Author Topic: Lapping (and honing) - some techniques for discussion  (Read 70804 times)

Offline ths

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Lapping (and honing) - some techniques for discussion
« Reply #30 on: May 09, 2013, 10:07:30 AM »
Thanks Ramon, very informative, and I'm looking forward to the next class.

Hugh.

Offline gbritnell

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Re: Lapping (and honing) - some techniques for discussion
« Reply #31 on: May 09, 2013, 12:29:34 PM »
Hi Ramon,
Excellent tutorial on lapping. While I have lapped a lot of my engine cylinders with commercially made hones I have never tried making my own. Yours look to be quite simple and effective. Is there a chance we could get a sketch of the parts. I don't quite understand the shank being of the 'D bit' style and then the copper band being silver soldered to it.
Thanks,
gbritnell
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Offline b.lindsey

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Re: Lapping (and honing) - some techniques for discussion
« Reply #32 on: May 09, 2013, 02:53:12 PM »
Nice intro to the topic Ramon, I am also looking forward to the next installment!

Bill

Offline Bearcar1

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Re: Lapping (and honing) - some techniques for discussion
« Reply #33 on: May 09, 2013, 04:12:23 PM »
Hi Ramon, WOW! This is REALLY an interesting post and thank you for providing it to us. I can not wait to see how you went about making those industrial looking laps. I get the gist of them but am having a small problem envisioning their insides. I'll 'get it' when you show us the internals. This thread is going to be a real eye opener.  :o


BC1
Jim

Offline Ian S C

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Re: Lapping (and honing) - some techniques for discussion
« Reply #34 on: May 09, 2013, 04:30:26 PM »
I really must try a lap like yours Ramon, I'v been using wooden laps with variable results after hours of work.     Ian S C

Offline ScroungerLee

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Re: Lapping (and honing) - some techniques for discussion
« Reply #35 on: May 09, 2013, 05:29:32 PM »
Thanks Ramon for the thorough introduction, I am following along.  I too don't really understand what you meant about a d-bit being part of the tool.

Lee
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Offline Ramon Wilson

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Re: Lapping (and honing) - some techniques for discussion
« Reply #36 on: May 09, 2013, 10:48:52 PM »
Hi Guys - can't believe it - having spent some time going into the next bit I've just gone and lost the lot  :facepalm:
(I hit the back button - when you come back the box is empty  :o)

It's been a long day I guess and I'm just too tired to begin again - please bear with me - I'll get onto it tomorrow night - promise

Best laid plans an all that eh  ::)

Ramon
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(a very apt phrase - thanks to a well meaning MEM friend)

Offline steamer

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Re: Lapping (and honing) - some techniques for discussion
« Reply #37 on: May 09, 2013, 11:12:00 PM »
Happens to me too Ramon!....Sorry to hear man!
Tomorrow is another day.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline ref1ection

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Re: Lapping (and honing) - some techniques for discussion
« Reply #38 on: May 09, 2013, 11:29:11 PM »
There will be lots of us anxiously waiting for your next post.

Ray
Indecision... the key to flexibility!

Offline Bezalel

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Re: Lapping (and honing) - some techniques for discussion
« Reply #39 on: May 10, 2013, 04:45:02 AM »
This is Great stuff Ramon
Thanks
 
I'm just lapping it up  ::)
 
 
If your still reading... let me tell you what I do for a long post. ( I've lost a few long posts myself in the past)
 
Just write your post in notepad/wordpad or some other plain text editor, take as long as you need to, even save it if you have to shut down the computer. Then when you're ready to post it Cut and past the text into the reply box, add a few smilies and hit the Post button.
 
Bez :cheers:
Queensland - wet one day, humid the next

Offline Ramon Wilson

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Re: Lapping (and honing) - some techniques for discussion
« Reply #40 on: May 11, 2013, 09:48:31 PM »
Hi guys - well we'll have another try - hopefully I won't hit the wrong 'key' tonight  ::) Thanks for the tip Bez but where the problem lies is moving back and forth getting pics from the web album - I just hit the back button by mistake.

I'd like to say how surprised I am in the interest in this subject - it's very pleasing to see but I can't reiterate enough that there are several ways of going about this - it's very much down to what suits the individual. That said I'm quite happy to continue - as said I hope it lives up to your expectations  :)

First off , my apologies Harry (GWR) - didn't mean to ignore you - I'm about 45 miles from Sudbury so if you're up around Beccles way and have some time to kill you'd be welcome to call. Theres also a very good stationary steam engine museum  about 9 miles south of Norwich - it'll be in steam first Sunday of June just in case you need a fix ;)

Okay back to the lapping  ;) -

If you discount the wet and dry wrapped around a smooth mandrel I guess the next best thing would be a hardwood dowel turned to fit a bore, split down the end with a screw to expand it. This provides an expandable lap but one of 'single point' form though agreed, as the lap wears, the land will widen. Providing the amount to come off really is minimal this would suffice to apply a better finish but not neccessarily keep the dimensions uniform down the length of the bore.

