Author Topic: Strictly.... Hot Air  (Read 38082 times)

Offline Jasonb

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Re: Strictly.... Hot Air
« Reply #435 on: November 19, 2020, 06:40:35 PM »
Colin. you can't use the carriage to cut a tapered keyway as the movement is along the lathe's axis. There is a way to do it by taking out the topslide leadscrew and making a lever feed for that or making a complete slotting attachment. carriage works fine for straight cuts

I usually make a bush with a tapered slot and use a keyway broach.

Offline Twizseven

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Re: Strictly.... Hot Air
« Reply #436 on: November 19, 2020, 09:20:05 PM »
Jason,
Thanks for the reminder.  Of course it only works for straight keyways. :Doh:  I think I meant using the topslide,  :old:but I guess that would be rather slow.  I do have a slotting attachment but it is somewhat on the large size  :ThumbsDown: 

Need to rethink.

Colin

Offline ettingtonliam

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Re: Strictly.... Hot Air
« Reply #437 on: November 19, 2020, 09:23:30 PM »
Take the bulk out using the carriage, then just use the topslide to add the taper. It takes for ever doing the whole thing with the topslide.
To be honest, with these small engines I tend to make the keyways parallel and fit a tight parallel key. Naughty me!

Offline Twizseven

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Re: Strictly.... Hot Air
« Reply #438 on: November 19, 2020, 09:52:21 PM »
Liam,
That may be the way to go.  I do have a slotting attachment for the Myford, which came from a mate of mine but have never used it.  It is quite bulky and the current toolholders are designed for larger bores than 5/16", so would need to make a suitable holder for the cutter I have ground up.  It has a tenon key on it to locate it in the cross-slide and hopefully parallel to bed travel.  If I use this to take out most of the material  then as you say the topslide only has to remove a very small amount.  Will need work out the best method set the1:100.

Colin

Offline Jasonb

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Re: Strictly.... Hot Air
« Reply #439 on: November 20, 2020, 07:37:26 AM »
Will need work out the best method set the1:100.

Colin

Bit of flat bar, parallel if you have one in the toolpost and clock it true along the lathe axis as the carriage is moved. Now put two marks on the bar 100mm apart and adjust the topslide until your dti shows 1mm movement between the two marks as the carriage is moved.

To do the matching tapered key put equal packing either side of your vice such as 123 blocks and lay a 1.5mm drill on one of the blocks. use a rule as a parallel resting on block and drill at the 150mm division and then set your gib material on that.

Offline Twizseven

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Re: Strictly.... Hot Air
« Reply #440 on: November 21, 2020, 09:03:08 PM »
Jason,

Your technique worked great.  Took a long time to setup, about 1hr, I have a big Bison vice and took me ages going through all my 1-2-3 blocks and parallels to get the height right so that only 5/64" was gripped in the vice jaw.  Ended up with combination of 4 parallels/123blocks and a 20thou plastishim each side.  I doubly checked the height with digital height gauge to be certain equal heights prior to adding 2mm drill to the equation (needed 200mm to get across the vice).  Machined nicely but went very slowly and surely.

Cut 2.5mm keyway in crankshaft.  Cocked up, initially picked up 2mm drill and did full slot with that, and realised,   :facepalm: when key would not fit and went over with 2.5mm slotmill.

Key fits firmly in slot, so pleased with that.  Flywheel will be Mondays job.  Wife comes out of hospital tomorrow after haveing a second knee replacement so think my time in workshop may be curtailed a little.

Colin

Offline ettingtonliam

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Re: Strictly.... Hot Air
« Reply #441 on: November 23, 2020, 06:47:55 PM »
There are 4 core holes in the top of the engine bedplate, going through into the water space. 2 of them are under the cylinder, the other 2 are open to fresh air. Obviously one is needed to fill the water jacket, but is there any good reason why the other 3 can't be plugged?
A 3/8" BSP plug looks to be about right. It would avoid having to rely on sealant under the cylinder flange stopping leakage into the air passage. Maybe I'm just worrying unnecessarily.

Offline Alyn Foundry

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Re: Strictly.... Hot Air
« Reply #442 on: November 24, 2020, 11:55:17 AM »
Good morning Richard.

The simple answer is no....

We just used a " lick " of Silicone sealant to seal the two surfaces prior to bolting the cylinder down.

As for the " visible " holes I'm guessing your platform is our early version? We since made them oval to be in keeping with those that Gardner built. They were never plugged.

Cheers Graham.

Offline ettingtonliam

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Re: Strictly.... Hot Air
« Reply #443 on: November 24, 2020, 12:19:04 PM »
We had a discussion ages ago about the likely age of my castings, and I think we settled on it being about 1991.

Richard

Online Jo

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Re: Strictly.... Hot Air
« Reply #444 on: November 24, 2020, 12:47:43 PM »
They must date from before Graham perfected his special coating  :thinking:

Jo
Enjoyment is more important than achievement.

Offline ettingtonliam

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Re: Strictly.... Hot Air
« Reply #445 on: November 24, 2020, 01:36:41 PM »
Indeed, when I got them they were still in the original box and packaging, and entirely free from Graham's Special coating.

Offline Twizseven

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Re: Strictly.... Hot Air
« Reply #446 on: November 24, 2020, 09:17:15 PM »
Jason,
You mentioned making a tapered bush.  Any hints on ensuring I get the depth correct for the broach.  I have managed to source a suitable broach with parallel bush.  I have made a bush, which is longer in order to cover the full length of the flywheel bore.  I have made a collar to go round it with machined flats on either side, which once it has a slit (wider than the required broach width) in it will support/clamp the bush in the vice.  I can use the collar as a support guide to set at the appropriate angle as before.  I can then mill the slot for the broach in the bush.

Thanks,

Colin

Offline Alyn Foundry

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Re: Strictly.... Hot Air
« Reply #447 on: November 24, 2020, 10:12:05 PM »
Hi Colin.

As you have bought a broach and bush set which should have included a shim for the second and final cut? You can use the original bush as your " datum " for the correct depth. You can then upend it by the required angle.

Alternatively you could use my method and that is to push the broach to the last cutting tooth, retract the broach, fit the shim and re push it to the same spot as before. The cutters are set at the right taper themselves.

I have always worked " dry " with cast Iron but you could use a light smear of cutting fluid to ease the progress.

We use the small fly press here to push but an arbour press will work equally well.

Cheers Graham.

Offline Twizseven

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Re: Strictly.... Hot Air
« Reply #448 on: November 24, 2020, 10:46:33 PM »
Graham,

The broach set does include 1 shim (0.03205).  Are you saying the actual cutting taper on the broach is 1:100?  So by pushing the broach in to the same position you will end up with taper, rather than pushing all the way through to get a parallel slot.

I have a couple of arbor presses (1small - 1/2ton, and a larger one which is either 2 or 3 ton).  Also have flypress or hydraulic press. I think the larger of the two arbor presses would be the best option.

Lots of learning curves here, never having used a broach before.  :headscratch:

Thanks,

Colin

PS Like the V twin CHUK

Offline Alyn Foundry

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Re: Strictly.... Hot Air
« Reply #449 on: November 24, 2020, 11:00:12 PM »
Hi Colin.

Well if it's not, ( 1:100 ) it's pretty damn close. I've used the method described above for every keyway I've ever done over the last thirty odd years or so.

The " key " to success, pardon the pun, is to watch, very carefully what the broach is doing as you push. If things " ain't  " square you're very likely to snap it like a Carrot.

I'm still using the same 3/32"  " A " series broach that was bought to build the prototype Robinson 29 years ago.

Good luck, cheers Graham.