Using a Makita 3-3/8" saw to re-groove teak seams?

Hi All, I'm about to tackle re-grooving the teak deck seams on a new-to-me GB 42 I bought in Oct. 2015. There are plenty of posts here and on the Grand Banks Owners site and I'm reading all I can. For now I'm trying to find some details on using the small Makita battery powered saw to deepen the seams. I'm hoping some folks can help me out.

I've seen posts on making a shoe for the saw and adding a 1/4 bolt or nylon dowel at the back end to use as a guide pin. Folks also talk about stacking multiple blades to cut a wider groove (1/4" width).

My questions (which I've also posted on the GB site) are:

How many teeth on the blade (regular cut vs fine cut, etc.)?
What kind of spacers to use?
Any tricks to stacking the blades besides making sure the teeth are offset? I believe you also have to remove the blade guard too.
Is the need for a "shoe" just to create a surface to attach the guide pin to?
Any details on what to make the shoe out of (plywood, lexan, etc.) and how big to make it? Same size as the saw base, etc.?

Luckily the Teak Decking Systems factory is on my drive to my boat - I've visited and talked w/them numerous times and bought their tools and caulk. Good folks.

Any tips or guidance on using the Makita to do the seams would be greatly appreciated. Thanks!

What you want for that job is a Fein Multimaster with the fitting that is purpose-designed for this very job.... and you do NOT want to try and deepen the seams, especially with a saw, unless you are a top tier master craftsman (which given the post, I assume you are not). Personally, using a saw seems like a Really Bad Idea to me.

I've got the Fein tool and it is excellent. I'm not bad with a regular size circular saw and the Makita is quite small in comparison. Plus I plan to practice on a lot of scrap lumber before I try my decks. I think I can handle it - I'm pretty handy with tools.

But it never, ever hurts to ask questions and seek advice. Thanks.

Most of the small battery saws I have used turn too slowly to give nice finished results and accuracy. I used to have the 3 inch old 9 volt makita which I found particularly slow running and difficult to obtain finished results

The new 3" saws are a far cry from that old saw. Maybe still not the right tool, I don't know so no comment for this application.

Could you use a dremel tool and a metal straight edge ?

Since you’re so close to Teak Decking Systems, I think you should be talking to them, not us. You are planing to use their calking compound aren’t you?

Why do you feel the need to cut the grooves deeper?

I’m no expert, but I’d be inclined to try it with a router, not a saw.

HopCar said:

...I’m no expert, but I’d be inclined to try it with a router, not a saw.

Click to expand...

Before I decided my teak was past rejuvenation and needed new teak I explored the router idea. Problem seemed to be securing the router to precisely recut the groove.
A screwdriver, maybe bent to create a scraper, might work, after running a blade down either side of the caulk. The degraded condition of the caulk may come in handy.

is this what you're trying to do...

Silicone removal tools come in handy .Many different shapes and sizes .
https://www.google.com.au/search?q=...vcDYAhUQ5rwKHbObDIcQ_AUICygC&biw=1680&bih=898

When I need to re-groove teak deck planks I use a small very sharp chisel, a straight edge, a very sharp utility knife and I take my time. Power tools are great when the wood is off the boat as in replacing a piece of decking. Never tried that Fein tool though.

Jig. Edge guide. Depth guide. Seeing as you go. Tight quarters. Dust in the face.

Given that the Teak veneer on our decks was only 3/8" thick and already grooved about 3/16", and the screws and bungs are about 3/16" down, I really wonder about wholesale regrooving. Maybe a little touch up here and there for aesthetics at badly worn spots.

I think I'd lean toward some sort of router for regrooving/cutting wood. I have a laminate trimmer which as a small motor and base. I recently saw pics of a large Dremel kitted out with a router blade and base - even smaller.

If you're trying to replace failed sealant, then I suspect knives, chisels and scrapers would be a far better thing. Plus time. The chisels and scrapers would be made to the correct width.

And, perhaps the 'knife' could be doubled to do both edges at once. The bevel - cutting edge - could not be symmetrical, but should be on one face (like a broad axe vs an ordinary axe). Here's a multiply-bladed knife, a tape slitter, that I cobbled together to cut 1" tape into 1/5" tapes for my purpose. I could imagine a two-bladed knife made with ordinary Stanley blades, instead of the dainty little Exacto #11s.

I think the blade you should have is a “dado” blade.
It’s a blade for cutting knotches for interlocked 90 degree jionts. Only straight not “tailed”.

Oh I see it’s a deck job. Are all the edge seams far enough away from cabin ect to give clearence for the saw?
You must also probably take into consideration the curve of the deck planks. Where the seams curve the kerk you cut w the saw will be wider than where they are straight. It will be dificult to keep from wandering as you go along. So your saw kerf may not be very smooth or fair.

Have you considered a router?

Benthic2 said:

is this what you're trying to do...

Click to expand...

Really nice video. I liked the sweater, what was she talking about?

I really appreciate the interest and the comments. The previous owner sanded the decks a bit "too much" and there are a number of popped bungs w/screw heads showing. That usually indicates the deck seam is probably now too shallow and needs to be re-grooved. Most of the seams are still tight so I'm thinking I'll try just re-grooving (if needed) where I replace the caulk that's come loose.

The Teak Decking System (TDS) folks and others say to stay away from a router as it's too easy for it to get away from you. They recommend a minimum seam depth of 1/4" - so I don't expect to have to cut very deep w/the saw. Set it for a 1/4" depth and it will actually cut probably 1/8" or less of teak.

A dado blade set would be perfect, but they don't make one for that size blade. I'll need to do what others have done and make one up on my own.

I posted my questions to the Grand Banks section of this forum to see if anyone on the site had some experience w/this job on their Grand Banks. It's not uncommon to need to do this if the decks have been sanded over the years. My boat's teak is still thick and in good enough shape to re-work the seams and replace the missing bungs. The TDS folks say their caulk will last for years. This isn't going to be a fun job, but I'm sure I can do it if I take my time. I'm retired...

There are plenty of posts about re-grooving teak decks over on the Grand Banks Owners site, but it's not as active as it used to be and most of the posts are some years old. I'm still researching this project and looking to see if I can find someone who's done this recently. Thanks for all the replies.

I have found a router is the best tool to remove the joint seal PROVIDED the router is in a guide. The concept is the same as the router guide used recess hinges on a door. I constructed a large guide 30" x 9" with stops in all four directions to restrict movement of the router base. The opening into which the router bit extended was not in the center but close to one side so the guide could be turned to get close to the edge. Note: some hand work is required to clean up along the edges and the ends. I aligned the guide and used body weight to hold it in position which cutting. I used the same technique to route out whole areas where the teak was split or damaged, to about 3/16" deep. If the repair is short it looks better to butt the end rather than make a caulked joint.

The Fien Multimaster. You can clean the seams in 1/3rd the time with fewe or no mistakes. Finish the cleaning with sandpaper wrapped around a paint stir stick.

I have the Fein, awesome tool as everyone knows. The hardest part of the teak caulking blades is swallowing your price and going ahead and purchasing them despite their stupid price. Ridiculous but they are the only show in town as far as I can tell.

I agree. The Fein is one very nice tool and I wish I had started using it years ago. And I did splurge on the caulk removal blade. All their blades are expensive compared to substitutes. I used the Fein a few months ago while replacing my sanitation hoses. The original hoses were 17 years old and you could smell them. They were stiff as a board and impossible to remove from the fittings. I got a Fein depth stop to keep from cutting through the fittings and cut the old hose up in pieces. Turned a very difficult task into a breeze.

But sometimes the Fein blade was cutting in a tough spot and my face and hands were pretty close. I decided then and there that the price of an original Fein blade was worth it.

However, I'm still looking for any comments from anyone who's ever used the Makita to deepen their teak seams. The Fein doesn't really work for that. Thanks.

One of the boats I looked at before I bought the one I have had tired teak decks in need of complete renovation. One of my hesitations was the possible need to deepen the seams. I investigated the subject much like you are. Then, armed with the knowledge, I went to look at the boat again. I stood there staring at the seams imagining myself guiding a saw or router up and down all of the seams. Could I accomplish that without a mistake which would result in a nasty scare in the deck. I am brave to the point of stupid but I had to say no way on that project. Just can't see doing it all without error. The other thing was the time and place obsticle. Even if I committed to the time I have no way of doing it under cover without paying a bazillion dollars for a shed somewhere. So, I passed on thinking I could do that project even piecemeal. Ended up passing on the boat for this and some other reasons.

