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  1. #1
    I've got rubber antivibration mounts like in the picture. There is a central steel bush moulded into the rubber. The rubber circle is dia 38mm to give the scale.

    The through hole is about 6.5mm. I reamed a few of them using a cordless drill succesfully to 6.60mm But I would like to take the holes out to 7.00mm

    If it was solid metal I'd just run a 6.9mm drill through and then ream to 7.00mm (I assume, this is my first reaming experience). But I'm not sure about drilling into this wobbly bush. I could just try it and see what happens but I want to ask about reaming.

    What sort of steps should I be able to ream?
    6.60,6.70,6.80,6.90, 7.00
    or 6.60, 6.80, 7.00
    or 6.80, 7.00
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  2. #2
    Drill diameter to reamer diameter difference should be about 0.2mm for soft material, 0.13mm for hard material. (equivalent to imperial 8 thou and 5 thou)
    Last edited by EddyCurrent; 25-10-2014 at 01:03 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  3. #3
    Thanks. I suppose mild steel counts as hard?

    If so I'm looking at the 5 steps of reamer,

    or I see what happens with a drill. I'm not hopeful, but I'd better try it.

  4. #4
    Hi Jimbo
    Easy enough if you have a pillar drill, if so i will explain.

  5. #5
    I've got a pillar drill.

  6. #6
    OK Jim
    You will have to clamp the central bush, you need some round bar faced on both ends to support the bushing from underneath, now you need a strongback to clamp the bush from the top, you want a piece of substantial flatbar with a hole larger than the size you want to open the bush out to in the middle with a couple of holes clear of the mounting main body and so you can allign with the slots in your drill table so you can secure the strongback to you drill table with studiron(allthread) make a dolly to go in your chuck with one dia original bush size and second dia size of clearance hole in strongback, then allign the strongback with the bush bore and tighten the job down using the studiron.
    Sorry it took so long to reply had a visitor.

  7. #7
    Quote Originally Posted by jimbo_cnc View Post
    If so I'm looking at the 5 steps of reamer,
    You could use an adjustable reamer that covers a range of sizes.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  8. #8
    They are a bit fiddly(if that's a word) with the job clamped it's just drill & ream.

  9. #9
    Thanks for the jig design. This will be my first metalwork jig.

    I like the dolly in the chuck plan. But I might be doing 50 or so at a time and I'm wondering if I can avoid taking the drill bit in and out.

    If I bring the 6.9mm drill down onto the 6.5mm hole, that might centre it OK, do you think? I could position the strongback manually or slip a length of tube over the drill bit.

  10. #10
    What about something like this, a counterbore with pilot, the problem will be getting the sizes you need;
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

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