Expanding Mandrel

[kiwi2]

Hi,
I came across this video on youtube.
[ame]https://www.youtube.com/watch?v=cYeFlDaxMCM[/ame]
About 8 minutes in the guy (keith Appleton) shows an expanding mandrel inside a cylinder bore using o-rings to lock the cylinder onto the mandrel.
Has anyone here had experience with one of these? I'm not sure of the details of the mandrel or how he managed to face off the cylinder without running into the mandrel.
Regards,
Alan C.

 

[Swifty]

I haven't seen an O ring mandrel before, but it looks like a great idea. Of course, the mandrel will have to be a close fit on the bore before you start, the clamp part of the mandrel has an undercut, I assume that this is where the part was faced and the tool bit took some of the mandrel away.

Paul.

 

[SmithDoor]

The best way is to use Expanding Mandrel
http://www.shars.com/precision-expanding-mandrel-5-piece-set
The only draw back is the price
The rubber does work not as good expanding or tapper mandrels
It not hard to make one for just one size of work


Dave

I haven't seen an O ring mandrel before, but it looks like a great idea. Of course, the mandrel will have to be a close fit on the bore before you start, the clamp part of the mandrel has an undercut, I assume that this is where the part was faced and the tool bit took some of the mandrel away.

Paul.

 

[kiwi2]

Hi,
I've had a bit of a play with this today as the mandrel is relatively quick to make. What I ended up with is shown in the pictures. I've gone for a 1/4" shaft with a 1/16" wall o-ring to expand into a reamed 1/2" hole.
I mounted the cylinder (a scrap one I managed to destroy when I was trying to silver solder it onto the valve plate) as shown. I then faced across both ends and the sides of one of the flanges.
The results were a bit disappointing with a runout of 0.2mm on the flange when the cylinder was rotated on a 1/2" tool steel shaft. The ends of the flanges weren't parallel either.
I then mounted the mandrel alone in the lathe and tightened the nut to expand the o-rings. It was apparent that the extent of protrusion of the o-rings was not uniform so I ran a sharp tool along the mandrel to level them out. I then mounted the cylinder again and faced the side of the flange again. There didn't seem to be any run out. I was knackered by that stage but I'll get back onto it again over the next few days.
One other thing I may try is to make a mandrel with a 3/8" shaft and a 1/16" o-ring.
Regards,
Alan C.

 

[kiwi2]

Sorry,
I used a 1/8" wall o-ring for the 1/4" shaft not a 1/16" wall.
Alan C.

 

[Hopper]

I just use a solid steel mandrel that the cylinder will just slide onto, then Loctite it in position. Machine outside and face of cylinder then heat with propane torch to destroy the Loctite and tap the cylinder off.

 

[goldstar31]

Probably the cheapest way is to turn up a spigot( a stub mandrel) and cut four slots in it with - a hacksaw(?) and drill and tap with a taper tap and expand it with a socket screw.

It's how Sparey did it!

Today,I've been on making 'special ' bolts to expand in wall cavities. There wasn't any standard ones in the UK.
So I got bits of 8mm studding and silver soldered a couple of nuts on each and then reduced them to be round and then turned a taper to expand the insert.

Actually, it is much the same- and cost me pennies.
I can now get my sit on lawn mower in an out of the gardens by removing part of the gates to the lawns.

Norman

 

[Wizard69]

I just use a solid steel mandrel that the cylinder will just slide onto, then Loctite it in position. Machine outside and face of cylinder then heat with propane torch to destroy the Loctite and tap the cylinder off.

I like this idea! It does make me wonder how well super glue would work in this situation. The main thing here is wait time which superglue might minimize.

The other thing I like here is that your mandrel should remain highly reusable and be of minimal run out.

 

[bazmak]

Anybody tried commercial masonary exp anchors such as rawlbolts etc
machined to suit.I have seen it used before

 

[goldstar31]

Anybody tried commercial masonary exp anchors such as rawlbolts etc
machined to suit.I have seen it used before

See my comments above.

If you play it right, you can go to t'other end and a get a mandrel handle set up.

Great for tapping. Ok, I use a staking tool for most of my tapping but a mandrel handle is great for awkward screw cutting especially large diameters and coarse threads

Cheers

Norman

 

[bazmak]

I have used simple PARA BOLTS with the hardened steel threaded and tapered section and a thin slotted sleeve.A set of split dias as requ can be made to fit over and produce a full range of expanding mandrels

 

[kiwi2]

Hi all,
Thanks for the suggestions. I've done a bit of work on this today and have come up with the system shown in the photos.
The work is held on a 1/4" mandrel which is mounted between centres. I reamed a 1/2" hole in a length of 1" aluminium and mounted it in the lathe as shown. I then machined the ends and along the piece. The ends were parallel to within +/- .015mm and the cylinder rotated freely on a shaft with a similar run out.
I think this may be good enough for what I want but the only way to know for sure is to make the cylinder and see what happens to the piston when I tighten the head down.
If this doesn't work I may give the loctite idea a goRegards,
Alan C.

 

[mcostello]

I've made expanding mandrels using pipe plugs for the angle expander. Also countersunk Allen bolts, but the angle is much steeper and require more torque. Use what You have.

 

[kiwi2]

Hi all,

Thanks for all the comments.
I've made a cylinder by drilling and reaming the bore on a drill press and turned the flange ends between centres after mounting it on the mandrel shown in the pictures above. The piston moved freely in the bore after the head was tightened down showing the end of the flange was at right angles to the bore.
It looks like the concept of using an o-rings in an expanding mandrel is a good one. I was a bit wary of putting some o-ring grease in the bore to help get the mandrel in position but it didn't matter. When the end nuts were tightened the work was solidly held and showed no signs of slipping.

Regards,
Alan C.