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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: Boxford missing a Nut
23/05/2020 21:33:50

It's a 1/4" BSW round nut with a slight dome top and a slot across it. You need a screwdriver with a slot ground in the middle of the blade to tighten it.

Thread: Myford S7 Cutting Barrel Shaped Cylinders
23/05/2020 21:26:57
Posted by Tony Pratt 1 on 23/05/2020 20:26:30:

I doubt if the head stock is 'out of line' but it could be? I will await developments maybe a twisted bed is causing barreling but wear in the bed is the likely cause, note OP's wear figures

Tony

How is the headstock located on the bed? Is it on the bolts or keyed between the shears? You wouldn't need much of a gap, or much of a bump on one corner of the key to cause a few thou out over a few inches.

23/05/2020 19:57:14
Posted by Mike Donnerstag on 23/05/2020 19:48:35:

Tony Pratt 1: Whenever I've set up the bed in the past (only had the lathe since Jan 2019) I used the collar method, but then I found discrepancies when turning a shaft of a shorter or longer length, hence why I tested the bed by machining the whole length of the shaft today under power at the slowest gearbox speed.

This is a classic symptom of compensating for an out-of line headstock by inducing twist in the bed.

Can you get your hands on a machinist's level to get the bed un-twisted?

23/05/2020 19:55:24
Posted by Mike Donnerstag on 23/05/2020 19:48:35:

Tony Pratt 1: Whenever I've set up the bed in the past (only had the lathe since Jan 2019) I used the collar method, but then I found discrepancies when turning a shaft of a shorter or longer length, hence why I tested the bed by machining the whole length of the shaft today under power at the slowest gearbox speed.

This is a classic symptom of compensating for an out-of line headstock by inducing twist in the bed.

Can you get your hands on a machinist's level to get the bed un-twisted?

Thread: Myford MG9 grinder
23/05/2020 19:42:38

Andrew,

Does your manual contain general setup, maintenance and lubrication info? If it does then at least it'll give me some pointers.

Pete.

Thread: Myford S7 Cutting Barrel Shaped Cylinders
23/05/2020 18:49:46
Posted by Martin Kyte on 23/05/2020 17:36:13:

Are we talking about a shaft or a bore

I'm thinking combunation of spindle bearings not set up correctly plus bed not level.

So acombination of work deflection which get smaller towards the chuck and a taper because you have adusted the bed to compensate for the deflection.

What does everyone else think?

regards Martin

All sorts of weird thing happen when you induce twist. What he has going on is very unusual if a tailstock centre is not being used.

Thread: Myford MG9 grinder
23/05/2020 18:05:20

Does anyone here own one of these little grinders?

I've been lucky to get hold one, collecting it tomorrow. The seller has no literature for it and couldn't find any when he tried. I'm surprised at how little info of any kind there is about for this machine given the abundance of it for the lathes etc.

If anyone has or had one of these and has any literature I'd pay a token fee for a scan of it. Equally any current owners feel free to chip in with any tips for operation etc I'd be happy to hear from them.

I'll post pics of it when I have it home and assembled of course, it's easy to find on the homeworkshop site in the meantime.

Thanks

Pete.

Thread: DRO error
23/05/2020 12:26:22
Posted by Andrew Johnston on 23/05/2020 12:11:56:

Is this a case of more not necessarily being better?

Andrew

I dunno Andrew, it sounds like mine is just like yours except you have to specify 360 for a full-circle. It remembers the setting though so I never change it and like you I've never had to drill an arc of holes.

I suppose it's no harm having that function even if you never use it, when it doesn't complicate 'normal' useage.

23/05/2020 11:55:03

Different DRO's handle it differently too you'll have to experiment (or read the manual)

For instance, mine will give an error if you set the end angle to 0. If you specify end angle as 360 it'll put a full-circle pattern in starting from the start angle (regardless of the value) but if you specify anything below 360 it'll put a part-circle pattern in between the start angle and the end angle. It might seem strange at first but it makes a lot of sense.

