Gunsmithing Flush Cup Tap

[Jig Stick]

Can someone please double check me? Im getting ready to tap a stock for McMillan flushcups. I believe they are made by Grovetec. The proper tap is a 9/16-18 bottom tap?

 

[2156SMK]

Re: Flush Cup Tap

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jig Stick</div><div class="ubbcode-body">The proper tap is a 9/16-18 bottom tap? </div></div>

Yes.

Make sure you have a big chamfer at the skin of the stock so you don't split it when starting the tap.

 

[sawman556]

Re: Flush Cup Tap

Use a 1/2" forstner bit to drill the hole and you'll be fine. I'd be willing to let you borrow the tap and drill bit if you promise to send them back.

 

[Jig Stick]

Re: Flush Cup Tap

Thanks guys. Where are you located sawman? I may take you up on that. Would you recommend using a beveled tap to get the hole started? And then go in with the bottom tap?

 

[2156SMK]

Re: Flush Cup Tap

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jig Stick</div><div class="ubbcode-body">Would you recommend using a beveled tap to get the hole started? And then go in with the bottom tap? </div></div>

That's not really necessary.
The hole is only 1/2" deep and you will barely get 3 threads started before a plug tap bottoms out.
Just use a bottoming tap.

 

[sawman556]

Re: Flush Cup Tap

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jig Stick</div><div class="ubbcode-body">Thanks guys. Where are you located sawman? I may take you up on that. Would you recommend using a beveled tap to get the hole started? And then go in with the bottom tap? </div></div>

I'm in New Jersey just across the river from Philly. You're other question was answered above.