Engineers Assemble!

My_Teenage_Self · Oct 28, 2020

I'm reaching out to all you smart folk - this has me flummoxed.

I have an M12 cap head allen key machine screw in 10mm plate. it's one of 4 holding a motor in place.

I'd like to countersink it for clearance, but an M12 countersink bolt needs roughly a 25mm countersink bit which is both spendy, and I doubt I'd get a decent result with a hand drill. There's no way I'd get the steel frame in my drill press.

So... can anyone think of a decent solution to get the bolt out of the way? A workaround is fine, a bodge may be tolerated, zip ties and gaffa tape will not.

TLDR; How do I get that bolt out of the way without countersinking it in the proper manner?

foz · Oct 28, 2020

do you need it completely countersunk? would a low head bolt not give you enough clearance?

My_Teenage_Self · Oct 28, 2020

I could tolerate a maximum of 2-3mm proud, but really would prefer flush. There's a belt that runs on that Alloy wheel, and I'd prefer to remove the chance of interference at all.

The wheel in the pic needs to be 5mm from the frame, not the current 15mm.

foz · Oct 28, 2020

hard to tell without seeing more... mill the hole out so that it's stepped (rather than countersunk), then the head will fit further into it? might not be enough material there though in the 10mm plate. Might need some reinforcement on the inside? maybe combine that with a low head bolt and you could get it flush?

Only other thing I can think of is mounting the motor to a separate plate, than mounting that plate to the existing one, with holes that are further apart and out of the way. it would be less rigid though, and the motor might sit too far inwards

probably easier, quicker and cheaper all round to just get the countersink though...

Peachy! · Oct 28, 2020

Would a button/dome head be low profile enough?

My_Teenage_Self · Oct 28, 2020

Peachy!":2qu5mo1h said:
Would a button/dome head be low profile enough?

Unlikely - there will basically be a belt flying past the main frame with about 5mm clearance, so 5mm clearance minus the bolt head height. as these belts don't always run completely true, I have to expect 2-3mm 'wobble'.

really needs to be flush...

I have one idea left, but want to see if anyone has a proper solution before I bodge it...

Foz, I can't face spending £60-70 for a single countersink bit. I'm cheap.

jimo746 · Oct 28, 2020

Can the Alloy wheel be moved out at all instead?

Would an M12 hexagon head bolt fit? The head might protrude less?

Can you drill out the plate to accommodate the head of the current bolt? Appreciate this is basically countersinking, but shouldn't need a 25mm bit? What's the diameter of the current bolt head +2mm?

My_Teenage_Self · Oct 28, 2020

jimo746":2rv7dd5t said:
Can the Alloy wheel be moved out at all instead?

Would an M12 hexagon head bolt fit? The head might protrude less?

Can you drill out the plate to accommodate the head of the current bolt? Appreciate this is basically countersinking, but shouldn't need a 25mm bit? What's the diameter of the current bolt head +2mm?

The wheel as it sits is 10mm too far off the shaft - I need to move it 10mm further onto the shaft. As soon as I do that the belt will foul the bolt. That'll leave only 5mm clearance to the frame, less by the time belt wobble is taken into account.

Fair point about sinking the existing bolt in - I suspect 3mm would be plenty of thickness meaning I can sink the bolt upto 7mm... I'll have a measure.

The History Man · Oct 28, 2020

How deep is the Allen key needing to go to tighten the bolt? If it’s just one of four that needs recessing could you file off the top of the bolt still leaving enough to sufficiently tighten it? We used to assemble with a countersunk Allen bolt, loctite and file flush on stuff that wouldn’t be expected to be moved. Left enough to break the bond if required.

Combined with a bit of drilling/reaming might give you enough.

dyna-ti · Oct 28, 2020

What the 'eck is it :shock:

What about a 25mm drill bit ? They're under a tenner.
Or
https://www.ebay.co.uk/itm/127406-90-De ... SwBLxfdCkS

I'd see if you can get the drill bit first if you think it would work, rather than a countersink you'll use once. Drill bit you should find a use for somewhere down the line.

Engineers Assemble!

My_Teenage_Self

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