What is a "Coarse Tap"

[HOTFLASH]

In the tips and other references to reinstalling the water jacket side plate, there is mention made of using a 5/16 "coarse tap" to clean out the holes the bolts screw the side plate to the block. I understand what a tap is. What is a "coarse" tap? The old bolts--not original--were mushy when removed. I have no trouble screwing the new MM brass ones in and have the washers too. Do I need a 5/16 "coarse tap" to prep the holes before reattaching the plate?

[baileyem]

Hotflash
There are many different types of threads on bolts, plumbing pipes, etc. , but generally you only have to worry about two of them when you are dealing with nuts and bolts. The one used most often is referred to as coarse, the other as fine.

Mike

[Kurt]

I did use a coarse tap on a bolt that I broke off my water jacket side plate. I was able to scrape the old corroded bolt out of the threaded area and, even though my threads were in good shape and I could have screwed a new bolt in, I used a coarse tap to ensure that the threads were clean. I think it's a good idea to use one and they are only a couple of bucks. If your threads are good like mine are, I found it easy to just screw the tap in by hand. I have read on Don's materials that it's called 'dressing' the threads.

[HOTFLASH]

Thanks Kurt and Mike. Where would I buy it?
Mary

[baileyem]

Mary
Any hardware store will have one. Tell them what you need it for and they will get you the correct type of tap.
Mike