HHIP 4100-0040 Center Line Gage Set for 4", 6" and 8" Calipers

Looks like it will fit most calipers

set screws were so tight you cannot loosen them, and they strip out. It is impossible to get them to line up with no gap. You get what you pay for

Measurement of my set if off by about 0.003in total. OD on both is exactly 9.50mm. Offset of OD to groove is 4.70mm for one and the other is at 4.72mm which adds up to 0.08mm == 3 thou runout. Not too bad. Strangely enough one of the center gages uses a 1.5mm set screw, the other one uses a 1/16in set screw. The Allen wrench which comes with it is 1/16in, it did not fit in the 1.5mm set screw.,

Set screws had stripped heads. I don't know who has 12" calipers with jaws as thick as the slots on these but I guess it would work for them. For my Mitutoyo 8" calipers this set is gigantic and unwieldy.

You will probably want to dedicate a set of calipers to these, as they do take a little time to attach and mount perfectly.

Quality is sub par for precision measuring use. Rough surface finish on jaws. The cutting of the slot for mounting is uneven. At least two lengths of set screws are used on the jaws. Having said that these are still a deal for the price. Make sure you drill two holes at know distance and then mount and use the center line gage set and verify it reads the same. It is possible and perhaps likely that the jaws will not mount parallel to one another the first time. This is another reason to mount to a purposed set of calipers then leave alone.

One tip is rounded off to one side, other than that they seem okay. Easy fix and still worth the money.

Fussy to put on, need to be dedicated to a caliper (no quick change), and you need to use a caliper with "ABSOLUTE ORIGIN" such as iGaging ABSOLUTE ORIGIN 0-6" Digital Electronic Caliper - IP54 Protection / Extreme Accuracy because you can't zero it out once you put these on, but once they're setup they work great.

Poor quality, the precision of the caliper face in reference to the center point is questionable, mine you could clearly see that they did not look centered at all. The fit was also very poor when installed. I ended up returning.