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Member postings for Hopper

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

Thread: How can I remove this mould from painted surface?
02/04/2020 05:36:08

Here in the tropics where we get 8 feet of rain a year snd things tend to go a bit mouldy we generally use a mix of household detergent and bleach. Bloke i pay to do the outside of my house swears by it too .

Thread: Model of an epicyclic gear made by apprentices
02/04/2020 01:05:20

Bit like the sound of water hammer/priming in a super-heated steam line between power station boiler and turbine, which was what caused the above turbine failure to start with. Still makes my buttocks clench 40 years later!

Edited By Hopper on 02/04/2020 01:05:59

02/04/2020 00:03:58

I vaguely remember working on Allen diesel engines years ago. Great big ones that you could stand up inside the crankcase -- as you could do after one tossed a con rod right out through the side of the case!. Used as start-up-from-cold power in an oil- fired power station to power the boiler feed pumps and control systems on start up. But when the power station suffered a major turbine failure and the engineers hooked the diesel generators into the grid to stop the alumina refinery from setting soild like concrete and ran them flat out for two days they did not like it so much! Probably a result of having sat unused for years.

Edited By Hopper on 02/04/2020 00:04:46

Thread: Bottom of the beginners heap
01/04/2020 23:51:36

Welcome to the forum. Plenty of us on here who mess about with ancient machine tools. Look forward to seeing the pics of your latest treasures.

Thread: Sourcing gunmetal for leadscrew nuts.
01/04/2020 10:51:46

You're welcome. Have fun with your old machine tool, and post some pics when you get the job done. Sounds interesting.

Thread: Threading and the tables
01/04/2020 10:45:51
Posted by Howard Lewis on 01/04/2020 10:27:22:

...

As an Apprentice, we were taught to truncate threads, to prevent interference between root and crest.

Exactly where I learned it. I vaguely remember seeing a Standard thread form drawing at tech college but they were certainly never referred to on the machine shop floor. The only crest radius in sight might have been from running a file down the thread to knock the burrs off.

I think the angst about radiuses and perfect forms has come about with the availabiliity of readymade full-form carbide inserts designed for use in production CNC work which is a whole different ball game. We just ground our own HSS tools and rubbed the tip on an oilstone a few times to round the end to stop edge chipping. Those were simpler times I guess.

Thread: Sourcing gunmetal for leadscrew nuts.
01/04/2020 04:51:57

Might pay to check the slide lock on your shaper too. If it is not clamping the tool slide solid while shaping is taking place, could be transferring too much load to the leadscrew which might account for your worn out nut.

Thread: Threading and the tables
01/04/2020 00:40:31
Posted by Nigel Graham 2 on 01/04/2020 00:13:39:

It's worth remembering that an insert tool or a chaser will only cut true rounded crests if the thread requires the full depth of the tool.

That's certainly true. But I never worry about getting the perfect tip radius etc -- that is all part of the angst brought about by looking at BS thread form drawings and the like. As Tubal Cain points out in his ME Handbook, you get something like 95 per cent thread strength with only 65 per cent thread engagement. What you want on the tips and roots of your threads is working clearance. So if the radius has a bit of a flat on the top of it, or is just one big flat, no big deal at all. In fact its good, because its providing working clearance and ensuring the thread is engaging on the flanks as it should do, and not on the tips and roots.

If we were making wing pivot bolts for space shuttles, things might be different. But for general work, not so. Horses for courses.

Thread: Square thread cutting
01/04/2020 00:34:21

Its a good idea and worth a try. Only problem might be a bit of weakness on the sides of the tool where the semi-circular shape does not support the edge as well as a conventionally ground square tool. But most of the cutting is on the front edge that would be well supported in the conventional manner so well worth trying out.

Thread: Sourcing gunmetal for leadscrew nuts.
01/04/2020 00:09:41

7/16" x 10 tpi square/acme thread is going to have a very small hole up the middle, necessitating a small and bendy boring bar for screwcutting. You might be best off using a tap, maybe rough out the thread form via screwcutting first. Or even screw cut a V thread to suitable dimension and then finish off with a tap. Tracy Tools does a lot of those types of tap for not too much loot. Be sure whether you want left or right hand thread before ordering though.

LG2 machines yes much like mild steel or even a bit easier thanks I suppose to the lead in it. Flat topped tool bit though. It's your tougher phosphor bronzes and the like that can be tough to machine.

Thread: Box-Ford travelling steady
31/03/2020 23:59:33
Posted by Roderick Jenkins on 31/03/2020 13:10:00:

The lathes database **LINK** Shows that the hyphen disappeared sometime around 1960

Rod

Edit: Too slow yet again!

Edited By Roderick Jenkins on 31/03/2020 13:11:27

I think that was the time of the great international hyphen shortage caused when they were all bought up and reforged into the ubiquitous grocer's apostrophes. (Or should that be apostrophe's?) Rarer than loo paper in a plague they were.

