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Thread: Drilling and tapping shaper table for accessories: How to?

  1. #1

    Drilling and tapping shaper table for accessories: How to?

    I need to drill and tap a series of holes in the top of a used PM26 shaper to mount aftermarket guards and a stock feeder. My only experience of drilling into cast iron machines came in connection with attaching Unifence and Biesemeyer rails onto saws--and that didn't require much precision or any tapping. So basically I am coming at this with no background. I don't want to remove the top for the machine and am envisioning--correctly??--an approach using a portable drill and guide blocks to establish the correct hole pattern/spacing and keep the bit perpendicular. Guidance, advice and/or links to good threads or videos would be much appreciated.

  2. #2
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    Drilling cast iron is actually pretty easy. The starting point is where you need to focus a bit of your energy because the better you mark and punch your center, the better the end result. A magnetic portable DP would be amazing for this job, but you can do good work with careful layout and center punching. And creating a guide block isn't a horrible idea, either!
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  3. #3
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    Tap it dry, no lube of any kind.
    Bill D

  4. #4
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    As Jim said, drilling cast iron is not hard. If not already known, measure the bolt circle/pattern and make a matching drill template out of something flat like MDF. Place, carefully mark and punch with a center punch. Drill with steady pressure at a slow to moderate rpm. I generally drill CI dry but you can use simple motor oil as a lubricant. (messy)
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  5. #5
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    The easiest way is with a magnetic drill press, if the top is thick enough for it to get a good bite. You didn't say where you are, but if you were close enough, I would loan you one.

    I don't understand the recommendation to tap dry. I always use Dark cutting oil for drilling, or tapping cast iron. You can buy the dark cutting oil in the plumbing aisles of the big box stores. The dark cutting oil has extra sulfur in it, and is designed especially for drilling, and tapping cast iron.

    You can't tap stopped holes with the drill press though. For those, you need a set of three taps, with the last one being a bottoming tap. I had to retap some holes in a tractor block up to 1", for holding on the loader frame.

    You don't need to use a tap wrench. For those large holes, I ended up using 8 point sockets, and breaker bars. I bought some large tap wrenches off ebay, thinking that was what I needed, but couldn't get a full swing on the tractor. A ratchet will work, but with a breaker bar, you can go back, and forth easier.

    Good quality cast iron, as I expect that machine top to be, is easy to thread.
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    Last edited by Tom M King; 10-11-2020 at 8:42 PM.

  6. #6
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    David ... what the experienced guys ... all good answers ... did not mention is tapping technique. Use a guide to keep the tap vertical. Start with about 3 turns ... pushing down ... to engage the tapered part of the tap. From there-on, it's ... 1/2 turn 'forward' ... 2 turns 'back'. When you turn 'back' you'll feel a a burr break.

  7. #7
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    Cast iron basically turns to powder when drilled or tapped. Before buying the tap you need do some quick research as to what size drill bit you will need to match the tap. From there it's easy. Often with cast iron I'll just tap it without stopping. With steel you'll want to go forward for a 1/4 to a half turn then reverse. If you do use lubrication (I don't always) then you'll need to clean the threads of the tap after each hole. A guide would be nice but as long as you are careful it's not needed as long as you can hold the tap straight when starting to tap the hole. The only guide I have fits in my drill press so it's useless for something that can't be taken to the drill press like a table top. Just remember that cast iron to keep the dust out of everything. If it get's on metal to metal surfaces it'll work it's way in between them and wear things out.

  8. #8
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    Quote Originally Posted by David Stone (CT) View Post
    I need to drill and tap a series of holes in the top of a used PM26 shaper to mount aftermarket guards and a stock feeder. My only experience of drilling into cast iron machines came in connection with attaching Unifence and Biesemeyer rails onto saws--and that didn't require much precision or any tapping. So basically I am coming at this with no background. I don't want to remove the top for the machine and am envisioning--correctly??--an approach using a portable drill and guide blocks to establish the correct hole pattern/spacing and keep the bit perpendicular. Guidance, advice and/or links to good threads or videos would be much appreciated.
    I have mounted stock feeders on cast iron tables with through bolts, when the bottom is open. I use 7/16" holes and 3/8" bolts. The bolts then seat flat on the stock feeder
    base. With real metal working tools, I could drill holes square to the table. With a little hand drill, that won't happen.