As you can see most of the laps made so far have been of one type. I think I first saw it in an article by Len Mason - a well known engine maker - but whoever it was the merits of it's consistency were praised. Having made that first one for the Quorn there's been no reason to change since until I did the last engines - the Super Tigres - when a differing kind was tried. This was successful too but nowhere as easy to operate as this kind.

I don't know how small they could be made as there is this need to silver solder a small controlled area but I would think about 3/8 / 10mm would be the limit without it becoming a technical challenge.

George  - I hope the following will be self explanatory without a sketch
So far they've been based around a 1/2" shaft - to fit a collet and if larger then a head is soldered on relative to the size required. The head is cut back like a D bit and a copper wrap is soldered to the leading edge. The cut off piece is inserted in the gap, A grubscrew locating it which is also used to expand it and the OD turned to about 1-2 thou / 0.025/0.05mm down on bore size.

The constituent parts


The head is split and half cut away


The wrap is annealed and formed around something to give the right diameter to fit the head - obviously the head has to be of such size as to leave sufficient for turning the od but not so big as once turned to leave little left for lapping. The wrap is drilled  clearance for the expanding screw, the fixed half is tapped for it and the insert is dimpled to act as a locater to stop it falling out.


The inside leading edge is cleaned and the rest coated with a soft pencil - I believe Tippex makes a good resist for Silver Slder but haven't tried it and the same done to the head. Fluxed carefully on the cleaned areas the copper is held in place by a small screw through the copper and the edge soldered.


It's then set in the lathe and the OD turned, as said to a couple of thou max down on the bore - the abrasive has to have somewhere to go  ;)


Bear in mind if you solder it to the wrong edge this is the op where you find out as it unwraps itself  :o - no it hasn't, not yet  :D

In use abrasive is mixed to a paste, applied to the lap and the part slid over - if it's too loose its witdrawn and the screw adjusted and tried until a good restriction is felt. Work the lap up and down to spread the abrasive then holding firmly set the lathe running at around 200 rpm slower is better to start with but not too slow. The part might grab at first but a good grip will soon have the two surfaces acting against each other as the abrasive begins to bite. I let the oil in the paste act as a lube for the first few seconds as the abrasive spreads out to an even film then I apply Paraffin (Kerosene) with some light lube oil mixed in (about 90-10) to keep things nice and wet. This is a messy process - I've tried using gloves but the loss of 'feel' and the problem of Nitrile gloves catching and winding up makes it much easier to get plenty of barrier cream on and volunteer to do all the washing up for a week  :D  It should go without saying but make sure the lathe ways are covered too.

Here are a few more pics of the same ops - this time it's the lap used for the first Eta engines being 're-wrapped' - the first time this has been done. Not quite as neat as the first time but successful never the less






Despite the coating of graphite the solder has run a little further round than liked but none the less this worked well for all four cylinders


The lap turned and coated with abrasive for the first lapping. The grade is 320 grit silicon carbide - we'll cover abrasive later


The single point expansion gives a parallel lap at all times. I confess when I made that first one I could not see how it would remain round as it was gradually expanded but of course it is defined by the process - as mentioned before they gradually  become slightly eccentric to the shaft but retain perfect (within the remit of what they are) circularity. As the op is one of a floating nature the slight eccentricity has no effect on performance. I think it would be fair to say that to lap successful bores for  diesel engines goes some way to proving their viability.

I'd like to call it a day there - late night last night, early start this morning and a nice day sailing in the fresh air has finally caught up with me.

Regards for now - Ramon.

PS I see elsewhere Harry's preferrence not to have his post on his engine interupted. Without wishing to be seen as disagreeing with him, personally I would much prefer others to chip in/comment etc. To my way of thinking that way it's clear that the exercise is continually viable - I'm an inveterate worrier you see ;)
"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 steamer

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Re: Lapping (and honing) - some techniques for discussion
« Reply #41 on: May 11, 2013, 11:02:14 PM »
Outstanding write up Ramon!.....Can't wait to make one for the Wallaby
 :praise2: :praise2: :praise2:

We need lots of this.   This is good.   Thanks again

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Don1966

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Re: Lapping (and honing) - some techniques for discussion
« Reply #42 on: May 11, 2013, 11:19:34 PM »
I am loving it Ramon, a big thank you is in order. Great write up and presentation.  :praise2:  :praise2:

Don


Offline AussieJimG

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Re: Lapping (and honing) - some techniques for discussion
« Reply #43 on: May 12, 2013, 12:29:32 AM »
Great explanation Ramon. One question: would soft solder be sufficient to hold the copper in place?

Jim

Offline Bearcar1

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Re: Lapping (and honing) - some techniques for discussion
« Reply #44 on: May 12, 2013, 01:23:16 AM »
I 'gots it' now, Ramon, and thank you for setting my feeble mind straight on the innards of these laps. They certainly are a huge step above the wooden laps that I have used in the past. Your tooling seems much more controllable and robust for the task at hand. Well done  :DrinkPint:


BC1
Jim

 

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