Sawsmith Radial Arm Saw -- Enlarge Arbor Hole on a Regular Blade

24,035

17

20

Introduction: Sawsmith Radial Arm Saw -- Enlarge Arbor Hole on a Regular Blade

About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first to…

A friend has a Sawsmith radial arm saw in good working condition, but getting blades is a problem. A special mount holds the blade on the shaft and uses a 1 1/4 inch hole rather than the standard 5/8 inch hole. The establishment that once sharpened his original blades is no longer in business. I suggested enlarging the 5/8 inch hole in a carbide tipped blade to a 1 1/4 inch hole. The challenge is to be precise and keep the hole centered so the blade does not wobble when finished.

In the photo you see an original blade with 1 1/4 inch hole (satin finish). It is resting on top of a new 9 inch 40 tooth carbide tipped blade with a 5/8 inch arbor hole (chrome finish). You can also see the special mount that requires a 1 1/4 inch arbor hole. The blade fits onto the shoulder on the left piece. The nut on the right screws onto the fitting at the left to lock the blade between the two pieces.

I used a marking pen to outline the size of the new hole on the carbide tipped blade.

Step 1: Mount the Blade for Enlarging the Hole

I do not have machine tools and decided I could do the job with a faceplate on a wood lathe and a Dremel tool. I have a plywood disc mounted on my faceplate.

I glued a scrap piece of fiberboard at the center of the plywood disc and marked the center while the lathe was running. I scribed a 5/8 inch circle on the scrap of fiberboard.

Step 2: Turn the Scrap to Make a Center for Mounting the Saw Blade

I turned the scrap of fiberboard to make a round center 5/8 inch in diameter. The hole in the saw blade will fit snugly over this round center and will center the saw blade on the plywood disc with precision. It is important to stop regularly and check so the fit of the blade on the fiberboard is as exact as possible.

Step 3: Mount the Saw Blade

Here you see the saw blade centered on the fiberboard disc. You can see the outline of the 1 1/4 inch hole marked on the saw blade. I also used three screws to secure the blade to the plywood disc at its outer perimeter. After the center has been cut out with a Dremel tool and a cutting wheel these screws will keep the blade centered and attached to the plywood disc. I used #10 machine screws 1/2 inch long and drilled holes for them in the sawtooth gullets. The holes are just a little undersize so the screwthreads grab in the wood enough to hold the blade well.

Step 4: Begin Cutting Out the Center to Enlarge It

Use a cutting wheel on a Dremel tool while the lathe is spinning at its slowest speed. While doing the actual work I held the Dremel tool with two hands. There is a little slope to the edges of the cut, so cut a slightly smaller circle than necessary to avoid making the hole too large. It can be dressed with a grinding stone on the Dremel tool at the end. See the next step.

When I thought I had cut about half of the way through the blade blank, I turned the blade over and began cutting from the other side. You can do this while the fiberboard center is in place, but after it no longer supports the blade you will not want to disturb the blade's position in any way.

If the blade did somehow move off center while you are working on enlarging the hole, you could always glue a larger piece of fiberboard to the center of the plywood disc and turn a centering piece the exact size of the hole at that point. That process would center the blade exactly again. Then fasten the blade firmly to the plywood disc and remove the fiberboard centering disc so you can continue to grind the size of the hole to the size needed.

I tried to keep the blade from getting hot. It did not seem to be a problem, anyway.

Step 5: Grind to Size and Finish the Arbor Hole

When you have removed the metal ring formed in the previous step and removed the fiberboard centering button, put a grinding stone in your Dremel and gently enlarge the new arbor hole while the lathe is spinning. (I did not take a photo while I was actually enlarging the hole in the blade, but made this illustration in Google Sketch Up later.)

I used a draftsman's divider to compare the size of the shoulder on the Sawsmith blade mount with the size of the hole. When I was sure the size of the new hole was very close to fitting, I removed the blade from the lathe's faceplate. The shoulder of the blade mount almost fit into the hole. I very lightly went around the inside edge of the new hole twice with the grinding stone while holding the Dremel by hand. That was just enough so that the Sawsmith blade mount fit into the hole easily, but without any looseness.

Step 6: The Final Product

Here you see the final product with the Sawsmith fitting on the new blade with the newly enlarged hole.

The blade runs true and on center without any vibration. This blade will make my friend's Sawsmith radial arm saw more useful for many, many more years.

Update--May 16, 2009: My friend was laid up with a badly broken leg at the time I fitted this blade for his saw. He has also been traveling since his leg is out of its cast. He just got his first opportunity to use the saw with the new blade. He cut some birch veneer plywood for a project. He said the blade works perfectly.

Update--January 26, 2010: I recently considered buying a corded 5 1/2 inch Skil circular saw (sidewinder with left-hand blade).  That saw uses a 1/2 inch arbor.  Blades are not widely available.  People are usually told to buy 5 1/2 inch blades with 5/8 inch arbor holes and add to that a special bushing to make up the difference.  But, 5 1/2 inch blades for battery powered circular saws are widely available.  The only problem is that blades for these battery saws use a 10 mm arbor (2.7 mm smaller than 1/2 inch).  The process described in this Instructable could be used to enlarge a 10 mm hole to 1/2 inch, but not step 4.  Make a wooden center 10 mm in diameter.  Mount the blade to a faceplate as in step 3.   Remove the wooden center and grind the hole size to 1/2 inch.

Be the First to Share

    Recommendations

    • Summer Fun: Student Design Challenge

      Summer Fun: Student Design Challenge
    • Water Speed Challenge

      Water Speed Challenge
    • DIY Summer Camp Contest

      DIY Summer Camp Contest

    20 Comments

    0
    devonh7272
    devonh7272

    4 months ago

    Wouldn't the double hole saw trick be a much easier way to enlarge the hole? Use a hole saw the size of the existing hole as a guide for the larger hole saw to cut?

    0
    Phil B
    Phil B

    Reply 4 months ago

    Many things are good in theory. I wanted this to be exactly absolutely precise. I was willing to take whatever steps were necessary to eliminate any possibility of chatter or other inaccuracy. And, I got the results I wanted. Meanwhile, I did Internet searches and found people who tried other methods that should have worked in theory, but the finished product was not quite centered, and they had vibrations of various kinds seasoned with regret.

    0
    johan.carolus
    johan.carolus

    5 months ago

    This is an ingenious solution! I have a Moody / Darra James 12" table saw from the 1950s with a 3/4" arbor. Until finding your process the options I could find were either using a bushing with a 1" arbor blade or paying $50 to have a machinist rebore a 5/8" arbor. Do you think in removing the 1/8" of material around a 5/8" arbor it would be possible to just use the final grinding stone technique rather than cutting? Thanks for sharing your innovations.

    0
    Phil B
    Phil B

    Reply 5 months ago

    Thank you, John. I would go directly to the grinding part of the process. An eighth of an inch is not much. I hope it goes well for you.

    0
    xyloeye
    xyloeye

    1 year ago

    This is a really old post but in case you're listening, I want to thank you for taking time to create this. I just finished machining a 5/8" saw to 3/4" using your method. I have a Milwaukee beam saw with a 3/4 arbor. Apparently, a blade with that bore is no longer available. You saved my saw.

    0
    Phil B
    Phil B

    Reply 12 months ago

    Thank you very much for your comment. I am pleased to have been of help in even a small way. I am curious how difficult it was to find what was helpful to you. You made my day. I also added Milwaukee, Beam, and Saw to the keywords to assist anyone else in your situation.

    0
    xyloeye
    xyloeye

    Reply 12 months ago

    Thanks for the note, Phil. I have a 12" metal lathe but couldn't figure out how to chuck a rotating 10" blade without killing myself. Your solution worked great. I get to keep my saw. As far as difficulty finding your post, it took a while. All I could find originally was how to enlarge the bore using a boring head on a vertical mill - which I don't have.Thanks again. Ken

    0
    Phil B
    Phil B

    Reply 12 months ago

    Ken,

    Thank you for your reply. A few times people found an Instructable I did and it had a solution they needed. It always amazes me that they were able to find what I had posted.* When a person submits an Instructable at least two meta-tags are required before it can be uploaded. I knew about Sawsmith radial arm saws and their odd arbor size, but did not know about Milwaukee Beam Saws. I suppose if a person did not have a lathe, any kind of disc that can rotate and a Dremel tool would do the job, even if the disc were a pottery wheel or a plywood disc on a bearing mandrel. By the way, I would have responded a few days earlier, but I did not get a notification of your first comment from Thursday until yesterday, which was Sunday.
    * Instructables also has a Community Forum section for all kinds of questions and comments. A couple of times I put things there that are an idea, but not involved enough to need a series of steps with photos. One concerns a NordicTrack ski machine. Those use one-way needle bearings in the drive rollers. When the drive rollers get older, they hiccup and people replace them at around $100 for the set plus labor plus perhaps shipping the machine to a repair station and back. I posted an idea in the Community Forum that ski machine users should try floating fine metallic dust from wear out of the one-way needle bearing with a light penetrating oil and letting the bearings dry by air before they decide to replace the rollers. The professional repair guys tell me I will ruin the ski machine, my teeth will rot, and my hair will fall out; but, a bunch of us have restored the performance of our machines that way and saved a bundle of money by flushing the fine metallic dust out of the bearings. About 35,000 people have found that post, so far.

    Phil

    0
    xyloeye
    xyloeye

    Reply 11 months ago

    Hey Phil,

    I used the blade with the enlarged bore on some big beams last week for a cabin we're building. It worked perfectly! No chatter or wobble. Thanks again.

    Ken

    0
    Phil B
    Phil B

    Reply 11 months ago

    Isn’t it great to make something that is like an old friend work again? Thank you for letting me know it works for you.

    0
    RainDog07
    RainDog07

    9 years ago on Introduction

    This is a bit off topic, but new 1 1/4 arbor blades are available from Shopsmith www.shopsmith.com and from Forrest www.forestblades.com but I didn't confirm the latter. I just wanted to mention this in case there are folks out there who need a new blade but don't want to modify one.

    0
    Phil B
    Phil B

    Reply 9 years ago on Introduction

    Your comment is not really off-topic, at all. After I adapted the blade for my friend I found the Shopsmith blades with 1 1/4 inch arbor holes. My friend has always used a 9 inch blade and wanted that size. The Shopsmith blades are 10 inches in size.

    I checked the Forrest Blades site, but could not find blades for a 1 1/4 inch arbor.

    Thank you for looking and for commenting.

    0
    leadpencil
    leadpencil

    10 years ago on Introduction

    Did you try using a hole saw in the tail stock? It seems like it would be a little easier than the dremel.

    0
    Phil B
    Phil B

    Reply 10 years ago on Introduction

    The primary concern with the task of enlarging the arbor hole is to maintain a hole that is absolutely on center. My lathe is not capable of mounting a hole saw in the tailstock, but if it were, there is too much possibility some chattering would cause the expanded hole to be a tiny bit off center. I read stories of people who tried to expand the arbor hole in a saw blade with some type of drilling operation, but the final result was not entirely centered. They had to deal with the fact they had ruined a good blade, or manage with a blade that ran with a lot of vibration. Using the Dremel was easy enough and worked very well.

    0
    Don Rieg
    Don Rieg

    12 years ago on Introduction

    Check with the SawSmith users group on Yahoo. They have a file copy of the drawing needed to reproduce the 5/8 inch acme thread LH and RH nuts which came with the saw originally and allowed the use of 5/8 inch bore blades. I quit using the original 1-1/4 bore blade when the saw was new and never looked back. I believe one of the group members had found a machinist who would make the nuts for $25 a copy.

    0
    Phil B
    Phil B

    Reply 12 years ago on Introduction

    That is another option. Thank you for the information. After I published this Instructable I poked around the Internet and found several posts on various forums by people new to a Sawsmith who were wondering what to do about blades. There will come a time when original owners of the Sawsmiths will pass them to new users. It will be good for those new users to have several options for the blade problem. So far, Google turns up my solution pretty readily and it is easy for a home user to make work.

    0
    rimar2000
    rimar2000

    12 years ago on Introduction

    You are very smart, Phil. You make me remember an uncle that I had, who was very intelligent and able to fix almost everything that fell into their hands.

    0
    Phil B
    Phil B

    Reply 12 years ago on Introduction

    Thank you, Rimar. You are very kind. I am thankful to be able to do things like these. They seem simple and easy to me. But, other people have talents for other things I have never been able to do. Those things seem simple and easy to them.

    0
    grunthos
    grunthos

    12 years ago on Introduction

    Great explanation. I love seeing adaptations which enhance or extend the life of tools.

    0
    Phil B
    Phil B

    Reply 12 years ago on Introduction

    Thanks. I am glad all of the steps were clear for you. Later I always think I should have added or changed this or that. I did another Instructable a few weeks ago on restoring accurate settings to a Sears radial arm saw after the indexing holes have worn into egg-shaped patterns due to wear. It is another one of those that extends the original useful life of a good tool.