Question on mod of receiver for para top cover

[ratas calientes]

Okay, I have looked at the photos in FWRA's posting in the marketplace on the modification to the receiver to accomodate the para dust cover. My question:

What is the diameter and depth of the counterbore? Depth relative to the inside flat of the receiver where the bolt carrier contacst.

Link to FWRA's post: (http://www.falfiles.com/forums/showthread.php?s=&threadid=45216&pagenumber=2)

Thanks -

[TapperMan]

It's a 19/32 counterbore with a 9/32 pilot. I just did mine on my drill press following DeanD's advice in this thread (http://www.falfiles.com/forums/showthread.php?s=&threadid=16042&highlight=para+receiver+counterbore) . I did it in steps, checking the top cover fit until it would close with the cover flush at the recoil plate. It looks perfect.

I got the piloted aircraft counterbore from MSC.

Here's the part numbers and links...

08840381 19/32 HS SS 1/8 HOLE 884 1/4 SH.AIRCR CBRE. $24.99 (http://www.mscdirect.com/mscProductSearch.process?RestartFlow=t&RowsPerPage=15&searchmanufpartno=&dispmanufpartno=&operator=AND&QuickFlag=1&Merchant_Id=1&query=08840381+&search_cat=K&x=13&y=8)
08902181 9/32 BODY 1/8 SHANK PILOT $4.1700 (http://www.mscdirect.com/mscProductSearch.process?RestartFlow=t&RowsPerPage=15&searchmanufpartno=&dispmanufpartno=&operator=AND&QuickFlag=1&Merchant_Id=1&query=08902181&search_cat=K&x=11&y=10)

It's about $38 dollars with shipping. You'll probably need the 12" long 1/4" drill extension, too. It's another $2-3 at your local hardware store.Here's a link (http://www.tools-plus.com/irw88601.html) that shows the extension.

[W.E.G.]

Excellent post TapperMan!

[ratas calientes]

Gracias, hermano. Good info. :)

[W.E.G.]

If I secure the receiver in a receiver wrench clamped in a vise, is there any reason why I can't use these tools with a high-torque variable speed hand drill?

It seems to me that the pilot controls the location of the cutter. So, its not like the cutter is going to be wandering all over the place if I use a hand-drill to drive it.

TapperMan, do you use cutting fluid when making this cut? If so, what sort/brand of cutting fluid do you prefer?

[TapperMan]

I think DeanD referred to using a hand drill when he first mentioned the piloted counterbore. The drill extension did have a warning on it not to use it in a drill press (a warning I promptly disregarded). I used a slow speed and plenty of cutting fluid. The pilot should take care of the alignment.

I don't recall what brand the cutting fluid was. I got it at my local hardware store.

[HD99FXR3]

Go slow, very slow if you use a hand drill, And very,very,very low,low,low RPM's or you might WECSOG yourself a broke wrist/hand/arm!!!!!!

[W.E.G.]

(insert image of Wile E. Coyote locked-down on a BA hand drill with the bit seized in the part, and WEC spinning ferociously around the axis of the bit) :wink:

[derek huffman, azexarms]

I brazed an end mill onto a long piece of axle.

Then I used an old gas tube extension and made a reverse pilot from a gas piston. brazed a large spring inside to keep the tension on the mill as it is cutting so it doesnt "yaw" out while cutting.

Works great.

50 bucks for this operation. D.

[JohninVT]

....Or you could cover the shipping and not ruin my backspot facing tool and I'd ship it to you for nada. It looks just like the pic Jeter posted only the extension runs through the face of the tool so that it acts as a guide spinning in the gas port hole and can be used with a hand drill or large dremel. :biggrin: