I got a lapmaster how do I use it.

kpotter · Mar 6, 2016

I picked up an old lapmaster that was sitting outside for about twenty years. I got it running and I put some clover 180 grit on the lap and have been using it to flaten some dies that I make. It seems to work well but the slurry system is shot. I have been glopping the stuff on with a brush and letting it run. I just ordered some 80 grit and some 120 grit powder that I will charge the lap with. I need it to cut faster. I just want the parts flat they dont need to be mirrors. I have never seen one of these run except in a you tube video. I think I am using it correctly. Just wanted to make sure.

Demon69 · Mar 7, 2016

kpotter said:
I picked up an old lapmaster that was sitting outside for about twenty years. I got it running and I put some clover 180 grit on the lap and have been using it to flaten some dies that I make. It seems to work well but the slurry system is shot. I have been glopping the stuff on with a brush and letting it run. I just ordered some 80 grit and some 120 grit powder that I will charge the lap with. I need it to cut faster. I just want the parts flat they dont need to be mirrors. I have never seen one of these run except in a you tube video. I think I am using it correctly. Just wanted to make sure.

Nice. Id like to get my hands on a lapping machine.
I might be speaking outta turn here (very limited knowledge) but how many plates do you have? If youve a few you could a use diamonds to charge each plate with different grade grits, rolling them in with a bearing.
An 'abrasive free' lube of some sort could be as simple as bucket mounted over head with a inline tap to control flow.

Do you have any pics?

brucecu · Mar 7, 2016

Lapping is a FREE abrasive machining process. No need to charge the plates. Get a system together with an agitator to keep the abrasive suspended and feed the slurry to the plates with a peristaltic pump. A good starting point for lapping pressure is 5 pounds multiplied by the area in square inches to be lapped. Aluminum oxide is the least aggressive abrasive followed by silicon carbide and boron carbide. I would stay away from diamond especially if your lapping ferrous materials. The abrasive will dull over time and need replenishment. This is characterized by improving surface finished and longer cycle times. You get to decide when the time is right for replenishment.

Use as much of the plate as possible and move the work around to help maintain plate flatness. Normally conditioning rings are used to bring the plates back to "flat". In a pinch old grinding wheels can be used. A typical process control for plate flatness is .001" across the radius of the plate. A simple checker can be fabricated from flat stock. Put a small pad at each end with an indicator mounted in the middle. Zero the indicator on a known flat surface then place the fixture on your plate to read flatness.

Best of luck with your machine.

Demon69 · Mar 7, 2016

brucecu said:
Lapping is a FREE abrasive machining process. No need to charge the plates. Get a system together with an agitator to keep the abrasive suspended and feed the slurry to the plates with a peristaltic pump. A good starting point for lapping pressure is 5 pounds multiplied by the area in square inches to be lapped. Aluminum oxide is the least aggressive abrasive followed by silicon carbide and boron carbide. I would stay away from diamond especially if your lapping ferrous materials. The abrasive will dull over time and need replenishment. This is characterized by improving surface finished and longer cycle times. You get to decide when the time is right for replenishment.

Use as much of the plate as possible and move the work around to help maintain plate flatness. Normally conditioning rings are used to bring the plates back to "flat". In a pinch old grinding wheels can be used. A typical process control for plate flatness is .001" across the radius of the plate. A simple checker can be fabricated from flat stock. Put a small pad at each end with an indicator mounted in the middle. Zero the indicator on a known flat surface then place the fixture on your plate to read flatness.

Best of luck with your machine.

my ignorance is confirmed

brucecu, you sound like youve some experience with the lapping gig. Ive a few questions if youve a moment.

When using silicon carbide etc.
Am i right in saying that larger grits fracture down to smaller grits with use?
When changing grit sizes, im guessing the same plate is used for all grits?
Does the slurry tank and feed system need to be washed through thoroughly to avoid cross contamination when changing finer / coarser grit?
How would you go about polishing surface thats been lapped with Silicon carbide?
When you say 'FREE abrasive machining process', does that refer to the abrasive being literally 'free' to roll around, ie not embedded in the lap surface or just thats its usually applied as a slurry?

Thanks.

----------------------------

I found this a quick easy read.

LabProcedures:Lapmaster12 U of T - MistiWiki

brucecu · Mar 7, 2016

comments added in line to answer questions

Please see my responses to your questions.

Demon73 said:
my ignorance is confirmed

brucecu, you sound like youve some experience with the lapping gig. Ive a few questions if youve a moment.

When using silicon carbide etc.
Am i right in saying that larger grits fracture down to smaller grits with use? If the down force on the workpieces is correct, the abrasive will break down exposing new sharp edges as the original edges round off. Too light a pressure abrasive dulls and doesn't cut extending lapping time. Too high a down force and you have excess abrasive consumption and increase the risk of embedding abrasive in the workpiece or lapping plate. Basically, you are using a three body wear mechanism to remove material in a controlled manner.
When changing grit sizes, im guessing the same plate is used for all grits? In an ideal world you would have separate machines for each abrasive size and type. Next best is a different plate for each abrasive. Last is a common plate. It only takes one oversize grain, especially if embedded in the plate to ruin a finish and cause scratches. If you have the problem, holding a light at an oblique angle to the plate will cause the embedded particle to glint. Once you find it, it can be picked out, the plate reconditioned or the abrasive punched deeper into the plate (to irritate you another day). Don't forget to stone the resulting high spot.
Does the slurry tank and feed system need to be washed through thoroughly to avoid cross contamination when changing finer / coarser grit? Absolutely. Definitely. Unequivocably.
How would you go about polishing surface thats been lapped with Silicon carbide? Progressively finer abrasives on a felt or knapped pad. Expect some roll off at the edges of the workpiece.
When you say 'FREE abrasive machining process', does that refer to the abrasive being literally 'free' to roll around, ie not embedded in the lap surface or just thats its usually applied as a slurry? The abrasive is free to move.

Thanks.

----------------------------

I found this a quick easy read.

LabProcedures:Lapmaster12 U of T - MistiWiki

kpotter · Mar 7, 2016

The slurry pump is trashed I have been charging the lap by sprinkleing 80 grit silon carbide on it. I have been using oil to keep the slurry suspended. The charge doesnt last very long and it seems to take a long time to grind the pieces down. I am lapping two inch diameter slugs made of `12L 14. They dont need to be perfect I just want the saw marks off of them.

Heavey Metal · Mar 7, 2016

Mill

Grind

Than lap

Use naptha instead of oil.

Add weight as per^^^^

CalG · Mar 7, 2016

A belt sander will be a better tool.

brucecu · Mar 8, 2016

Lapping is a slow material removal method. The slowness is compensated by the ability to run many piece simultaneously and the wide process window. Do yourself a favor and repair the slurry system. Figure out the run and put it on a timer. Then go do something else. Time is money.

sable · Mar 8, 2016

brucecu said:
Lapping is a FREE abrasive machining process. No need to charge the plates. Get a system together with an agitator to keep the abrasive suspended and feed the slurry to the plates with a peristaltic pump. A good starting point for lapping pressure is 5 pounds multiplied by the area in square inches to be lapped. Aluminum oxide is the least aggressive abrasive followed by silicon carbide and boron carbide. I would stay away from diamond especially if your lapping ferrous materials. The abrasive will dull over time and need replenishment. This is characterized by improving surface finished and longer cycle times. You get to decide when the time is right for replenishment.

Use as much of the plate as possible and move the work around to help maintain plate flatness. Normally conditioning rings are used to bring the plates back to "flat". In a pinch old grinding wheels can be used. A typical process control for plate flatness is .001" across the radius of the plate. A simple checker can be fabricated from flat stock. Put a small pad at each end with an indicator mounted in the middle. Zero the indicator on a known flat surface then place the fixture on your plate to read flatness.

Best of luck with your machine.

That is interesting ,I have a Lapmaster guage that I picked up at an auction years ago, I always wondered it's exact purpose and it is exactly what you just described ,I thought it was for checking the lapped parts but checking the lapping plates makes much more sense. See pic above.

Philabuster · Mar 8, 2016

kpotter said:
I am lapping two inch diameter slugs made of `12L 14. They dont need to be perfect I just want the saw marks off of them.

Wrong process for a lapping machine. Lap machines are designed to make a large part flat to itself within .0002" across the entire surface. We use them all the time for steel rings and many other types of parts, but they are not a heavy stock removal tool.

It would be 100x faster to throw a bunch of parts on a small 16" to 18" rotary surface grinder (DCM, Blanchard grinder) with a magnetic chuck and face them off all at once, flip over and grind other side. Probably take less than 5 minutes a side with just 21 pcs on the table arranged in a circular ring under a 16" diameter circle with all the parts touching each other. Two rows would be 36 pcs, and only 4" wide. Wheel is 8" in diameter, so plenty of overlap without moving anything. Just plunge down slowly and spark out. Done.

Larger used grinders tend to sell for less than smaller grinders, probably due to floor space issues. Check HGR and ebay as they come up now and then.

This is certainly a lot less work than throwing each of them in the lathe one at a time.

