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Reaming Holes in Fixture Plate - What Type of Reamer

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Twizseven:
I am currently making a fixture plate for use on my Bridgeport clone milling machine. Plate will be dual purpose as it will be also used to mount a Bison Indexer on the table.

The fixture plate is 7/8" thick cast aluminium tooling plate and is 330mm x410mm in size. It will have rows of holes drilled into it, every alternate row will be drilled and then tapped M10. The alternate rows of holes are intended to take 10mm locating dowels made from 100mm silver steel bar. None of the holes will be through holes. I will be drilling to depth of 20mm and then either tapping or reaming as necessary.

I have a MT1 long M10 reamer which is about 12inches long but I feel this too long.

What type of reamer should I used as these are non through holes. I have seen some advertised which specifically say must only be used for through holes. Am I better with spiral (right or left hand?) blade reamer or straight blade reamer. Would prefer to stay with MT1 but could use chucking if this is all I can get.  The spiral on the reamer I have looks as though it would move the swarf into the hole not out of it, so I guess is meant for a through hole

Colin

derekwarner:
Colin......you say cast aluminium......there are so many varients here.....[not only Grade, but also of Heat]

Is the plate gang milled for flatness?.......if so, it was probably heat treated post casting & before milling

I would be more concerned with a trial drill & ream M10 to see how it responded to the chip/swarf removal..

50 something years ago  :old: as apprentices we were taught to use 100% Kerosene as the cutting fluid........these days, I find Rapid Tap or T-Cut provide a superior finish

Just another thought...have you considered predrilling say 3mm diameter x the full depth of the plate, then set the 9.5?mm diameter drill to say 17mm deep & flat side ream to full available depth [14.5?]....this will allow any 9.5mm diameter drill swarf to be pushed down and also a path for any 10mm diameter reaming swarf as opposed for the possible pickup & galling to be an oversized M10 sloppy hole?

So apart from this, if you did achieve true good fitting M10 diameter fitted dowels, a simple way to remove them....a gentle tap :hammerbash: from underneath

Derek

john mills:
needs to be a machine  or a chucking reamer  the citing is done on the 45 degree chamfer .so will cut closer to the end .the hole should be bored first to get precise position and only leave a minimum amount for the reamer to cut
but clean up the hole .5 would be way to much  the flutes will just fill up .for cutting fluid modern cutting funds work  as apprentices 50 years ago we were shown the hazard of using kerosene machines and factories burnt down factories soluble oil work. WD 40 has to many fumes for me.  try on some scrap first to see how the size comes out   .the long reamer is not a problem if you have the hight.and don't run too fast.


           John

petertha:
I made this fixture plate from 3/8" cast aluminum. It has 8-32 tapped holes every 0.5". The only reamed hole is the center one 0.250". All I have is straight flute style & it was uneventful, but all mine are through holes.

Tapping this stuff is a bit different than regular alloys I found. Rather than a nice spiral swarf (on ejecting style taps kind of suited to aluminum) the cast material kind of like to pack in the flutes a bit more. because I had to do so many mind numbing holes (with a tapping head) I broke up the monotony by trying a row of one cutting fluid then another. Interesting exercise. Tapmatic regular, Tapmatic aluminum, some higher viscosity stuff (didnt like that), some 'natural' cutting oil based... Generally I find WD-40 works as good as any & this was my conclusion again. And seem like the better they work, the more they like to make by face rouge up a bit over time as it heats or vaporizes or whatever. I just happened to have simple N95 mask handy (COVID way of life these days). It made a positive difference so I think I'm going to keep a mask handy.

But what worked noticeably better than any of the liquids was a white creme tapping compound I bought a while back & just haven't used much. You could just feel the tap glide in with less force & the chips had much less propensity to stick. Good luck!.

Jasonb:
Never heard of an M10 reamer, 10mm would be more like it and keep the M10 to describe threads ;)

To reduce risk of drill wandering and any reamer following I'd use a stub length drill of 9.8mm dia and then a plain shank machine reamer held in a collet to finish the hole. Probably H8 reamer as H7 may be a bit loose though a test cut will determine that or if you need to go for an incremental reamer rather than 10mm nominal. Slightly larger chamfer on the dowel than the reamer's end will stop it getting stuck.

As suggested elsewhere you could drill them all and then set the boring head to your desired "fit" on the first hole and then not much longer to move around the plate and finish bore each hole to size

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