Thread: Threading and the tables
31/03/2020 23:53:33

Thread tables and British Standard diagrams etc etc cause way too much angst for use in the home workshop. They describe a theoretically perfect thread suitable only for a theoretically perfect world. You should throw them away.

In practice, you are better off to follow SOD's advice and instead calculate your thread depth for BSW or BSF etc as .6403 X pitch.

BUT you need to allow working clearance on real world threads. So for external threads, start with the outside diameter at least five thou smalller than the nominal size. So a 1/2" thread would have an actual diameter of .495". For larger threads, increase this clearance. A 1" diameter thread I would probably make outside diameter .990", so ten thou clearance.

Ditto internal threads. Make the hole up the middle five to ten thou larger than the nominal root diameter. And you find your nominal root diameter by deducting two thread depths (as calculated in the above formula.) from the nominal OD of the external thread.

Final sizing is done by try and fit with the nut or bolt the part is going to mate with. Or by using a tap for the final few thou if available. No shame in that. Quick and effective is always the best way of machining.

Get any of the old books by the old timers who screwcut all their lives without ever using a BS drawing in the workshop and learn the way screwcutting was done on manual lathes for the past 100 years or more. It is quite simple. Recommended: The Amateurs Lathe by LH Sparey for basics and Screwcutting in the Lathe by Martin Cleeve for more than anyone ever really wanted to know on the subject. .

Thread: Sourcing gunmetal for leadscrew nuts.
31/03/2020 11:54:31

You didnt say it was a shaper downfeed screw and nut. Subject to shaper impact forces. Much more than a lathe leadscrew. Consider using the LG2 for more tensile strength and toughness.

31/03/2020 09:35:24
Posted by not done it yet on 31/03/2020 09:33:24:
 

There are several (even many?) different ‘white’ metals. I have two lumps of either about ten or twenty kg each but I’m not sure of the grade.

LOL so much for it being hard to obtain then! You've got the market cornered.

(You havent been rushing out buying it up like toilet paper have your? wink )

Edited By Hopper on 31/03/2020 09:36:22

Thread: Pressure
31/03/2020 09:33:01

So if all this lockdown goes on for say six months as some gurus are predicting, and consequently most emissions are drastically reduced, I wonder if there will be a measurable slowdown in global warming, or even a reversal, as shown in recorded temps worldwide?

Baro pressure here in Sticksville, Australia, is the usual 1010 BTW. Still waiting for blue skies.

Thread: Box-Ford travelling steady
31/03/2020 09:27:06

On a British lathe, most likely If it looks (or feels) coarse it will be BSW or if it looks fine it will be BSF. Diameter will be the next standard fractional size up from the hole down the middle as measured with digital calipers or a rule. Threads tapped into cast iron on old Brit machinery seem to most often be BSW but not always.

 

Edited By Hopper on 31/03/2020 09:28:08

Thread: Lathe
31/03/2020 09:18:57

The marks on the piece in the photo look maybe like the feed is still in screwcutting mode. Looks like one set of marks about 1mm apart going in the right hand thread direction, then another set coming back in the left hand direction.

Looks like you maybe need to check your lathe owners manual and the settings of all your gearbox levers and change gears or whatever you changed when you went from fine feed to screw cutting. Sometimes you have to jiggle the headstock spindle back and forth as you change the gear levers on the gearbox so they can move to the new position fully.

A picture of the work after one cut without winding the carriage back would give a clearer view of how the tool is cutting. The return marks are somewhat confusing the issue I think.

Edited By Hopper on 31/03/2020 09:20:18

Thread: Sourcing gunmetal for leadscrew nuts.
31/03/2020 09:13:14

I would think it's easier to screwcut a lump of commonly available brass or bronze in the lathe. It's a basic job and no need for a furnace, crucible etc. (Or sneaking in to use the kitchen stove and a stainless saucepan while 'er indoors is out shopping.) . Plus, probably harder to buy white metal than gun metal these days. Kind of a lost art that stuff is.

I reckon white metal might be a bit soft and allow chips of swarf to embed and score the leadscrew in the long run too.

31/03/2020 09:01:12

Yes but commonly referred to these days by most suppliers as LG2 Bronze, rightly or wrongly.

Edited By Hopper on 31/03/2020 09:13:57

Thread: New 3 jaw
31/03/2020 05:53:37

Talk to your supplier. They should pay the shipping on a replacement if item is not fit for purpose -- which 0.15mm would seem to indicate.

Providing of course you have machined the backplate in situ on both the face and the locating spigot diameter to get all running true both radially and axially.

Also presuming spigot is correct depth with clearance so mounting faces meet correctly and there is a clearance chamfer on spigot recess so it is not riding on the tool radius at base of spigot.

Pics of your set up would help.

 

Edited By Hopper on 31/03/2020 05:55:03

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