    Also, drilling holes for jigs in the miter bar slot, if possible, saves having rough surfaces crop upon the table.

  9. #9
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    I second what William says in the post above me. Unless your machine has a table that is 3/8''thick or more on the flat it is better to drill and run the bolts thru and just use a washer and nut.

  10. #10
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    Hi David,
    I drilled and tapped thru holes in my TS for a stock feeder and it was easy to do. Check for webbing on the bottom of the table-- I positioned the feeder so the holes would miss any webbing. I didn't use oil for drilling and did for tapping. My tap and die set is a cheapo and the socket bolts I used seemed a little sloppy but hold just fine. I would get a better-more precision??- tap if I were to do it again. I used the feeder base to punch hole positions and made a guide to keep the drill vertical. Hardest part was getting the courage to punch holes in my new SS table!! Good luck.

  11. #11

    Something to help old it vertical...

    edit: can't post a pic

    I've a tool similar to this for years.Helps a lot with getting holes square to the surface. And, to aid in starting the tap, it can be chucked in the tool also. You can't really tap it very far, but can at least start it straight.

    Locating the holes to match the add-on fixtures is a whole 'nother issue.

    Quote Originally Posted by David Stone (CT) View Post
    I need to drill and tap a series of holes in the top of a used PM26 shaper to mount aftermarket guards and a stock feeder. My only experience of drilling into cast iron machines came in connection with attaching Unifence and Biesemeyer rails onto saws--and that didn't require much precision or any tapping. So basically I am coming at this with no background. I don't want to remove the top for the machine and am envisioning--correctly??--an approach using a portable drill and guide blocks to establish the correct hole pattern/spacing and keep the bit perpendicular. Guidance, advice and/or links to good threads or videos would be much appreciated.
    Last edited by Jim Becker; 10-12-2020 at 2:48 PM.

  12. #12
    Thought: Not sure what the ribbing situation is like on the underside of your cast iron table but what if you through-drilled rather than tapping? Then, you wouldn't have to worry about alignment.

    Erik
    Felder USA Territory Representative: Central & South Texas

  13. #13
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    Another vote here for drilling through holes and not tapping unless your table surface is very thick. Most machines that come with tapped holes for feeders have boss's cast into the underside of the top to support the thread engagement. Holes in a thin top for fences and light accessories may not be an issue but you get a feeder loaded up or bound up out on the corner of a thin table and youll possibly blow the corner of the table off or blow the tapped holes right out of the cast iron surface.

    We put a feeder on a slider that had no tapped holes and we punched clearance holes for the bolts and mounted a steel plate under the table permanently attached with the tapped holes so the bolts drop clear through the cast iron top and thread into the steel plate. That way we dont have to fuss around with nuts/washers/plates when we pull the feeder.

    Have a band saw with tapped holes in a thin top and it alway gives me the willies when we mount a feeder on it and Im very careful not to heavily load the feeder for fear of blowing out the table.
    Last edited by Mark Bolton; 10-12-2020 at 6:00 PM.
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  14. #14
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    Couple of thoughts...

    I would check with a local tool-rental place about renting a magnetic drill (press). They are tailor-made for this job. They are expensive to purchase, so seldom worth buying if you only need it for a single job or two.

    With regards to tapping technique, the forward then back (to break the chip and keep it from fouling the next flute) is not required if you use spiral taps. They are more expensive that straight-flute taps, but are much quicker to use, though I doubt it would make much difference in this application in cast iron.

    As mentioned, those portable drill guides can also be used, after a fashion, as a tapping guide, to keep the tap normal to the table surface. Even if precision location is is not required, a tilted, threaded hole can cause an attached piece to loosen (or tighten) depending on which way the lateral load pushes on the tilted fastener.

    -- Andy - Arlington TX

  15. #15
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    Quote Originally Posted by Ken Combs View Post
    edit: can't post a pic
    Posting photos is a benefit of being a Contributor for a minimum $6 annual donation. Click on the "Donate" link at the top of the page to support SMC and gain that benefit plus access to Private Messages, the Free Classifieds, etc.
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