Taper Cut for Bifold Door with Table Saw

[Mike Schoaf]

I need some help in correcting a problem with a finished opening for a bifold door. The top of the door fits fine but the bottom of the door needs about 3/4" cut off. I want to use a table saw to cut this angle but I'm not quite sure how to do it. Basically I want my door to be 30" at the top and 29.25" at the bottom, with a smooth transition in between. I am certainly no expert with the table saw...probably considered a nivice still, so the simplest explanation would be great. Thanks.

[Mark Rios]

Welcome to the Creek Mike. I wouldn't do it with a tablesaw. I would do it with a circ saw and a straightedge or a guided rail system.

[Joe Unni]

Mike,

First, welcome to the Creek. You'll find tons of great knowledge, wisdom and friendly banter here. Frequent often.

Your door...

You'd probably be better off with a straight edge and a circular saw. This can be anything from a scrap piece of plywood with a factory edge to a Guided Circular Saw system of one type or another. Since you're new, please don't ask which type is better - it's a can of worms that you don't wish opened ;) . Just do a search.

But again, skip the table saw. The jig you'd have to make would take you twice as long as a straight edge.

Good luck,
-joe

[Kevin Herber]

Hi Mike and welcome to the creek. After installing new carpet a few weeks ago I had to trim my doors too. I echo the others in urging you to use a circular saw and a straight edge. Unless you have a very big sled I think trying to maneuver something as ungainly as the end of a door across the tablesaw is a recipe for problems.

Good luck and hope to hear more from you -- Kevin

[Eric Shields]

Mike,

I would have to echo the above suggestions. That is too long of a cut for such a small taper to do on a tablesaw. Use a piece of scrap to guide your circular saw. I'd also suggest you tape (blue painters tape works well) the top and bottom of the door on the cut line to reduce tearout.

And welcome to the Creek, plenty of people to give/get friendly advise here so don't hold back.

Eric

[Kevin Herber]

Mike – I just reread your post and realized that you are working with doors that are only 30 inches tall rather than full size doors. That makes the cut on the table saw doable, but I still recommend the skill saw and straight edge.

If you decide to do it on your table saw, this is what I would do:
1. Mark the actual cut line on the bottom of the door. This line will be the reference for all other measurements.
2. Transfer the cut line up from the bottom to a few inches from the TOP of the door by measuring up from the cut line the same distance along each SIDE of the door.
3. Get a straight edge that is wide enough to align with the transferred line and extend beyond the top of the door. This is what will slide along your fence.
4. Attach the straight edge to the face side of the door. Double sided carpet tape will work fine.
5. DOUBLE CHECK YOUR MEASUREMENTS AND MAKE SURE THE STRAIGHT EDGE LINES UP PERFECTLY WITH THE ACTUAL CUT LINE. The distance along both SIDES of the door should be the same from the straight edge to the cut line on the bottom of the door. If they are not something is not right. Most likely the straight edge is not positioned properly.
6. Place your door face side up on the saw with the straight edge on top and against the fence.
7. Move the fence so the cut line lines up with your blade. Keep the kerf to the waste of the cut.
8. Once you are happy with the position of the straight edge rehearse the cut with the blade lowered and power off. Keep the straight edge against the fence as you make the cut.
9. If you don’t have a table extension at the top of your saw, have someone support the door as it comes off the table. There will be a good bit of leverage on the front of the door as it extends off the saw.
10. Look at the rehearsal results and make sure the angle will be correct. Adjust anything as necessary.
11. Make the cut!

Good Luck – Kevin

[Gary Herrmann]

If you're dead set on doing this on the table saw, you'll have to build a jig. If you don't want to do that, I seem to remember seeing a very nice looking taper jig on Woodhaven's site.

[Frank Chaffee]

Mike,
If for whatever reason(s), your preferred tool for this cut is a tablesaw, you can do it very easily and with little expense.

Two narrow strips of either 1x stock or plywood could be affixed to the long edges of the door with an easy release glue, such as one of the hot melts, or rubber cement. The strip along the edge to be cut, and which bears against the fence, is scribed with a line to the appropriate angle for your cut before gluing.

Frank

[Frankie Hunt]

I would think the tool of choice would be a straight edge / skill saw. Perhaps this is that perfect opportunity to get a Festool setup..;)

What about the opening? Is it new construction? Can it be made square/plumb instead of modifying the doors?

Frankie

[Peter Lyon]

Mike,

I'd like to echo the sentiments of the previous poster -- if at all possible, I would square up the opening. Is the opening cased out? If so, and you're really lucky, you might be able to remove enough shims to square things up a bit. If there aren't any shims already in place, add a 1/2" of shim to the top to square the opening to 29 1/2".

At least this way, your cut will end up being straight.

My $.02 :)

[Doug Shepard]

Another vote for trying to square up the opening. I cant imagine how you're going to get hinges to work correctly with the tapered door. It would seem like one would have to be angled slightly and would always bind somewhat or pull on the screws over time. ??

[Mike Schoaf]

Thanks for all the responses. First of all, the door is 30" wide by 80" tall and it is a bifold. The opening is already finished...by your truly. I didn't realize the error until I was finished with the entire basement. I did the complete basement myself so this one error is bareable...but I digress. I need to make the cut the entire 80" length of the door. Sounds like a circ saw is the best solution. Would a nice straight 2x4 or 2x6 clamped to the door be the way to go as far as a guide? Again, thanks for all your thoughts and I'm glad to be a part of this great site!
Mike

[Frankie Hunt]

Would a nice straight 2x4 or 2x6 clamped to the door be the way to go as far as a guide?
Mike
Yes, this will work. The problem you will face with this is: The straight edge you use (ie your 2x4) should be on the keeper side of the cut. This means that your circular saw's motor will likely ride over top of the 2x4. You will have to raise up the circular saw motor to clear the 2x4. You then might not have enough blade below it's shoe for the depth of cut you may need. Also you will need to measure very carefully too because of the offset of the blade. (distance from the blade to the straight edge)

A quick google on the topic found this example: http://www.woodzone.com/tips/saw_guide.htm


An even better choice is to make yourself a guide. With this guide you don't have to measure for the offset of your blade. Its easy to make and is worth having around.

Google found these two examples: http://hometown.aol.com/woodmiser1/sawbd.htm
http://benchnotes.com/Skillsaw%20Guide/skillsaw_cutting_guide_boa.htm


Frankie

[Per Swenson]

Or, if you feel the need to buy something.
The borg has a 2 piece aluminum saw guide for $15.
They hide them next to the levels.
I used these for years untill I upgraded to my Germanic thingy.

Per