Model engine brass shim 0.05mm thick

[EmgeeParticipant @emgee]

.Hi All

I need to make or obtain 20 off brass or steel shims as picture. I guess it is a job for a laser but wonder if anyone has used the sandwich method to make something similar on a mill. I have a mill but not a laser.

Thickness is 0.05mm, OD is 35mm, ID is 29.2mm, the 4 x 2.6mm diam holes are on a 24mm square, the lugs are 3mm rad centred on the holes, a DXF file is available ,

Emgee

[EmgeeParticipant @emgee]

Shim for spacing backplate from crankcase.

[JAParticipant @ja]

I would consider etching. I have not used the technique to cut out thin brass but it is worth a try.

JA

[HopperParticipant @hopper]

Brass shim that thin can be cut nicely with a pair of nail scissors or very sharp stainless kitchen scissors etc if either marked out or a template is used. The large hole in the middle (and most of the outer profile) can be cut using a pair of dividers run around the circle a few times with a little bit of gentle pressure.

The small holes can be punched out first. Either with a wad punch, which leaves a bit of a raised edge that can be hammered down, or you can make a simple punch and die out of two pieces of flat plate held together with countersunk screws for location and a hole drilled and reamed which a pin is then turned to fit as a punch.

You don't say what the application is so not sure how accurate it all needs to be. But with suitable care it can be done.

[EmgeeParticipant @emgee]

Posted by Hopper on 22/02/2017 11:39:22:

You don't say what the application is so not sure how accurate it all needs to be. But with suitable care it can be done.

Thanks Hopper but I was hoping for an offer from a laser user as the shims need to be quite accurate, they are for fitting on the engine backplates as below.

My attempts at punch and die making for this thickness of material has always ended in failure !!! I may have a go at the sandwich method but using cyno to make the stack, with light cuts with a sharp cutter may produce a result.

Emgee

[speelwerkParticipant @speelwerk]

Brass of 0.05 mm also cuts easily with a knive around a template. Niko.

Edited By speelwerk on 23/02/2017 12:27:35

[EmgeeParticipant @emgee]

Thanks for the suggestions, now need to source a small amount of brass shimstock.

Emgee

[HOWARDTParticipant @howardt]

As it is so thin I would make two steel parts to the shape and clamp the shim in between, then pare round and punch the holes through.

[CirclipParticipant @circlip]

For thickness and type of material a concave end on the punch (Like a paper punch) would help. Diametrically opposite edges cut first and then pare the material through. "Q-max" punches worked this way.

 

Regards Ian

Edited By Circlip on 24/02/2017 10:41:35

[Ian PParticipant @ianp]

Rather than making shims why not make the mating part (or shaft assembly?) 0.05mm thicker?

Shims are usually used for adjustment purposes so possibly you need them so that you can fit several shims to get the total thickness you need, although your original question inferred there was one per joint.

Ian P

[EmgeeParticipant @emgee]

Posted by Ian Phillips on 24/02/2017 10:41:08:

Rather than making shims why not make the mating part (or shaft assembly?) 0.05mm thicker?

Shims are usually used for adjustment purposes so possibly you need them so that you can fit several shims to get the total thickness you need, although your original question inferred there was one per joint.

Ian P

Ian, yes the shims will be used on the backplate to increase the clearance between the backplate and the engine crankpin on a model 2s engine. I have made over 100 of these all to the same dimension but now a user wants to have more clearance hence the shim. I believe he may have had a plating of some kind put on the front surface of the unit which has reduced the running clearance provided by a std unit. This is the 2nd user to request more clearance than the std 0.10mm. The engines are very well made (not by me) and there is no variation on the lengths of the crankpin or the crank case from engine to engine so it comes back to the backplate tolerance.

I also considered Niko good suggestion but preferred to clamp the material,

I like HowardT suggestion and had already planned to do as he suggests, cutting with dividers and scissors would work but quite a long processs.

Thanks for all inputs.

Emgee

Edited By Emgee on 24/02/2017 14:11:13

[Neil WyattModerator @neilwyatt]

For 20 off the cost of laser cutting should add virtually nothing to the cost of the shimstock.

You could try Malcolm Hiugh at Model Engineers Laser or try this lot:

http://www.stephensgaskets.co.uk/laser-cut-shim

Or just look up your local laser cutting company.

Neil

[EmgeeParticipant @emgee]

Thanks Neil, too thin for Malcolm, awaiting reply from the linked company, guess they close early Fridays.

Emgee

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