Modifying cheap steel devices

ValleyMichael · Nov 8, 2019

I have a Chinese A271. It's great, except for two factors. One, the 50mm ring results in regular ball escapes, while the 45mm is a bit too tight. Two, there are bands of metal within the tube which are narrower than the rest.

For the ring, I can see two options. One, I could grind down the 45mm to be a bit bigger. Lots of spare material, so it should be feasible. I'm not sure what tool I should be using for that though - any suggestions? It's stainless, some soft variety. Two, I could build up the 50mm to prevent my balls from slipping out. Maybe some hobby putty type stuff would do it, need to look at what's available.

For the tube it's a bit more difficult since it's on the inside of the tube. I tried for a bit with a Dremel this morning but it's quite difficult to get the right angle, plus I think I have the wrong attachments. Any suggestions for the right tool there, too?

Guest 3729 · Nov 10, 2019

I used to wear the same cage but has gone into semi retirement. I also had to do some customizing to it just like you described. You will need a quality Dremel style hand held grinding/polishing tool. You will want to buy special grinding wheels called mizzy wheels, then you will want to buy “sanding drums” of various grits that get finer and finer. Then you will want to polish the rough spots with a polishing compound and what’s called a “Muslin” wheel.

Whether the ring is an ergo ring or a round, use a set of calipers to measure the inside diameter from a few different positions so you know exactly what size you’re starting out at. Then put your mizzy wheel on your Dremel and start grinding away in a consistent circular motion trying keep it all symmetrical as you grind. One you reach your desired size. I.e 40mm up to 42mm then start using your sanding drums starting with the roughest grit to the finest smoothing out the rough metal. Then you finish off by using the muslin wheel and polishing compound on high speed to smooth the rest of it out and give it a high shine and polish. Then just wash it with soap and water and see if you’ve polished out all the rough spots.
You can also grind down and smooth out the bands on the tube but don’t thin the outer ring out to much it will be comfortable.

https://www.lowes.com/pd/Dremel-400...mJC9TlAnSP17p1lsB9hoCmI4QAvD_BwE&gclsrc=aw.ds

https://optimusdentalsupply.com/key...93vBViWXfU0BOPY6nsa_LhL3luIJMUhBoC9O0QAvD_BwE

https://www.esslinger.com/7-8-mini-muslin-mounted-buffs-3-32-mandrels/

https://www.pjtool.com/stainless-st...dbMfEPym_yxV5X8Aed9fmAOHLpTtHnDhoChDwQAvD_BwE

shop around for cheapest price I just did a quick search so you knew what to look for. You will need a decent Dremel that’s capable of high speed otherwise it will take forever to grind out and you’ll never get the polish you want so don’t go cheap on the hand too, the more powerful the better. PM me with any questions, I’m a goldsmith I do this stuff all day long.

ValleyMichael · Nov 11, 2019

Thanks! I have an old Dremel MultiPro 395 which does 35k RPM, so same as the current corded models, so I should be set there. All the current attachments I have are aluminum oxide, not silicon carbide, which is probably why it was going so slowly. I see that they come in packs of many - should I expect to wear them out doing this? I can also see how they could get loaded with the material and stop grinding properly. Not sure how I'd get a bunch of metal dust out (water spray, if it's not packed in, maybe), so swapping to a new wheel when the old one is fouled may be the easiest approach.

It's not clear that a Dremel mandrel will hold one of those Mizzy wheels, and it's clearly cheaper to buy just the wheel and not the tool pre-attached to a shaft like Dremel sells directly, so the order is a mandrel, a couple different sizes of heatless wheels (1/2" and 3/4", both 1/8" thick), some abrasive bands (80, 180, 320; might not need the 180 tbh), an arbor for the bands, and a miniature muslin wheel plus some medium cut polishing compound. Should be set for a while on these, there's way too many in a pack. Grand total is $69.04 (nice), 4x as much as the cage but 1/8 as much as a custom cage.

Should probably get a bench clamp though, doing this in the hand is tiresome and probably results in more chatter. I think I have one down in the basement somewhere, but it's really more for electronics, may not be good enough for grinding.

collaredhubby · Nov 30, 2019

Sandpaper in the right grit and compositions works wonders and you don't have to worry about over-doing it with the Dremel as you can go slowly and get a really smooth mirror finish if you prefer and work out any inconsistencies or rough areas on the rings and cage.You just go up grit by grit to maybe a 2000 or 3000 grit. it works, it's cheap, it only requires a little time, you can work wet to cut down on dust, the risk of weakening the metal by heating it too much with the rotary tool is all but eliminated, and you can get excellent results if you just invest a little time and elbow grease. I would caution you that if you have a cheaper Chinese style device and you experience or see any flaking of metal, toss it, as the metal flakes can get in your skin and cause all kinds of bad. It means that your device has some kind of coating and true stainless steel doesn't flake and leave discolored sections of steel that look different when polished or sanded. If it's true stainless, it will take on a brushed look until the scratches you create by sanding (polishing) are so small that the surface reflection is one of a mirror or very shiny without large scratches or indentations. Hope this helps.

locked_top · Nov 30, 2019

Nice thread. I'm never going to do something like this myself, but I like knowing that there are others who do.

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Modifying cheap steel devices

ValleyMichael Junior Member

Guest 3729 Long term member

ValleyMichael Junior Member

collaredhubby Long term member

locked_top Caged tiger