Model Engine Maker

Supporting => Tooling & Machines => Topic started by: Lauri on June 21, 2020, 02:32:28 PM

Title: Honing question.
Post by: Lauri on June 21, 2020, 02:32:28 PM
Hi.

 I wonder if someone could help me with this.
I have to hone conrod bushing holes (nominal ø6mm, bronze bushing) and wristpin hole in piston (RSA-444 high silicon alloy).
Untill now I have borrowed my friends Pemamo #102 hand hone. But, at first, it got a bit complicated as I'm in Switzerland and he is in the Netherlands.
Secondly, the resin bond hone (diamond, grit D15) is not ideal. It wears too quickly.
I think in reality such hone is meant for finishing/super finishing holes in harder materials.
I just bought my own Pemamo honing machine (type 220). Other than resin bond hones, Pemamo offers hones with bronze bond, and galvanic bond. Which one would be best for my use?
I can machine the parts to very close tolerances, so that I have less than 0,01mm left for honing.

Cheers, Lauri
Title: Re: Honing question.
Post by: Admiral_dk on June 21, 2020, 10:03:35 PM
I can only think of two other members here that has a professional honing equipment - Jo and Jim (strictlybusiness1). While Jo probably reads all posts here, I'm guessing that Jim only reads posts in his own thread http://www.modelenginemaker.com/index.php/topic,3890.0.html (http://www.modelenginemaker.com/index.php/topic,3890.0.html)

I hope one of them will chime in.

Per
Title: Re: Honing question.
Post by: Roger B on June 22, 2020, 07:26:34 AM
I have only used Acrolaps with diamond paste which I would think are a step below the Pemamo ones. Jo has a Delapena machine.

http://acrolaps.com/index.htm

Have you contacted Pemano for their suggestions?
Title: Re: Honing question.
Post by: Jo on June 22, 2020, 07:45:51 AM
Sorry read this yesterday and my reaction was  :o that's a small hole can't do anything that small, sounds all too technical to me  :paranoia:


This morning trotted out to look at my Delapena hone to find I have mandrels down to 5mm but no stones to fit them so time to read the manual:

Delapena do standard stones in four different types of abrasive:

The bond hardness for a honing stone refers to the tenacity with which the bonding material holds the abrasive particles together. The choice of grade depends on the material being honed. On a hard material a soft grade should be used allowing the abrasive particles to be released as soon as their sharp cutting points have been worn away. A hard grade is used on soft materials since the cutting points of the abrasive particles will wear away more slowly and need to be held together for a longer period before being released.

Diamond and CBN Hones: The main application of diamond honing stones is for honing tungsten carbide and ceramics where conventional abrasives are unsuccessful.

Three bonding materials are used with these hones: Cobalt Iron, Bronze and Resinoid. These bonding materials determine the hardness of the diamond hone, Cobalt iron being the hardest through to resinoid, the softest.

With diamonds it is important to use the lowest pressure that will give a good cutting action. Increasing the pressure beyond this point will result in increased stone wear with very little stock removal.


 :thinking: Now I need to read the rest of Delapena manual again

Jo


Title: Re: Honing question.
Post by: nj111 on June 22, 2020, 10:59:32 AM
I also have a delapena, similar to Jo's,  the range of tooling I have with it goes very small. Small enough to hone valve guides internally for our model engines.
The range of stones from Delapena for these machines (with parts held by hand) starts at 1.14mm dia and goes up to 79mm. Delapena and sunnen and the lesser know (but also excellent) British made  "Raybrook" machines all have identical tooling - ie sunnen fits delapena etc.   Raybrook machines are much cheaper to buy simply as not so well known. All of these machines are a delight to use and produce fabulous results in no time.  As for stone choice, all of my tooling is used or new old stock so I use what I have, hence not always the optimum stone for the material but seems to work just fine for small volume.
Title: Re: Honing question.
Post by: Admiral_dk on June 22, 2020, 11:46:57 AM
I forgot to mention that you really should read Jim thread on how to build his IC World Speed record holding model engines as he gives ALL his secrets away and will answer your questions if you still need some details.
Title: Re: Honing question.
Post by: nj111 on June 22, 2020, 11:52:44 AM
I agree its a wonderful thread
Title: Re: Honing question.
Post by: Lauri on June 22, 2020, 05:34:18 PM
Thank you all for replies.
I have been in contact with Pemamo, but it hasn't been the easiest company to deal with. But I will keep trying.
A real honing machine would be nice for sure, but I don't think it would be a good idea as I work at home.
The Pemamo 220 unit can be mounted in a lathe or milling/drilling machine. It's supposed to be very good for small jobs like what I do. And it's quite amazing, their hones start from ø0,6mm...

