Thread chaser vs Bottoming Tap

[michael950]

When do you use one or the other?


I'm reassembling a short block and installing the manifolds, flywheel cover, etc. Should I be chasing the bolt holes or use a bottoming tap?

 

[RMBC Freeride]

Its my understanding that a thread chaser is better for the threads. A tap will tend to remove too much material (part of your good threads) as it goes. That being said, I dont have any thread chasers :banghead:

Tap is for cutting new threads in a drilled hole... chaser for cleaning/repairing existing threads.

 

[stanton]

you could use a form tap.

 

[DangerBoy]

Bottom taps are for a Blind holes that need threads almost to the bottom. has poor ability to start new threads, holds the chips in the flutes of the tap
spiral / helical taps great for thru holes pushes the chips forward into the hole
Taper tap 1st 7-10 threads not fully formed use in thru holes
plug tap fist 3-5 threads not fully formed best all around
bottom tap 1-2 threads not fully formed use in blind holes

than there are the specialty taps....

use a good tapping fluid and make sure you run the tap in true to the hole.

if you are chassing threads use a bottom tap and dont force it.
Db

 

[stanton]

x2! i just didnt want to type all that lol
hey db what kinda cutting fluid you like? right now emuge is at the top of my list
a9 for aluminum.

 

[DangerBoy]

since we cant get good stuff anymore with 111 in it

A9 for alum
Rustlik for steel

Db

 

[stanton]

yea that was before my time but all the guys i work with said it was like magic. gotta conform tho..
you gotta try out emuge, we use it in everything exept aluminum.

 

[#ZERO]

Use both..... tap all the case holes and use a die to clean all the bolt threads form debris before assembling your engine.

 

[fittyx2]

For aluminum I use kerosene or diesel fuel.
-Scotty

 

[michael950]

Which is recommended for chasing threads for an exhaust manifold (of cylinder)?
(cant find any on Matco or Snap-on).


Looking on McMaster for a bottoming tap:
Spiral Flute Taps

Also called helical flute taps. Best choice for tapping blind-holes. Channels chips back, removing stringy chips formed when tapping soft materials such as aluminum, brass, copper, and magnesium.

Hand Taps

Straight flutes. Suitable for hand or machine threading. Can be used in blind-holes or through-holes.

 

[stanton]

either one will work, since you are just chasing existing threads you wont be making too many chips so evacuation wont be an issue.
straight flute taps are stronger and cheaper.

 

[michael950]

Which pitch diameter limit?

D3 or D5?

Uncoated (Bright Finish)?

TiN (Titanium Nitride)-Coated?
Most common coating. Can be used in a wide range of applications. Not for use on wrought aluminum and titanium alloys.

Nitride-Treated?
Increases toughness. Use with softer metals. Particularly good for aluminum, cast iron, brass, bronze, die castings, magnesium, zinc, and copper.

 

[The Penguin]

Bumpty - looking to buy some taps today and was thinking about this thread.

I also wanted to know what the difference is in the "pitch diameter limit" (D3 vs. D5)

Looking to buy M6x1.0, M8x1.25 and M10x1.25 - any other sizes I need?

 

[dbrutherford]

If you are chasing already tapped holes, any old tap will do. I have an american and a metric Craftsman set and they both have worked great over the years. Iwill say get a nice set and not a cheapo Harbor Freight one. You will snap off a tap and they are a pain to get out! I am going to buy myself a "chasing" tap set soon.

DBR

 

[The Penguin]

I have a good set of SAE sizes, but not metric.

I called McMaster-Carr, the difference between D3 and D5 is the tolerance. D3 being a tighter tolerance.

For thread chasing, a D5 should be sufficient.

so - that leaves the question of what sizes to get?

6x1.0
8x1.25
10x1.25

are there any others on a ski?

 

[kevbo]

Those sizes should cover the engine and most of the hull. You may run into small screws that are M5x.80. I think they are used on the stator coils and 61X reed blocks.