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Member postings for Pete Rimmer

Here is a list of all the postings Pete Rimmer has made in our forums. Click on a thread name to jump to the thread.

Thread: 3 leg hone
29/12/2020 00:02:44

Take care that you don't bell-mouth both ends. Go slow and take measurements often.

Edited By Pete Rimmer on 29/12/2020 00:15:46

Thread: South Bend Heavy Ten Fixed Steady
28/12/2020 21:02:20
Posted by Roger Best on 28/12/2020 19:50:03:
Posted by Pete Rimmer on 27/12/2020 19:00:11:

I would appreciate it if I could get a good pic of the metric setup diagram Roger. I mean to make a metric banjo and gear set of my own. Would you be able to take a photo of it do you think?

Pete.

I have put three images in my album at different resolutions, I probably should have cropped them down. (DOH!)

cimg9370.jpg

Seems like the forum has re-sized them all to 1024. No matter, they are legible so I'm off to make a set of gears and a banjo.

Thanks Roger.

Thread: From a leaky nose to a bent nose
28/12/2020 00:27:54
Posted by fizzy on 28/12/2020 00:17:46:

not a bent spindle - what do you percieve a bent spindle would do? non of the proposed issues would show as a face plate out by 10 thou per half revolution...parts are rocking well and good...bent spindle. The other factors wouldnt cause the face plate to wobble.

Slow down there's no need to get defensive. You never mentioned rocking parts or face plate wobbling - you just said it was 'well out' which given the taper issue I took to mean you were running a DTI across the face and the reading was changing. Your main concern was the taper you're turning and that IS the one thing that wouldn't be caused by a bent spindle.

Gotta be more concise with your info if you're hoping for good advice.

27/12/2020 23:38:33

A bent spindle shouldn't produce a taper. Once you've done a clean-up pass the part is turning on the spindle axis so every pass after that should be consistantly true regardless of the state of the spindle nose or the chuck etc, so long as the chuck isn't rocking on the seat or the part rocking in the jaws but that should be evident in the finish.

Turning an unwanted taper is a geometry issue. Mis-aligned headstock, twisted bed, severe wear, but not a bent spindle.

Thread: South Bend Heavy Ten Fixed Steady
27/12/2020 19:00:11

I would appreciate it if I could get a good pic of the metric setup diagram Roger. I mean to make a metric banjo and gear set of my own. Would you be able to take a photo of it do you think?

Pete.

27/12/2020 17:23:13

Lucky to find that steady, they are rare as hens teeth. I have the same machine (less the taper attachment) which I'm just finishing rebuilding. I don't know of any other small lathe with a larger spindle bore. I put a dial gauge on the internal taper on mine and it didn't even move as much as a tenth.

Do you have the metric threading banjo on yours?

Thread: cateracts.
25/12/2020 23:22:01
Posted by Clive Hartland on 25/12/2020 22:29:12:

I did read in the paper that the eyehospital in London are to increase cateract ops. by 9 teams doing 30 a day as the backlog has increased enormously since corona virus disrupted things.

Moorfields? I had an eye operation there about 12 or 15 years ago to remove a piece of metal that had been fired javelin-style into my eyeball. I wouldn't hesitate to go back there for cataract surgery (which is almost inevitable since the aforementioned injury started one).

Nowhere better IMO but equally I would pay 5 grand all day long privately to get the results you did Clive.

Thread: Thread Dial Indicator Chart?
24/12/2020 13:08:21

DC31K is correct there is no need for a threading dial for any metric thread than is an integer of a metric leadscrew pitch. No need for waiting for a dial either, all you need is a little light pressure on the lhalf-nut lever until it drops in.

Posted by Bo'sun on 24/12/2020 11:16:50:

I now need to digest the above and maybe undertake some practical exercises to help me get my head around it.

It's easy to explain. Any thread pitch that will divide into 3mm will always line up every 3mm. So let's say you're cutting a 0.75mm thread. there are four of those every 3mm. If you had your tool engaged in the thread and stopped the machine, released the half-nuts and moved one pitch along the screw (3mm) then re-engaged the half-nuts the tool would now line up perfectly four threads from the previous. Do it again and it'll line up 8 threads away, again you'll be 12 threads away. It's literally impossible to get it wrong.

This is why some metric threading dial charts have a lot of pitches with no gear specified - it's not necessary.

There's some more info on it here:

https://www.model-engineer.co.uk/forums/postings.asp?th=131889

Thread: lost drive to power feed
21/12/2020 14:22:28
Posted by Mark Rand on 21/12/2020 13:32:16:

There is good news and bad news...

The old gearbox was still there under the surface table.

However

There is only the 20T gear because the 42T gear is part of the saddle assembly. The 20T gear is also rather badly worn. I suspect that it won't last all that well. One or more previous owners weren't all that bothered about lubrication, protection from brute force, moisture etc.