Lauri
Title: Re: Honing question.
Post by: Admiral_dk on June 22, 2020, 10:16:04 PM
I just watched a demo video on their site and I'm impressed enough not to dare ask for the price  :-X
Title: Re: Honing question.
Post by: Jo on June 23, 2020, 07:13:08 AM
If you keep your eyes open the little bench top machines like my Delapena turn up at car boot sales etc as not many garages use them any longer. My supplier brought mine for the sum of £20 at an auto jumble and then sold it on to me for a vast profit  :stickpoke: He didn't even clean it up or fit the motor/contactor in the price he charged me  :ShakeHead:

Jo
Title: Re: Honing question.
Post by: Mcgyver on June 23, 2020, 11:20:56 AM
Quote from: Jo on June 23, 2020, 07:13:08 AM
If you keep your eyes open the little bench top machines like my Delapena turn up at car boot sales etc as not many garages use them any longer.

Those Delapena's seem identical to our Sunnens?  Different branding like Victoria/Elliot or a copy?  They are an amazing contraption, will easily get a bore straight and true to a tenth of thou. 

The only complaint with Sunnen is they want your first born for tooling.  I've even resorted to making mandrels.  The do come up for reasonable dollars, but imo hold out for one with a good selection of mandrels.  i think I've got a dozen and if I don't have one, I starting thinking how else to do it.

Lauri I figured yours was the next level up.  With the Sunnen you worry what grit of stone do use, but when the question is are what bond to use for diamond tooling I've afraid I don't have much to contribute!

A few pics of mine - The only room I had was over top the RPC so I made a custom stand/tank.

(https://i.imgur.com/vuvhKj5.jpg)

(https://i.imgur.com/CjcwfX7.jpg)

(https://i.imgur.com/OD6VrUH.jpg)









Title: Re: Honing question.
Post by: Jo on June 23, 2020, 12:23:22 PM
Yes they are identical  ::)

Looking at the price of the honing mandrels I may have got a bargain  :thinking:

Jo
Title: Re: Honing question.
Post by: Lauri on June 23, 2020, 04:30:08 PM
Thank you again!
It's funny, because before I bought the #220 Pemamo machine (or actually 2), I contacted Pemamo and asked then if I could buy as similar hand hone #102 (no need for machine, just s simple adjustment screw for expansion) than what I have borrowed from Robbie many times. Accordind to Rob, the price should've been 200-300€.
When Pemamo finally answered, their offer for one tool was about 1300€. Welcome to Switzerland! L
Title: Re: Honing question.
Post by: nj111 on June 23, 2020, 05:39:40 PM
Not surprised,  but for decades the Swiss have been renowned for accuracy of machinery and equipment. I'm sure it's the ultimate bit of kit for the job!
Title: Re: Honing question.
Post by: john mills on June 24, 2020, 02:05:52 PM
Reading this bring back memories i started using these types of machines in the late 60's
Did not go to these small sizes.i would think the diamond would suit harder materials soft materials would tend to pull the diamond from the bond would be my thought.
accuracy is dependant on the operator the hole can be easily made tappered or bell mouthed ,it helps if the stones are kept dressed straight the dressing sleeves can help.also watch that the rubbing strips are not to worn to much.
for conrod bushes we preferred to use a pin boring machine which could bore to half a tenth of a thou and to a much finer finish than honing. 
                                                     John
Title: Re: Honing question.
Post by: Lauri on June 27, 2020, 08:42:37 AM
Hi.
After some research I’ll answer myself in my question;
It seems that for my use the best is metallic bond, I guess the diamond is in sintered bronze matrix. The resin bond D15 sure leaves a nice surface but according to my friend the wear is not acceptable; it’s too worn after about 20 pistons.
I made tests with my Pemamo device and D80 grit tool. Even when it’s a little on rough side, it’s amazing how precise holes it produces. And how easily!
As I usually need to remove 0,02...0,03mm, I’ll keep using the rough tool, and then do Just the finishing with D15. Theoretically bronze bond would be better because it’s more porous, but for final touch, I doubt if it matters if I use that or galvanic bond (like diamond file surface)

But thanks for all info!

Lauri

Lauri
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