bobt Posted May 30, 2012 Share Posted May 30, 2012 Hi chaps, I have a very thick aluminium part (25mm) that has an 8.5mm hole through it. I need the hole to take an M8 thread. The bolt that would screw into that thread would be fitted and and removed regularly. What would be a good solution here? Thanks Rob Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted May 30, 2012 Share Posted May 30, 2012 How much torque is this going to take ? Could you use an M10, as you have enough metal left to tap it M10 Link to comment Share on other sites More sharing options...
Roger Ford Posted May 30, 2012 Share Posted May 30, 2012 8mm helicoil requires a 21/64th hole drilled - which is 8.33mm. If the hole is definitely no more than 8.5mm I reckon you'd get away with it. Link to comment Share on other sites More sharing options...
kenny. Posted May 30, 2012 Share Posted May 30, 2012 If the hole is more than 8.5 and scuppers Rogers idea, I think I'd be drilling for a 1/2" threaded bung/grub screw, loctite it in then redrill for the 8mm thread required. Link to comment Share on other sites More sharing options...
bobt Posted May 30, 2012 Author Share Posted May 30, 2012 The hole is bang on 8.5mm. It's a drilled hole, not an old knackerd thread. My concerns are with having the thread cut direct into the ali given the part will be assembled/disassembled regularly. In terms of torque, the 8mm bolt that will screw into it as a big 5cm knurled head on it which will be tightened tight by hand. Link to comment Share on other sites More sharing options...
Roger Ford Posted May 30, 2012 Share Posted May 30, 2012 with a Helicoil (other thread inserts are available) the thread you'd be screwing into isn't directly into the ali, it's into the helcoil which is steel. The Helicoil itself sits in the ali, but that's not going to be moving so shouldn't wear. Link to comment Share on other sites More sharing options...
Grubbster Posted May 30, 2012 Share Posted May 30, 2012 You could look at using Timesert or something similar, I've had a few threads repaired using these on Ka cylinder head Link to comment Share on other sites More sharing options...
Roger Ford Posted May 30, 2012 Share Posted May 30, 2012 8mm Timesert actually requires a slightly smaller hole - 0.323 inches or 8.2mm - see here. So although Timeserts are rather better than Helicoils, I'd still go for the Helicoil. I think I'm right in saying that I've used a 8.5mm drill with 8mm Helicoils in the past because I didn't have the proper 21/64th drill. Seemed to work OK. If you don't want to buy the helicoil kit you're welcome to borrow mine. Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted May 30, 2012 Share Posted May 30, 2012 Tightening a 5cm dia head by hand won't be very tight. I wouldn't be too worried about that ! Link to comment Share on other sites More sharing options...
bobt Posted May 31, 2012 Author Share Posted May 31, 2012 Well, I ended finishing the job lastnight in a slightly different was. As the metal thickness is about 25mm, on the reverse side of the part I opened out the hole to 13.5mm for 10mm depth. With the aid of a press a then drove in an M8 nut There's no way that's coming out! Link to comment Share on other sites More sharing options...
BBL Posted June 1, 2012 Share Posted June 1, 2012 A keensert® would have worked, provided you had ample material around the hole. One with a M8 internal thread will require a M14 threaded hole to install. Link to comment Share on other sites More sharing options...
Barbarossa. Posted June 1, 2012 Share Posted June 1, 2012 *arrowup*Keensert. Lightweight M8 only needs an M12 hole. Link to comment Share on other sites More sharing options...
millsn Posted June 1, 2012 Share Posted June 1, 2012 Consider using a stud instead Link to comment Share on other sites More sharing options...
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