Author Topic: Stentor  (Read 60015 times)

Offline Maryak

  • Rest In Peace
  • Full Member
  • *
  • Posts: 1818
  • Aldinga Beach South Australia
Re: Stentor
« Reply #30 on: August 21, 2014, 09:57:22 PM »
Not seen it done that way before, most people turn the main shaft first and then just hold by that in a keats plate or similar homemade jig to turn the pin/form pin hole, far easier than working between two webs an no need to drill pairs of ctrs at each end of the bar.

J

Just goes to show how many ways to skin the same cat. I was taught to do one piece cranks the way Jo has made hers.

Best Regards
Bob
Если вы у Тетушки были яйца, она была бы Дядюшкой

Online Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 15294
  • Hampshire, england.
Re: Stentor
« Reply #31 on: August 22, 2014, 07:43:33 AM »
Turning between centres on a small crank has its challenges but is easy and you know everything is square  :ThumbsUp: I started machining for the pin:



And then realised that my centre for turning the crank was rapidly being turned away  :facepalm: So had to quickly put a much deeper centre in:



Luckily even on such a small lathe as the Prazimat I have a very nice three jaw chuck that can swallow a 32mm diameter piece of bar  ;) It was then a simple turning job to finish the crank pin



Then I found that the pin was too close to the centre to be able to use a normal centre and had to support one end using a half centre and as the crank was now very thin the carrier was struggling to clamp :-\



The final cut needed that carrier to be removed. So I drove it using a piece of brass slid over the crank pin on the flat surface of the centre:



I then started the thread on the Myford and as I have never actually cut a full/good thread on the lathe finished it using a die  ;) I must get around to learning how to cut threads on a lathe  :shrug:



I still need to drill out the pin and drill the oil hole but other than that one crank done. Hopefully I will be able to sweet talk  :embarassed: a very nice man out of a piece of meehanite for the liner and piston when I go visiting tomorrow with my friend

Jo
« Last Edit: July 13, 2017, 09:10:21 PM by Jo »
Enjoyment is more important than achievement.

Offline Stuart

  • Full Member
  • ****
  • Posts: 1785
  • Tilchestune UK
Re: Stentor
« Reply #32 on: August 22, 2014, 08:10:42 AM »
Jo

Please use a either a properly ground HSS tool or a proper threading insert with the correct anvil to get the helix angle correct in your threading endeavours

That tool shown may be the correct angle but a threading tool it is not

My choice for small threads would be HSS

Set the compound to the thread half angle less a Nats and go at it. But you know all that it's just a confidence thing

Good work on the crank has as been said many ways to do the same job ,after all it's the end result that matters the rest is the journey to get there

No Brum Brums from the other infernal a yet :stir:

Stuart
My aim is for a accurate part with a good finish

Online Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Stentor
« Reply #33 on: August 22, 2014, 08:15:15 AM »
part of the reason for doing one of these tiddlers is to learn if and why machining them might be different than bigger engines and if there is any advantages or disadvantages of those techniques.

Be interesting if you try the alternate method on one of the other engines and see if you find it easier. It works well for the single web crankshafts where the pin sticks out the end. Between ctrs is still the way I do all other types of one piece crank.

Online Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 15294
  • Hampshire, england.
Re: Stentor
« Reply #34 on: August 22, 2014, 08:46:28 AM »
Jo

Please use a either a properly ground HSS tool or a proper threading insert with the correct anvil to get the helix angle correct in your threading endeavours

That tool shown may be the correct angle but a threading tool it is not

I did buy myself a proper threading tools but as I was turning between centres the outside tool would not fit  :shrug:

That setting the top slide over at an angle was the bit I always forget. When I get some spare time I must learn how to cut threads on a lathe :-[

My other infernal not running is being used to attract fellas  :mischief:, one does not want to rush/spoil a good thing  ;)

Jo
Enjoyment is more important than achievement.

Offline Stuart

  • Full Member
  • ****
  • Posts: 1785
  • Tilchestune UK
Re: Stentor
« Reply #35 on: August 22, 2014, 08:57:19 AM »
while we are on threading

the best method of deputing the thread is set out in one of the GHT books

the best bit is no maths involved other that reading the thread data

If anyone is interested you set the tool to touch the work , set both dials to zero move the carnage carriage to the left off the work , advance the cross slide to half the total thread depth, zero the cross slide , then wind back the top slide to clear the work , and thread when both dials are at zero the threads done

if it does not infringe any copyright i will scan the pages and post it in a new tread

the tools look ok Jo

Stuart

Edited do to me not being able to spell :happyreader:
« Last Edit: August 22, 2014, 09:21:25 AM by Stuart »
My aim is for a accurate part with a good finish

Offline Ramon Wilson

  • Full Member
  • ****
  • Posts: 1942
  • Suffolk in the UK
Re: Stentor
« Reply #36 on: August 22, 2014, 09:12:47 AM »
set both dials to zero move the carnage to the left off the work ,