I believe it was Mr. Lowe over on the GB Owners forum who described how to build a shoe for a Makita to do this project. Did you find that thread? May have even been my thread. side note, you are correct, that forum has really slowed down, almost to a halt. Not sure why....

You have a good memory - it was Bob Lowe who described using the Makita and making a shoe and guide pin for it. You're also spot on about this being a major job. I've been doing a lot of research, gathering tools and trying out various techniques. Luckily, most of the seams look tight and I have plenty of time for the job. One step at a time. I knew going into the purchase that I'd eventually have to tackle this and that time's approaching. One way or the other, the seams need some TLC...

Put this blade in your Fein tool

https://www.jamestowndistributors.com/mobileportal/show_product.do?pid=3332

It's made specifically for what you are trying to do. Why reinvent the wheel?

Yes that's the blade being discussed earlier but it is for getting the old caulk out not for deepening the grooves. It will cut through the caulk like butta'. Teak ...not so much. Need some form of guided jig with a blade or router bit. i think any attempt involving hand guiding only would be a disaster. At least for me it would a disaster.

What is so special about the Fein tool? It looks like a simple oscillating saw. With the right blade, it would make quick work of the caulk. I think if you are going to deepen the joints, you are playing with fire doing it in place with power tools. The precision you need just isn’t possible.

Not sure that there is anything special about the Fein Multimaster beyond good quality and assortment of blades, adapters, etc. I read about people who use Harbor Freight equivalent with great success. Not sure how it would hold up in the long run though but for occasional use seems to work fine. Or Fein. Whichever

I've already talked to Fred ( FBoykin) but I wanted to post this.

On our last boat, some of the existing groves were less than 1/8” deep with no caulk due to wear/exposure/poor installation, some caulk was loose in other areas and some plugs missing. The overall thickness of the decks was 3/8" or greater (which is considered serviceable) and with no moisture in the core, re-cutting the groves, re-caulking and replacing the plugs was the only way to fix the decks or remove the teak. NOT!

We used a 4” 120 VAC Makita. We put 2 blades together with a thin spacer to get the approximate 1/4” wide groove and set the blade(s) to ~3/8” depth. We ending up cutting over 800 linear feet of deck with that saw. The saw was very easy to guide using 2 hands. It had no tendency to wander. You just went slow and easy after some practice on some scrap. For the radiuses/curved sections and butt ends of the planks, I used chisels. I have a file I used to clean the groves. I would not suggest sandpaper, you can't keep the fresh cut square. The goal is to keep the upper edge sharp, if not, it will look wider and/or the width will not be even after you've finished it. Now that TDS sells a newer generation tool (s), I'd suggest those.


Before/during we replaced over 250 plugs and screws. We used 12 cases of TDS caulk. It took 3.5 of us (Lena was the half), 2.5 weeks working 10 hour days, 6 days a week and that included replacing the teak on the house on our 43' sailboat. It’s no wonder I’ve had to have a knee and hip replaced.


I wish I had better pictures but these are the afters. There's also a picture of my repair box. We still have teak decks.


If it was just a matter of replacing the caulk, you can do it manually but if the groves are not at least a 1/4” deep you have deepen them and powers tools are needed. I'm not suggesting the Makita is the best but it worked for us.

Larry, you are da man my friend. Can't imagine taking it on. Thought about the physical part as well when I was looking at that boat I mentioned.
I need a knee replacement. Last week I replaced one (1) bung, on the flybridge. My knee let me know it did not think highly of me doing so. That was 1 bung. As in less than 2 bungs. 250? Um, OK.

I'm going to keep ignoring my knee. Maybe it will grow back.

Larry M, thanks for the extended post & great pictures. A really big thanks for contacting me directly the other day. I greatly appreciate your time! Thanks again.

It looks like there are a number of good ways to do this. I was too scared to go the makita saw route method fearing that one false move and I would destroy my deck. The Fein tool looks fine but a bit expensive an electric. I went with one of these

Veritas® Router Plane - Lee Valley Tools

I think it worked really well in both removing the old caulk, cleaning and re-grooving. I keep it on the boat for quick repairs.

Did you use progressively deeper passes when removing the caulk with the plane or were you able to sink the blade deep and get most out in one pass? Not much in this world as nice as a fine hand tool....