Author Topic: Chester 7x minilathe - the headstock of doom (Read 14507 times)

Andy · « **on:** November 16, 2009, 04:21:48 AM »

I stripped my Chester branded 7x minilathe down, intending to do some work on the bed and make a start on adding some proper gibs to the carriage. I also wanted to have a look at lubrication inside the headstock. I had squirted some white lithium grease in there (through the screw holes) when I got the lathe, but it has always felt a bit rough when swapping from high to low, and when turning the chuck by hand.

Here’s my ‘pride and joy’ at the moment –

The bed isn’t that curved – it is the wide angle lens doing that. The only sort of lens to use in the 6 foot x 6 foot ex-coal cellar that I call my workshop.

Anyway, this has now turned into a bigger job because I discovered a problem with the countershaft bearings that must have been there since the lathe was manufactured (if that is the right word).

Turning the shaft by hand (with the gears in the central neutral position) was very difficult and rough feeling. Bear in mind that this was without the motor connected, just the shaft itself turning.

I hadn’t planned to strip the headstock but ended up doing so to find out what was going on. I got the countershaft out. One bearing came with it, the other stayed put. Both bearings felt as rough as a badger’s bum. Both were the same size, but with different types of shielding. The one still in the casting had two dents in the metal shielding (highlighted) –

It looks like the ‘fitter’ was having a bad day when he knocked this one in, or maybe it was already damaged before he picked it up. The other bearing has plastic shielding and shows no outward signs of damage. I think it is just a cr*p bearing.

So I’ve ordered some new bearings from Arc Euro. I had to strip the whole head down to do this job properly, so all will get a good coat of looking at and a generous application of the appropriate grease before it goes back together. If I can get hold of some metal gears in the very near future I’ll put them in – it would seem sensible while it is stripped. Trouble is, ARC are out of stock until early next year and I don’t want to order from USA just now.

Andy · « **Reply #1 on:** November 16, 2009, 04:23:49 AM »

Here is the gear change selector fork thing from my headstock.

Lovely isn’t it? Are they having a laugh? It rotates on the round bit, which fits into a lever. I can see me making a new one of these. It needs to be a bit smoother than the original shown here so I will try making it whilst wearing a blindfold and with one hand tied behind my back.

Gerhard Olivier · « **Reply #2 on:** November 16, 2009, 05:56:22 AM »

Someone took pride in that job???? Good luck with rebuild.

Are you going to replace with tapered roller bearing while u got it all open??

Gerhard

Darren · « **Reply #3 on:** November 16, 2009, 06:30:59 AM »

Andy,

If it were me I would avoid purchasing a bearing from someone who supplies these lathes, they might be from the same source. Just go to your local "Bearing Man" with the numbers on the bearings. They will be able to help you. At the same time fit taper rollers to the spindle, you will find a good improvement.

btw in no way am I putting Arc Euro down, they are first class to deal with and I use them all the time.

http://www.bmltd.co.uk/

Andy · « **Reply #4 on:** November 16, 2009, 06:50:50 AM »

Yes, thought about that - no point in buying more of the same junk - but the ones I've ordered from ARC are Japanese ones made by Nachi so I was thinking they'd be alright. I will be able to tell the difference when they arrive - I think the ones in my machine were knackered from new, not as a result of wear.

Darren · « **Reply #5 on:** November 16, 2009, 06:52:24 AM »

OK then they should be fine? It was just a thought

Andy · « **Reply #6 on:** November 16, 2009, 06:58:01 AM »

Darren - very much hope so. Sale of Goods, fit for purpose? Much on my mind at the moment...

Gerhard, thanks, I'd like to fit taper bearings but originals seem fine and I can't really afford it. Will think about this a bit more. At this rate I will have replaced quite a bit of the lathe. Perhaps the suppliers would like to just sell us the good bits and tell us where to buy the rest (or how to make it).

andyf · « **Reply #7 on:** November 16, 2009, 07:08:21 AM »

As to the headstock gears, many on the Yahoo 7x12 group seem to favour plastic for one or both of them, to act as a mechanical fuse and prevent more expensive damage if you crash the tool But you'll never ever do that, will you? No, I thought not

If you can't wait, Little Machine Shop in California is the place to go. I have bought stuff from them in the past which arrived here in the UK a week later, and the shipping charges were very reasonable.

Andy

Andy · « **Reply #8 on:** November 16, 2009, 07:17:03 AM »

That's interesting Andy, didn't know that about the gears.
I'm aware of LMS but I'm not in the habit of buying direct from overseas. Maybe I should give it a go. I must admit that the thought of carriage costs and possible import duty has put me off. I need to change my mindset, maybe.

websterz · « **Reply #9 on:** November 16, 2009, 07:28:53 AM »

I bought my metal gear set from MicroMark. All the tools for the changeout were included. Got the kit on sale for under $60.00.

2 sets of tapered roller bearings (same bearings in my lathe and mill) from an online supplier cost another $60.00. Now I just have to install it all.

As for the mechanical fuse theory, just replace the spindle gears with metal since they are the hardest of the gears to get to. Keep using the plastic gear on the countershaft as it is much easier to change. This still offers crash protection but in the end is much simpler to repair.