Thread: Making new gib strip for cross slide
21/05/2020 22:17:47
Posted by David Davies 8 on 21/05/2020 22:03:59:

Pete

I hadn't considered using the top slide for Infeed but in that circumstance the gib should be nearest the tailstock as you have stated. In that case the Myford would have its gib nearest the chuck.

I wasn't aware that the Boxford had a facility for a cross slide stop. Can you expand on this as I can see it would be useful for screwcutting instead of checking the dial before starting the next pass?

cheers

Dave

Sure Dave. On the front of the cross slide is a tapped hole. You clamp a stop on the front of the dovetail and a bolt passes through it and screws into that hole. You can adjust the bolt depth to set the stop distance.

Here it is posted previously on this site.

Pete.

Thread: The sneering detractors
21/05/2020 18:09:51

I believe that it is your duty to point out bad or dangerous practices, especially on Youtube. Some people believe that content at any cost is the way to go. That's fine for funny cat videos but not so good when the uninitiated watch popular content providers using practices that make sense to them not realising that they are entirely unsuitable.

How you go about it is another matter.

Thread: Making new gib strip for cross slide
21/05/2020 18:04:59
Posted by David Davies 8 on 21/05/2020 07:06:43:

Hopper commented:-

"Cutting forces are borne by the opposite solid dovetail surface."

Yes, but one exception is the Boxford top slide. Heaven knows why they made it that way round. I presume that the Southbend and all its other clones are the same?

Cheers

Dave

You mean why is the Boxford top slide gib away from the operator? That is probably because the cross slide has the facility for a threading stop. You would swing the top slide around so that it can be used for in-feed and the cross-slide threading stop used for rapid retract and re-positioning. With the top slide swung around to either 0 degrees or 30/whatever your preference the gib would now be away from the chuck and the fixed way carrying the bulk of the cutting forces when threading towards the chuck. My South Bend and my Monarch both have threading stops and both are like this.

Thread: Internal threading question
21/05/2020 06:21:15

The tool can do it if you can. You need the thread diameter less double depth for comfort 16-2-2=12mm so you have 2+mm clearance up the hole (actual minor diameter is 13.84mm). The only thing to check is that they do a 2mm insert for that holder.

You could buy quite a few taps for the cost of it mind.

Edited By Pete Rimmer on 21/05/2020 06:24:59

Thread: Making new gib strip for cross slide
21/05/2020 06:12:14
Posted by Jon Cameron on 20/05/2020 19:05:57:

I've been watching this thread and replies with interest it was a question I was going to ask.

I intended to use black steel, and then Polish it on plate glass with fine abrasive paper. Working upto using simply some brasso or autosol, on the backing paper. The gib I have is too thick for the new saddle I have for my ML4. The old one had been previously machined and included a 10thou error when traversing the cross slide from front to back. (Ie was higher at the far end than when it started it's journey).

The whole bed needs grinding or scraping, but it isn't a skill I've practiced and will leave that for another day, also on the ML4 is not likely to see any return in any future sale/upgrade, despite the return of accuracy over the next few years of using it. But that's another story.

Edited By Jon Cameron on 20/05/2020 19:06:19

Jon,

Steel is fine for a gib strip but the very last thing you want is a polished surface. It leaves no room for the oil film and promotes stick-slip and wear. Milling a piece of steel to thickness and using it as-is would be preferable. Scraping the finish on it would be better still.

Rowan.

Brass is easy to work and looks good but it's a poor choice of material for a gib strip. It's too soft and will pick up dirt which then starts to lap the opposing face. The contact face polishes up quickly and then wrings out the oil film as above. Brass also tends to smear if lubrication is even mildly neglected.

Steel is a good material, so long as you don't use something super-gummy. Unhardened gauge plate is very good. Cast iron is also very good material for gibs. A nice hard bronze would also be good, again with a milled or scraped finish.

Thread: Large rotary tool holding device
20/05/2020 20:23:04

Thanks Alan, it appears to be in typical Jones and Shipman blue and a quick search on google images brings up several matching items.

It's a Jones and Shipman Radius Dresser. Should fetch a pretty penny Craig if you decide to sell it.

