Drilling and taping chassis

[innesw]

Hi,

The time has come for me to drill and tap my replacement chassis (been putting it off) all the chassis holes line up very well, I just need to drill and tap the reinforced areas on the chassis (2x Front Uprights, 2x Backbone @ gearbox, 2x Rear Uprights) I've misplaced my workshop and parts manuals so thought it would be quicker looking on here but no avail, so i'll ask; what hole size should I drill and what thread do I need to tap?

Here's another question for the enigeers on here; I need to lift up my body by shimming it to aline the bobbin with the front upright's reinforcement area, what is the minimum thickness of metal I need to the side of the tapped drill hole in the reindorced area. This is so I only have to raise the body a minimal amount, or should I raise the body so the bobbin is centred and the hole will be drilled in the middle of the reinforcement area.

(I ask this simply because I think the area is quite large so there isn't too much adjustment between bodies with replacement chassis).

Also can anybody recommend any specific drill bits/tap brands? And the power/type of drill I should use...

Cheers,
Innes

[paddy]

Aren't you advised to check bonnet clearance as well before finalising the fit?

Paddy

[GrUmPyBoDgEr]

Hi Innes,

you will need a 3/8"UNF tap & the correct drill size is 8.4mm.
Also a 7/16"UNF tap & a 9,8mm drill.

You'll also need a couple of sharp smaller drills in order to step drill the holes up to the correct finished diameter.
A centre drill is always a good way to start any hole

I bought mine together with a body to chassis bolt set from Spyder, you should be able to buy either from them now; It's good quality gear.

No the holes don't need to be dead centre in the chassis bosses; they're made big enough in anticipation of variations.
Anything closer than say 2mm from the outside of the thread to the edge off any boss might be problematic to drill & tap but will be OK from the strength side of things.

I made up some special centre punches from locally hardened (tip end) silver steel & chose suitable diameters that would slide through the body bobbins, they made the marking of the hole centres child's play.

Cheers
John

[innesw]

Thanks Paddy, bonnet clearance is already good without raising the body.

John, you say I need 3/8 UNF and 7/16 UNF taps, which ones go where?

Major thanks!
Innes

[elansprint71]

Also... if it's not too late(!) Check the body is centralised (side to side) by measuring the gap between the tyre and the edge of the wheel-arch.
I know nothing about the +2 but on my Sprint I could move the body side to side nearly an inch on the chassis, so clearance could be badly compromised.

Not sure of your engineering expertise but be aware that taps are VERY brittle and need to be treated carefully, I would (after the thread has been started) go in half a turn and then reverse, repeat, and use lubricant, if you don't have cutting fluid, engine oil will do. There are taper and second taps available, make sure you use the taper one first!

Good luck.

[GrUmPyBoDgEr]

Thanks Paddy, bonnet clearance is already good without raising the body.

John, you say I need 3/8 UNF and 7/16 UNF taps, which ones go where?

Major thanks!
Innes

There you go; let's see if the sketch is attached to this answer

John

[mikealdren]

I think it's Spyder who recommend mounting the front end and then bouncing in the back of the cabin to seat it properly on the frame so the mountings on the rear uprights are correct.

You also need to put spacers between the chassis and body at some point to fill the inevitable gaps.

I found (and I don't think I'm alone) that the mounting height of my Spyder chassis in front of the rack seems very high (in other words it tries to raise the nosecone).

To get accurate centring of the holes, I took bolts that fitted the various bobbins and drilled a smaller through the centre of them using my bench drill. I then put the dummy bolts into the bobbins and drilled a central starter hole.

Mike

[innesw]

Perfect! Thanks for the replies guys, I have used taps before and was simply wandering if there where any preferred brands before I go out and buy some. I had about 6mm side to side play which I think I've centred. The picture is great John, cheers!

Innes

[gerrym]

Innes, from memory, the critical issue is to centre punch the steel chassis dead on centre of each bobbin hole.

A set of imperial TRANSFER PUNCHES will have a parallel shank which will nicely centre up in your bobbin holes and provide a punched dimple exactly in the middle. Or make your own as per John's email (from hardenable silver steel)

Seach on the internet for the punches: from memory Warco have some good value transfer punches.

Re the thread taps, any decent HSS taps (taper) will do the job. There's plenty of ebay sellers.

Regards
Gerry

[stugilmour]

+1 on the transfer punches. A full set was only about $30 as I recall, and they line up the holes perfectly. Got the idea for this tool from here as well!