# Methods for countersinking screws on shop made base plates



## loninappleton (Jun 12, 2008)

I have one of those countersink bits for a hand drill. But the biggest on the rack in the store are always just shy of being wide enough. Bu the shank will ream out the screw hole too big.

What is used from your experience for this with making shop made bases?


I have Forstners, but the countersink and flat head screw tightens and 
centers the base plate during the install procedure.


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## istracpsboss (Sep 14, 2008)

You could try using a bigger drill like a blacksmith drill and using the tip to countersink. The include angle is different, but you might get away with it.

Cheers

Peter


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## jschaben (Jun 21, 2009)

loninappleton said:


> I have one of those countersink bits for a hand drill. But the biggest on the rack in the store are always just shy of being wide enough. Bu the shank will ream out the screw hole too big.
> 
> What is used from your experience for this with making shop made bases?
> 
> ...


Hi lon - I use one of these. Actually made for metal, usually around an 84* taper but works pretty well. Have also just used a standard 115*/135* drill bit a couple of sizes larger than the screw I'm countersinking. A lot depends on thickness of material and size of the fastener being countersunk.

Oh, if you are counting on the countersink doing the centering, put it in first. Then open the hole up for the fastener if necessary. The 84* may penetrate the stock by the time the countersink is deep enough.


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## bobj3 (Jan 17, 2006)

Hi 

Forstners bits work the best but you must pickup some pan head screws or button head Allens,,The Forstners holes can be off a little bit so you can line up the base plate just right, I like to use the 3/8"/1/2" Forstners bits most of the time, a little 1/8" hole to center the Forstners bit and drill down 1/8" deep the norm, I will say it's best to replace the cheap phil.head screws with Allens/socket type they don't don't strip out like the cheap screws do..for 15 cents you can replace all of them..


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loninappleton said:


> I have one of those countersink bits for a hand drill. But the biggest on the rack in the store are always just shy of being wide enough. Bu the shank will ream out the screw hole too big.
> 
> What is used from your experience for this with making shop made bases?
> 
> ...


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## loninappleton (Jun 12, 2008)

*solved*

Note to self:

A V-groove bit in the cheapest knockoff bit set available works fine as a countersink (and using a hand drill to boot.)

I believe I did this that last time but did not remember. A variable speed drill running very slowly will keep from any splitting in plexiglass.

My center finding jig as given by Bill Hylton in "Router Magic" is now complete.

I do not know if the center finding jig has been on Router Forums in the past.

But now that I can do a stop cut groove on center through a narrow piece to make a good straight edge jig, is there any off-the-shelf peg that is square at one end and round on the other?

The device made for Hylton's straightedge requires a square peg to match the through-groove being cut on the table saw. I'm looking for an alternative
to that since I do not have a table saw.


If there is a square nylon insert of some sort to hold the shop made clamp in place that might be another answer.


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## jschaben (Jun 21, 2009)

_"A V-groove bit in the cheapest knockoff bit set available works fine as a countersink"_

Hi lon --- duuuhh, why didn't I think of that.:agree: I've always wondered about an 84* angle on the countersinks anyway as you usually have to go so deep to get a flush countersink you enlarge the pilot /main hole. Haven't really been to happy with the 115* or 135* options either


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## loninappleton (Jun 12, 2008)

Hello John Schaben,

Admittedly I do not know the difference in cutting elements between the V groove and an actual countersink. I managed to get away with it this time.


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## paduke (Mar 28, 2010)

Countersink plastic using a Dremel and a 45 degree grinding bit. I but a cheap set of diamond surfaced bits @HF. Under 10 bucks. I used it mounting blocks to 1/8 UHMW. Also you can hand sharpen a drill bit that is same size as screw head.


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## loninappleton (Jun 12, 2008)

I was just out looking at v groove bits to use as countersinks a couple days ago. What I noticed in using some v groove bits is the widening of the hole along with the countersink. To avoid this the angle has to be greater than 45d. The standard v-groove bits appeared to be 45d. This for construction purposes, I realize, but a wider angle would be welcome
for countersinks in making sub bases.


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## RJM (Apr 11, 2010)

loninappleton said:


> I was just out looking at v groove bits to use as countersinks a couple days ago. What I noticed in using some v groove bits is the widening of the hole along with the countersink. To avoid this the angle has to be greater than 45d. The standard v-groove bits appeared to be 45d. This for construction purposes, I realize, but a wider angle would be welcome
> for countersinks in making sub bases.


 
V-groove bits are 60° and 90° with the most common angle being 90° the norm.

Using a larger angle will keep the thru hole in the center smaller but this is not important and actually makes the joint weaker bu forcing the contact area between the screw head and the plate closer to the bottom of the plate where the nmaterial is thinner (i.e. the extreme would be at the hole itself where the countersink forms a knife edge.

Use a countersink with an angle as close to the screw countersink angle as possible. Most screws in the US have an 82° csk angle.