20/05/2020 19:44:46

I would say that it's very likely a radius dressing tool for abrasive wheels. The hole is to hold a dressing diamond.

Thread: Lathe work
18/05/2020 17:57:16

John,

Give me the jaw width, slot width and tooth pitch of your jaws. I'll check what I have.

Also, a better check than using the square is to put two jaws on your surface plate with the gripping faces against each other, that way you aren't measuring any error in the square.

Finally, if those two jaws really are touching at the tips whatever you clamp in them (lightly) should rock about in the chuck if you wrench the other end about with your hand. You should easily feel (or hear) this. Does it happen?

17/05/2020 15:14:41

Give me the dimensions off your jaws I have three loose sets here.

That is not to say that I am agreeing with your diagnosis, there could be any number of things going on there, but if I have a suitable set you are welcome to them.

17/05/2020 12:54:02

John,

Don't be dismayed it can take a bit of getting your head around.

Firstly, you don't want to check that the jaws are parallel to the axis of the lathe, they need to be parallel with the axis of the spindle. The spindle might not (probably is not) parallel to the axis of the lathe. The bed might not be free of twist, it might (will) have wear or the headstock might not be exactly aligned with the axis of the lathe - easily possible with the the Myford 7 because of the flat ways. For all these reasons you cannot rely on any measurement which involves moving the saddle.

Your problem is that the axis of the test bar is not parallel with the axis of the spindle when it's turning. I would suggest that you work through my points 1-5 above and eliminate each in turn. You could start by testing the face and OD of the chuck, because being a fairly good quality item so long as it has been handled well it should run very close to true. If the face runs out, you have a register issue on the chuck or on the spindle. If the OD runs out you might have a burr on either register or trapped swarf in the threads. In any case I would start with that check and if you find an anomaly, remove the chuck and check for dirt, swarf and bruised registers. If you check the chuck and find no runout on either the OD or the face, leave the jaws and check the bar on vee blocks.

You are quite right in that you will never turn your test bar in the 3-jaw, that is a between-centres job.

17/05/2020 11:31:40
Posted by John Baron on 17/05/2020 10:45:57:

Hi Guys,

Pete is the winner I think.

[quote] The chuck body runs true but the jaws do not hold the part straight. If all of the above check out OK, this is the last option.[/quote]

Comments below the pictures. By the way I somehow managed to take a video but the forum won't let me upload it.

17-05-2020-01.jpg

I used a 1" inch parallel to check how straight the jaw was. I used a piece of postcard and a small dowel to hold the parallel tight up against the jaw face. I set the dial gauge so that it was level with the edge of the parallel.

17-05-2020-02.jpg

In this picture you can see the arrangement. This is jaw No:4. I used the lower jaw to support the parallel.

17-05-2020-03.jpg

In this picture I've run the dial gauge down to the end of the parallel. It shows that its moved away by about 0.6 mm.

17-05-2020-04.jpg

Sorry about the colour, fluorescent lighting. This jaw No1 was the worst one. I stopped taking pictures at this point.

All the jaws have some runout when measured in this way ! I'm not sure why but they all seem to run away from the tool holder. The worst ones were jaws 1 and 2. When I gripped the parallel by the flat sides you could see that the indentations in the cardboard were deeper on one side.

 

It also explains why I can set the work piece true at either end and its out at the other.

 

So it seems that I've got the source of the problem... badly or wrongly ground jaws. After all this time I doubt that there is any point in having a word with Pratt Burnard.

 

To answer some questions:

Yes the chuck is the original slim body one that was supplied with the lathe when I bought it directly from Myford. They arranged with Denford to deliver and set the lathe up. At the time Denford made bridgeport mini mills that were badged and sold by Myford. Its had three homes since I bought it.

 

Thanks for all the comments and suggestions. Now to think about what I'm going to do about it.

 

 

Edited By John Baron on 17/05/2020 10:48:16

I'm sorry John but that test you show could be reading bed twist (or wear). All of the checks you make need to be rotational checks. Your issue is one of runout, so all your checks need to be for runout.

Edited By Pete Rimmer on 17/05/2020 11:32:54

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