Thank you for the confirmation - I need to work out whether I can make something similarIts a rubber seal, similar to what you see in a slave cylinder on a car drum brake.
Thank you for the confirmation - I need to work out whether I can make something similarIts a rubber seal, similar to what you see in a slave cylinder on a car drum brake.
O rings are not great for sealing hydraulic pressure without them sitting on a shoulder. You need a seal.My current plunger mod (plunger with o-ring) works for a while but eventually fails for the following reasons (at least afaiac):
- internal thread is damaging the o-ring
- small dia of the plunger (6.4mm) limits the size of o-ring I can use
With external thread, I can increase dia of the plunger to (up to 8mm?), which means I can use larger o-ring, plus it doesn't get ripped to shreds when I am inserting the plunger in.
Well worth trying...
I will get you a proper picture and dimensions tomorrowThanks @Brad93
They have a whole bunch of 8mm OD to choose from: https://www.123bearing.co.uk/sectio...exterieur=8.0&fld_hauteur=&fld_shore=&family=
perhaps, if I have removed the boss and inserted the plunger from the other end (not past the threads) it might have been OKbit of a bummer that your seal failed - I'd have thought that once you managed to get it in and sealed, you would be fine until the next maintenance cycle, which should hopefully have been years away!
Not quite sure I follow your words I will send you a message with Fusion 360 id so that can have a look at it, pleaseThe design I'm working on is using an 8.5mm piston, with an O ring seal. This is about as large as I was comfortable going while still leaving some wall thickness. This is a large enough bore that the 8mm threaded actuator can fit inside without touching and damaging the bore. Because the bore is full depth, it can have a tapered entry to seat the O ring
That's what I said, honing. Polished is no good for the bore, that's why the hone hydraulic cylinders.Funnily enough, I don't think it's a polished surface you want. Talking to an old mate who was in the brake business, and he commented that you typically need to hone brake slave and master cylinders for the hydraulics to work properly. His belief was the cross hatching captured a miniscule amount of oil, and that is what provided the seal.
And just checked the links above, and there is a 8.5 od cup seal available, so that is the direction I'll go. Be interesting to see if I can find them here in the antipodes, but mailing one from the UK is no big deal.
I just downloaded a pdf for the Hofmann UTH series from https://www.machinemanuals.co.uk/manual.php?p=100 it cost 9.95 GBP but is a pretty good clean scan.I recently purchased a hofmann dividing head. Does anyone have the manual they would be willing to share? I tried to contact hofmann multiple times but never received any reply.