thread taps

[DeanR]

Somehow I've never had to use a thread tap before. The beginning female threads for a handlebar bolt began to get messed up and I'm not gonna crank it further to compound the problem.
Is there anything I need to know while starting the tap? just to clean up the first few threads. Also, would a cheap auto parts store tap made in China do the trick or should I go to Sears. They just happen to have the right size (8x1.25).
Thanks to all the mechanics!

[DiverRay]

I've had both the cheap, and the Vermont/American from Sears or the local Ace hardware store. Buy the good one! the cheap one is a little off in the diameter or the depth of cut. a good tap is about $5.00 for 8mm, and you WILL use it again!
JMHO
To clean up the threads, starting it IS very important. Just give it a start, go about one or two turns until it gets hard, back it out about 1/3 of a turn, and go in again. Use oil to lubricate as you cut, it will help clean the metal bits out of the hole, and helps the tap to cut a smooth thread.

[xswilly]

the cheeper taps may break easy, and you don't want a tap stuck in your hole

when you buy your tap, get a tap that is bottoming
that means that it can tap a hole that has a bottom to it
verses a hole with no bottom

line the tap up as stright to the hole as you can, and put a little oil on the tap, WD-40 will work.

slow and easy is the way to go

[DeanR]

95% of the threads are still OK. Will the tap just cut/lead the first few bad threads right into the rest?

[xswilly]

if there is enough of the worn threads to guide the tap into the hole, you should be OK

[COOL TOM]

Taps

If you are starting a hole get a starter tap it has a log taper on it to help line up the threads. Then finish up with a bottom tap that cuts threads down to the bottom. Like they said get GOOD taps and use cutting oil to help it cut better. If you can't get cutting oil just use regular car oil. Like Ray said slow and easy and back and forth. Don't get rammie or you will be in trouble.

[vanhump]

Having spent 40 years as a machinist and tool and dye maker I think I can give you good advice. The Sears taps will be ok for a one time job. Get the better taps at a tool supply place. Get two taps..... a starter tap and a bottoming tap. The starter tap will pickup the threads with less chance of cross threading. Get a small can of cutting oil or a mixture of kerosene and cooking oil. Do not use any type of regular oil or penetrating oil. Oil is a lubricant and works against what you are doing. Cutting oil is a coolant and keeps the metals from bonding, ie the tap to the chips of whatever you are tapping.

[DeanR]

Perhaps I only need a "starter" tap because it is only the very beginning of the hole that is messed up? Rest of the way down is ok. Just need to get the bolt started properly...

[AlanB]

Hi Laxdad,

there is some good advice on here, but most of it tells you how to cut a new thread; this is not what you need to do! Generally, if you wind a cutting tap into a damaged thread, you will end up cutting a new path through the material, leaving a weakened thread.

You need to find a way through the damage to the existing thread. For this, you do not need a "cutting tap"......... as sold by anyone. You need a "Clearing Tap"... made at home!

Find an undamaged bolt which would have fitted the thread before it was damaged. use a hacksaw to cut three grooves down the bolt; if you can manage to make 'em slightly "spiral"... it is better, but not essential.

The plan is that the modded bolt can shift the displaced aluminum, but is not hard enough to actually cut a new thread; it should find it's way into what was there before!

Wind it in a turn or two, take it back out, clean the grooves, wind it in, and repeat until bored!......... I now cut the grooves with a triangular file, to make something approaching a "proper" Tap, but still too soft to cut a new path.

Alternatively, if the clamp is threaded right through, put a bolt in from the other side; again, it will clear a way through the damage.......

Best of luck!

AlanB

[erithanis]

I actually have had the same issue as posted here. This last comment is really helpful THANKS! I have been very uneasy about using a tap when only a small amount of the threads were damaged.

[xswilly]

i doubt if you can find one in a hardware store
but a thread forming tap would work great at that
it doesn't cut it pushes the metal around to form a thread

they are also called a roll tap or a form tap

[planedick]

best taps

The best taps are made of tool steel and labeled HSS (high speed steel) will last a long time, but most importantly, epsecially in aluminum, use tapmatic cutting fluid for aluminum, it prevents the material from sticking to the tap and makes a clean thread. If you can't get tapmatic a solution of 50% crisko and kerosene works really well. Sears taps are carbon steel which IMHO are garbage. Only good for cleaning threads and only once.

[Czekus21]

A good tool store should have a thread wrasp. It's a tool that is long like a file, not flat. Square. The file part that looks like the teeth of a wrasp are in place to match up the threads that need cleaned up. I believe there are 8 different size thread cleaners. It will not cut new threads, only clean up mashed or dirty threads without ruining the integrity of the bolt. I forget what the name of the tool is, but, I'm sure someone here knows what I'm talking about and can enlighten us.
I had one when I turned wrenches in the Army. Was a great tool to have.
This is used on bolts or studs. Not holes.

[Ken Talbot]

Top tool is a 14mm thread tap.
Bottom tool is a 14mm thread chaser.

[xswilly]

the rasp you are talking about is called a thread file
and has different pitch threads on each side

but it only does outside threads