Fixing the sidescreens to the windscreen

[martinclan56]

I don't know I'd anyone can actually remember what they did back in the day but....
The Roadster build manual suggests fixing the durable dot bases to the windscreen frame using self tapping screws. It's difficult to believe this would be successful as self tappers are designed for sheet metal. I tried experimenting with a piece of scrap and as I expected they just sheered off.
Would not tapped holes be better?
Cheers Robin

[listerjp2]

I drilled and tapped a thread in mine.

Adrian

[listerjp2]

I Qoute

Drill the three 5/32 " Dia holes through into the glass groove. Take care not to drill into the glass itself. Tap 2BA using a bottoming tap. When tapping use plenty of oil or special thread cutting grease. Establish thread squarely for three turns, thereafter advance by 1/2 turns only and wind back 1 full turn each time to cut off the chip. After 10 turns, remove tap and blow chips out of flutes before continuing.

Hope this helps

Adrian

[listerjp2]

Or if using press studs to go around the front

I quote

The press studs are fixed with the small self tapping screws provided. Drill 1/8 diameter holes in the screen frame for the self tapping screws. There is an additional press stud on the front bottom edge of each side screen, this fits to the outside of the screen frame.

Again, I hope this helps.

Adrian

[martinclan56]

Thanks Adrian
It's the press studs on the front of the screen surround that I have. But I think I am going to drill and tap...

[TVRFan]

from the basics.....

You have to drill a blind hole of just the right size - there are handbooks which have 'tapping sizes' for most threads. Standard thread on lift-the-dots is 2BA (maybe they do metric now...). You have to keep drill vertical as possible and drill a 'straight' hole, otherwise tap may snag and it will snap.
The right size is VERY important, as too small will break the tap (too much force) and too big will not cut the thread correctly. Taps are very hard carbon steel, and very brittle. Some people use a tiny bit of grease, but it can grab the swarf, so use light machine oil.

There are THREE taps in a set, first being tapered most, second less tapered , and third even less (3rd is for for blind holes). GENTLY start with tap one, max of 3/4 turn (or 1/2) and then REVERSE. This breaks the swarf, which otherwise may gum up (and snap) the tap. Go slowly down, clockwise/anticlockwise, maybe take it out and clean it a few times, until you feel tap hit the bottom of the hole.
Then use tap 2 and still reverse every turn, maybe clean it.
Then use tap 3 to finish thread further down for blind hole.
then blow it out and check the bolt (or whatever) fits
And don't EVER force it, especially for smaller sizes.

That's how I was taught anyway.

And that's what I did on my Marlin.

[duncan]

When you want to drill the hole first get a piece of a hard wood - drill a nice vertical hole in that - you can use your drill press
Then clamp that to the screen surround and use it as a drill guide to get a nice hole perpendicular to the surface

[martinclan56]

When you want to drill the hole first get a piece of a hard wood - drill a nice vertical hole in that - you can use your drill press
Then clamp that to the screen surround and use it as a drill guide to get a nice hole perpendicular to the surface

Great tip! Getting precise vertical holes "in location" is always tricky. The vertical hole through a piece of hardwood as a jig is a great idea and I am sure I will use it elsewhere as well.

[martinclan56]

from the basics.....

You have to drill a blind hole of just the right size - there are handbooks which have 'tapping sizes' for most threads. Standard thread on lift-the-dots is 2BA (maybe they do metric now...). You have to keep drill vertical as possible and drill a 'straight' hole, otherwise tap may snag and it will snap.
The right size is VERY important, as too small will break the tap (too much force) and too big will not cut the thread correctly. Taps are very hard carbon steel, and very brittle. Some people use a tiny bit of grease, but it can grab the swarf, so use light machine oil.

There are THREE taps in a set, first being tapered most, second less tapered , and third even less (3rd is for for blind holes). GENTLY start with tap one, max of 3/4 turn (or 1/2) and then REVERSE. This breaks the swarf, which otherwise may gum up (and snap) the tap. Go slowly down, clockwise/anticlockwise, maybe take it out and clean it a few times, until you feel tap hit the bottom of the hole.
Then use tap 2 and still reverse every turn, maybe clean it.
Then use tap 3 to finish thread further down for blind hole.
then blow it out and check the bolt (or whatever) fits
And don't EVER force it, especially for smaller sizes.

That's how I was taught anyway.

And that's what I did on my Marlin.

I've ordered the correct sized drill and a set of the 3 taps. I have tapped quite a lot of holes over the years but the ones I dread are the small, blind ones so not taking any chances...
I am using M4 screws. The heads are a bit big but once turned down a nats they fit fine in the press stud bases.

[TVRFan]

True, much smaller than M5 ish can be a real pain. I've snapped a few M4 taps. I like the hardwood trick, neat. Yep, have to be careful with 4mm in a steel blind hole...

For those that don't know - the slower taper on tap 1 helps you get the thread straight, and therefore cuts threads more slowly. tap 2 (and 3) cut the right size. This is all for hand taps of course, machine taps (for drills etc) are different.