shep28

iTrader: (4)

Machine shops drill out and retap hole with a drill press- I think. I am drilling a hole larger and rethreading it and then screwing in a timesert thread insert that has a stock sized hole.
http://www.timesert.com/
which will be stronger than a helicoil.

I want to drill and rethread by hand at the correct angle. Any suggestions.

Roadrunner 45

iTrader: (1)

What size is the hole now and what size will it be? how much room do you have to work? Since you don't have a drill press I assiume you don't have access to a mill to make a drill bushing to bolt down/clamp. In that case your best option would be to drill in small increments like a 1/16" at a time- drills always tend to follow an existing hole anyway so if you are careful you should be ok.

87gnx

iTrader: (3)

True, machine shops use a drill press on slow speed.You may even try a light oil like WD 40.Like roadrunner said,take your time and size up the hole slowly in small increments if possible, don't start by drilling a 1/4 inch hole. If you want since your drilling by hand, hold the drill like a pistol, pointing down with your first finger, using your middle finger on the trigger to slowly drill the hole.We do this alot in aviation hope that it helps you.

shep28

iTrader: (4)

Those are helpful tips.

I had a thought. I could find a pipe or spacer of the correct diameter and place it flush and centered over the area that will be tapped. I could then place the drill bit through the spacer whole and use the spacer/pipe as a guide.

Does that sound like it will work?

shep28

iTrader: (4)

neat idea

shep28

iTrader: (4)

rocker arm bolt hole. tap is .463 in diameter. I drilled out a broken rocker arm bolt- drilled slightly over the holes original diameter. at first I drilled with a hand held drill- not enough rpms to drill through the bolt. I then used my air dremel with a carbide tip and it cut through the bolt like butter. The bigsert timesert
http://www.timesert.com/bigsert.html
has oversized threads that will correct the problem. I have enough room and material in the head to drill and insert the oversized insert into. I just want to make sure I drill at the correct angle or else I will be buying new heads.

87gnx

iTrader: (3)

If it were me drilling into a head, I'd find someone with a drillpress or go to a shop and tell them what you want done.. those angles can be tricky and mess up the valvetrain geometry.

Rhysamedrae

You might try building a little jig to hold your drill...something along the lines of a couple of dowels inserted into adjacent rocker arm holes for the angle and a couple other shortened legs on other points of the cyl. head, all supporting a base with a cutout for the drill.

The thought of tapping an alum. cylinder head with a hand drill scares me, though. Be VERY careful of your rpm and feed rate...and use a little cutting fluid.

Just for thought, a small drill press can be bought for less than a cylinder head...

If you've got the head off already, any machine shop can do the work for you, as well. Most shops only charge $80-$100 for a helicoil, the TimeSert is the same basic idea.

EDIT: Incidentally, it was mentioned that a hand drill didn't have enough speed to drill into aluminum...you shouldn't need any more than half-speed on your drill. If you were revving it faster and faster and getting nowhere, most likely your pilot hole was far too small.

Roadrunner 45

iTrader: (1)

Do not use the drill to drive the tap- if it began to pack up with chips you wouldn't feel it and you could end up galling the new threads as you tap. Get a tap handle and do it by hand once you have the hole to size.

If you mess up, or it looks like it won't work for you I can have one of our guys spruce it up if you send me the head (I have a machine shop- not an engine shop, but we do precision machining and can fix this easily).

shep28

iTrader: (4)

No, I meant that I did not have enough speed to drill out/through the broken rocker arm bolt that was stuck in the hole. I had to disintergrate it due to way that it was broken off in the hole. If I had used the air dremmel in the first place I would not be having this problem. Even with the carbide tipped/sided drill bit, the hand held drill could not eat through the bolt.

shep28

iTrader: (4)

That is very nice of you Roadrunner.