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Post by Deleted on Sept 28, 2010 15:37:46 GMT
Am just starting work on the 4F 0-6-0 "Project" loco with the help of the G1MRA book - this is my first foray into locos - previously only played around with stationary engines. The few reamers that I already have are metric. The axle dimensions in the "Project" book show OD of axle as 1/4" with the OD of the shoulders on each end being 3/16". The "difference" in diameter between the axle and shoulders is thus 1/16" (which equates to 1.5875mm if my calculations are correct). As I already have (a) 5mm and 6mm reamers (which I can use for the axle hole in the wheels and the brass bushings respectively) plus (b) 6mm rod in both silver steel and BMS, can I substitute 6mm for the OD of axle (rather than 1/4") and 5mm diameter for the shoulders (rather than 3/16")? Will the 1mm difference be sufficient - am I worrying unnecessarily that it is comparatively much smaller than the 1.5875mm per the book? Lots more daft questions to follow ....... ;D Thanks in advance, A  |
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brozier
Part of the e-furniture
Posts: 335
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Post by brozier on Sept 28, 2010 15:56:00 GMT
I don't see any problem with using the 5mm reamer for the wheel.
But you won't be successful with a 6mm Shaft in a 6mm reamed hole as this will almost certainly end up being a press fit.
You'll need to either carefully step drill the axle bushes to 6mm (and theyfore probably slightly oversize) or bore them out to get the required finish and clearance. (Sliding fit).
I made the mistake of reaming the axle boxes on Spencer only to find the hole was too tight for the axle. Even using a reamer made from the Silver Steel I was using wasn't good enough...
Hope this helps
Bryan
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Post by ilvaporista on Sept 28, 2010 16:04:06 GMT
As imperial reamers are not available here in Italy I have done exactly as you describe for my R-302 loco. The axles are 6mm and the wheel seats 5mm., enough to press the wheel home to the shoulder. The only item to watch is not to mix imperial and metric measurements where they can cause problems, Yes I know that's an obvious statement but I still managed to ream a hole 1/4" for a dowel when I only had 6mm ones. Keep reamers and drills in separate racks for metric and imperial (I should write this out 100 times so I do not forget..)
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Post by Deleted on Sept 28, 2010 16:16:20 GMT
Many thanks Brozier and Ilvaporista for the speedy responses and advice. Re "Keep reamers and drills in separate racks for metric and imperial (I should write this out 100 times so I do not forget..)" - I will join the class and do the same 100 lines as I am certain to get them muddled otherwise..... Also point about 6mm shaft in 6mm hole taken - will use my smallest boring bar and aim for a sliding fit. I'm learning this hobby all the time, and loving it - but find the more I do the less I seem to know......  Ta again, A |
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Post by havoc on Sept 28, 2010 17:48:16 GMT
A standard commercial H7 reamer and commercial silver steel work perfectly together for this.
Only get one set of them, no trouble them. I see no reason to get or use imperial stuff as I cannot find it anyway here.
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abby
Statesman
Posts: 925
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Post by abby on Sept 28, 2010 22:38:25 GMT
Havoc the problem we old farts have is thinking of a thou rather than 0.025 of a millimetre , just like our sensible monetary system , our sensible engineering measurements are giving way to Europe , at least the yank's are standing their ground.
I have never found a problem fitting a 1/4" axle into a box reamed 1/4" , just polish the axle a little if it needs it.
It is also very easy to make a reamer cut half a thou bigger , one of the first things we learned at big school.
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Post by ilvaporista on Sept 29, 2010 4:24:32 GMT
A standard commercial H7 reamer and commercial silver steel work perfectly together for this. Only get one set of them, no trouble them. I see no reason to get or use imperial stuff as I cannot find it anyway here. Very sound advice if you are starting out new. I have too much baggage from 20 years in England before coming here, plus all the locos I built and started in England were born imperial. Most of 'our' standard size reamers will make a hole sufficient to work as running fit on standard size material. Go right along to almost the end of the flutes of the reamer if you can as this part sees less use and is more likely to be 'on size'. That is if your collection has been built up like mine from second hand sources. Whilst the bushes are in the chuck use a test piece of the axle material and it will soon tell you if the clearance is sufficient. |
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Post by havoc on Sept 29, 2010 10:39:29 GMT
Abby, this was just as advise as to avoid interchanging imperial and metric.
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Post by drjohn on Sept 29, 2010 11:29:50 GMT
It is also very easy to make a reamer cut half a thou bigger , one of the first things we learned at big school. I never went to "big school" abby, but I can manage to work out how to make reamers cut oversize too. Regards DJ |
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abby
Statesman
Posts: 925
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Post by abby on Sept 29, 2010 11:57:40 GMT
Havoc my reply was "tongue in cheek" , the wonderful thing about model engineering is that there are no constraints , no right or wrong , you can do what the hell you like and use whatever measuring system suits. The main purpose is your personal pleasure and entertainment and if this is the result , well then you are a model engineer.
Mike if you drag a piece of sharp HSS along the flutes of your reamer against the cutting edge it will raise a burr, doesn't need to be very hard. This will cause the reamer to cut a tad bigger.
You may find subjects of interest on my website and forum unionsteam.co.uk
DJ---lol, You must have gone to big school - from 11 years to 15years , or 5th and 6th form if you were clever and your mam could afford it!
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