Don't worry too much about the size of the thru hole. It's the head of the screw that does the clamping and locating. Material thickness is a concern so you don't want to make the csk any larger than necessary. If you make the csk diameter just a tiny bit larger than the diameter of the screw head, you will be using almost all the material thickness to carry the load. Make sure that the material thickness is more than the height of the screw head, otherwise the screw head will bottom before clamping.


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## loninappleton (Jun 12, 2008)

Well just for reference it might be helpful for others who make sub-bases regularly to describe what they do.

I'm getting better at the countersink. Initially I was using those countersinks sold int he hardware store which are stepped and so got some really big holes by the the time the angle kicked in. I had a groove bit and finally put 2 and 2 together that this was the tool to use. 

I've made a number of sub bases now. Pretty soon I'll do a real project. ;-)


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## jschaben (Jun 21, 2009)

loninappleton said:


> Well just for reference it might be helpful for others who make sub-bases regularly to describe what they do.
> 
> I'm getting better at the countersink. Initially I was using those countersinks sold int he hardware store which are stepped and so got some really big holes by the the time the angle kicked in. I had a groove bit and finally put 2 and 2 together that this was the tool to use.
> 
> I've made a number of sub bases now. Pretty soon I'll do a real project. ;-)


Hi Lon - I was trying out your method using the 90* bit in the drill press. Works really well except with Lexan, sometimes got some chatter. Could be I need to speed up the press some, I think it is set on 900 rpm.


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## bobj3 (Jan 17, 2006)

Hi

I use the stones in the kit below most of the time, I like a nice clean countersink and the stones do that for me... I was lucky I got two kits for 9.99ea. on sale..

1/4" Air Die Grinder Kit

and the stones below that work well for the small holes
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=tools&field-keywords=dremel+stones&x=12&y=22
and cutting tools below
http://www.amazon.com/CC250-Diamond...f=sr_1_49?ie=UTF8&s=hi&qid=1283265268&sr=1-49
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loninappleton said:


> Well just for reference it might be helpful for others who make sub-bases regularly to describe what they do.
> 
> I'm getting better at the countersink. Initially I was using those countersinks sold int he hardware store which are stepped and so got some really big holes by the the time the angle kicked in. I had a groove bit and finally put 2 and 2 together that this was the tool to use.
> 
> I've made a number of sub bases now. Pretty soon I'll do a real project. ;-)


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## loninappleton (Jun 12, 2008)

This grind wheel technique looks like it should work well and avoid chipping.

Thanks


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## jschaben (Jun 21, 2009)

bobj3 said:


> Hi
> 
> I use the stones in the kit below most of the time, I like a nice clean countersink and the stones do that for me... I was lucky I got two kits for 9.99ea. on sale..
> 
> ...


Don't those load up with plastic though?


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## bobj3 (Jan 17, 2006)

Hi John

They do but a quick brush with a steel wire wheel cleans them right out..

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jschaben said:


> Don't those load up with plastic though?


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## RJM (Apr 11, 2010)

loninappleton said:


> Well just for reference it might be helpful for others who make sub-bases regularly to describe what they do.
> 
> I'm getting better at the countersink. Initially I was using those countersinks sold int he hardware store which are stepped and so got some really big holes by the the time the angle kicked in. I had a groove bit and finally put 2 and 2 together that this was the tool to use.
> 
> I've made a number of sub bases now. Pretty soon I'll do a real project. ;-)


When I drill a custom base plate, I agree with Bobj3; use a forstner bit and make counterbores instead of countersinks. This will let you make adjustments and the the holes don't need to be perfectly located.


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## Ayrton (Sep 12, 2010)

I used this tonight on a base I made out of plexi, and it worked perfect. 

*EDIT* I don't have 10 post yet...

Search "counter sink" at Harbor Freight.


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## loninappleton (Jun 12, 2008)

Ayrton said:


> I used this tonight on a base I made out of plexi, and it worked perfect.
> 
> *EDIT* I don't have 10 post yet...
> 
> Search "counter sink" at Harbor Freight.


3-In-1 Countersink

Right item?

Can you post a picture yet?


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## Ayrton (Sep 12, 2010)

loninappleton said:


> 3-In-1 Countersink
> 
> Right item?
> 
> Can you post a picture yet?


This one

1/2" Six Flute Countersink

I just chucked it up in the drill press, and it worked perfect for 1/4" plexi. 

I can't say it works as well in wood, but it is cheap.


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## loninappleton (Jun 12, 2008)

I think the grinder attachment described earlier is a 60 degree rather than 45 degree.
This should allow for less hole drill-out when making the base pattern. The trick seems to be getting a small hole diameter (for the base screws) and a large countersink "dish" for their flat head and get everything just below flush at the surface. The ones I've made have been ok but could be better using the right tools.

So far I've only used the 60d grinder bit to polish what was a ragged countersink "dish" using the metal countersink bit in plexiglass.

To those who have used Lexan: has this material worked better in shaping a base?


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## dutchman 46 (May 23, 2007)

My thought is that any time You are using a drill bit with a center pin, screw pin, or anything to get the drill started to drill, They are all centered by the pin. Therefore,You can use a starter drill of 1/8 in, or so and then use the larger drill with the pin, it is always centered.


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