The 18" DCM we have at work has a tiny footprint and can really chew off some stock. I was amazed when the tech who set up the grinder showed us what that grinder can do. I was a bit freaked out to hear the 10HP motor start to bog down as he "animalized" the workpiece (his word). :eek:

He said let it eat. It can take it. :cool:

Holy shit! This thing is bad ass. I wanted one for my home shop right then. :drool5:

Here's the one we bought: DCM IG 080 M

rotary surface grinder, surface grinder, vertical spindle surface grinder, rotary table surface grinder

kpotter · Mar 8, 2016

I got everything working including the slurry pump. I used eighty grit and light oil and it worked alot better. The thing is still crazy slow, I ran the parts for 5 hours and they looked great but dang five hours. They were smooth as glass but five hours. I may build a pallet and face mill them. I would love a vertical grinder but blanchards are expensive and big. How much was the dcm grinder

Demon69 · Mar 8, 2016

kpotter said:
I got everything working including the slurry pump. I used eighty grit and light oil and it worked alot better. The thing is still crazy slow, I ran the parts for 5 hours and they looked great but dang five hours. They were smooth as glass but five hours. I may build a pallet and face mill them. I would love a vertical grinder but blanchards are expensive and big. How much was the dcm grinder

5 hours!! Sounds you dont need that hunk of junk!!... So what the postage to surbiton uk?

Philabuster · Mar 9, 2016

kpotter said:
I would love a vertical grinder but blanchards are expensive and big. How much was the dcm grinder

I want to say our grinder brand new was $8k, but that was 3 years ago, so don't quote me on that.

The machine is a piece of cake to use. Throw the parts on the mag chuck, bring live wheel down and touch parts, rotate wheel dial to amount of stock you wish to remove and push the AUTO button.

Machine will creep feed down at the rate you set on grind feed (slow to fast), and also self-regulate cutting pressure based on how aggressive you want to cut stock. This is similar to how an old DoAll horizontal bandsaw regulates during a cut.

When machine reaches zero, it sparks out and incrementally backs up a thou at a time until no pressure is "felt" on the wheel via current monitoring, then it automatically retracts .100" and stops the table.

Grinding is totally enclosed and has it's own mist collector and cheese cloth separator built in. We are running it right next to a brand new wire EDM, both of which are in a small room less than 500 sq/ft. Zero problems with dust contaminating anything. Very clean machine to actually use. Wear ear protection because 10HP makes some noise when ripping off stock.

HGR has two Blanchard grinders right now--one 16" and one huge 36" machine. I know nothing about running a Blanchard other than they are beasts that take no prisoners. :leaving:

tdmidget · Mar 9, 2016

36" is a small Blanchard. I think they made them to 140". I have worked on an 84".
Kevin , Vroom has 2 or 3 Blanchards and they are big, like 120". I think they have a smaller one too. You might ask for a price. It cost them no more to fill the chuck up than to grind 1 or 2 so you might want to keep that in mind.

brucecu · Mar 10, 2016

smooth as glass?

kpotter said:
I got everything working including the slurry pump. I used eighty grit and light oil and it worked alot better. The thing is still crazy slow, I ran the parts for 5 hours and they looked great but dang five hours. They were smooth as glass but five hours. I may build a pallet and face mill them. I would love a vertical grinder but blanchards are expensive and big. How much was the dcm grinder

If the finish is smooth as glass the abrasive is not working hard enough. The finish should be matte. Double down force until you get the abrasive to cut. There's a sweet spot in there someplace. It won't be as fast as a vertical spindle grinder but should be able to improve on the five hours.

kpotter · Mar 10, 2016

I ran it today with 80 grit and it worked better it took about two hours the surface was matt finish. I ran six inch pucks of ar 500 plate and they looked great. I used to surface grind them and now I am doing the lapping and it takes alot less effort.

rogertoolmaker · Apr 17, 2016

Lapping and laps

kpotter said:
The slurry pump is trashed I have been charging the lap by sprinkleing 80 grit silon carbide on it. I have been using oil to keep the slurry suspended. The charge doesnt last very long and it seems to take a long time to grind the pieces down. I am lapping two inch diameter slugs made of `12L 14. They dont need to be perfect I just want the saw marks off of them.

The lap has to be softer than the workpiece to be a lap or the workpiece becomes charged and becomes the lap. 12L14 is as soft as the "lap". Granted the work will finally be worn in. but it will take some time for results. machining, grinding or sanding would be more in line for this job. Lapping is usually reserved for only the finest of flatness and finish for very close dimensional tolerences as in hardened gage blocks and special gages.

Rogertoolmaker

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