20201221_130621[1].jpg

As for the feedscrew key,the dogs should slide on to it without any force, but no noticeable clearance.. You may either have a small burr on the key or it isn't all the way into the keyseat.

You are welcome to the gears if you want them. Just PM me an address.

For what it's worth, I'd probably just use a collection of Myford changewheels, bore them out and Loctite them on to either manufactured bushes or the turned down originals.

Edited By Mark Rand on 21/12/2020 13:46:07

Mark can I impose on you to measure the centre distances for me?

21/12/2020 09:54:40

That's handy - saves me making them!

When will you know Mark? I have time right now if I have to make the gears but I won't have in the new year when I go back to work.

20/12/2020 22:46:29
Posted by DC31k on 20/12/2020 21:54:34:

Easiest way to confirm centre distances if it is difficult to do a direct measurement is to turn up two discs that are the pitch diameter of the two gears and bored to the correct measurement. Install on their shafts. If they interfere, the PDs are too big. If there is an excessive gap, the PDs are too small.

That'll work if directly measuring isn't feasible.

Pitch diameters should be 2.067" and 0.984"

20/12/2020 22:02:50

Yes a scotch/Dutch key would be a good way of fitting the replacement gear to the hub and there's plenty of room for it. I see no reason why the teeth would need to be timed in a power feed gearbox so that should be no issue IMO.

20/12/2020 21:35:54

Nothing's ever easy is it? Are the gears each end completely identical?

20/12/2020 21:33:09
Posted by Mark Guy on 20/12/2020 21:19:11:

Sorry My mistake the small gear is only 20 teeth and I’ve checked and checked them both again 20 and 42 teeth

Thank gawd for that I was going a bit crazy with those numbers.

These are 1.25mod gears. Measure every dimension and I'll knock them out for you. You will have to give me centre distance as close as you can measure it. It should be 1.526"

20/12/2020 21:03:17

Maing a new gear is easier.

For 1.25 mod gears the base diameters should be 1.942" and 0.971"

For 20DP they should be 1.973" and 0.987"

That is if neither are profile-shifted. What is your measurements across the bottom of the tooth gaps? You'll have to do a best-effort for the 21T seeing as it's an odd number and small diameter to boot.

20/12/2020 19:44:12

2.164" is almost exactly 55mm that makes it work out perfectly as a 1.25 MOD gear.

The 21 tooth should be 28.75mm dimeter and the centre distances should be 39.375mm supposing they are not profile shifted.

If you can give me the centre distances VERY accurately I can make both for you. The only concern I have is the big gear looks to have a bushing pressed into it, which usually means it engages with two gears. Is that the case?

Thread: Cross drilling in the lathe
17/12/2020 15:17:18

He has a 150mm piece of 50mm bar, and wants to cross-drill it 50mm from the end and put a 1.25" thread in the hole.

Thread: Shimming Techniques
17/12/2020 12:17:50
Posted by John Hinkley on 14/12/2020 14:26:51:

If you really want to squirt epoxy in the gap to tram it, you could look at Stefan Gotteswinter's YouTube video where he does just that. I wouldn't want to try it myself, but he gets it to work. I don't have anywhere near his skill level, though.

Link to Epoxy tramming

John

Slower typer than Tony!

Edited By John Hinkley on 14/12/2020 14:27:21

There is a fundamental step missing from that video.

In order for the mill geometry to be aligned properly you need to align the column way not to the table but to the table's x and y ways. Using the table is fine so long as you first check that the table's surface IS parallel to the working ways. Doing this is easy - just put a parallel on the table surface and indicate the top of it with a dial whilst traversing the table in X, then turn the parallel and do the same check in Y.

Note that this isn't the only check that you should make if you're properly re-aligning the machine, but it is all you can do without dismantling it. It will at least confirm if the table top is parallel to it's direction of travel which is what you require if you're going to follow the video in your efforts. If you make the above checks and you find that your indicator moves, you'll have to decide what to do next to bring your errors to a minimum because if the top of the table isn't parallel to the direction of travel all you'll be doing is machining steps in your work.

Also note that you cannot use the spindle's rotation to do any of the above (in the traditional sense of 'tramming' ), that would be aligning the table to the spindle's axis, not the column. Aligning the spindle's axis would be the last step in aligning the machine.

Edited By Pete Rimmer on 17/12/2020 12:18:54

Thread: Cross drilling in the lathe
16/12/2020 17:31:37

You need a crotch centre for your tailstock. An old-school method for using large drills in the lathe but very effective. Drill a pilot hole using the crotch centre then put the drill in the tailstock, slide the part onto the drill then clamp it to a faceplate whilst using the drill as a guide to keep it aligned. Once it's all clamped up, drill and bore the hole then cut the thread.

Edited By Pete Rimmer on 16/12/2020 17:34:37

Thread: Pull-Push Scraper
16/12/2020 11:54:11

That's a nice looking design Graham.

Is there any amount of spring in the scraper or is it fairly rigid?

Pete.

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