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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: Facing parallel between centres.
13/09/2020 08:26:18

Whilst that is true the practicalities are that for bringing two clamping faces of a riser parallel, eye-balling the points will be sufficient.

The most likely source of error is that the live centre was not turning on axis.

Robin you should put your centre in the spindle and set a DTI on the side near the point. It must not have any runout.

Thread: Eagle 3 Surface Grinder - Moving Query
11/09/2020 17:57:06

You can split the head-column-base then 2 strong men can load it into a car but I think a hatchback might need 2 trips. I'm fairly strong and the bare column/base casting is about all I could manage.

As for inspection - a couple of things to watch out for is the z-axis ways tend to get neglected for lube. The cast iron picks up on the opposing way and you can get a gouge in the middle of the way. There's no lubrication points that I could find and I had to add some. The y-axis (up and down) screw wears heavily in one spot. The spindle bearings are rare as a dodo that's been crapped on by a rocking horse, so take a part along and grind it. If you get a fish-scale finish your bearings are probably shot. Dress the wheel and grind again. If no improvement then figure on new bearings. You can probably hear them clattering if they are worn.

 

Edited By Pete Rimmer on 11/09/2020 17:58:05

Thread: More Alba a1 advise
06/09/2020 15:11:14

14 thou interference will break the casting for sure. I'd go for a light press fit and use Loctite. Perhaps relieve the middle a couple of thou so you don't squeeze out all the Loctite completely.

Thread: Emco 8.6 - Tumble Reverse Position for Screwcutting?
04/09/2020 17:10:22

The tumbler reverse only changes the direction of the leadscrew, so it will cut a left hand or right hand thread as required. Most threads are right hand.

If the spindle and leadscrew are turning the same direction you'll cut a right hand thread. If they are turning opposite directions you'll cut a left hand thread.

Thread: Faceplate workholding.
01/09/2020 06:44:50

You'll never achieve your best results by bolting to the faceplate. Any runout in the face of the plate will be reflected in the end of the part, and the OD. Turning between a pair of solid centres is the proper way.

 

Edited By Pete Rimmer on 01/09/2020 06:47:09

Thread: Grinding my own external grooving cutter
30/08/2020 18:41:02

If the groove is shallow then you won't have any problem. If the groove is deeper or if you're parting (especially with that 1/8" tool) then you'll need to use coolant. Most of the problems that people have with parting, on machines that would otherwise not struggle, is from not using coolant. Parting generates a lot of heat which makes both the tool/tip and the swarf expand. Because the tool (and the swarf) is the exact same width as the cut you're making it takes an incredibly small amount of expansion to make the tool expand in the groove and start to bind. If the swarf backs up in the cut it'll trap heat in there and exacerbate the problem. Once that expansion starts the heat generated sky-rockets and in moments your tool is buried in the groove, the lathe stalls and if you're really unlucky something breaks.

30/08/2020 15:43:04

If you feel that you'll need to touch up the front edge often, grind it steep like the diagram (but not so much) and put a much shallower primary angle right under the cutting edge. That way when you do need to touch it up you'll only have a small facet to dress, not the whole face.

Thread: Is a hand scraper pulled or pushed?
25/08/2020 20:50:31

Apprentice masters needed something to keep them entertained through the mayhem I suppose :D

I wonder how much scraping work was required from fresh-planed to finished article?

25/08/2020 18:57:14

I see the 'three plate' test often quoted but it's not very relevant in these days of good quality affordable granite plates. They make a more than adequate reference for scraping in other references such as straight edges and smaller iron plates.

Thread: Blown band saw circuit.
23/08/2020 18:06:56

I don't think that the capacitor is designed to be switched out of the circuit, not by looking at that circuit diagram anyway. Two leads come out of the motor and go to only one switch terminal (one with the cap in series). This suggests that the cap and start winding are always live with the run winding.

What's not apparent is how the contacts are connected by switching.

Thread: Computer Disaster! Help needed!
23/08/2020 14:28:20
Posted by Martin King 2 on 23/08/2020 13:35:54:

Delete and escape keys during restart have no effect, same problem, gets to desktop background image for few seconds then green screen.

Bahhhhh!

Martin

This smacks of an overheating issue. How long since the case was blown out? If it's full of dust - don't hoover it, use a brush or an air line.

23/08/2020 12:16:51

Martin,

Check the power light on the front.when you try to start it up. If it's orange instead of green then you have a failing power supply.

Pete

Thread: Hydraulic ram machining
23/08/2020 07:08:38

Our machines at work have induction-hardened hydraulic ram piston rods. They are machinable with carbide and give a superb finish until you're through the hardened layer then the machinability increases but the finish is not nearly so good.

Thread: Is a hand scraper pulled or pushed?
22/08/2020 21:34:37

I've used all sorts of things, some old flat carbide facemill tips that someone had a bunch of, some carbide slips, some carbide that a guy I know got made quite cheaply. They all work to varying degrees but nothing I've used so far had compared to the Sandvik or Biax tips for holding an edge.

I got lucky a while ago and bought a box of 5 tips from eBay America quite cheaply. Those have all gone now, mostly passed on to other budding scrapers so I've just bought another box of 5 which have worked out about £20 each.

22/08/2020 19:47:37

Thank you Bill I just bought a pack of those. I'm going to try them out as scrapers for small dovetails, where the larger blades are too cumbersome.

Pete.

22/08/2020 06:33:31

By the way - test your scraper on your thmb nail. If it slides it's not sharp, it should dig in on the edge very readily. Check the middle of the scraper edge then test one side of middle (where you barely use it). If the edge cuts more then the middle you're not sharp.

I self-taught and never knew what a sharp blade really was until I took some instruction.

22/08/2020 06:29:39

It's down to the amount you grind off. The 3000 grit in the photo is already done - I have a pile of them like that. The amount you'll blunt the edge by is more than the amount you'll be grinding off so you can't bring the edge back truly sharp. Also you're very sensitive to the angle you are grinding at - just like the novice HSS tool grinder who produces a beautiful facet but neglects the cutting edge.

Use the 1500 and when you grind the initial shape grind it square then do your sharpening at 2-5 degrees negative. That way your first dozen or so sharpens will be grinding a very thin land taking less time and using less diamonds. If you can, clean the wheel with a spritz of brake cleaner on a paper towel or rag.

Pete.

21/08/2020 22:11:13

Bill, use a 1500 grit disc at 400rpm or less. You'll get a great cutting edge. your 3000 grit disc is too fine and the 1500 will give a huge improvement IMO.

Thread: Home Workshop site
21/08/2020 21:36:18

Adam, thanks for the update, and your efforts. Homeworkshop is one of my favourite sites and seems to be quite unique in what it does.

Thread: Is a hand scraper pulled or pushed?
21/08/2020 21:34:10

There are push scrapers and pull scrapers. The majority will be push scrapers. Push scraping tends to remove more material. Pull scrapers should be easy to spot since they will hold the cutting tip vertically, but it's not a rule.

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