a mill for some reason. When that drag is felt, lock down the adjustment nuts & run the spindle first at the lowest rpm for about five minutes, monitoring the temp at each end of the spindle bore (an infrared thermometer (IRT) is really handy for this). You should get almost no temp rise at the lowest rpm. Go one speed higher, run for another five minutes, monitor temps, etc. When correctly set, the lathe should be able to run in the highest speed setting with no more than 20-30°F rise at either end of the spindle.

KBC has a good explanation here: http://www.promshop.info/cataloguespdf/kbc10.pdf

Nachi has a more detailed description: http://www.global.estgp.pt/engenhar...talogos/CatalogoRolamentos/NACHI/pdf/Tech.pdf

Here's what Nachi says (on page 223)

Generally, rolling contact bearings are mounted so that in operation, there will be a small amount of internal clearance.

Applications may sometimes require that the bearings be provided with appropriate negative clearance called "preload" when assembled. Preload has various purposes and effects. Since an incorrect amount of preload may adversely affect the rolling resistance, life, temperature rise, sound, etc. of bearings; extreme care must be taken when applying preload.

8.2.1 Purposes of Preload
(1) Increases rigidity of a shaft (that is, preloading can help to decrease the deflection of shafting).
(2) Enhances rotating accuracy of shaft. Minimizes axial movements and helps to prevent vibration and decrease noise.
(3) Prevents fretting caused by external vibration.

Item 1 and 2 are pertinent with respect to proper gear engagement, rotating accuracy of precision machinery and resonance of
electric motor rotors.

All high accuracy machines (lathe, mill, surface grinder, etc.) perform better with correct preload.

 

[precisionworks]

Interesting what preload does ...

Dialed in the Bison Set-Tru (with a piece of Thomson Linear shafting), had it running about .0004" TIR, which is acceptable. This was done with a cold spindle.

Set the levers to 2000 rpm, left the tip of the indicator on the shafting, and powered up the spindle. The needle wiggled back & forth at .0004" Tir for about 15 seconds, then the needle arc started to narrow. In 30 more seconds, the TIR showed .0003", and 60 seconds after that the needled barely moved, showing .0002" TIR (+/- .0001")

When the power is cut, the heavy 8" chuck spins down for quite a while, but when it is nearly stopped - it stops right now. If the chuck spins down and wants to coast forever, preload is probably not quite enough.

 

[tino_ale]

Hi,

Is there a way to adjust the preload using a torque wrench ? Just an idea, I wonder if it can be done

 

[Davo J]

Thats what I was referring to Dave.

😳
Sorry John I missed that bit.

Dave

 

[Programmergeek]

RUN AWAY FROM THIS LATHE!

THIS LATHE IS A NIGHTMARE!

I needed, actually let’s say wanted a lathe I am a home hobbyist and wantedsomething that would look nice in the shop and be fun to work on so after allotof research and taking advice of people on the web I ordered a PM1236 with DROetc. Had a 3 month wait to get one and then I was traveling so about 5 monthslater last month I took delivery. Have been in hell ever since this hunk ofmetal had been sitting on my garage floor.

1. Every piece had been hit bent or paint scraped off I called PM about sometouch up and they said sorry out of luck. The back panel is so bad I have tounbend it and completely respray it just not to be to pissed off when I go inand look at it and so the machine looks somewhat nice.
See pics
http://photobucket.com/jasonlathe

2 Both cabinets are bent and smashed I called PM and have gotten differentstories. I figure I would just send them back and they would send mereplacements, right, no luck, no help 4 weeks after they have not called Icalled them 4 times and no one followed up guess they are hoping I will just goaway but not before I post every where my experience and pics. The left door issmashed in and I have to pry it open with a screw driver. When talking withMatt about 3 weeks ago he wants to try to get me a door and I have to grind offthe hinges and maybe reweld a hinge on or try to grind out the pin. The othercabinet is so bad bent it doesn’t sit on the floor level. He said this isnormal because concrete floors are not level, guess my square is not square,last time I checked square is 90deg all around. So no big deal right I figuredI could compensate so I ordered leveling feet from him this should help melevel it and it really should come with them anyhow. After an hour of retappingthem and cleaning out the threads they are on.

