Sanding (Emery) rolls with closed tip

arcticXS

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I am now trying to do a light cleanup of the ports in a XT250 head, valve sizes are 38 and 32 mm. The only sanding rolls small enough to get into the "valley" both sides of the guide bosses are the cylindrical/ open end 8 mm Dremel type.
These do not work the way I would like.
Now, some years ago, on a ship I worked on, we had some lightly tapered, closed end sanding rolls, and the rubber mandrel heads had lengthwise slots. I suspect these may have been ordered from Graingers or other US supplier. These rolls will allow to use the end as well as the side, so would be perfect if available in, say 1/4" OD.
Any idea if something like that is available, and where? Or something that will give a similar finish (grit impregnated rubber maybe?)
 
It turns out that even those porting tool specialists do not have something with a small enough diameter. So after a lot of head scratching, I had sort of an "Eureka moment". In many generic Dremel accessory kits, there are these felt wheels/ drums with a threaded mandrel. Unfortunately, those felt drums are too large in diameter. But when cleaning one of my rifles, I realized that I have plenty of .264 and .30 caliber felt "drums" for cleaning rifle barrels. So using those with the Dremel type mandrel, and a coarse polishing compound or even lapping paste, it is possible to reach into most areas in the XT250 ports.
 

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I got one of these from Aliexpress they are of good quality. Note there are several sizes of bullet shaped pads. Hold up well, perfect for buffing the O-ring seats on vacuum petcocks
 
I recently got some of these.
1680032357648.png

I've only used them a couple times, but they worked great to remove the end of the butterfly retaining screws sticking through the throttle shaft.
Might be issues with plugging when grinding aluminum. On similar work I find keeping the area wet with stoddard solvents (mineral spirits in the US) helps reduce plugging up files and abrasive bits. Also try to keep the speed down.
 
Yes, I did use a ball type diamond rotary file, maybe 6 mm OD. It was able to reach most spots, but did not give quite the finish I wanted, especially in the exhaust port. I am aware that a polished surface is not desirable in an inlet port, but should be better for the exhaust port. I will have to look into those AliExpress buffing wheels, they may work better than my gun cleaning stuff.
 
For getting into tight areas like those "valleys" on either side of the guide bosses, as well as smoothing the macining marks in the areas around the seats, I like these Dremel ball cutters. I use the 191 and 192 most .....

BallCutters.JPG


And for generally smoothing out the rest of the port, I like these rubber grit impregnated wheels and "points". I believe the brand name is "Cratex" but generic ones are all over eBay .....

Cratex Wheels.jpg
 
Thanks 5twins!
Cratex definitely appears to be a serious supplier of rubber bonded and other specialty abrasives. Unfortunately, their smallest bullet points are 9/32" diameter, and most items come in packs of 100 pcs.
So I searched eBay for alternatives, and ended up ordering this kit, 50 pcs ranging from 4 to 12 mm, bullet points and cylinders (5 of each):
https://www.ebay.com/itm/393735784682

I always try to order from a European or US manufacturer when possible, but this time around it unfortunately ended up with a chinese vendor...
 
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