Andy · « **Reply #10 on:** November 16, 2009, 07:34:10 AM »

Websterz - thanks for that. More to think about there.

SKIPRAT · « **Reply #11 on:** November 16, 2009, 07:55:06 AM »

Hi Andy

just go to your local bearing supplier as i know from experience that there is no way a supplier of bearings to industry is going to sell you junk i have used them for washing machine and tumbler dryer bearings in the past and theese suppliers have a reputation to keep up as industry dont want bearings failing to frequently by the way the numbers on the bearings relate to the size,type and working conditions of the bearings listed in what is known as "the international bearing catalouge " you just search for the numbers and lettters engraved on the bearing and you come up with the goods good hunting.By the way my lathe is a BV20 8X14 with a geared head taper roller headstock and steel changewheels wiith a vee belt drive from the motor to the headstock gearbox this belt if set on the easy side would act as a mechanical fuse.I was put off buying a new 7X12 lathe by those dreaded plastic gears and waited till a used lathe with geared head and steel change wheels came along at the right price .I have found by working on machinery in industry both operating and repairing it has been the practice for many years to incorparate a "weak link " it can be a non metal gear or a "shear pin " usually in the drive or the gear train because sooner ar later you are going to dig in or clout the chuck yes i have done both and the weak link has kicked in every time so i would not recomend too positive a drive as in the past the office dollys walking through the machine shop can be quite distracting ,

Cheers Paul

Andy · « **Reply #12 on:** November 16, 2009, 10:25:01 AM »

Thanks Skiprat. From what you and others have said it looks like I should keep one plastic gear. I've been doing some fairly heavy work on that lathe for over a year now and had no 'incidents', maybe due to the absence of dolly birds passing by (there is no room for them in the shop

). I will play safe and fit plastic to the countershaft, easier to replace, as websterz advises, if it all goes wrong.

I looked at the BV20 lathe but ended up with the minilathe due to lack of funds at the time. I think with hindsight I should have gone for something a bit bigger for what I do. Anyway, my mission is to get this one in a better state for now. Who knows, the Machinery Fairy may pay a visit some day.

SKIPRAT · « **Reply #13 on:** November 16, 2009, 11:39:26 AM »

Hi Andy

The reason i ended up with my BV20 was that it was advertised in Home Workshop Ads. the price was right at £350 and it was fairly local to me in cleethorpes about 45 miles away and belonged to a model engineer who was upsizing and had just bought a larger Warco lathe and needed workshop space.My lathe is the Axminster Tools version and is a sort of ivory colour not much bigger in capacity than the minilathe but built a lot more ridgid and heavier it weighs around 140 Kilos i dont think it was made by Seig as fit of things and workmanship such as hand scraped and fitted slides and the general finish seems a lot better than their products.I have also carefully adjusted the pre load on the spindle bearings and it can do a 3mm depth of cut on EN24 tensile steel with no problems the other thing i have done is i as the bottom speed was 170 RPM i have changed the pulleys on the motor and headstock gearbox to give me a more usable bottom speed of 75R RPM as screwcutting at 170 RPM can be quite hairy to say the least by dropping the speed down it has also increased the torque and as i still have the original pulleys by swapping pulleys around i have also got choice of different ratios between the motor and the headstock pulleys plus the six speeds in the gearbox

Andy · « **Reply #14 on:** November 16, 2009, 11:55:58 AM »

Sounds great. I remember Axminster doing a little feature on it in their magazine when they started selling that lathe. I have bought a few bits of machinery from them and not been disappointed for the price.

Back on track, I've had a close look at the countershaft. Really scuffed where it went into one of the bearings, and has (or rather, had - sorted now) a lot of little dings and sharp crests on it where the gear slides up and down. It looked like it was thrown up and down the factory before being installed. At least it is straight.

Stilldrillin · « **Reply #15 on:** November 16, 2009, 01:07:40 PM »

Andy,

Don`t replace those orrible original bearings!

The taper roller transformation is well worth the £15, from Arc......

David D

John Rudd · « **Reply #16 on:** November 16, 2009, 01:29:14 PM »

Just as a slight aside,

I changed the bearings in my mini mill for tapers....much better...

Andy · « **Reply #17 on:** November 16, 2009, 01:50:04 PM »

OK, you lot have convinced me! Taper bearings it is then. In for a penny, in for a pound...

John Rudd · « **Reply #18 on:** November 16, 2009, 02:40:36 PM »

Quote from: Andy on November 16, 2009, 01:50:04 PM

OK, you lot have convinced me! Taper bearings it is then. In for a penny, in for a pound...

Errmmm more like a few pounds....

I got my bearings from George Lodge in Hull and iirc they were around £29.....

but then they were SKF bearingsnot some dubious Chinese articles....

Stilldrillin · « **Reply #19 on:** November 17, 2009, 03:22:17 AM »

I didn`t think Arc sold dubious Chinese articles!

I believe a many forum members are very satisfied with their quality.....

David D

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Author Topic: Chester 7x minilathe - the headstock of doom (Read 14507 times)