Is that before or after one has 'buggered' it up Stuart  :lolb:

Ramon
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline Rivergypsy

  • Full Member
  • ****
  • Posts: 186
Re: Stentor
« Reply #37 on: August 22, 2014, 09:14:02 AM »
LMAO!!  :lolb:

Offline Stuart

  • Full Member
  • ****
  • Posts: 1785
  • Tilchestune UK
Re: Stentor
« Reply #38 on: August 22, 2014, 09:18:47 AM »
Ramon

Oops
What with my dyslexia and this darned iPad spell changer I am doomed


Stuart
My aim is for a accurate part with a good finish

Offline Ramon Wilson

  • Full Member
  • ****
  • Posts: 1942
  • Suffolk in the UK
Re: Stentor
« Reply #39 on: August 22, 2014, 09:26:25 AM »
Hi Stuart - whilst I would never poke fun at anyone with dyslexia nor a lack of spelling skill  that was just too good to resist  ;)

I remember when I was first using one of these word producing 'thingy's' I was heavily involved in the Forncett ME day - every time I wrote Forncett it would automatically change it to 'Fornicate'   :o which was a bit of problem seeings how I had no idea how to stop it doing it - fast learning curve there then  ;)

Regards - Ramon
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline Stuart

  • Full Member
  • ****
  • Posts: 1785
  • Tilchestune UK
Re: Stentor
« Reply #40 on: August 22, 2014, 10:54:39 AM »
Ramon

its no problem I have had it all my life well since i tried to write

My english teacher put on my report his work would be good if only i could understand the forgien language he writes in  :cheers:

it get bad some days I evan have to ask Linda how to spell some two letter words  :lolb:


but it has never bothered me I am who I am take it or leave it. I was a EE at the bank and have lots of qualification almost to the level of Jo in EE so it has not held me back you lean to work round it

so no offence taken

Stuart
My aim is for a accurate part with a good finish

Online Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 15294
  • Hampshire, england.
Re: Stentor
« Reply #41 on: August 22, 2014, 11:21:58 AM »
I only have a CSE in English :-[ Something to do with me having the basics of reading and writing at the age of 5 when I first went to school and no one else in the class could so they left me in the corner reading whilst they taught the others strange stuff called grammar :headscratch:

I had a look at my thread cutting books.... "Screw cutting in the Lathe" by Martin Cleeve is  :o very thick (= very discouraging). Only on page 136 does he get to actually cutting metal and introduces three methods.

The other thing that discourages me is the confusion of change wheels, gear boxes and leadscrews. The Prazimat/Cowells have metric lead screws and no leadscrew indicator and talk about using the complete reversal method. The Myford and the Colchester have imperial lead screws and have indicators.

Jo
Enjoyment is more important than achievement.

Offline Stuart

  • Full Member
  • ****
  • Posts: 1785
  • Tilchestune UK
Re: Stentor
« Reply #42 on: August 22, 2014, 11:30:03 AM »
Jo with that mixture you have no hope all those lead screws with different languages

better make a G Meek dog clutch for the myford then no worries its a Hardinge wannabe   :Jester:

but you are in the market for a Hardinge if my brain cell is active :mischief:

Stuart
My aim is for a accurate part with a good finish

Online Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 15294
  • Hampshire, england.
Re: Stentor
« Reply #43 on: August 22, 2014, 11:40:16 AM »
The Myford is going  :'( to make space for the new bigger mill  ;D

I am still looking out for a nice Hardinge but having just paid for a boiler :shrug: This was the one I had been offered: http://www.homeworkshop.org.uk/index.php?option=com_adsmanager&view=show_ad&adid=20345&catid=2  :disappointed: I can wait, they turn up often enough.

Jo
Enjoyment is more important than achievement.

Offline Maryak

  • Rest In Peace
  • Full Member
  • *
  • Posts: 1818
  • Aldinga Beach South Australia
Re: Stentor
« Reply #44 on: August 22, 2014, 12:56:57 PM »

The other thing that discourages me is the confusion of change wheels, gear boxes and leadscrews. The Prazimat/Cowells have metric lead screws and no leadscrew indicator and talk about using the complete reversal method. The Myford and the Colchester have imperial lead screws and have indicators.

Jo

Hi Jo,

The Asian lathes I have had since I started in model engineering have metric lead screws and being an old imperialist I had to take on the reversal method of thread cutting; either that or start chalking change wheels, (which take quite some time between cuts to re-align the chalk marks). I have to say that once you get used to it.............. it is quick and easy and you never lose alignment or re-engage on a wrong number etc. If you are nervous about stopping the cut in the correct place, no worries do the last couple of turns by hand, on bigger threads with the assistance of he chuck key, but please isolate the power to the lathe. Please try it and I hope that like me, you will be pleasantly surprised.

Best Regards
Bob

Best Regards
Bob
Если вы у Тетушки были яйца, она была бы Дядюшкой

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal