Dust Collection on old Powermatic 77

[Joe Wood]

I bought this 12' table saw in 1993, I think it was made in the early '50s but it's been a great saw for us. To control the dust we turn on a couple big fans, one blowing across the table, and it all gets sucked out the back door. I'd like to hook it up to the dust collector now as the sawdust pile outside the back door is getting pretty big! Image 1.

I have a question about sealing up the case so there's better suction and collection out the 4" hole at the bottom rear of the saw. How do you seal that large side area around the motor? Image 2. I used to use a piece I cut out of cardboard for the large side area, cut around the motor. It helped but there were a lot of gaps so it wasn't sealing well and I just stopped using dust collection on it.


and the two open areas on the front of the saw? Image 3. What do you use?

[Jim Becker]

Joe, you don't want to "seal" up the cabinet, but you do want to close off the major areas like you show. You need air flow for dust collection. DC isn't about "suction"...it's about moving air at a given velocity which in turn moves the chips and dust. For the motor area, you'll need to build a box that attaches to the cabinet (or find on from a similar machine you can adapt to yours) so that the motor can move when you tilt the arbor. For the slot where the hand-wheel is, many folks will use a piece of magnetic sheet so that you can remove it easily when you want to tilt the arbor. There should otherwise be enough air flowing from under the edges of the table and through the throat plate to provide the air you need to do the job you want. Cutting the cabinet for your collection port is what it is...that's metal. Consider installing a larger 5" or 6" port instead of 4" so you can benefit from better collection capability from a decent DC system. You may also want to consider installing a sloped floor in the cabinet that helps direct the chips dust toward your port, rather than permitting it to accumulate in the bottom of the cabinet like it does now.

[Joe Wood]

I never thought about needing the airflow, and I like the idea of using magnetic sheets to close off just part of the main opening.

I already have a nice large piece of cardboard inside acting like a funnel down to the opening.

Is a 3Hp dual bag setup large enough to use the 5 or 6" hose?

I need to rethink this whole setup now. I've had the DC on an extension cord and moved it as needed. I want to put it back against the rear wall now.

I also have a 15" planer, in this pic it's in the place it usually is when we're planing. I'm starting to get ideas about the piping layout, I'll make a drawing and see what people think.IMG_5532.jpg

[Kevin Jenness]

I used to work in a shop with two PM 66's hooked up to a central DC system through the 4" ports at the base of the saw. One had a factory plastic cover over the motor opening, the older one did not. I never saw that much difference between the two- if you kept the ports clear with frequent manual cleaning they did a moderately effective job of dust control. They both had overhead guards w/dust collection as well which helped.

For a more effective setup locate the dust pickup as close to the blade as possible and in line with the particle flow. I modified a Unisaw with a crudely cobbled sheet metal chute and flange hung from the trunnion and connected to a 2 1/2" hose (sorry, no pictures) that was as effective as the pickup on my present Paoloni slider. I occasionally had to dislodge some debris that got through the throat plate but only had to clean out the cabinet every couple of months instead of every week. If you have room in your saw's cabinet you might try something similar.

[Jim Becker]

"Modern" north American design saws do use a shroud that's near the blade to assist with collection efficiency. A handy person might be able to retrofit that as long as they can attach the shroud such that it tilts with the blade when the arbor is tilted, too. As Kevin mentions, the shroud is pretty much defacto standard on sliders which means pickup is right at the source and theoretically more efficient.

[Tom Bender]

Depending on how you use your saw you may be able to generate less dust and distribute it with less energy. This is better than marginal improvements in collection.

Slow down your saw. Cut quality is determined by many factors; tip speed, feed rate, number of teeth and others. I find that in my case quality is not affected by running the saw at 20% to 55% of the original tip speed. On some cuts I have to feed a little slower. This wastes minutes of my valuable time per month. I'm counting on getting that time back in cleanup and extended use of my lungs.

The saw makes bigger sawdust and spews it out more gently. The saw is much more pleasant to use and I feel that it is safer. It will never throw anything at 100 mph, wood, sawdust, push sticks.

I replaced the 3600 rpm motor with 1800 rpm and a VFD. Table saws are made with the smallest possible pulley on the motor. This is not optimal. I increased this about 10% to get a more optimal drive. If I ever want more tip speed I can increase the size of the motor pulley some more.

[Kevin Jenness]

To locate the dust pickup close to the source without too much fooling around you could cut a 4" hole in the rear of the saw cabinet just below the blade housing and mount pipe flanges back to back with a section of pipe extending under the blade with the top sliced off to form a gutter. Not optimal for bevel cuts, but so what. It would be a big improvement over the stock setup.

[Bill Adamsen]

The Unisaw has a similar opening with a metal shroud or box built around the motor like shown below. I replaced the original "poorly engineered" dust collection with a larger hood fabricated from plywood. It should be possible to build the entire motor enclosure the same way if you can't find a factory motor shroud.

Unisaw_34-802.jpg

[Joe Wood]

OK here's my overall plan. I really only use the dust collector and flex hose for my mobile 15" planer which I park right next to the table saw, and the DCs been on an extension cord which is a real hassle. I want to put the DC against the far wall and run smooth piping under the work bench, over to the table saw, and also up and over to where I'll hook a 3' flex hose up to the planer.

it looks pretty easy to do but I'm not sure about the fittings, or the design and I'd like to hear your thoughts!

this is the area behind the saw,

[Jim Becker]

Instead of a "cap" for the planer connection, just use another blast gate plus a short piece of duct to connect your hose to when you need to use it.

[Joe Wood]

Where can I get a 90* sweep with a straight thru (shown in my last drawing), that's what's holding me up now.

all I can find are the 45* Y fittings?

[Kevin Jenness]

I don't think you will find what you are looking for. Use a 45 wye with an added 45 sweep.

If you are set on entering the saw cabinet through the existing port at floor level, I would suggest running 4" pipe inside the cabinet with a 90 wye terminating just below the blade surround with a hood fitting like this https://airhand.com/product/flat-nozzle/

[Joe Wood]

I might do that Kevin. I need to find another part. The intake on my DC has three couplings angling out, and I need just one intake pointing straight out. Anyone know where I can get different style intakes? Mine would need a 5 7/8 ID

[Jim Becker]

While using PVC pipe for dust collection can be easy and cost effective, you're limited to fittings that are designed fluids, not moving air. So you may need to use multiple components as Kevin mentions to accomplish your goal. Most folks are using S&D (sewer and drain) type pipe which is thinner than the heavy Schedule 40 material used for septic work.

[Mike Wilkins]

I had a mid 60's Unisaw that I purchased without the side motor cover. I fabricated one using 1/4" plywood and some weather stripping material , and some small hinges. I left the other openings in the base cabinet as-is to facilitate air movement to the dust port at the rear. Give it a try; finding an OEM replacement dust door will be like finding a frog hair.