Minnie 1″

[JasonBModerator @jasonb]

15/64th or 6mm would be OK

Yes you can use hand reamers under power but run quite slowly say 200rpm or less.

[james huxstepParticipant @jameshuxstep40895]

Hi chaps!

I am fast approaching the front wheels.I have not done the rear wheel first so I have no experience on the process.

What wood would you suggest for creating the jig?and what type of tool to use?

Any tips on turning the ally cast rims?

Next job ATM is milling the spoke recesses in the front wheel hubs.

I've made a jig for the rotary table to keep the alignment .One end spigot for the hole in table,and one for the undersized hole in the hub.

Thanks

James

[Michael BelferParticipant @michaelbelfer47979]

This seems to be for general questions about a minnie build, so perhaps here.

O-rings…. something of a black art it seems. I have looked up the ztubal Cakn book and I am only a tiny bit less in the dark.

LC Mason speaks of d-bit sizes, and that various supplies of rings vary a little in size, but several times through the book looking and I dont seem to be successful in finding what size rings are required It would be nice to know, in case what I buy are not the same as he originally used

Michael dow nunda

[Michael BelferParticipant @michaelbelfer47979]

Same applies to cylinder mounting studs: I cant find dimensions, although there is mention of:

a) drill and tap 1/4 depth into cylinder block

b) hex nut depth plus a few threads showing

c) the two chests finish to 5/16" and 3/8" thick

d) both chest covers 3/32 thick

e) 7BA nuts 3/32 thick

giving 3/4 and 13/16 plus say 2 threads showing = 1/32 more,

or calculated lengths of 25/32 and 27/32

Do they sound right? Be nice to see it verified in the text or drawings somewhere, but I couldn't find it

Michael dow nunda

[JasonBModerator @jasonb]

O Rings 1 x bs111, 1 x bs006, 1 x bs010, 1 x bs007 and 1 x Ref B (3/32" ID) nitrile.Plus two to suit your gauge glass.

Make the holes the size Mason gives

As for studs I've never seen their lengths given that is down to the builder to establish. For example it may say drill 1/4" deep but depending on your individual taps the thread will not go right to the bottom of the hole so best do a test of the first one in each group and work it out from there

[Michael BelferParticipant @michaelbelfer47979]

Well, (as frequently the case, it seems). Jason rides to the rescue. Thanks Jason.

I find Numbers BS006, 007, 010, and 111 without too much bother but what is a reference B?

Michael

[JasonBModerator @jasonb]

0.064" section, 3/32ID, 7/32" OD Viton according to Blackgates but expect you will have to source something locally, no BS number given

[james huxstepParticipant @jameshuxstep40895]

Hi all

Im stil going!

Front end done.

Front wheels done

Rear wheels almost done.

Boiler parts all formed and sent off to western steam to be brazed up. [i chickened out of doing it myself]

But im having an issue with the rear wheels rear hub castings. More on that in a minute. Time for some progress photos.

[james huxstepParticipant @jameshuxstep40895]

[james huxstepParticipant @jameshuxstep40895]

[james huxstepParticipant @jameshuxstep40895]

[james huxstepParticipant @jameshuxstep40895]

[james huxstepParticipant @jameshuxstep40895]

[james huxstepParticipant @jameshuxstep40895]

ok so onto the issue in hand………

Im trying to turn the phos brons rear hub castings but they seem to be flexing/bending/bell mouthing.

I first placed the casting in the three jaw chuck with the face that lays flat on the hub facing outwards, and machined that face and the 5/8" 1/16" deep recess that goes into the little pocket on the hub. all good. I then drilled and reamed it 7/16" also all good.

The problem was when i made an arbor 7/16" enabling to turn the casting round to machine the otherside. [See pic]

I made a good fitting arbor, loctite retaining compound all good. The problem arose when i started to machine the otherside of the 1/16" wide egg shaped face. It began to bend away from me instead of get cut by the tool. grrrrrrrr.

ok. fine. i get that. make a better arbor with support behind the thin web so it cant bend away from me.

So i made a two part arbor. essentially a large flat surface with a 5/8" recess to take the casting spigot with a hole tapped m12 to take the 7/16" arbor pin. Allowing the casting to lay flat against it so it would not flex.

This worked to a point. it then began to bell mouth on the under side thus loosing the nice flat mating surface and my 5/8"D spigot is now no longer protruding like it should..

 

What am i doing wrong? Im using carbide indexable tipped tooling. Loctite high strength retaining compound [allowing to dry for 10mins].

Thanks for any help

 

 

james

Edited By james huxstep on 23/12/2021 11:09:27

[james huxstepParticipant @jameshuxstep40895]

[james huxstepParticipant @jameshuxstep40895]

[james huxstepParticipant @jameshuxstep40895]

[james huxstepParticipant @jameshuxstep40895]

[Clive Brown 1Participant @clivebrown1]

I'd suspect that the tool is rubbing and not cutting well. What type of carbide tip are you using and is it in "as new" condition? It needs to be the ground and polished type suitable for aluminium, non-ferrous etc.

A really well sharpened HSS tool might do better.

[JasonBModerator @jasonb]

Gun Metal can be very soft and unless the tool is sharp will bend away from it, as clive says an insert for aluminium and non ferrous metals will be a lot better so depending on what shape you use thats TCGT, CCGT or DCGT, etc. If you can't get inserts this side of Xmas then sharp HSS will also do the job

Take light cuts about 10thou (0.25mm) deep with a fine feed.

[james huxstepParticipant @jameshuxstep40895]

ok i understand.

The tools i used are of the usual carbide indexable tooling. The ones i use for steel etc, there is no special insert ive inserted for non ferrous metals. So thats good to know. Il grind up a hss tool tomorrow, i have ordered a pair of new castings.

Thanks very much for your assistance as usual. Have a good christmas. And il keep you updated.

thanks

james

[bernard towersParticipant @bernardtowers37738]

+1for Jason you need razor sharp tools

[james huxstepParticipant @jameshuxstep40895]

Ok thanks very much. ill grind up a hss version tomorrow. ill post a couple of pictures of the two usual carbide tools i use. i would like to get some non ferrous cutting tips for these for the future as my grinding skills are ok but not perfect.

It looks like out of jasons list, that the ally versions i need are DCGT and CCGT. Are the aluminum versions sharper on the tips than the DCMT/CCMT standard versions? Which is why they work on non ferrous metals?

thanks

james

[james huxstepParticipant @jameshuxstep40895]

[james huxstepParticipant @jameshuxstep40895]

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