When it comes to woodworking, it is important to choose the right screws for your project. Most of the screws either have a coarse thread or a fine thread. But how do I know which one to use? Does coarse thread screw hold better than a fine thread screw, or vise versa? Does it really matter what screws I use? Should I be using coarse or fine thread Kreg screws? After some research, this is what I found.
Coarse-thread screws are used mainly for plywood and softwood like pine, cedar, and fir. Fine-threaded screws are used for hardwood such as oak, maple, and cherry.
You must be always sure about your tools and the screws that you should be using. To the normal eye, there may be no difference between two types of screws but if you wish to get your job done in the best possible way, choosing the right screw can be the decider between the success and the failure of any project.
Though there are hundreds and thousands of screw types to select from in the industrial and the construction sectors, we will focus on the Kreg screws for wood and carpentry work. Every sector has its own needs and specifications and the same stands true for screws used in woodworking.
Before you choose the screw that is best for your project you need to determine certain characteristics of the screw that you want to use. So what are the characteristics that you need to check?
Characteristics to look for in a Screw
Based on the type of work and the type of surface that the screw is to be used, there are certain characteristics of the screw that you need to watch out for in order to ensure that the same is usable and can be utilized for your project.
1. Length of the Screw – You need to figure out the length of the screws that you would need to use for the project. The screw length is determined based on the wood thickness that you’re using for your project.
2. Non Corrosiveness – You must ensure that the screw that you are using must be non-corrosive in nature so that it does not rust or corrode. More so, if you are aware that the project that you are building will be exposed to moisture for prolonged periods, the screws would need to be covered with anti-corrosion layers.
3. The thickness of the Screw – The next thing to consider is the thickness of the screws that are to be used in your woodwork projects. Based on the needs of your project you can decide on the thickness of the screws to be used.
4. Threading on the screws – Different screws would have different threadings on them and based on the project requirements you would need different types of screw threadings to fasten and complete different projects. This is where you determine the type of threading – coarse or fine.
We will focus more on the type of threading – coarse and fine and will find out more on whether you need coarse Kreg screws or fine Kreg screws for all your Kreg jigs.
Let us understand the difference between Coarse Thread and Fine thread screws, to begin with.
What is the difference between Coarse and Fine Thread Kreg Screws?
When it comes to comparison of the two types of threads in screws, the coarse threaded screws are a fantastic choice owing to the fact that they can be used under rough conditions and still turn out to be very useful. In such rough usage conditions, coarse threaded screws are more durable and can withstand heavy-duty usage and light damages.
When it comes to usage of specific measurements, fine threaded screws are the best option. The fine thread screws feature a very high tensile strength which makes these screws ideal for applications needing strength. The fine threading including a shallow pitch in these fine thread screws makes them less prone to loosening due to vibrations in heavy-duty applications. Moreover, you don’t need to cut for fixing these fine threaded screws and hence making holes on surfaces for fixing these fine threaded screws is much easier.
Having seen the basic differences between the two, let us point out some of the other differences as well.
Coarse Threads Vs Fine Threads
- Coarse thread screws are less likely to cross thread as compared to Fine Thread Screws
- Handling is easier with coarse thread screws than with fine thread screws.
- Coarse thread screws strip less when fastened to wood surfaces with less thickness as compared to Fine threads.
- Fine thread screws are more prone to damage than the coarse thread screws that have lesser thread engagements.
- Fine thread screws are best for applications with smaller, shorter and specific measurements – coarse thread screws are better for comparatively bigger applications.
- Coarse thread screws are suitable for applications that need to be done with high speed and precision. Fine thread applications need more time and need to be handled with care.
- Fine threads are more prone to thread galling than the coarse thread screws.
- Fine thread screws have better tensile strength than the coarse thread screws due to larger stress area and diameter.
- Fine thread screws loosen comparatively less during vibrations as they have comparatively less helix angle than the coarse thread screws
- Fine Threads screws maintain better clamping force and tightness than the coarse thread screws due to the smaller helix angles of the fine thread screws.
Now that we have seen the differences between the two thread types let us look at some of the other aspects of these threads.
Types of wood to use Coarse-Thread Screws
Coarse thread screws work best with woods that are soft and not too dense. That is because these types of woods need screws that have deep aggressive threads that will bite in easily into those softwood fibers. As such the coarse thread Kreg screws find their applications in these types of woods such as plywood and MDF. Coarse threads on these wood types ensure the strength and durability that the applications need. They fasten to these surfaces better than other wood surfaces.
There are many other wood types as well where these coarse thread screws are used as well which include woods such as Pine, Cedar, Spruce, Fir, Aspen, Poplar, Basswood, Plywood, Butternut, MDF, Particle Board, Melamine, etc.
Types of wood to use fine Thread Screws
When it comes to fine thread screws, hardwoods are more preferable. These hardwood surfaces are too hard and dense and hence coarse thread screws may not be the best fit for all such hardwood surfaces. If you use coarse thread screws for these surfaces, their aggressive threading may result in tearing and splitting of the wood surface that you are using in your project. As such you need less aggressive threading and as such fine thread screws ensure that you get the desired holding and clamping power without the splitting apart of the wood.
As such, choose Kreg screws with fine threads for use on hardwood surfaces such as Oak, Cherry, Maplewood, Walnut, Hickory, Mahogany, etc.
Now, let us look at a couple of more FAQs on the same.
When can you use Fine-threaded screws?
With all that we have seen in defining and describing the fine threaded screws, these fine threaded screws are stronger in terms of their tensile strength and their claiming capability as they are harder to shake and vibrate. However, these screws are not so popular in their usage or are less commonly used as they are pretty delicate to handle and work with. There are more chances of damage to the threads and cross-threading with fine thread screws. Also, with fine thread screws, there are more chances of galling since there are more rotations and they may just slide against the friction.
So, to answer this question – these fine threaded screws can still be used almost anywhere you want but for best results, as we saw earlier, they should be used with harder and more dense wood surfaces. So, harder and denser the material finer shall be the threading of the screw for best fastening and clamping results.
Having said that, is fine thread screw better in terms of holding capacity than the coarse thread screw? Let us find out.
Does Coarse thread hold better than fine thread screws?
This is one of the most asked questions and is a legitimate one. Though fine thread screws have a larger tensile strength and higher stress area that makes them good with hardwood surfaces, the coarse thread screws are more preferred due to their greater overall resistance to stripping and cross-threading. So for all major applications, the coarse thread screws have certain advantages to fine thread screws due to the following characteristics:
- Higher Resistance to cross-threading and stripping.
- Not affected due to thread nicking
- Do not usually gall – no galling effect
- Easy to handle and work with
- Faster the assemble and fasten
- Better plating on coarse threads hence better results.
So to answer the question – Yes Coarse thread screws hold better due to all the characteristics that we discussed and provided that the wood type that is used is softwood and not the harder wood types.
But does that make the fine thread screws any less – No, the fine thread screws too find their appropriate usage and applications in wood types they are suitable for. Use this piece to find out which screw type to use and when. Keep it as a ready reference for all the questions that you may have in your mind and more.