3. Missing parts I went to mount this are there are no screws to mount it tothe bases they said they are in the cabinets, hence me prying the door off butthey are not in there. I don’t even know what else is missing. But I am goingon 3 weeks of calling missing parts ordering feet etc and the thing is a hunkof metal taking up 12 my garage. There was also an extra gear that was supposedto be included I have yet to find.
Overall I have been trying to get this thing together and every step of theway had been put on hold because of missing parts smashed parts that needrepair and retaping. This has some plastic parts on it I know I will break. Noinstructions.

I AM SO SORRY I BOUGHT THIS POS. Anyhow it may be ok once assembles tweaked,unbent, painted and rebuilt but, but I will never again buy a machine off theinternet without looking at it. Even the manual readouts are total crap theyare stamped pieces of metal riveted on and not even straight. I think I havehad better Harbor Freight machines. Maybe at one point this was good but qualityis just not there and customer service when you need something is lacking Iguess they just got to busy and just want to sell machines Chinese machines andforget about them if they have an issues. I am willing to go way out of my wayto make this work considering it was new I should have to retouch repain unbendand order extra parts but I with all my effort still can't make it workable .

 

[precisionworks]

Re: RUN AWAY FROM THIS LATHE!

As frustrating as this has been for you, there are some points you may want to keep in mind ...

Every piece had been hit bent or paint scraped off ... Both cabinets are bent and smashed ...

It is always the customers responsibility to inspect a freight shipment, whether that shipment is a lathe or a bag of Styrofoam packing peanuts. If the customer does not inspect each & every carton in the shipment, and signs the Bill of Lading, the trucking company is no longer responsible for any damage that they've done - much like giving the freight line a Get Out Of Jail Free card.

Had you inspected each carton, the damage should have been easy to spot. Bent and smashed cabinets never arrive in pristine shipping cartons. Had you reported the damage to the driver, or refused to accept the shipment, the freight line would have been responsible. Since you did neither, it's now your responsibility (not Matt's) to fix the damage. Tough way to learn a lesson.

I ordered leveling feet from him this should help me level it and it really should come with them anyhow

There isn't a lathe sold today or in years past that comes with leveling feet. Used lathes sometimes do. Leveling feet are provided by the owner of the machine.

I will never again buy a machine off the internet without looking at it.

Even looking at a lathe & running it under power is no guarantee that there will be no problems. To get a problem free lathe in the year 2011 means paying a minimum of $20,000 or more. There are ready to run machines from the USA & Eastern Europe that are plug-n-play, but they cost ten times more than a similar size Chinese machine.

Here's one example ... my Chinese 14x40 heavy costs $11,950 (with taper attachment, DRO, & 5C collet chuck) plus truck freight. Fit & finish aren't terrible, but certainly nothing to write home about. Before starting the boring & reaming of flash lights, the alignment of the tailstock was checked - thank Goodness. Left-to-right alignment was dead on, which is no surprise since the set over is easily adjusted by even the lowest skilled Chinese worker. BUT the tailstock sat .010" low. No big deal, just five miserable hours of milling, grinding, scraping & shimming to correct a major defect that should have never passed quality control. The inside surfaces of the TS looked like they had been ground with a brick. All this on a machine costing nearly $12k.

Chinese machines, whether from Matt or Enco or Grizzly, will need some amount of work. Figure 40 hours more or less, normally done a few hours at a time as issues arise. Not much way around this, other than spending $20k or more.

Don't give up. You'll learn a lot about your machine as you work through each small problem. After a while, it will run the way you want it to & turn out nice work. It's a process that we all go through.