Author Topic: Not a model engine!  (Read 946 times)

Offline Steamer5

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Re: Not a model engine!
« Reply #15 on: July 17, 2019, 10:01:32 AM »
Hi Allan,
 Just catching up.
Made some knobs along those lines for my bandsaw upgrade.

I turned up the large part from aluminum, the threaded bit I turned up from steel & glued it in. The finger grooves were cut on the mill, you need to hold the part tight, donít ask how I found that out, you need to spend a bit of time taking the sharp edges off the grooves. Hope that make sense. In your case the flanged bit at the bottom would be part of the steel insert.

Cheers Kerrin
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Offline Allen Smithee

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Re: Not a model engine!
« Reply #16 on: July 27, 2019, 08:34:56 PM »
The stuff arrived, so here's how I finished the job. The remaining part comprises the plastic knob (22p each from a UK supplier) and a part turned from stainless:

AS

« Last Edit: July 27, 2019, 08:57:17 PM by Allen Smithee »
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Offline Allen Smithee

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Re: Not a model engine!
« Reply #17 on: July 27, 2019, 08:50:00 PM »
As this would need a lot of metal removed I decided rather than risk poor machining from "gash" stainless I bought some pukka 1" 303 bar from M-Machine. This machined beautifully with a cheapish carbide insert tool, and the central bore drilled easily with a standard HSS drill bit.

I decided to do all bar the final tapping without removing the the bar from the chuck, just parting off and then reversing in the chuck to face to length before tapping the bore. This plan worked well, except for the usual hazard of turning a reverse taper - I swung the topslide to get the 13.5deg taper and it worked well EXCEPT that on one cut I forgot that you have to back the tool fully clear of the largest diameter before winding the saddle back for the next cut  :-[

Fortunately the tip survived and the gashed-up surface was all in the waste metal that was cut away later.

My lathe (Myford S7b) is not brilliant for measuring along the bed axis - the leadscrew handwheel has a micrometer dial, but both the handle and the dial are tucked under the right-hand end of the bed and are a pain to use. I have a DRO which I keep meaning to fit to the saddle but haven't gotten around to yet. So mostly I set up a saddle stop and use the topslide for accurate dimensions, but of course I couldn't do this with it set up for the taper. So my cunning plan here was to mount the material in the chuck and then cut a shallow parting groove to use as a datum - all axial dimensions were measured from here using a vernier and steel rule. Crude though it was the method worked well enough, but I must get that DRO mounted!

AS
« Last Edit: July 27, 2019, 09:09:45 PM by Allen Smithee »
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Offline Allen Smithee

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Re: Not a model engine!
« Reply #18 on: July 27, 2019, 08:56:47 PM »
Finally the plastic knob was simply drilled 10mm and then opened up to 11.8mm with a boring bar. The resulting firm press fit was extremely satisfying and seems more than adequate. I'm quite pleased with the result. The final picture is one of the existing ones that's still in the boat, to show how it's supposed to work.

Now I just have to make a couple more and work out how much to charge him...

AS
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Offline Jo

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Re: Not a model engine!
« Reply #19 on: July 28, 2019, 07:34:06 AM »
Now I just have to make a couple more and work out how much to charge him...

I would just keep the spare stainless as payment and give him the bills for all the materials used  ;) .

Jo
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Offline Allen Smithee

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Re: Not a model engine!
« Reply #20 on: July 28, 2019, 12:02:28 PM »
Job finally finished. The attacked show the stainless machined part and the finished latches (one with the original knob and LH thread). I've learned a lot in the process. I'm quite pleased with the way my little myford handles biggish chunks of 303 stainless, and I'm learning more about which types/shapes of tips cut better at what kind of cut. I still found that all the insert tools were better than the toolsteel ones, which isn't what others tell me, but I guess that's telling me I need to learn how to grind them. I also now see the benefit of buying pukka materials rather than some "might be" materials from cheaper sources...

AS
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Offline Ian S C

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Re: Not a model engine!
« Reply #21 on: July 28, 2019, 12:55:41 PM »
I'm no good when someone asks"How Much", so I tend toward asking the customer for their idea of a price, and more often than not it is above what I had thought of.
Ian S C

Online Vixen

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Re: Not a model engine!
« Reply #22 on: July 28, 2019, 01:07:49 PM »

Now I just have to make a couple more and work out how much to charge him...


The price you ask should reflect how much you want them to return with more work for you. Better way than offending them by saying NO
« Last Edit: July 28, 2019, 01:29:40 PM by Vixen »
It is the journey that matters, not the destination

Offline Allen Smithee

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Re: Not a model engine!
« Reply #23 on: July 28, 2019, 05:49:21 PM »

Now I just have to make a couple more and work out how much to charge him...


The price you ask should reflect how much you want them to return with more work for you. Better way than offending them by saying NO

I'm not looking for more work - this was just a favour for a mate. I told him that the bought-out costs (knobs and materials) came to around £30, and invited him to bung in whatever he thought appropriate for my couple of afternoons. He came straight back with an amount I'm quite happy with. For me the time spent was just further useful familiarisation with my machines, learning how to get better results from them. I wasn't really looking to make money on it - if I was then I'd have to charge the £110/hr rate that my company bills projects for my time and that would have made the whole project non-viable.

AS
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